MQTTvue/mqtt-vue-dashboard/node_modules/less/dist/less-node.cjs

/**
 * Less - Leaner CSS v4.6.4
 * http://lesscss.org
 *
 * Copyright (c) 2009-2026, Alexis Sellier <self@cloudhead.net>
 * Licensed under the Apache-2.0 License.
 *
 * @license Apache-2.0
 */

'use strict';

var path = require('path');
var nodeFs = require('fs');
var url = require('url');

function _interopDefaultLegacy (e) { return e && typeof e === 'object' && 'default' in e ? e : { 'default': e }; }

var path__default = /*#__PURE__*/_interopDefaultLegacy(path);
var nodeFs__default = /*#__PURE__*/_interopDefaultLegacy(nodeFs);
var url__default = /*#__PURE__*/_interopDefaultLegacy(url);

function createRequire() { return require; }

const require$6 = createRequire();

class SourceMapGeneratorFallback {
    addMapping(){}
    setSourceContent(){}
    toJSON(){
        return null;
    }
}
var environment = {
    encodeBase64: function encodeBase64(str) {
        // Avoid Buffer constructor on newer versions of Node.js.
        const buffer = (Buffer.from ? Buffer.from(str) : (new Buffer(str)));
        return buffer.toString('base64');
    },
    mimeLookup: function (filename) {
        try {
            const mimeModule = require$6('mime');
            return mimeModule ? mimeModule.lookup(filename) : "application/octet-stream";
        } catch (e) {
            return "application/octet-stream";
        }
    },
    charsetLookup: function (mime) {
        try {
            const mimeModule = require$6('mime');
            return mimeModule ? mimeModule.charsets.lookup(mime) : undefined;
        } catch (e) {
            return undefined;
        }
    },
    getSourceMapGenerator: function getSourceMapGenerator() {
        try {
            const sourceMapModule = require$6('source-map');
            return sourceMapModule ? sourceMapModule.SourceMapGenerator : SourceMapGeneratorFallback;
        } catch (e) {
            return SourceMapGeneratorFallback;
        }
    }
};

/** @typedef {import('fs')} FS */

const require$5 = createRequire();

/** @type {FS} */
let fs;
try {
    fs = require$5('graceful-fs');
} catch (e) {
    fs = nodeFs__default["default"];
}
var fs$1 = fs;

class AbstractFileManager {
    getPath(filename) {
        let j = filename.lastIndexOf('?');
        if (j > 0) {
            filename = filename.slice(0, j);
        }
        j = filename.lastIndexOf('/');
        if (j < 0) {
            j = filename.lastIndexOf('\\');
        }
        if (j < 0) {
            return '';
        }
        return filename.slice(0, j + 1);
    }

    tryAppendExtension(path, ext) {
        return /(\.[a-z]*$)|([?;].*)$/.test(path) ? path : path + ext;
    }

    tryAppendLessExtension(path) {
        return this.tryAppendExtension(path, '.less');
    }

    supportsSync() {
        return false;
    }

    alwaysMakePathsAbsolute() {
        return false;
    }

    isPathAbsolute(filename) {
        return (/^(?:[a-z-]+:|\/|\\|#)/i).test(filename);
    }

    // TODO: pull out / replace?
    join(basePath, laterPath) {
        if (!basePath) {
            return laterPath;
        }
        return basePath + laterPath;
    }

    pathDiff(url, baseUrl) {
        // diff between two paths to create a relative path

        const urlParts = this.extractUrlParts(url);

        const baseUrlParts = this.extractUrlParts(baseUrl);
        let i;
        let max;
        let urlDirectories;
        let baseUrlDirectories;
        let diff = '';
        if (urlParts.hostPart !== baseUrlParts.hostPart) {
            return '';
        }
        max = Math.max(baseUrlParts.directories.length, urlParts.directories.length);
        for (i = 0; i < max; i++) {
            if (baseUrlParts.directories[i] !== urlParts.directories[i]) { break; }
        }
        baseUrlDirectories = baseUrlParts.directories.slice(i);
        urlDirectories = urlParts.directories.slice(i);
        for (i = 0; i < baseUrlDirectories.length - 1; i++) {
            diff += '../';
        }
        for (i = 0; i < urlDirectories.length - 1; i++) {
            diff += `${urlDirectories[i]}/`;
        }
        return diff;
    }

    /**
     * Helper function, not part of API.
     * This should be replaceable by newer Node / Browser APIs
     * 
     * @param {string} url 
     * @param {string} baseUrl
     */
    extractUrlParts(url, baseUrl) {
        // urlParts[1] = protocol://hostname/ OR /
        // urlParts[2] = / if path relative to host base
        // urlParts[3] = directories
        // urlParts[4] = filename
        // urlParts[5] = parameters

        const urlPartsRegex = /^((?:[a-z-]+:)?\/{2}(?:[^/?#]*\/)|([/\\]))?((?:[^/\\?#]*[/\\])*)([^/\\?#]*)([#?].*)?$/i;

        const urlParts = url.match(urlPartsRegex);
        const returner = {};
        let rawDirectories = [];
        const directories = [];
        let i;
        let baseUrlParts;

        if (!urlParts) {
            throw new Error(`Could not parse sheet href - '${url}'`);
        }

        // Stylesheets in IE don't always return the full path
        if (baseUrl && (!urlParts[1] || urlParts[2])) {
            baseUrlParts = baseUrl.match(urlPartsRegex);
            if (!baseUrlParts) {
                throw new Error(`Could not parse page url - '${baseUrl}'`);
            }
            urlParts[1] = urlParts[1] || baseUrlParts[1] || '';
            if (!urlParts[2]) {
                urlParts[3] = baseUrlParts[3] + urlParts[3];
            }
        }

        if (urlParts[3]) {
            rawDirectories = urlParts[3].replace(/\\/g, '/').split('/');

            // collapse '..' and skip '.'
            for (i = 0; i < rawDirectories.length; i++) {

                if (rawDirectories[i] === '..') {
                    directories.pop();
                }
                else if (rawDirectories[i] !== '.') {
                    directories.push(rawDirectories[i]);
                }
            
            }
        }

        returner.hostPart = urlParts[1];
        returner.directories = directories;
        returner.rawPath = (urlParts[1] || '') + rawDirectories.join('/');
        returner.path = (urlParts[1] || '') + directories.join('/');
        returner.filename = urlParts[4];
        returner.fileUrl = returner.path + (urlParts[4] || '');
        returner.url = returner.fileUrl + (urlParts[5] || '');
        return returner;
    }
}

const require$4 = createRequire();

const FileManager = function() {};
FileManager.prototype = Object.assign(new AbstractFileManager(), {
    supports() {
        return true;
    },

    supportsSync() {
        return true;
    },

    loadFile(filename, currentDirectory, options, environment, callback) {
        let fullFilename;
        const isAbsoluteFilename = this.isPathAbsolute(filename);
        const filenamesTried = [];
        const self = this;
        const prefix = filename.slice(0, 1);
        const explicit = prefix === '.' || prefix === '/';
        let result = null;
        let isNodeModule = false;
        const npmPrefix = 'npm://';

        options = options || {};

        const paths = isAbsoluteFilename ? [''] : [currentDirectory];

        if (options.paths) { paths.push.apply(paths, options.paths); }

        if (!isAbsoluteFilename && paths.indexOf('.') === -1) { paths.push('.'); }

        const prefixes = options.prefixes || [''];
        const fileParts = this.extractUrlParts(filename);

        if (options.syncImport) {
            getFileData(returnData, returnData);
            if (callback) {
                callback(result.error, result);
            }
            else {
                return result;
            }
        }
        else {
            // promise is guaranteed to be asyncronous
            // which helps as it allows the file handle
            // to be closed before it continues with the next file
            return new Promise(getFileData);
        }

        function returnData(data) {
            if (!data.filename) {
                result = { error: data };
            }
            else {
                result = data;
            }
        }

        function getFileData(fulfill, reject) {
            (function tryPathIndex(i) {
                function tryWithExtension() {
                    const extFilename = options.ext ? self.tryAppendExtension(fullFilename, options.ext) : fullFilename;

                    if (extFilename !== fullFilename && !explicit && paths[i] === '.') {
                        try {
                            fullFilename = require$4.resolve(extFilename);
                            isNodeModule = true;
                        }
                        catch (e) {
                            filenamesTried.push(npmPrefix + extFilename);
                            fullFilename = extFilename;
                        }
                    }
                    else {
                        fullFilename = extFilename;
                    }
                }
                if (i < paths.length) {
                    (function tryPrefix(j) {
                        if (j < prefixes.length) {
                            isNodeModule = false;
                            fullFilename = fileParts.rawPath + prefixes[j] + fileParts.filename;

                            if (paths[i]) {
                                if (paths[i].startsWith('#')) {
                                    // Handling paths starting with '#'
                                    fullFilename = paths[i].substr(1) + fullFilename;
                                }else {
                                    fullFilename = path__default["default"].join(paths[i], fullFilename);
                                }
                            }

                            if (!explicit && paths[i] === '.') {
                                try {
                                    fullFilename = require$4.resolve(fullFilename);
                                    isNodeModule = true;
                                }
                                catch (e) {
                                    filenamesTried.push(npmPrefix + fullFilename);
                                    tryWithExtension();
                                }
                            }
                            else {
                                tryWithExtension();
                            }                            

                            const readFileArgs = [fullFilename];
                            if (!options.rawBuffer) {
                                readFileArgs.push('utf-8');
                            }
                            if (options.syncImport) {
                                try {
                                    const data = fs$1.readFileSync.apply(this, readFileArgs);
                                    fulfill({ contents: data, filename: fullFilename});
                                }
                                catch (e) {
                                    filenamesTried.push(isNodeModule ? npmPrefix + fullFilename : fullFilename);
                                    return tryPrefix(j + 1);
                                }
                            }
                            else {
                                readFileArgs.push(function(e, data) {
                                    if (e) {
                                        filenamesTried.push(isNodeModule ? npmPrefix + fullFilename : fullFilename);
                                        return tryPrefix(j + 1);
                                    }   
                                    fulfill({ contents: data, filename: fullFilename});
                                });
                                fs$1.readFile.apply(this, readFileArgs);
                            }

                        }
                        else {
                            tryPathIndex(i + 1);
                        }
                    })(0);
                } else {
                    reject({ type: 'File', message: `'${filename}' wasn't found. Tried - ${filenamesTried.join(',')}` });
                }
            }(0));
        }
    },

    loadFileSync(filename, currentDirectory, options, environment) {
        options.syncImport = true;
        return this.loadFile(filename, currentDirectory, options, environment);
    }
});

var logger = {
    error: function(msg) {
        this._fireEvent('error', msg);
    },
    warn: function(msg) {
        this._fireEvent('warn', msg);
    },
    info: function(msg) {
        this._fireEvent('info', msg);
    },
    debug: function(msg) {
        this._fireEvent('debug', msg);
    },
    addListener: function(listener) {
        this._listeners.push(listener);
    },
    removeListener: function(listener) {
        for (let i = 0; i < this._listeners.length; i++) {
            if (this._listeners[i] === listener) {
                this._listeners.splice(i, 1);
                return;
            }
        }
    },
    _fireEvent: function(type, msg) {
        for (let i = 0; i < this._listeners.length; i++) {
            const logFunction = this._listeners[i][type];
            if (logFunction) {
                logFunction(msg);
            }
        }
    },
    _listeners: []
};

/* eslint-disable no-unused-vars */

const require$3 = createRequire();

const isUrlRe = /^(?:https?:)?\/\//i;
let request;

const UrlFileManager = function() {};
UrlFileManager.prototype = Object.assign(new AbstractFileManager(), {
    supports(filename, currentDirectory, options, environment) {
        return isUrlRe.test( filename ) || isUrlRe.test(currentDirectory);
    },

    loadFile(filename, currentDirectory, options, environment) {
        return new Promise((fulfill, reject) => {
            if (request === undefined) {
                try { request = require$3('needle'); }
                catch (e) { request = null; }
            }
            if (!request) {
                reject({ type: 'File', message: 'optional dependency \'needle\' required to import over http(s)\n' });
                return;
            }

            let urlStr = isUrlRe.test( filename ) ? filename : url__default["default"].resolve(currentDirectory, filename);

            /** native-request currently has a bug */
            const hackUrlStr = urlStr.indexOf('?') === -1 ? urlStr + '?' : urlStr;

            request.get(hackUrlStr, { follow_max: 5 }, (err, resp, body) => {
                if (err || resp && resp.statusCode >= 400) {
                    const message = resp && resp.statusCode === 404
                        ? `resource '${urlStr}' was not found\n`
                        : `resource '${urlStr}' gave this Error:\n  ${err || resp.statusMessage || resp.statusCode}\n`;
                    reject({ type: 'File', message });
                    return;
                }
                if (resp.statusCode >= 300) {
                    reject({ type: 'File', message: `resource '${urlStr}' caused too many redirects` });
                    return;
                }
                body = body.toString('utf8');
                if (!body) {
                    logger.warn(`Warning: Empty body (HTTP ${resp.statusCode}) returned by "${urlStr}"`);
                }
                fulfill({ contents: body || '', filename: urlStr });
            });
        });
    }
});

/**
 * @todo Document why this abstraction exists, and the relationship between
 *       environment, file managers, and plugin manager
 */

class Environment {
    constructor(externalEnvironment, fileManagers) {
        this.fileManagers = fileManagers || [];
        externalEnvironment = externalEnvironment || {};

        const optionalFunctions = ['encodeBase64', 'mimeLookup', 'charsetLookup', 'getSourceMapGenerator'];
        const requiredFunctions = [];
        const functions = requiredFunctions.concat(optionalFunctions);

        for (let i = 0; i < functions.length; i++) {
            const propName = functions[i];
            const environmentFunc = externalEnvironment[propName];
            if (environmentFunc) {
                this[propName] = environmentFunc.bind(externalEnvironment);
            } else if (i < requiredFunctions.length) {
                this.warn(`missing required function in environment - ${propName}`);
            }
        }
    }

    getFileManager(filename, currentDirectory, options, environment, isSync) {

        if (!filename) {
            logger.warn('getFileManager called with no filename.. Please report this issue. continuing.');
        }
        if (currentDirectory === undefined) {
            logger.warn('getFileManager called with null directory.. Please report this issue. continuing.');
        }

        let fileManagers = this.fileManagers;
        if (options.pluginManager) {
            fileManagers = [].concat(fileManagers).concat(options.pluginManager.getFileManagers());
        }
        for (let i = fileManagers.length - 1; i >= 0 ; i--) {
            const fileManager = fileManagers[i];
            if (fileManager[isSync ? 'supportsSync' : 'supports'](filename, currentDirectory, options, environment)) {
                return fileManager;
            }
        }
        return null;
    }

    addFileManager(fileManager) {
        this.fileManagers.push(fileManager);
    }

    clearFileManagers() {
        this.fileManagers = [];
    }
}

var colors = {
    'aliceblue':'#f0f8ff',
    'antiquewhite':'#faebd7',
    'aqua':'#00ffff',
    'aquamarine':'#7fffd4',
    'azure':'#f0ffff',
    'beige':'#f5f5dc',
    'bisque':'#ffe4c4',
    'black':'#000000',
    'blanchedalmond':'#ffebcd',
    'blue':'#0000ff',
    'blueviolet':'#8a2be2',
    'brown':'#a52a2a',
    'burlywood':'#deb887',
    'cadetblue':'#5f9ea0',
    'chartreuse':'#7fff00',
    'chocolate':'#d2691e',
    'coral':'#ff7f50',
    'cornflowerblue':'#6495ed',
    'cornsilk':'#fff8dc',
    'crimson':'#dc143c',
    'cyan':'#00ffff',
    'darkblue':'#00008b',
    'darkcyan':'#008b8b',
    'darkgoldenrod':'#b8860b',
    'darkgray':'#a9a9a9',
    'darkgrey':'#a9a9a9',
    'darkgreen':'#006400',
    'darkkhaki':'#bdb76b',
    'darkmagenta':'#8b008b',
    'darkolivegreen':'#556b2f',
    'darkorange':'#ff8c00',
    'darkorchid':'#9932cc',
    'darkred':'#8b0000',
    'darksalmon':'#e9967a',
    'darkseagreen':'#8fbc8f',
    'darkslateblue':'#483d8b',
    'darkslategray':'#2f4f4f',
    'darkslategrey':'#2f4f4f',
    'darkturquoise':'#00ced1',
    'darkviolet':'#9400d3',
    'deeppink':'#ff1493',
    'deepskyblue':'#00bfff',
    'dimgray':'#696969',
    'dimgrey':'#696969',
    'dodgerblue':'#1e90ff',
    'firebrick':'#b22222',
    'floralwhite':'#fffaf0',
    'forestgreen':'#228b22',
    'fuchsia':'#ff00ff',
    'gainsboro':'#dcdcdc',
    'ghostwhite':'#f8f8ff',
    'gold':'#ffd700',
    'goldenrod':'#daa520',
    'gray':'#808080',
    'grey':'#808080',
    'green':'#008000',
    'greenyellow':'#adff2f',
    'honeydew':'#f0fff0',
    'hotpink':'#ff69b4',
    'indianred':'#cd5c5c',
    'indigo':'#4b0082',
    'ivory':'#fffff0',
    'khaki':'#f0e68c',
    'lavender':'#e6e6fa',
    'lavenderblush':'#fff0f5',
    'lawngreen':'#7cfc00',
    'lemonchiffon':'#fffacd',
    'lightblue':'#add8e6',
    'lightcoral':'#f08080',
    'lightcyan':'#e0ffff',
    'lightgoldenrodyellow':'#fafad2',
    'lightgray':'#d3d3d3',
    'lightgrey':'#d3d3d3',
    'lightgreen':'#90ee90',
    'lightpink':'#ffb6c1',
    'lightsalmon':'#ffa07a',
    'lightseagreen':'#20b2aa',
    'lightskyblue':'#87cefa',
    'lightslategray':'#778899',
    'lightslategrey':'#778899',
    'lightsteelblue':'#b0c4de',
    'lightyellow':'#ffffe0',
    'lime':'#00ff00',
    'limegreen':'#32cd32',
    'linen':'#faf0e6',
    'magenta':'#ff00ff',
    'maroon':'#800000',
    'mediumaquamarine':'#66cdaa',
    'mediumblue':'#0000cd',
    'mediumorchid':'#ba55d3',
    'mediumpurple':'#9370d8',
    'mediumseagreen':'#3cb371',
    'mediumslateblue':'#7b68ee',
    'mediumspringgreen':'#00fa9a',
    'mediumturquoise':'#48d1cc',
    'mediumvioletred':'#c71585',
    'midnightblue':'#191970',
    'mintcream':'#f5fffa',
    'mistyrose':'#ffe4e1',
    'moccasin':'#ffe4b5',
    'navajowhite':'#ffdead',
    'navy':'#000080',
    'oldlace':'#fdf5e6',
    'olive':'#808000',
    'olivedrab':'#6b8e23',
    'orange':'#ffa500',
    'orangered':'#ff4500',
    'orchid':'#da70d6',
    'palegoldenrod':'#eee8aa',
    'palegreen':'#98fb98',
    'paleturquoise':'#afeeee',
    'palevioletred':'#d87093',
    'papayawhip':'#ffefd5',
    'peachpuff':'#ffdab9',
    'peru':'#cd853f',
    'pink':'#ffc0cb',
    'plum':'#dda0dd',
    'powderblue':'#b0e0e6',
    'purple':'#800080',
    'rebeccapurple':'#663399',
    'red':'#ff0000',
    'rosybrown':'#bc8f8f',
    'royalblue':'#4169e1',
    'saddlebrown':'#8b4513',
    'salmon':'#fa8072',
    'sandybrown':'#f4a460',
    'seagreen':'#2e8b57',
    'seashell':'#fff5ee',
    'sienna':'#a0522d',
    'silver':'#c0c0c0',
    'skyblue':'#87ceeb',
    'slateblue':'#6a5acd',
    'slategray':'#708090',
    'slategrey':'#708090',
    'snow':'#fffafa',
    'springgreen':'#00ff7f',
    'steelblue':'#4682b4',
    'tan':'#d2b48c',
    'teal':'#008080',
    'thistle':'#d8bfd8',
    'tomato':'#ff6347',
    'turquoise':'#40e0d0',
    'violet':'#ee82ee',
    'wheat':'#f5deb3',
    'white':'#ffffff',
    'whitesmoke':'#f5f5f5',
    'yellow':'#ffff00',
    'yellowgreen':'#9acd32'
};

var unitConversions = {
    length: {
        'm': 1,
        'cm': 0.01,
        'mm': 0.001,
        'in': 0.0254,
        'px': 0.0254 / 96,
        'pt': 0.0254 / 72,
        'pc': 0.0254 / 72 * 12
    },
    duration: {
        's': 1,
        'ms': 0.001
    },
    angle: {
        'rad': 1 / (2 * Math.PI),
        'deg': 1 / 360,
        'grad': 1 / 400,
        'turn': 1
    }
};

var data = { colors, unitConversions };

// @ts-check
/**
 * @typedef {object} FileInfo
 * @property {string} [filename]
 * @property {string} [rootpath]
 * @property {string} [currentDirectory]
 * @property {string} [rootFilename]
 * @property {string} [entryPath]
 * @property {boolean} [reference]
 */

/**
 * @typedef {object} VisibilityInfo
 * @property {number} [visibilityBlocks]
 * @property {boolean} [nodeVisible]
 */

/**
 * @typedef {object} CSSOutput
 * @property {(chunk: string, fileInfo?: FileInfo, index?: number, mapLines?: boolean) => void} add
 * @property {() => boolean} isEmpty
 */

/**
 * @typedef {object} EvalContext
 * @property {number} [numPrecision]
 * @property {(op?: string) => boolean} [isMathOn]
 * @property {number} [math]
 * @property {Node[]} [frames]
 * @property {Array<{important?: string}>} [importantScope]
 * @property {string[]} [paths]
 * @property {boolean} [compress]
 * @property {boolean} [strictUnits]
 * @property {boolean} [sourceMap]
 * @property {boolean} [importMultiple]
 * @property {string} [urlArgs]
 * @property {boolean} [javascriptEnabled]
 * @property {object} [pluginManager]
 * @property {number} [rewriteUrls]
 * @property {boolean} [inCalc]
 * @property {boolean} [mathOn]
 * @property {boolean[]} [calcStack]
 * @property {boolean[]} [parensStack]
 * @property {Node[]} [mediaBlocks]
 * @property {Node[]} [mediaPath]
 * @property {() => void} [inParenthesis]
 * @property {() => void} [outOfParenthesis]
 * @property {() => void} [enterCalc]
 * @property {() => void} [exitCalc]
 * @property {(path: string) => boolean} [pathRequiresRewrite]
 * @property {(path: string, rootpath?: string) => string} [rewritePath]
 * @property {(path: string) => string} [normalizePath]
 * @property {number} [tabLevel]
 * @property {boolean} [lastRule]
 */

/**
 * @typedef {object} TreeVisitor
 * @property {(node: Node) => Node} visit
 * @property {(nodes: Node[], nonReplacing?: boolean) => Node[]} visitArray
 */

/**
 * The reason why Node is a class and other nodes simply do not extend
 * from Node (since we're transpiling) is due to this issue:
 *
 * @see https://github.com/less/less.js/issues/3434
 */
class Node {
    get type() { return ''; }

    constructor() {
        /** @type {Node | null} */
        this.parent = null;
        /** @type {number | undefined} */
        this.visibilityBlocks = undefined;
        /** @type {boolean | undefined} */
        this.nodeVisible = undefined;
        /** @type {Node | null} */
        this.rootNode = null;
        /** @type {Node | null} */
        this.parsed = null;

        /** @type {Node | Node[] | string | number | undefined} */
        this.value = undefined;
        /** @type {number | undefined} */
        this._index = undefined;
        /** @type {FileInfo | undefined} */
        this._fileInfo = undefined;
    }

    get currentFileInfo() {
        return this.fileInfo();
    }

    get index() {
        return this.getIndex();
    }

    /**
     * @param {Node | Node[]} nodes
     * @param {Node} parent
     */
    setParent(nodes, parent) {
        /** @param {Node} node */
        function set(node) {
            if (node && node instanceof Node) {
                node.parent = parent;
            }
        }
        if (Array.isArray(nodes)) {
            nodes.forEach(set);
        }
        else {
            set(nodes);
        }
    }

    /** @returns {number} */
    getIndex() {
        return this._index || (this.parent && this.parent.getIndex()) || 0;
    }

    /** @returns {FileInfo} */
    fileInfo() {
        return this._fileInfo || (this.parent && this.parent.fileInfo()) || {};
    }

    /** @returns {boolean} */
    isRulesetLike() { return false; }

    /**
     * @param {EvalContext} context
     * @returns {string}
     */
    toCSS(context) {
        /** @type {string[]} */
        const strs = [];
        this.genCSS(context, {
            add: function(chunk, fileInfo, index) {
                strs.push(chunk);
            },
            isEmpty: function () {
                return strs.length === 0;
            }
        });
        return strs.join('');
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add(/** @type {string} */ (this.value));
    }

    /**
     * @param {TreeVisitor} visitor
     */
    accept(visitor) {
        this.value = visitor.visit(/** @type {Node} */ (this.value));
    }

    /**
     * @param {EvalContext} [context]
     * @returns {Node}
     */
    eval(context) { return this; }

    /**
     * @param {EvalContext} context
     * @param {string} op
     * @param {number} a
     * @param {number} b
     * @returns {number | undefined}
     */
    _operate(context, op, a, b) {
        switch (op) {
            case '+': return a + b;
            case '-': return a - b;
            case '*': return a * b;
            case '/': return a / b;
        }
    }

    /**
     * @param {EvalContext} context
     * @param {number} value
     * @returns {number}
     */
    fround(context, value) {
        const precision = context && context.numPrecision;
        // add "epsilon" to ensure numbers like 1.000000005 (represented as 1.000000004999...) are properly rounded:
        return (precision) ? Number((value + 2e-16).toFixed(precision)) : value;
    }

    /**
     * @param {Node & { compare?: (other: Node) => number | undefined }} a
     * @param {Node & { compare?: (other: Node) => number | undefined }} b
     * @returns {number | undefined}
     */
    static compare(a, b) {
        /* returns:
         -1: a < b
         0: a = b
         1: a > b
         and *any* other value for a != b (e.g. undefined, NaN, -2 etc.) */

        if ((a.compare) &&
            // for "symmetric results" force toCSS-based comparison
            // of Quoted or Anonymous if either value is one of those
            !(b.type === 'Quoted' || b.type === 'Anonymous')) {
            return a.compare(b);
        } else if (b.compare) {
            return -b.compare(a);
        } else if (a.type !== b.type) {
            return undefined;
        }

        let aVal = a.value;
        let bVal = b.value;
        if (!Array.isArray(aVal)) {
            return aVal === bVal ? 0 : undefined;
        }
        if (!Array.isArray(bVal)) {
            return undefined;
        }
        if (aVal.length !== bVal.length) {
            return undefined;
        }
        for (let i = 0; i < aVal.length; i++) {
            if (Node.compare(aVal[i], bVal[i]) !== 0) {
                return undefined;
            }
        }
        return 0;
    }

    /**
     * @param {number | string} a
     * @param {number | string} b
     * @returns {number | undefined}
     */
    static numericCompare(a, b) {
        return a  <  b ? -1
            : a === b ?  0
                : a  >  b ?  1 : undefined;
    }

    /** @returns {boolean} */
    blocksVisibility() {
        if (this.visibilityBlocks === undefined) {
            this.visibilityBlocks = 0;
        }
        return this.visibilityBlocks !== 0;
    }

    addVisibilityBlock() {
        if (this.visibilityBlocks === undefined) {
            this.visibilityBlocks = 0;
        }
        this.visibilityBlocks = this.visibilityBlocks + 1;
    }

    removeVisibilityBlock() {
        if (this.visibilityBlocks === undefined) {
            this.visibilityBlocks = 0;
        }
        this.visibilityBlocks = this.visibilityBlocks - 1;
    }

    ensureVisibility() {
        this.nodeVisible = true;
    }

    ensureInvisibility() {
        this.nodeVisible = false;
    }

    /** @returns {boolean | undefined} */
    isVisible() {
        return this.nodeVisible;
    }

    /** @returns {VisibilityInfo} */
    visibilityInfo() {
        return {
            visibilityBlocks: this.visibilityBlocks,
            nodeVisible: this.nodeVisible
        };
    }

    /** @param {VisibilityInfo} info */
    copyVisibilityInfo(info) {
        if (!info) {
            return;
        }
        this.visibilityBlocks = info.visibilityBlocks;
        this.nodeVisible = info.nodeVisible;
    }
}

/**
 * Set by the parser at runtime on Node.prototype.
 * @type {{ context: EvalContext, importManager: object, imports: object } | undefined}
 */
Node.prototype.parse = undefined;

// @ts-check

/** @import { EvalContext, CSSOutput } from './node.js' */

//
// RGB Colors - #ff0014, #eee
//
class Color extends Node {
    get type() { return 'Color'; }

    /**
     * @param {number[] | string} rgb
     * @param {number} [a]
     * @param {string} [originalForm]
     */
    constructor(rgb, a, originalForm) {
        super();
        const self = this;
        //
        // The end goal here, is to parse the arguments
        // into an integer triplet, such as `128, 255, 0`
        //
        // This facilitates operations and conversions.
        //
        if (Array.isArray(rgb)) {
            /** @type {number[]} */
            this.rgb = rgb;
        } else if (rgb.length >= 6) {
            /** @type {number[]} */
            this.rgb = [];
            /** @type {RegExpMatchArray} */ (rgb.match(/.{2}/g)).map(function (c, i) {
                if (i < 3) {
                    self.rgb.push(parseInt(c, 16));
                } else {
                    self.alpha = (parseInt(c, 16)) / 255;
                }
            });
        } else {
            /** @type {number[]} */
            this.rgb = [];
            rgb.split('').map(function (c, i) {
                if (i < 3) {
                    self.rgb.push(parseInt(c + c, 16));
                } else {
                    self.alpha = (parseInt(c + c, 16)) / 255;
                }
            });
        }
        /** @type {number} */
        if (typeof this.alpha === 'undefined') {
            this.alpha = (typeof a === 'number') ? a : 1;
        }
        if (typeof originalForm !== 'undefined') {
            this.value = originalForm;
        }
    }

    luma() {
        let r = this.rgb[0] / 255, g = this.rgb[1] / 255, b = this.rgb[2] / 255;

        r = (r <= 0.03928) ? r / 12.92 : Math.pow(((r + 0.055) / 1.055), 2.4);
        g = (g <= 0.03928) ? g / 12.92 : Math.pow(((g + 0.055) / 1.055), 2.4);
        b = (b <= 0.03928) ? b / 12.92 : Math.pow(((b + 0.055) / 1.055), 2.4);

        return 0.2126 * r + 0.7152 * g + 0.0722 * b;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add(this.toCSS(context));
    }

    /**
     * @param {EvalContext} context
     * @param {boolean} [doNotCompress]
     * @returns {string}
     */
    toCSS(context, doNotCompress) {
        const compress = context && context.compress && !doNotCompress;
        let color;
        let alpha;
        /** @type {string | undefined} */
        let colorFunction;
        /** @type {(string | number)[]} */
        let args = [];

        // `value` is set if this color was originally
        // converted from a named color string so we need
        // to respect this and try to output named color too.
        alpha = this.fround(context, this.alpha);

        if (this.value) {
            if (/** @type {string} */ (this.value).indexOf('rgb') === 0) {
                if (alpha < 1) {
                    colorFunction = 'rgba';
                }
            } else if (/** @type {string} */ (this.value).indexOf('hsl') === 0) {
                if (alpha < 1) {
                    colorFunction = 'hsla';
                } else {
                    colorFunction = 'hsl';
                }
            } else {
                return /** @type {string} */ (this.value);
            }
        } else {
            if (alpha < 1) {
                colorFunction = 'rgba';
            }
        }

        switch (colorFunction) {
            case 'rgba':
                args = this.rgb.map(function (c) {
                    return clamp$1(Math.round(c), 255);
                }).concat(clamp$1(alpha, 1));
                break;
            case 'hsla':
                args.push(clamp$1(alpha, 1));
            // eslint-disable-next-line no-fallthrough
            case 'hsl':
                color = this.toHSL();
                args = [
                    this.fround(context, color.h),
                    `${this.fround(context, color.s * 100)}%`,
                    `${this.fround(context, color.l * 100)}%`
                ].concat(args);
        }

        if (colorFunction) {
            // Values are capped between `0` and `255`, rounded and zero-padded.
            return `${colorFunction}(${args.join(`,${compress ? '' : ' '}`)})`;
        }

        color = this.toRGB();

        if (compress) {
            const splitcolor = color.split('');

            // Convert color to short format
            if (splitcolor[1] === splitcolor[2] && splitcolor[3] === splitcolor[4] && splitcolor[5] === splitcolor[6]) {
                color = `#${splitcolor[1]}${splitcolor[3]}${splitcolor[5]}`;
            }
        }

        return color;
    }

    //
    // Operations have to be done per-channel, if not,
    // channels will spill onto each other. Once we have
    // our result, in the form of an integer triplet,
    // we create a new Color node to hold the result.
    //
    /**
     * @param {EvalContext} context
     * @param {string} op
     * @param {Color} other
     */
    operate(context, op, other) {
        const rgb = new Array(3);
        const alpha = this.alpha * (1 - other.alpha) + other.alpha;
        for (let c = 0; c < 3; c++) {
            rgb[c] = this._operate(context, op, this.rgb[c], other.rgb[c]);
        }
        return new Color(rgb, alpha);
    }

    toRGB() {
        return toHex(this.rgb);
    }

    toHSL() {
        const r = this.rgb[0] / 255, g = this.rgb[1] / 255, b = this.rgb[2] / 255, a = this.alpha;

        const max = Math.max(r, g, b), min = Math.min(r, g, b);
        /** @type {number} */
        let h;
        let s;
        const l = (max + min) / 2;
        const d = max - min;

        if (max === min) {
            h = s = 0;
        } else {
            s = l > 0.5 ? d / (2 - max - min) : d / (max + min);

            switch (max) {
                case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                case g: h = (b - r) / d + 2;               break;
                case b: h = (r - g) / d + 4;               break;
            }
            /** @type {number} */ (h) /= 6;
        }
        return { h: /** @type {number} */ (h) * 360, s, l, a };
    }

    // Adapted from http://mjijackson.com/2008/02/rgb-to-hsl-and-rgb-to-hsv-color-model-conversion-algorithms-in-javascript
    toHSV() {
        const r = this.rgb[0] / 255, g = this.rgb[1] / 255, b = this.rgb[2] / 255, a = this.alpha;

        const max = Math.max(r, g, b), min = Math.min(r, g, b);
        /** @type {number} */
        let h;
        let s;
        const v = max;

        const d = max - min;
        if (max === 0) {
            s = 0;
        } else {
            s = d / max;
        }

        if (max === min) {
            h = 0;
        } else {
            switch (max) {
                case r: h = (g - b) / d + (g < b ? 6 : 0); break;
                case g: h = (b - r) / d + 2; break;
                case b: h = (r - g) / d + 4; break;
            }
            /** @type {number} */ (h) /= 6;
        }
        return { h: /** @type {number} */ (h) * 360, s, v, a };
    }

    toARGB() {
        return toHex([this.alpha * 255].concat(this.rgb));
    }

    /**
     * @param {Node & { rgb?: number[], alpha?: number }} x
     * @returns {0 | undefined}
     */
    compare(x) {
        return (x.rgb &&
            x.rgb[0] === this.rgb[0] &&
            x.rgb[1] === this.rgb[1] &&
            x.rgb[2] === this.rgb[2] &&
            x.alpha  === this.alpha) ? 0 : undefined;
    }

    /** @param {string} keyword */
    static fromKeyword(keyword) {
        /** @type {Color | undefined} */
        let c;
        const key = keyword.toLowerCase();
        // eslint-disable-next-line no-prototype-builtins
        if (colors.hasOwnProperty(key)) {
            c = new Color(/** @type {string} */ (colors[/** @type {keyof typeof colors} */ (key)]).slice(1));
        }
        else if (key === 'transparent') {
            c = new Color([0, 0, 0], 0);
        }

        if (c) {
            c.value = keyword;
            return c;
        }
    }
}

/**
 * @param {number} v
 * @param {number} max
 */
function clamp$1(v, max) {
    return Math.min(Math.max(v, 0), max);
}

/** @param {number[]} v */
function toHex(v) {
    return `#${v.map(function (c) {
        c = clamp$1(Math.round(c), 255);
        return (c < 16 ? '0' : '') + c.toString(16);
    }).join('')}`;
}

// @ts-check

class Paren extends Node {
    get type() { return 'Paren'; }

    /** @param {Node} node */
    constructor(node) {
        super();
        this.value = node;
        /** @type {boolean | undefined} */
        this.noSpacing = undefined;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add('(');
        /** @type {Node} */ (this.value).genCSS(context, output);
        output.add(')');
    }

    /**
     * @param {EvalContext} context
     * @returns {Paren}
     */
    eval(context) {
        const paren = new Paren(/** @type {Node} */ (this.value).eval(context));

        if (this.noSpacing) {
            paren.noSpacing = true;
        }

        return paren;
    }
}

// @ts-check

/** @import { EvalContext, CSSOutput } from './node.js' */

/** @type {Record<string, boolean>} */
const _noSpaceCombinators = {
    '': true,
    ' ': true,
    '|': true
};

class Combinator extends Node {
    get type() { return 'Combinator'; }

    /** @param {string} value */
    constructor(value) {
        super();
        if (value === ' ') {
            this.value = ' ';
            this.emptyOrWhitespace = true;
        } else {
            this.value = value ? value.trim() : '';
            this.emptyOrWhitespace = this.value === '';
        }
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        const spaceOrEmpty = (context.compress || _noSpaceCombinators[/** @type {string} */ (this.value)]) ? '' : ' ';
        output.add(spaceOrEmpty + this.value + spaceOrEmpty);
    }
}

// @ts-check

class Element extends Node {
    get type() { return 'Element'; }

    /**
     * @param {Combinator | string} combinator
     * @param {string | Node} value
     * @param {boolean} [isVariable]
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(combinator, value, isVariable, index, currentFileInfo, visibilityInfo) {
        super();
        this.combinator = combinator instanceof Combinator ?
            combinator : new Combinator(combinator);

        if (typeof value === 'string') {
            this.value = value.trim();
        } else if (value) {
            this.value = value;
        } else {
            this.value = '';
        }
        /** @type {boolean | undefined} */
        this.isVariable = isVariable;
        this._index = index;
        this._fileInfo = currentFileInfo;
        this.copyVisibilityInfo(visibilityInfo);
        this.setParent(this.combinator, this);
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        const value = this.value;
        this.combinator = /** @type {Combinator} */ (visitor.visit(this.combinator));
        if (typeof value === 'object') {
            this.value = visitor.visit(/** @type {Node} */ (value));
        }
    }

    /** @param {EvalContext} context */
    eval(context) {
        return new Element(this.combinator,
            /** @type {Node} */ (this.value).eval ? /** @type {Node} */ (this.value).eval(context) : /** @type {string} */ (this.value),
            this.isVariable,
            this.getIndex(),
            this.fileInfo(), this.visibilityInfo());
    }

    clone() {
        return new Element(this.combinator,
            /** @type {string | Node} */ (this.value),
            this.isVariable,
            this.getIndex(),
            this.fileInfo(), this.visibilityInfo());
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add(this.toCSS(context), this.fileInfo(), this.getIndex());
    }

    /** @param {EvalContext} [context] */
    toCSS(context) {
        /** @type {EvalContext & { firstSelector?: boolean }} */
        const ctx = context || {};
        let value = this.value;
        const firstSelector = ctx.firstSelector;
        if (value instanceof Paren) {
            // selector in parens should not be affected by outer selector
            // flags (breaks only interpolated selectors - see #1973)
            ctx.firstSelector = true;
        }
        value = /** @type {Node} */ (value).toCSS ? /** @type {Node} */ (value).toCSS(ctx) : /** @type {string} */ (value);
        ctx.firstSelector = firstSelector;
        if (value === '' && this.combinator.value.charAt(0) === '&') {
            return '';
        } else {
            return this.combinator.toCSS(ctx) + value;
        }
    }
}

const Math$1 = {
    ALWAYS: 0,
    PARENS_DIVISION: 1,
    PARENS: 2
    // removed - STRICT_LEGACY: 3
};

const RewriteUrls = {
    OFF: 0,
    LOCAL: 1,
    ALL: 2
};

function getType(payload) {
  return Object.prototype.toString.call(payload).slice(8, -1);
}

function isArray(payload) {
  return getType(payload) === "Array";
}

function isPlainObject(payload) {
  if (getType(payload) !== "Object")
    return false;
  const prototype = Object.getPrototypeOf(payload);
  return !!prototype && prototype.constructor === Object && prototype === Object.prototype;
}

function assignProp(carry, key, newVal, originalObject, includeNonenumerable) {
  const propType = {}.propertyIsEnumerable.call(originalObject, key) ? "enumerable" : "nonenumerable";
  if (propType === "enumerable")
    carry[key] = newVal;
  if (includeNonenumerable && propType === "nonenumerable") {
    Object.defineProperty(carry, key, {
      value: newVal,
      enumerable: false,
      writable: true,
      configurable: true
    });
  }
}
function copy(target, options = {}) {
  if (isArray(target)) {
    return target.map((item) => copy(item, options));
  }
  if (!isPlainObject(target)) {
    return target;
  }
  const props = Object.getOwnPropertyNames(target);
  const symbols = Object.getOwnPropertySymbols(target);
  return [...props, ...symbols].reduce((carry, key) => {
    if (isArray(options.props) && !options.props.includes(key)) {
      return carry;
    }
    const val = target[key];
    const newVal = copy(val, options);
    assignProp(carry, key, newVal, target, options.nonenumerable);
    return carry;
  }, {});
}

/* jshint proto: true */

function getLocation(index, inputStream) {
    let n = index + 1;
    let line = null;
    let column = -1;

    while (--n >= 0 && inputStream.charAt(n) !== '\n') {
        column++;
    }

    if (typeof index === 'number') {
        line = (inputStream.slice(0, index).match(/\n/g) || '').length;
    }

    return {
        line,
        column
    };
}

function copyArray(arr) {
    let i;
    const length = arr.length;
    const copy = new Array(length);

    for (i = 0; i < length; i++) {
        copy[i] = arr[i];
    }
    return copy;
}

function clone(obj) {
    const cloned = {};
    for (const prop in obj) {
        if (Object.prototype.hasOwnProperty.call(obj, prop)) {
            cloned[prop] = obj[prop];
        }
    }
    return cloned;
}

function defaults(obj1, obj2) {
    let newObj = obj2 || {};
    if (!obj2._defaults) {
        newObj = {};
        const defaults = copy(obj1);
        newObj._defaults = defaults;
        const cloned = obj2 ? copy(obj2) : {};
        Object.assign(newObj, defaults, cloned);
    }
    return newObj;
}

function copyOptions(obj1, obj2) {
    if (obj2 && obj2._defaults) {
        return obj2;
    }
    const opts = defaults(obj1, obj2);
    if (opts.strictMath) {
        opts.math = Math$1.PARENS;
    }
    // Back compat with changed relativeUrls option
    if (opts.relativeUrls) {
        opts.rewriteUrls = RewriteUrls.ALL;
    }
    if (typeof opts.math === 'string') {
        switch (opts.math.toLowerCase()) {
            case 'always':
                opts.math = Math$1.ALWAYS;
                break;
            case 'parens-division':
                opts.math = Math$1.PARENS_DIVISION;
                break;
            case 'strict':
            case 'parens':
                opts.math = Math$1.PARENS;
                break;
            default:
                opts.math = Math$1.PARENS;
        }
    }
    if (typeof opts.rewriteUrls === 'string') {
        switch (opts.rewriteUrls.toLowerCase()) {
            case 'off':
                opts.rewriteUrls = RewriteUrls.OFF;
                break;
            case 'local':
                opts.rewriteUrls = RewriteUrls.LOCAL;
                break;
            case 'all':
                opts.rewriteUrls = RewriteUrls.ALL;
                break;
        }
    }
    return opts;
}

function merge(obj1, obj2) {
    for (const prop in obj2) {
        if (Object.prototype.hasOwnProperty.call(obj2, prop)) {
            obj1[prop] = obj2[prop];
        }
    }
    return obj1;
}

function flattenArray(arr, result = []) {
    for (let i = 0, length = arr.length; i < length; i++) {
        const value = arr[i];
        if (Array.isArray(value)) {
            flattenArray(value, result);
        } else {
            if (value !== undefined) {
                result.push(value);
            }
        }
    }
    return result;
}

function isNullOrUndefined(val) {
    return val === null || val === undefined
}

var utils = /*#__PURE__*/Object.freeze({
    __proto__: null,
    getLocation: getLocation,
    copyArray: copyArray,
    clone: clone,
    defaults: defaults,
    copyOptions: copyOptions,
    merge: merge,
    flattenArray: flattenArray,
    isNullOrUndefined: isNullOrUndefined
});

const anonymousFunc = /(<anonymous>|Function):(\d+):(\d+)/;

/**
 * This is a centralized class of any error that could be thrown internally (mostly by the parser).
 * Besides standard .message it keeps some additional data like a path to the file where the error
 * occurred along with line and column numbers.
 *
 * @class
 * @extends Error
 * @type {module.LessError}
 *
 * @prop {string} type
 * @prop {string} filename
 * @prop {number} index
 * @prop {number} line
 * @prop {number} column
 * @prop {number} callLine
 * @prop {number} callExtract
 * @prop {string[]} extract
 *
 * @param {Object} e              - An error object to wrap around or just a descriptive object
 * @param {Object} fileContentMap - An object with file contents in 'contents' property (like importManager) @todo - move to fileManager?
 * @param {string} [currentFilename]
 */
const LessError = function(e, fileContentMap, currentFilename) {
    Error.call(this);

    const filename = e.filename || currentFilename;

    this.message = e.message;
    this.stack = e.stack;
    
    // Set type early so it's always available, even if fileContentMap is missing
    this.type = e.type || 'Syntax';

    if (fileContentMap && filename) {
        const input = fileContentMap.contents[filename];
        const loc = getLocation(e.index, input);
        var line = loc.line;
        const col  = loc.column;
        const callLine = e.call && getLocation(e.call, input).line;
        const lines = input ? input.split('\n') : '';

        this.filename = filename;
        this.index = e.index;
        this.line = typeof line === 'number' ? line + 1 : null;
        this.column = col;

        if (!this.line && this.stack) {
            const found = this.stack.match(anonymousFunc);

            /**
             * We have to figure out how this environment stringifies anonymous functions
             * so we can correctly map plugin errors.
             *
             * Note, in Node 8, the output of anonymous funcs varied based on parameters
             * being present or not, so we inject dummy params.
             */
            const func = new Function('a', 'throw new Error()');
            let lineAdjust = 0;
            try {
                func();
            } catch (e) {
                const match = e.stack.match(anonymousFunc);
                lineAdjust = 1 - parseInt(match[2]);
            }

            if (found) {
                if (found[2]) {
                    this.line = parseInt(found[2]) + lineAdjust;
                }
                if (found[3]) {
                    this.column = parseInt(found[3]);
                }
            }
        }

        this.callLine = callLine + 1;
        this.callExtract = lines[callLine];

        this.extract = [
            lines[this.line - 2],
            lines[this.line - 1],
            lines[this.line]
        ];
    }

};

if (typeof Object.create === 'undefined') {
    const F = function () {};
    F.prototype = Error.prototype;
    LessError.prototype = new F();
} else {
    LessError.prototype = Object.create(Error.prototype);
}

LessError.prototype.constructor = LessError;

/**
 * An overridden version of the default Object.prototype.toString
 * which uses additional information to create a helpful message.
 *
 * @param {Object} options
 * @returns {string}
 */
LessError.prototype.toString = function(options) {
    options = options || {};
    const isWarning = (this.type ?? '').toLowerCase().includes('warning');
    const type = isWarning ? this.type : `${this.type}Error`;
    const color = isWarning ? 'yellow' : 'red';

    let message = '';
    const extract = this.extract || [];
    let error = [];
    let stylize = function (str) { return str; };
    if (options.stylize) {
        const type = typeof options.stylize;
        if (type !== 'function') {
            throw Error(`options.stylize should be a function, got a ${type}!`);
        }
        stylize = options.stylize;
    }

    if (this.line !== null) {
        if (!isWarning && typeof extract[0] === 'string') {
            error.push(stylize(`${this.line - 1} ${extract[0]}`, 'grey'));
        }

        if (typeof extract[1] === 'string') {
            let errorTxt = `${this.line} `;
            if (extract[1]) {
                errorTxt += extract[1].slice(0, this.column) +
                    stylize(stylize(stylize(extract[1].slice(this.column, this.column + 1), 'bold') +
                        extract[1].slice(this.column + 1), 'red'), 'inverse');
            }
            error.push(errorTxt);
        }

        if (!isWarning && typeof extract[2] === 'string') {
            error.push(stylize(`${this.line + 1} ${extract[2]}`, 'grey'));
        }
        error = `${error.join('\n') + stylize('', 'reset')}\n`;
    }

    message += stylize(`${type}: ${this.message}`, color);
    if (this.filename) {
        message += stylize(' in ', color) + this.filename;
    }
    if (this.line) {
        message += stylize(` on line ${this.line}, column ${this.column + 1}:`, 'grey');
    }

    message += `\n${error}`;

    if (this.callLine) {
        message += `${stylize('from ', color) + (this.filename || '')}/n`;
        message += `${stylize(this.callLine, 'grey')} ${this.callExtract}/n`;
    }

    return message;
};

const _visitArgs = { visitDeeper: true };
let _hasIndexed = false;

function _noop(node) {
    return node;
}

function indexNodeTypes(parent, ticker) {
    // add .typeIndex to tree node types for lookup table
    let key, child;
    for (key in parent) { 
        /* eslint guard-for-in: 0 */
        child = parent[key];
        switch (typeof child) {
            case 'function':
                // ignore bound functions directly on tree which do not have a prototype
                // or aren't nodes
                if (child.prototype && child.prototype.type) {
                    child.prototype.typeIndex = ticker++;
                }
                break;
            case 'object':
                ticker = indexNodeTypes(child, ticker);
                break;
        
        }
    }
    return ticker;
}

class Visitor {
    constructor(implementation) {
        this._implementation = implementation;
        this._visitInCache = {};
        this._visitOutCache = {};

        if (!_hasIndexed) {
            indexNodeTypes(tree, 1);
            _hasIndexed = true;
        }
    }

    visit(node) {
        if (!node) {
            return node;
        }

        const nodeTypeIndex = node.typeIndex;
        if (!nodeTypeIndex) {
            // MixinCall args aren't a node type?
            if (node.value && node.value.typeIndex) {
                this.visit(node.value);
            }
            return node;
        }

        const impl = this._implementation;
        let func = this._visitInCache[nodeTypeIndex];
        let funcOut = this._visitOutCache[nodeTypeIndex];
        const visitArgs = _visitArgs;
        let fnName;

        visitArgs.visitDeeper = true;

        if (!func) {
            fnName = `visit${node.type}`;
            func = impl[fnName] || _noop;
            funcOut = impl[`${fnName}Out`] || _noop;
            this._visitInCache[nodeTypeIndex] = func;
            this._visitOutCache[nodeTypeIndex] = funcOut;
        }

        if (func !== _noop) {
            const newNode = func.call(impl, node, visitArgs);
            if (node && impl.isReplacing) {
                node = newNode;
            }
        }

        if (visitArgs.visitDeeper && node) {
            if (node.length) {
                for (let i = 0, cnt = node.length; i < cnt; i++) {
                    if (node[i].accept) {
                        node[i].accept(this);
                    }
                }
            } else if (node.accept) {
                node.accept(this);
            }
        }

        if (funcOut != _noop) {
            funcOut.call(impl, node);
        }

        return node;
    }

    visitArray(nodes, nonReplacing) {
        if (!nodes) {
            return nodes;
        }

        const cnt = nodes.length;
        let i;

        // Non-replacing
        if (nonReplacing || !this._implementation.isReplacing) {
            for (i = 0; i < cnt; i++) {
                this.visit(nodes[i]);
            }
            return nodes;
        }

        // Replacing
        const out = [];
        for (i = 0; i < cnt; i++) {
            const evald = this.visit(nodes[i]);
            if (evald === undefined) { continue; }
            if (!evald.splice) {
                out.push(evald);
            } else if (evald.length) {
                this.flatten(evald, out);
            }
        }
        return out;
    }

    flatten(arr, out) {
        if (!out) {
            out = [];
        }

        let cnt, i, item, nestedCnt, j, nestedItem;

        for (i = 0, cnt = arr.length; i < cnt; i++) {
            item = arr[i];
            if (item === undefined) {
                continue;
            }
            if (!item.splice) {
                out.push(item);
                continue;
            }

            for (j = 0, nestedCnt = item.length; j < nestedCnt; j++) {
                nestedItem = item[j];
                if (nestedItem === undefined) {
                    continue;
                }
                if (!nestedItem.splice) {
                    out.push(nestedItem);
                } else if (nestedItem.length) {
                    this.flatten(nestedItem, out);
                }
            }
        }

        return out;
    }
}

const contexts = {};

const copyFromOriginal = function copyFromOriginal(original, destination, propertiesToCopy) {
    if (!original) { return; }

    for (let i = 0; i < propertiesToCopy.length; i++) {
        if (Object.prototype.hasOwnProperty.call(original, propertiesToCopy[i])) {
            destination[propertiesToCopy[i]] = original[propertiesToCopy[i]];
        }
    }
};

/*
 parse is used whilst parsing
 */
const parseCopyProperties = [
    // options
    'paths',            // option - unmodified - paths to search for imports on
    'rewriteUrls',      // option - whether to adjust URL's to be relative
    'rootpath',         // option - rootpath to append to URL's
    'strictImports',    // option -
    'insecure',         // option - whether to allow imports from insecure ssl hosts
    'dumpLineNumbers',  // option - @deprecated The dumpLineNumbers option is deprecated. Use sourcemaps instead. All modes ('comments', 'mediaquery', 'all') will be removed in a future version.
    'compress',         // option - whether to compress
    'syncImport',       // option - whether to import synchronously
    'mime',             // browser only - mime type for sheet import
    'useFileCache',     // browser only - whether to use the per file session cache
    // context
    'processImports',   // option & context - whether to process imports. if false then imports will not be imported.
    // Used by the import manager to stop multiple import visitors being created.
    'pluginManager',    // Used as the plugin manager for the session
    'quiet',            // option - whether to log warnings
    'quietDeprecations', // option - whether to suppress deprecation warnings only
];

contexts.Parse = function(options) {
    copyFromOriginal(options, this, parseCopyProperties);

    if (typeof this.paths === 'string') { this.paths = [this.paths]; }
};

const evalCopyProperties = [
    'paths',             // additional include paths
    'compress',          // whether to compress
    'math',              // whether math has to be within parenthesis
    'strictUnits',       // whether units need to evaluate correctly
    'sourceMap',         // whether to output a source map
    'importMultiple',    // whether we are currently importing multiple copies
    'urlArgs',           // whether to add args into url tokens
    'javascriptEnabled', // option - whether Inline JavaScript is enabled. if undefined, defaults to false
    'pluginManager',     // Used as the plugin manager for the session
    'importantScope',    // used to bubble up !important statements
    'rewriteUrls'        // option - whether to adjust URL's to be relative
];

contexts.Eval = function(options, frames) {
    copyFromOriginal(options, this, evalCopyProperties);

    if (typeof this.paths === 'string') { this.paths = [this.paths]; }

    this.frames = frames || [];
    this.importantScope = this.importantScope || [];
};

contexts.Eval.prototype.enterCalc = function () {
    if (!this.calcStack) {
        this.calcStack = [];
    }
    this.calcStack.push(true);
    this.inCalc = true;
};

contexts.Eval.prototype.exitCalc = function () {
    this.calcStack.pop();
    if (!this.calcStack.length) {
        this.inCalc = false;
    }
};

contexts.Eval.prototype.inParenthesis = function () {
    if (!this.parensStack) {
        this.parensStack = [];
    }
    this.parensStack.push(true);
};

contexts.Eval.prototype.outOfParenthesis = function () {
    this.parensStack.pop();
};

contexts.Eval.prototype.inCalc = false;
contexts.Eval.prototype.mathOn = true;
contexts.Eval.prototype.isMathOn = function (op) {
    if (!this.mathOn) {
        return false;
    }
    if (op === '/' && this.math !== Math$1.ALWAYS && (!this.parensStack || !this.parensStack.length)) {
        return false;
    }
    if (this.math > Math$1.PARENS_DIVISION) {
        return this.parensStack && this.parensStack.length;
    }
    return true;
};

contexts.Eval.prototype.pathRequiresRewrite = function (path) {
    const isRelative = this.rewriteUrls === RewriteUrls.LOCAL ? isPathLocalRelative : isPathRelative;

    return isRelative(path);
};

contexts.Eval.prototype.rewritePath = function (path, rootpath) {
    let newPath;

    rootpath = rootpath || '';
    newPath = this.normalizePath(rootpath + path);

    // If a path was explicit relative and the rootpath was not an absolute path
    // we must ensure that the new path is also explicit relative.
    if (isPathLocalRelative(path) &&
        isPathRelative(rootpath) &&
        isPathLocalRelative(newPath) === false) {
        newPath = `./${newPath}`;
    }

    return newPath;
};

contexts.Eval.prototype.normalizePath = function (path) {
    const segments = path.split('/').reverse();
    let segment;

    path = [];
    while (segments.length !== 0) {
        segment = segments.pop();
        switch ( segment ) {
            case '.':
                break;
            case '..':
                if ((path.length === 0) || (path[path.length - 1] === '..')) {
                    path.push( segment );
                } else {
                    path.pop();
                }
                break;
            default:
                path.push(segment);
                break;
        }
    }

    return path.join('/');
};

function isPathRelative(path) {
    return !/^(?:[a-z-]+:|\/|#)/i.test(path);
}

function isPathLocalRelative(path) {
    return path.charAt(0) === '.';
}

// todo - do the same for the toCSS ?

class ImportSequencer {
    constructor(onSequencerEmpty) {
        this.imports = [];
        this.variableImports = [];
        this._onSequencerEmpty = onSequencerEmpty;
        this._currentDepth = 0;
    }

    addImport(callback) {
        const importSequencer = this,
            importItem = {
                callback,
                args: null,
                isReady: false
            };
        this.imports.push(importItem);
        return function() {
            importItem.args = Array.prototype.slice.call(arguments, 0);
            importItem.isReady = true;
            importSequencer.tryRun();
        };
    }

    addVariableImport(callback) {
        this.variableImports.push(callback);
    }

    tryRun() {
        this._currentDepth++;
        try {
            while (true) {
                while (this.imports.length > 0) {
                    const importItem = this.imports[0];
                    if (!importItem.isReady) {
                        return;
                    }
                    this.imports = this.imports.slice(1);
                    importItem.callback.apply(null, importItem.args);
                }
                if (this.variableImports.length === 0) {
                    break;
                }
                const variableImport = this.variableImports[0];
                this.variableImports = this.variableImports.slice(1);
                variableImport();
            }
        } finally {
            this._currentDepth--;
        }
        if (this._currentDepth === 0 && this._onSequencerEmpty) {
            this._onSequencerEmpty();
        }
    }
}

/* eslint-disable no-unused-vars */

const ImportVisitor = function(importer, finish) {

    this._visitor = new Visitor(this);
    this._importer = importer;
    this._finish = finish;
    this.context = new contexts.Eval();
    this.importCount = 0;
    this.onceFileDetectionMap = {};
    this.recursionDetector = {};
    this._sequencer = new ImportSequencer(this._onSequencerEmpty.bind(this));
};

ImportVisitor.prototype = {
    isReplacing: false,
    run: function (root) {
        try {
            // process the contents
            this._visitor.visit(root);
        }
        catch (e) {
            this.error = e;
        }

        this.isFinished = true;
        this._sequencer.tryRun();
    },
    _onSequencerEmpty: function() {
        if (!this.isFinished) {
            return;
        }
        this._finish(this.error);
    },
    visitImport: function (importNode, visitArgs) {
        const inlineCSS = importNode.options.inline;

        if (!importNode.css || inlineCSS) {

            const context = new contexts.Eval(this.context, copyArray(this.context.frames));
            const importParent = context.frames[0];

            this.importCount++;
            if (importNode.isVariableImport()) {
                this._sequencer.addVariableImport(this.processImportNode.bind(this, importNode, context, importParent));
            } else {
                this.processImportNode(importNode, context, importParent);
            }
        }
        visitArgs.visitDeeper = false;
    },
    processImportNode: function(importNode, context, importParent) {
        let evaldImportNode;
        const inlineCSS = importNode.options.inline;

        try {
            evaldImportNode = importNode.evalForImport(context);
        } catch (e) {
            if (!e.filename) { e.index = importNode.getIndex(); e.filename = importNode.fileInfo().filename; }
            // attempt to eval properly and treat as css
            importNode.css = true;
            // if that fails, this error will be thrown
            importNode.error = e;
        }

        if (evaldImportNode && (!evaldImportNode.css || inlineCSS)) {

            if (evaldImportNode.options.multiple) {
                context.importMultiple = true;
            }

            // try appending if we haven't determined if it is css or not
            const tryAppendLessExtension = evaldImportNode.css === undefined;

            for (let i = 0; i < importParent.rules.length; i++) {
                if (importParent.rules[i] === importNode) {
                    importParent.rules[i] = evaldImportNode;
                    break;
                }
            }

            const onImported = this.onImported.bind(this, evaldImportNode, context), sequencedOnImported = this._sequencer.addImport(onImported);

            this._importer.push(evaldImportNode.getPath(), tryAppendLessExtension, evaldImportNode.fileInfo(),
                evaldImportNode.options, sequencedOnImported);
        } else {
            this.importCount--;
            if (this.isFinished) {
                this._sequencer.tryRun();
            }
        }
    },
    onImported: function (importNode, context, e, root, importedAtRoot, fullPath) {
        if (e) {
            if (!e.filename) {
                e.index = importNode.getIndex(); e.filename = importNode.fileInfo().filename;
            }
            this.error = e;
        }

        const importVisitor = this,
            inlineCSS = importNode.options.inline,
            isPlugin = importNode.options.isPlugin,
            isOptional = importNode.options.optional,
            duplicateImport = importedAtRoot || fullPath in importVisitor.recursionDetector;

        if (!context.importMultiple) {
            if (duplicateImport) {
                importNode.skip = true;
            } else {
                importNode.skip = function() {
                    if (fullPath in importVisitor.onceFileDetectionMap) {
                        return true;
                    }
                    importVisitor.onceFileDetectionMap[fullPath] = true;
                    return false;
                };
            }
        }

        if (!fullPath && isOptional) {
            importNode.skip = true;
        }

        if (root) {
            importNode.root = root;
            importNode.importedFilename = fullPath;

            if (!inlineCSS && !isPlugin && (context.importMultiple || !duplicateImport)) {
                importVisitor.recursionDetector[fullPath] = true;

                const oldContext = this.context;
                this.context = context;
                try {
                    this._visitor.visit(root);
                } catch (e) {
                    this.error = e;
                }
                this.context = oldContext;
            }
        }

        importVisitor.importCount--;

        if (importVisitor.isFinished) {
            importVisitor._sequencer.tryRun();
        }
    },
    visitDeclaration: function (declNode, visitArgs) {
        if (declNode.value.type === 'DetachedRuleset') {
            this.context.frames.unshift(declNode);
        } else {
            visitArgs.visitDeeper = false;
        }
    },
    visitDeclarationOut: function(declNode) {
        if (declNode.value.type === 'DetachedRuleset') {
            this.context.frames.shift();
        }
    },
    visitAtRule: function (atRuleNode, visitArgs) {
        if (atRuleNode.value) {
            this.context.frames.unshift(atRuleNode);
        } else if (atRuleNode.declarations && atRuleNode.declarations.length) {
            if (atRuleNode.isRooted) {
                this.context.frames.unshift(atRuleNode);
            } else {
                this.context.frames.unshift(atRuleNode.declarations[0]);
            }
        } else if (atRuleNode.rules && atRuleNode.rules.length) {
            this.context.frames.unshift(atRuleNode);
        }
    },
    visitAtRuleOut: function (atRuleNode) {
        this.context.frames.shift();
    },
    visitMixinDefinition: function (mixinDefinitionNode, visitArgs) {
        this.context.frames.unshift(mixinDefinitionNode);
    },
    visitMixinDefinitionOut: function (mixinDefinitionNode) {
        this.context.frames.shift();
    },
    visitRuleset: function (rulesetNode, visitArgs) {
        this.context.frames.unshift(rulesetNode);
    },
    visitRulesetOut: function (rulesetNode) {
        this.context.frames.shift();
    },
    visitMedia: function (mediaNode, visitArgs) {
        this.context.frames.unshift(mediaNode.rules[0]);
    },
    visitMediaOut: function (mediaNode) {
        this.context.frames.shift();
    }
};

class SetTreeVisibilityVisitor {
    /** @param {boolean} visible */
    constructor(visible) {
        this.visible = visible;
    }

    /** @param {Node} root */
    run(root) {
        this.visit(root);
    }

    /**
     * @param {Node[]} nodes
     * @returns {Node[]}
     */
    visitArray(nodes) {
        if (!nodes) {
            return nodes;
        }

        const cnt = nodes.length;
        let i;
        for (i = 0; i < cnt; i++) {
            this.visit(nodes[i]);
        }
        return nodes;
    }

    /**
     * @param {*} node
     * @returns {*}
     */
    visit(node) {
        if (!node) {
            return node;
        }
        if (node.constructor === Array) {
            return this.visitArray(node);
        }

        if (!node.blocksVisibility || node.blocksVisibility()) {
            return node;
        }
        if (this.visible) {
            node.ensureVisibility();
        } else {
            node.ensureInvisibility();
        }

        node.accept(this);
        return node;
    }
}

/* eslint-disable no-unused-vars */

/* jshint loopfunc:true */

class ExtendFinderVisitor {
    constructor() {
        this._visitor = new Visitor(this);
        this.contexts = [];
        this.allExtendsStack = [[]];
    }

    run(root) {
        root = this._visitor.visit(root);
        root.allExtends = this.allExtendsStack[0];
        return root;
    }

    visitDeclaration(declNode, visitArgs) {
        visitArgs.visitDeeper = false;
    }

    visitMixinDefinition(mixinDefinitionNode, visitArgs) {
        visitArgs.visitDeeper = false;
    }

    visitRuleset(rulesetNode, visitArgs) {
        if (rulesetNode.root) {
            return;
        }

        let i;
        let j;
        let extend;
        const allSelectorsExtendList = [];
        let extendList;

        // get &:extend(.a); rules which apply to all selectors in this ruleset
        const rules = rulesetNode.rules, ruleCnt = rules ? rules.length : 0;
        for (i = 0; i < ruleCnt; i++) {
            if (rulesetNode.rules[i] instanceof tree.Extend) {
                allSelectorsExtendList.push(rules[i]);
                rulesetNode.extendOnEveryPath = true;
            }
        }

        // now find every selector and apply the extends that apply to all extends
        // and the ones which apply to an individual extend
        const paths = rulesetNode.paths;
        for (i = 0; i < paths.length; i++) {
            const selectorPath = paths[i], selector = selectorPath[selectorPath.length - 1], selExtendList = selector.extendList;

            extendList = selExtendList ? copyArray(selExtendList).concat(allSelectorsExtendList)
                : allSelectorsExtendList;

            if (extendList) {
                extendList = extendList.map(function(allSelectorsExtend) {
                    return allSelectorsExtend.clone();
                });
            }

            for (j = 0; j < extendList.length; j++) {
                this.foundExtends = true;
                extend = extendList[j];
                extend.findSelfSelectors(selectorPath);
                extend.ruleset = rulesetNode;
                if (j === 0) { extend.firstExtendOnThisSelectorPath = true; }
                this.allExtendsStack[this.allExtendsStack.length - 1].push(extend);
            }
        }

        this.contexts.push(rulesetNode.selectors);
    }

    visitRulesetOut(rulesetNode) {
        if (!rulesetNode.root) {
            this.contexts.length = this.contexts.length - 1;
        }
    }

    visitMedia(mediaNode, visitArgs) {
        mediaNode.allExtends = [];
        this.allExtendsStack.push(mediaNode.allExtends);
    }

    visitMediaOut(mediaNode) {
        this.allExtendsStack.length = this.allExtendsStack.length - 1;
    }

    visitAtRule(atRuleNode, visitArgs) {
        atRuleNode.allExtends = [];
        this.allExtendsStack.push(atRuleNode.allExtends);
    }

    visitAtRuleOut(atRuleNode) {
        this.allExtendsStack.length = this.allExtendsStack.length - 1;
    }
}

class ProcessExtendsVisitor {
    constructor() {
        this._visitor = new Visitor(this);
    }

    run(root) {
        const extendFinder = new ExtendFinderVisitor();
        this.extendIndices = {};
        extendFinder.run(root);
        if (!extendFinder.foundExtends) { return root; }
        root.allExtends = root.allExtends.concat(this.doExtendChaining(root.allExtends, root.allExtends));
        this.allExtendsStack = [root.allExtends];
        const newRoot = this._visitor.visit(root);
        this.checkExtendsForNonMatched(root.allExtends);
        return newRoot;
    }

    checkExtendsForNonMatched(extendList) {
        const indices = this.extendIndices;
        extendList.filter(function(extend) {
            return !extend.hasFoundMatches && extend.parent_ids.length == 1;
        }).forEach(function(extend) {
            let selector = '_unknown_';
            try {
                selector = extend.selector.toCSS({});
            }
            catch (_) {}

            if (!indices[`${extend.index} ${selector}`]) {
                indices[`${extend.index} ${selector}`] = true;
                /**
                 * @todo Shouldn't this be an error? To alert the developer
                 * that they may have made an error in the selector they are
                 * targeting?
                 */
                logger.warn(`WARNING: extend '${selector}' has no matches`);
            }
        });
    }

    doExtendChaining(extendsList, extendsListTarget, iterationCount) {
        //
        // chaining is different from normal extension.. if we extend an extend then we are not just copying, altering
        // and pasting the selector we would do normally, but we are also adding an extend with the same target selector
        // this means this new extend can then go and alter other extends
        //
        // this method deals with all the chaining work - without it, extend is flat and doesn't work on other extend selectors
        // this is also the most expensive.. and a match on one selector can cause an extension of a selector we had already
        // processed if we look at each selector at a time, as is done in visitRuleset

        let extendIndex;

        let targetExtendIndex;
        let matches;
        const extendsToAdd = [];
        let newSelector;
        const extendVisitor = this;
        let selectorPath;
        let extend;
        let targetExtend;
        let newExtend;

        iterationCount = iterationCount || 0;

        // loop through comparing every extend with every target extend.
        // a target extend is the one on the ruleset we are looking at copy/edit/pasting in place
        // e.g.  .a:extend(.b) {}  and .b:extend(.c) {} then the first extend extends the second one
        // and the second is the target.
        // the separation into two lists allows us to process a subset of chains with a bigger set, as is the
        // case when processing media queries
        for (extendIndex = 0; extendIndex < extendsList.length; extendIndex++) {
            for (targetExtendIndex = 0; targetExtendIndex < extendsListTarget.length; targetExtendIndex++) {

                extend = extendsList[extendIndex];
                targetExtend = extendsListTarget[targetExtendIndex];

                // look for circular references
                if ( extend.parent_ids.indexOf( targetExtend.object_id ) >= 0 ) { continue; }

                // find a match in the target extends self selector (the bit before :extend)
                selectorPath = [targetExtend.selfSelectors[0]];
                matches = extendVisitor.findMatch(extend, selectorPath);

                if (matches.length) {
                    extend.hasFoundMatches = true;

                    // we found a match, so for each self selector..
                    extend.selfSelectors.forEach(function(selfSelector) {
                        const info = targetExtend.visibilityInfo();

                        // process the extend as usual
                        newSelector = extendVisitor.extendSelector(matches, selectorPath, selfSelector, extend.isVisible());

                        // but now we create a new extend from it
                        newExtend = new(tree.Extend)(targetExtend.selector, targetExtend.option, 0, targetExtend.fileInfo(), info);
                        newExtend.selfSelectors = newSelector;

                        // add the extend onto the list of extends for that selector
                        newSelector[newSelector.length - 1].extendList = [newExtend];

                        // record that we need to add it.
                        extendsToAdd.push(newExtend);
                        newExtend.ruleset = targetExtend.ruleset;

                        // remember its parents for circular references
                        newExtend.parent_ids = newExtend.parent_ids.concat(targetExtend.parent_ids, extend.parent_ids);

                        // only process the selector once.. if we have :extend(.a,.b) then multiple
                        // extends will look at the same selector path, so when extending
                        // we know that any others will be duplicates in terms of what is added to the css
                        if (targetExtend.firstExtendOnThisSelectorPath) {
                            newExtend.firstExtendOnThisSelectorPath = true;
                            targetExtend.ruleset.paths.push(newSelector);
                        }
                    });
                }
            }
        }

        if (extendsToAdd.length) {
            // try to detect circular references to stop a stack overflow.
            // may no longer be needed.
            this.extendChainCount++;
            if (iterationCount > 100) {
                let selectorOne = '{unable to calculate}';
                let selectorTwo = '{unable to calculate}';
                try {
                    selectorOne = extendsToAdd[0].selfSelectors[0].toCSS();
                    selectorTwo = extendsToAdd[0].selector.toCSS();
                }
                catch (e) {}
                throw { message: `extend circular reference detected. One of the circular extends is currently:${selectorOne}:extend(${selectorTwo})`};
            }

            // now process the new extends on the existing rules so that we can handle a extending b extending c extending
            // d extending e...
            return extendsToAdd.concat(extendVisitor.doExtendChaining(extendsToAdd, extendsListTarget, iterationCount + 1));
        } else {
            return extendsToAdd;
        }
    }

    visitDeclaration(ruleNode, visitArgs) {
        visitArgs.visitDeeper = false;
    }

    visitMixinDefinition(mixinDefinitionNode, visitArgs) {
        visitArgs.visitDeeper = false;
    }

    visitSelector(selectorNode, visitArgs) {
        visitArgs.visitDeeper = false;
    }

    visitRuleset(rulesetNode, visitArgs) {
        if (rulesetNode.root) {
            return;
        }
        let matches;
        const allExtends = this.allExtendsStack[this.allExtendsStack.length - 1];
        const selectorsToAdd = [];
        const paths = rulesetNode.paths;
        const pathCount = paths.length;

        // look at each selector path in the ruleset, find any extend matches and then copy, find and replace

        for (let extendIndex = 0; extendIndex < allExtends.length; extendIndex++) {
            const extend = allExtends[extendIndex];
            for (let pathIndex = 0; pathIndex < pathCount; pathIndex++) {
                const selectorPath = paths[pathIndex];

                // extending extends happens initially, before the main pass
                if (rulesetNode.extendOnEveryPath) { continue; }
                const extendList = selectorPath[selectorPath.length - 1].extendList;
                if (extendList && extendList.length) { continue; }

                matches = this.findMatch(extend, selectorPath);

                if (matches.length) {
                    extend.hasFoundMatches = true;

                    const selfSelectors = extend.selfSelectors;
                    const isVisible = extend.isVisible();
                    for (let si = 0; si < selfSelectors.length; si++) {
                        selectorsToAdd.push(this.extendSelector(matches, selectorPath, selfSelectors[si], isVisible));
                    }
                }
            }
        }
        rulesetNode.paths = paths.concat(selectorsToAdd);
    }

    findMatch(extend, haystackSelectorPath) {
        //
        // look through the haystack selector path to try and find the needle - extend.selector
        // returns an array of selector matches that can then be replaced
        //
        let haystackSelectorIndex;

        let hackstackSelector;
        let hackstackElementIndex;
        let haystackElement;
        let targetCombinator;
        let i;
        const needleElements = extend.selector.elements;
        const potentialMatches = [];
        let potentialMatch;
        const matches = [];

        // loop through the haystack elements
        for (haystackSelectorIndex = 0; haystackSelectorIndex < haystackSelectorPath.length; haystackSelectorIndex++) {
            hackstackSelector = haystackSelectorPath[haystackSelectorIndex];

            for (hackstackElementIndex = 0; hackstackElementIndex < hackstackSelector.elements.length; hackstackElementIndex++) {

                haystackElement = hackstackSelector.elements[hackstackElementIndex];

                // if we allow elements before our match we can add a potential match every time. otherwise only at the first element.
                if (extend.allowBefore || (haystackSelectorIndex === 0 && hackstackElementIndex === 0)) {
                    potentialMatches.push({pathIndex: haystackSelectorIndex, index: hackstackElementIndex, matched: 0,
                        initialCombinator: haystackElement.combinator});
                }

                for (i = 0; i < potentialMatches.length; i++) {
                    potentialMatch = potentialMatches[i];

                    // selectors add " " onto the first element. When we use & it joins the selectors together, but if we don't
                    // then each selector in haystackSelectorPath has a space before it added in the toCSS phase. so we need to
                    // work out what the resulting combinator will be
                    targetCombinator = haystackElement.combinator.value;
                    if (targetCombinator === '' && hackstackElementIndex === 0) {
                        targetCombinator = ' ';
                    }

                    // if we don't match, null our match to indicate failure
                    if (!this.isElementValuesEqual(needleElements[potentialMatch.matched].value, haystackElement.value) ||
                        (potentialMatch.matched > 0 && needleElements[potentialMatch.matched].combinator.value !== targetCombinator)) {
                        potentialMatch = null;
                    } else {
                        potentialMatch.matched++;
                    }

                    // if we are still valid and have finished, test whether we have elements after and whether these are allowed
                    if (potentialMatch) {
                        potentialMatch.finished = potentialMatch.matched === needleElements.length;
                        if (potentialMatch.finished &&
                            (!extend.allowAfter &&
                                (hackstackElementIndex + 1 < hackstackSelector.elements.length || haystackSelectorIndex + 1 < haystackSelectorPath.length))) {
                            potentialMatch = null;
                        }
                    }
                    // if null we remove, if not, we are still valid, so either push as a valid match or continue
                    if (potentialMatch) {
                        if (potentialMatch.finished) {
                            potentialMatch.length = needleElements.length;
                            potentialMatch.endPathIndex = haystackSelectorIndex;
                            potentialMatch.endPathElementIndex = hackstackElementIndex + 1; // index after end of match
                            potentialMatches.length = 0; // we don't allow matches to overlap, so start matching again
                            matches.push(potentialMatch);
                        }
                    } else {
                        potentialMatches.splice(i, 1);
                        i--;
                    }
                }
            }
        }
        return matches;
    }

    isElementValuesEqual(elementValue1, elementValue2) {
        if (typeof elementValue1 === 'string' || typeof elementValue2 === 'string') {
            return elementValue1 === elementValue2;
        }
        if (elementValue1 instanceof tree.Attribute) {
            if (elementValue1.op !== elementValue2.op || elementValue1.key !== elementValue2.key) {
                return false;
            }
            if (!elementValue1.value || !elementValue2.value) {
                if (elementValue1.value || elementValue2.value) {
                    return false;
                }
                return true;
            }
            elementValue1 = elementValue1.value.value || elementValue1.value;
            elementValue2 = elementValue2.value.value || elementValue2.value;
            return elementValue1 === elementValue2;
        }
        elementValue1 = elementValue1.value;
        elementValue2 = elementValue2.value;
        if (elementValue1 instanceof tree.Selector) {
            if (!(elementValue2 instanceof tree.Selector) || elementValue1.elements.length !== elementValue2.elements.length) {
                return false;
            }
            for (let i = 0; i  < elementValue1.elements.length; i++) {
                if (elementValue1.elements[i].combinator.value !== elementValue2.elements[i].combinator.value) {
                    if (i !== 0 || (elementValue1.elements[i].combinator.value || ' ') !== (elementValue2.elements[i].combinator.value || ' ')) {
                        return false;
                    }
                }
                if (!this.isElementValuesEqual(elementValue1.elements[i].value, elementValue2.elements[i].value)) {
                    return false;
                }
            }
            return true;
        }
        return false;
    }

    extendSelector(matches, selectorPath, replacementSelector, isVisible) {

        // for a set of matches, replace each match with the replacement selector

        let currentSelectorPathIndex = 0, currentSelectorPathElementIndex = 0, path = [], matchIndex, selector, firstElement, match, newElements;

        for (matchIndex = 0; matchIndex < matches.length; matchIndex++) {
            match = matches[matchIndex];
            selector = selectorPath[match.pathIndex];
            firstElement = new tree.Element(
                match.initialCombinator,
                replacementSelector.elements[0].value,
                replacementSelector.elements[0].isVariable,
                replacementSelector.elements[0].getIndex(),
                replacementSelector.elements[0].fileInfo()
            );

            if (match.pathIndex > currentSelectorPathIndex && currentSelectorPathElementIndex > 0) {
                path[path.length - 1].elements = path[path.length - 1]
                    .elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
                currentSelectorPathElementIndex = 0;
                currentSelectorPathIndex++;
            }

            newElements = selector.elements
                .slice(currentSelectorPathElementIndex, match.index)
                .concat([firstElement])
                .concat(replacementSelector.elements.slice(1));

            if (currentSelectorPathIndex === match.pathIndex && matchIndex > 0) {
                path[path.length - 1].elements =
                    path[path.length - 1].elements.concat(newElements);
            } else {
                path = path.concat(selectorPath.slice(currentSelectorPathIndex, match.pathIndex));

                path.push(new tree.Selector(
                    newElements
                ));
            }
            currentSelectorPathIndex = match.endPathIndex;
            currentSelectorPathElementIndex = match.endPathElementIndex;
            if (currentSelectorPathElementIndex >= selectorPath[currentSelectorPathIndex].elements.length) {
                currentSelectorPathElementIndex = 0;
                currentSelectorPathIndex++;
            }
        }

        if (currentSelectorPathIndex < selectorPath.length && currentSelectorPathElementIndex > 0) {
            path[path.length - 1].elements = path[path.length - 1]
                .elements.concat(selectorPath[currentSelectorPathIndex].elements.slice(currentSelectorPathElementIndex));
            currentSelectorPathIndex++;
        }

        path = path.concat(selectorPath.slice(currentSelectorPathIndex, selectorPath.length));
        path = path.map(function (currentValue) {
            // we can re-use elements here, because the visibility property matters only for selectors
            const derived = currentValue.createDerived(currentValue.elements);
            if (isVisible) {
                derived.ensureVisibility();
            } else {
                derived.ensureInvisibility();
            }
            return derived;
        });
        return path;
    }

    visitMedia(mediaNode, visitArgs) {
        let newAllExtends = mediaNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length - 1]);
        newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, mediaNode.allExtends));
        this.allExtendsStack.push(newAllExtends);
    }

    visitMediaOut(mediaNode) {
        const lastIndex = this.allExtendsStack.length - 1;
        this.allExtendsStack.length = lastIndex;
    }

    visitAtRule(atRuleNode, visitArgs) {
        let newAllExtends = atRuleNode.allExtends.concat(this.allExtendsStack[this.allExtendsStack.length - 1]);
        newAllExtends = newAllExtends.concat(this.doExtendChaining(newAllExtends, atRuleNode.allExtends));
        this.allExtendsStack.push(newAllExtends);
    }

    visitAtRuleOut(atRuleNode) {
        const lastIndex = this.allExtendsStack.length - 1;
        this.allExtendsStack.length = lastIndex;
    }
}

/* eslint-disable no-unused-vars */

class JoinSelectorVisitor {
    constructor() {
        this.contexts = [[]];
        this._visitor = new Visitor(this);
    }

    run(root) {
        return this._visitor.visit(root);
    }

    visitDeclaration(declNode, visitArgs) {
        visitArgs.visitDeeper = false;
    }

    visitMixinDefinition(mixinDefinitionNode, visitArgs) {
        visitArgs.visitDeeper = false;
    }

    visitRuleset(rulesetNode, visitArgs) {
        const context = this.contexts[this.contexts.length - 1];
        const paths = [];
        let selectors;

        this.contexts.push(paths);

        if (!rulesetNode.root) {
            selectors = rulesetNode.selectors;
            if (selectors) {
                selectors = selectors.filter(function(selector) { return selector.getIsOutput(); });
                rulesetNode.selectors = selectors.length ? selectors : (selectors = null);
                if (selectors) { rulesetNode.joinSelectors(paths, context, selectors); }
            }
            if (!selectors) { rulesetNode.rules = null; }
            rulesetNode.paths = paths;
        }
    }

    visitRulesetOut(rulesetNode) {
        this.contexts.length = this.contexts.length - 1;
    }

    visitMedia(mediaNode, visitArgs) {
        const context = this.contexts[this.contexts.length - 1];
        mediaNode.rules[0].root = (context.length === 0 || context[0].multiMedia);
    }

    visitAtRule(atRuleNode, visitArgs) {
        const context = this.contexts[this.contexts.length - 1];

        if (atRuleNode.declarations && atRuleNode.declarations.length) {
            atRuleNode.declarations[0].root = (context.length === 0 || context[0].multiMedia);
        }
        else if (atRuleNode.rules && atRuleNode.rules.length) {
            atRuleNode.rules[0].root = (atRuleNode.isRooted || context.length === 0 || null);
        }
    }
}

// @ts-check

/**
 * @typedef {object} DebugInfoData
 * @property {number} lineNumber
 * @property {string} fileName
 */

/**
 * @typedef {object} DebugInfoContext
 * @property {DebugInfoData} debugInfo
 */

/**
 * @deprecated The dumpLineNumbers option is deprecated. Use sourcemaps instead.
 * This will be removed in a future version.
 *
 * @param {DebugInfoContext} ctx - Context object with debugInfo
 * @returns {string} Debug info as CSS comment
 */
function asComment(ctx) {
    return `/* line ${ctx.debugInfo.lineNumber}, ${ctx.debugInfo.fileName} */\n`;
}

/**
 * @deprecated The dumpLineNumbers option is deprecated. Use sourcemaps instead.
 * This function generates Sass-compatible debug info using @media -sass-debug-info syntax.
 * This format had short-lived usage and is no longer recommended.
 * This will be removed in a future version.
 *
 * @param {DebugInfoContext} ctx - Context object with debugInfo
 * @returns {string} Sass-compatible debug info as @media query
 */
function asMediaQuery(ctx) {
    let filenameWithProtocol = ctx.debugInfo.fileName;
    if (!/^[a-z]+:\/\//i.test(filenameWithProtocol)) {
        filenameWithProtocol = `file://${filenameWithProtocol}`;
    }
    return `@media -sass-debug-info{filename{font-family:${filenameWithProtocol.replace(/([.:/\\])/g, function (a) {
        if (a == '\\') {
            a = '/';
        }
        return `\\${a}`;
    })}}line{font-family:\\00003${ctx.debugInfo.lineNumber}}}\n`;
}

/**
 * Generates debug information (line numbers) for CSS output.
 *
 * @param {{ dumpLineNumbers?: string, compress?: boolean }} context - Context object with dumpLineNumbers option
 * @param {DebugInfoContext} ctx - Context object with debugInfo
 * @param {string} [lineSeparator] - Separator between comment and media query (for 'all' mode)
 * @returns {string} Debug info string
 *
 * @deprecated The dumpLineNumbers option is deprecated. Use sourcemaps instead.
 * All modes ('comments', 'mediaquery', 'all') are deprecated and will be removed in a future version.
 * The 'mediaquery' and 'all' modes generate Sass-compatible @media -sass-debug-info output
 * which had short-lived usage and is no longer recommended.
 */
function debugInfo(context, ctx, lineSeparator) {
    let result = '';
    if (context.dumpLineNumbers && !context.compress) {
        switch (context.dumpLineNumbers) {
            case 'comments':
                result = asComment(ctx);
                break;
            case 'mediaquery':
                result = asMediaQuery(ctx);
                break;
            case 'all':
                result = asComment(ctx) + (lineSeparator || '') + asMediaQuery(ctx);
                break;
        }
    }
    return result;
}

// @ts-check

class Comment extends Node {
    get type() { return 'Comment'; }

    /**
     * @param {string} value
     * @param {boolean} isLineComment
     * @param {number} index
     * @param {FileInfo} currentFileInfo
     */
    constructor(value, isLineComment, index, currentFileInfo) {
        super();
        this.value = value;
        this.isLineComment = isLineComment;
        this._index = index;
        this._fileInfo = currentFileInfo;
        this.allowRoot = true;
        /** @type {{ lineNumber: number, fileName: string } | undefined} */
        this.debugInfo = undefined;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        if (this.debugInfo) {
            output.add(debugInfo(context, /** @type {DebugInfoContext} */ (this)), this.fileInfo(), this.getIndex());
        }
        output.add(/** @type {string} */ (this.value));
    }

    /**
     * @param {EvalContext} context
     * @returns {boolean}
     */
    isSilent(context) {
        const isCompressed = context.compress && /** @type {string} */ (this.value)[2] !== '!';
        return this.isLineComment || isCompressed;
    }
}

// @ts-check

/** @import { EvalContext, CSSOutput } from './node.js' */

class Unit extends Node {
    get type() { return 'Unit'; }

    /**
     * @param {string[]} [numerator]
     * @param {string[]} [denominator]
     * @param {string} [backupUnit]
     */
    constructor(numerator, denominator, backupUnit) {
        super();
        /** @type {string[]} */
        this.numerator = numerator ? copyArray(numerator).sort() : [];
        /** @type {string[]} */
        this.denominator = denominator ? copyArray(denominator).sort() : [];
        if (backupUnit) {
            /** @type {string | undefined} */
            this.backupUnit = backupUnit;
        } else if (numerator && numerator.length) {
            this.backupUnit = numerator[0];
        }
    }

    clone() {
        return new Unit(copyArray(this.numerator), copyArray(this.denominator), this.backupUnit);
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        // Dimension checks the unit is singular and throws an error if in strict math mode.
        const strictUnits = context && context.strictUnits;
        if (this.numerator.length === 1) {
            output.add(this.numerator[0]); // the ideal situation
        } else if (!strictUnits && this.backupUnit) {
            output.add(this.backupUnit);
        } else if (!strictUnits && this.denominator.length) {
            output.add(this.denominator[0]);
        }
    }

    toString() {
        let i, returnStr = this.numerator.join('*');
        for (i = 0; i < this.denominator.length; i++) {
            returnStr += `/${this.denominator[i]}`;
        }
        return returnStr;
    }

    /**
     * @param {Unit} other
     * @returns {0 | undefined}
     */
    compare(other) {
        return this.is(other.toString()) ? 0 : undefined;
    }

    /** @param {string} unitString */
    is(unitString) {
        return this.toString().toUpperCase() === unitString.toUpperCase();
    }

    isLength() {
        return RegExp('^(px|em|ex|ch|rem|in|cm|mm|pc|pt|ex|vw|vh|vmin|vmax)$', 'gi').test(this.toCSS(/** @type {import('./node.js').EvalContext} */ ({})));
    }

    isEmpty() {
        return this.numerator.length === 0 && this.denominator.length === 0;
    }

    isSingular() {
        return this.numerator.length <= 1 && this.denominator.length === 0;
    }

    /** @param {(atomicUnit: string, denominator: boolean) => string} callback */
    map(callback) {
        let i;

        for (i = 0; i < this.numerator.length; i++) {
            this.numerator[i] = callback(this.numerator[i], false);
        }

        for (i = 0; i < this.denominator.length; i++) {
            this.denominator[i] = callback(this.denominator[i], true);
        }
    }

    /** @returns {{ [groupName: string]: string }} */
    usedUnits() {
        /** @type {{ [unitName: string]: number }} */
        let group;
        /** @type {{ [groupName: string]: string }} */
        const result = {};
        /** @type {(atomicUnit: string) => string} */
        let mapUnit;
        /** @type {string} */
        let groupName;

        mapUnit = function (atomicUnit) {
            // eslint-disable-next-line no-prototype-builtins
            if (group.hasOwnProperty(atomicUnit) && !result[groupName]) {
                result[groupName] = atomicUnit;
            }

            return atomicUnit;
        };

        for (groupName in unitConversions) {
            // eslint-disable-next-line no-prototype-builtins
            if (unitConversions.hasOwnProperty(groupName)) {
                group = /** @type {{ [unitName: string]: number }} */ (unitConversions[/** @type {keyof typeof unitConversions} */ (groupName)]);

                this.map(mapUnit);
            }
        }

        return result;
    }

    cancel() {
        /** @type {{ [unit: string]: number }} */
        const counter = {};
        /** @type {string} */
        let atomicUnit;
        let i;

        for (i = 0; i < this.numerator.length; i++) {
            atomicUnit = this.numerator[i];
            counter[atomicUnit] = (counter[atomicUnit] || 0) + 1;
        }

        for (i = 0; i < this.denominator.length; i++) {
            atomicUnit = this.denominator[i];
            counter[atomicUnit] = (counter[atomicUnit] || 0) - 1;
        }

        this.numerator = [];
        this.denominator = [];

        for (atomicUnit in counter) {
            // eslint-disable-next-line no-prototype-builtins
            if (counter.hasOwnProperty(atomicUnit)) {
                const count = counter[atomicUnit];

                if (count > 0) {
                    for (i = 0; i < count; i++) {
                        this.numerator.push(atomicUnit);
                    }
                } else if (count < 0) {
                    for (i = 0; i < -count; i++) {
                        this.denominator.push(atomicUnit);
                    }
                }
            }
        }

        this.numerator.sort();
        this.denominator.sort();
    }
}

// @ts-check

/** @import { EvalContext, CSSOutput } from './node.js' */

//
// A number with a unit
//
class Dimension extends Node {
    get type() { return 'Dimension'; }

    /**
     * @param {number | string} value
     * @param {Unit | string} [unit]
     */
    constructor(value, unit) {
        super();
        /** @type {number} */
        this.value = parseFloat(/** @type {string} */ (value));
        if (isNaN(this.value)) {
            throw new Error('Dimension is not a number.');
        }
        /** @type {Unit} */
        this.unit = (unit && unit instanceof Unit) ? unit :
            new Unit(unit ? [/** @type {string} */ (unit)] : undefined);
        this.setParent(this.unit, this);
    }

    /**
     * @param {import('./node.js').TreeVisitor} visitor
     */
    accept(visitor) {
        this.unit = /** @type {Unit} */ (visitor.visit(this.unit));
    }

    // remove when Nodes have JSDoc types
    // eslint-disable-next-line no-unused-vars
    /** @param {EvalContext} context */
    eval(context) {
        return this;
    }

    toColor() {
        const v = /** @type {number} */ (this.value);
        return new Color([v, v, v]);
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        if ((context && context.strictUnits) && !this.unit.isSingular()) {
            throw new Error(`Multiple units in dimension. Correct the units or use the unit function. Bad unit: ${this.unit.toString()}`);
        }

        const value = this.fround(context, /** @type {number} */ (this.value));
        let strValue = String(value);

        if (value !== 0 && value < 0.000001 && value > -0.000001) {
            // would be output 1e-6 etc.
            strValue = value.toFixed(20).replace(/0+$/, '');
        }

        if (context && context.compress) {
            // Zero values doesn't need a unit
            if (value === 0 && this.unit.isLength()) {
                output.add(strValue);
                return;
            }

            // Float values doesn't need a leading zero
            if (value > 0 && value < 1) {
                strValue = (strValue).slice(1);
            }
        }

        output.add(strValue);
        this.unit.genCSS(context, output);
    }

    // In an operation between two Dimensions,
    // we default to the first Dimension's unit,
    // so `1px + 2` will yield `3px`.
    /**
     * @param {EvalContext} context
     * @param {string} op
     * @param {Dimension} other
     */
    operate(context, op, other) {
        /* jshint noempty:false */
        let value = this._operate(context, op, /** @type {number} */ (this.value), /** @type {number} */ (other.value));
        let unit = this.unit.clone();

        if (op === '+' || op === '-') {
            if (unit.numerator.length === 0 && unit.denominator.length === 0) {
                unit = other.unit.clone();
                if (this.unit.backupUnit) {
                    unit.backupUnit = this.unit.backupUnit;
                }
            } else if (other.unit.numerator.length === 0 && unit.denominator.length === 0) ; else {
                other = other.convertTo(this.unit.usedUnits());

                if (context.strictUnits && other.unit.toString() !== unit.toString()) {
                    throw new Error('Incompatible units. Change the units or use the unit function. '
                        + `Bad units: '${unit.toString()}' and '${other.unit.toString()}'.`);
                }

                value = this._operate(context, op, /** @type {number} */ (this.value), /** @type {number} */ (other.value));
            }
        } else if (op === '*') {
            unit.numerator = unit.numerator.concat(other.unit.numerator).sort();
            unit.denominator = unit.denominator.concat(other.unit.denominator).sort();
            unit.cancel();
        } else if (op === '/') {
            unit.numerator = unit.numerator.concat(other.unit.denominator).sort();
            unit.denominator = unit.denominator.concat(other.unit.numerator).sort();
            unit.cancel();
        }
        return new Dimension(/** @type {number} */ (value), unit);
    }

    /**
     * @param {Node} other
     * @returns {number | undefined}
     */
    compare(other) {
        let a, b;

        if (!(other instanceof Dimension)) {
            return undefined;
        }

        if (this.unit.isEmpty() || other.unit.isEmpty()) {
            a = this;
            b = other;
        } else {
            a = this.unify();
            b = other.unify();
            if (a.unit.compare(b.unit) !== 0) {
                return undefined;
            }
        }

        return Node.numericCompare(/** @type {number} */ (a.value), /** @type {number} */ (b.value));
    }

    unify() {
        return this.convertTo({ length: 'px', duration: 's', angle: 'rad' });
    }

    /**
     * @param {string | { [groupName: string]: string }} conversions
     * @returns {Dimension}
     */
    convertTo(conversions) {
        let value = /** @type {number} */ (this.value);
        const unit = this.unit.clone();
        let i;
        /** @type {string} */
        let groupName;
        /** @type {{ [unitName: string]: number }} */
        let group;
        /** @type {string} */
        let targetUnit;
        /** @type {{ [groupName: string]: string }} */
        let derivedConversions = {};
        /** @type {(atomicUnit: string, denominator: boolean) => string} */
        let applyUnit;

        if (typeof conversions === 'string') {
            for (i in unitConversions) {
                if (unitConversions[/** @type {keyof typeof unitConversions} */ (i)].hasOwnProperty(conversions)) {
                    derivedConversions = {};
                    derivedConversions[i] = conversions;
                }
            }
            conversions = derivedConversions;
        }
        applyUnit = function (atomicUnit, denominator) {
            if (group.hasOwnProperty(atomicUnit)) {
                if (denominator) {
                    value = value / (group[atomicUnit] / group[targetUnit]);
                } else {
                    value = value * (group[atomicUnit] / group[targetUnit]);
                }

                return targetUnit;
            }

            return atomicUnit;
        };

        for (groupName in conversions) {
            if (conversions.hasOwnProperty(groupName)) {
                targetUnit = conversions[groupName];
                group = /** @type {{ [unitName: string]: number }} */ (unitConversions[/** @type {keyof typeof unitConversions} */ (groupName)]);

                unit.map(applyUnit);
            }
        }

        unit.cancel();

        return new Dimension(value, unit);
    }
}

// @ts-check

class Anonymous extends Node {
    get type() { return 'Anonymous'; }

    /**
     * @param {string | null} value
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     * @param {boolean} [mapLines]
     * @param {boolean} [rulesetLike]
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(value, index, currentFileInfo, mapLines, rulesetLike, visibilityInfo) {
        super();
        this.value = value;
        this._index = index;
        this._fileInfo = currentFileInfo;
        this.mapLines = mapLines;
        this.rulesetLike = (typeof rulesetLike === 'undefined') ? false : rulesetLike;
        this.allowRoot = true;
        this.copyVisibilityInfo(visibilityInfo);
    }

    /** @returns {Anonymous} */
    eval() {
        return new Anonymous(/** @type {string | null} */ (this.value), this._index, this._fileInfo, this.mapLines, this.rulesetLike, this.visibilityInfo());
    }

    /**
     * @param {Node} other
     * @returns {number | undefined}
     */
    compare(other) {
        return other.toCSS && this.toCSS(/** @type {EvalContext} */ ({})) === other.toCSS(/** @type {EvalContext} */ ({})) ? 0 : undefined;
    }

    /** @returns {boolean} */
    isRulesetLike() {
        return this.rulesetLike;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        this.nodeVisible = Boolean(this.value);
        if (this.nodeVisible) {
            output.add(/** @type {string} */ (this.value), this._fileInfo, this._index, this.mapLines);
        }
    }
}

// @ts-check

class Expression extends Node {
    get type() { return 'Expression'; }

    /**
     * @param {Node[]} value
     * @param {boolean} [noSpacing]
     */
    constructor(value, noSpacing) {
        super();
        this.value = value;
        /** @type {boolean | undefined} */
        this.noSpacing = noSpacing;
        /** @type {boolean | undefined} */
        this.parens = undefined;
        /** @type {boolean | undefined} */
        this.parensInOp = undefined;
        if (!value) {
            throw new Error('Expression requires an array parameter');
        }
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        this.value = visitor.visitArray(/** @type {Node[]} */ (this.value));
    }

    /** @param {EvalContext} context */
    eval(context) {
        const noSpacing = this.noSpacing;
        /** @type {Node | Expression} */
        let returnValue;
        const mathOn = context.isMathOn();
        const inParenthesis = this.parens;

        let doubleParen = false;
        if (inParenthesis) {
            context.inParenthesis();
        }
        const value = /** @type {Node[]} */ (this.value);
        if (value.length > 1) {
            returnValue = new Expression(value.map(function (e) {
                if (!e.eval) {
                    return e;
                }
                return e.eval(context);
            }), this.noSpacing);
        } else if (value.length === 1) {
            const first = /** @type {Expression} */ (value[0]);
            if (first.parens && !first.parensInOp && !context.inCalc) {
                doubleParen = true;
            }
            returnValue = value[0].eval(context);
        } else {
            returnValue = this;
        }
        if (inParenthesis) {
            context.outOfParenthesis();
        }
        if (this.parens && this.parensInOp && !mathOn && !doubleParen
            && (!(returnValue instanceof Dimension))) {
            returnValue = new Paren(returnValue);
        }
        /** @type {Expression} */ (returnValue).noSpacing =
            /** @type {Expression} */ (returnValue).noSpacing || noSpacing;
        return returnValue;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        const value = /** @type {Node[]} */ (this.value);
        for (let i = 0; i < value.length; i++) {
            value[i].genCSS(context, output);
            if (!this.noSpacing && i + 1 < value.length) {
                if (!(value[i + 1] instanceof Anonymous) ||
                    value[i + 1] instanceof Anonymous && /** @type {string} */ (value[i + 1].value) !== ',') {
                    output.add(' ');
                }
            }
        }
    }

    throwAwayComments() {
        this.value = /** @type {Node[]} */ (this.value).filter(function(v) {
            return !(v instanceof Comment);
        });
    }
}

// @ts-check

class Value extends Node {
    get type() { return 'Value'; }

    /** @param {Node[] | Node} value */
    constructor(value) {
        super();
        if (!value) {
            throw new Error('Value requires an array argument');
        }
        if (!Array.isArray(value)) {
            this.value = [ value ];
        }
        else {
            this.value = value;
        }
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        if (this.value) {
            this.value = visitor.visitArray(/** @type {Node[]} */ (this.value));
        }
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        const value = /** @type {Node[]} */ (this.value);
        if (value.length === 1) {
            return value[0].eval(context);
        } else {
            return new Value(value.map(function (v) {
                return v.eval(context);
            }));
        }
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        const value = /** @type {Node[]} */ (this.value);
        let i;
        for (i = 0; i < value.length; i++) {
            value[i].genCSS(context, output);
            if (i + 1 < value.length) {
                output.add((context && context.compress) ? ',' : ', ');
            }
        }
    }
}

// @ts-check

/**
 * Merges declarations with merge flags (+ or ,) into combined values.
 * Used by both the ToCSSVisitor and AtRule eval.
 * @param {Node[]} rules
 */
function mergeRules(rules) {
    if (!rules) {
        return;
    }

    /** @type {Record<string, Array<Node & { merge: string, name: string, value: Node, important: string }>>} */
    const groups    = {};
    /** @type {Array<Array<Node & { merge: string, name: string, value: Node, important: string }>>} */
    const groupsArr = [];

    for (let i = 0; i < rules.length; i++) {
        const rule = /** @type {Node & { merge: string, name: string }} */ (rules[i]);
        if (rule.merge) {
            const key = rule.name;
            groups[key] ? rules.splice(i--, 1) :
                groupsArr.push(groups[key] = []);
            groups[key].push(/** @type {Node & { merge: string, name: string, value: Node, important: string }} */ (rule));
        }
    }

    groupsArr.forEach(group => {
        if (group.length > 0) {
            const result = group[0];
            /** @type {Node[]} */
            let space  = [];
            const comma  = [new Expression(space)];
            group.forEach(rule => {
                if ((rule.merge === '+') && (space.length > 0)) {
                    comma.push(new Expression(space = []));
                }
                space.push(rule.value);
                result.important = result.important || rule.important;
            });
            result.value = new Value(comma);
        }
    });
}

/* eslint-disable no-unused-vars */

class CSSVisitorUtils {
    constructor(context) {
        this._visitor = new Visitor(this);
        this._context = context;
    }

    containsSilentNonBlockedChild(bodyRules) {
        let rule;
        if (!bodyRules) {
            return false;
        }
        for (let r = 0; r < bodyRules.length; r++) {
            rule = bodyRules[r];
            if (rule.isSilent && rule.isSilent(this._context) && !rule.blocksVisibility()) {
                // the atrule contains something that was referenced (likely by extend)
                // therefore it needs to be shown in output too
                return true;
            }
        }
        return false;
    }

    keepOnlyVisibleChilds(owner) {
        if (owner && owner.rules) {
            owner.rules = owner.rules.filter(thing => thing.isVisible());
        }
    }

    isEmpty(owner) {
        return (owner && owner.rules) 
            ? (owner.rules.length === 0) : true;
    }

    hasVisibleSelector(rulesetNode) {
        return (rulesetNode && rulesetNode.paths)
            ? (rulesetNode.paths.length > 0) : false;
    }

    resolveVisibility(node) {
        if (!node.blocksVisibility()) {
            if (this.isEmpty(node)) {
                return ;
            }

            return node;
        }

        const compiledRulesBody = node.rules[0];
        this.keepOnlyVisibleChilds(compiledRulesBody);

        if (this.isEmpty(compiledRulesBody)) {
            return ;
        }

        node.ensureVisibility();
        node.removeVisibilityBlock();

        return node;
    }

    isVisibleRuleset(rulesetNode) {
        if (rulesetNode.firstRoot) {
            return true;
        }

        if (this.isEmpty(rulesetNode)) {
            return false;
        }

        if (!rulesetNode.root && !this.hasVisibleSelector(rulesetNode)) {
            return false;
        }

        return true;
    }
}

const ToCSSVisitor = function(context) {
    this._visitor = new Visitor(this);
    this._context = context;
    this.utils = new CSSVisitorUtils(context);
};

ToCSSVisitor.prototype = {
    isReplacing: true,
    run: function (root) {
        return this._visitor.visit(root);
    },

    visitDeclaration: function (declNode, visitArgs) {
        if (declNode.blocksVisibility() || declNode.variable) {
            return;
        }
        return declNode;
    },

    visitMixinDefinition: function (mixinNode, visitArgs) {
        // mixin definitions do not get eval'd - this means they keep state
        // so we have to clear that state here so it isn't used if toCSS is called twice
        mixinNode.frames = [];
    },

    visitExtend: function (extendNode, visitArgs) {
    },

    visitComment: function (commentNode, visitArgs) {
        if (commentNode.blocksVisibility() || commentNode.isSilent(this._context)) {
            return;
        }
        return commentNode;
    },

    visitMedia: function(mediaNode, visitArgs) {
        const originalRules = mediaNode.rules[0].rules;
        mediaNode.accept(this._visitor);
        visitArgs.visitDeeper = false;

        return this.utils.resolveVisibility(mediaNode, originalRules);
    },

    visitImport: function (importNode, visitArgs) {
        if (importNode.blocksVisibility()) {
            return ;
        }
        return importNode;
    },

    visitAtRule: function(atRuleNode, visitArgs) {
        if (atRuleNode.rules && atRuleNode.rules.length) {
            return this.visitAtRuleWithBody(atRuleNode, visitArgs);
        } else {
            return this.visitAtRuleWithoutBody(atRuleNode, visitArgs);
        }
    },

    visitAnonymous: function(anonymousNode, visitArgs) {
        if (!anonymousNode.blocksVisibility()) {
            anonymousNode.accept(this._visitor);
            return anonymousNode;
        }
    },

    visitAtRuleWithBody: function(atRuleNode, visitArgs) {
        // if there is only one nested ruleset and that one has no path, then it is
        // just fake ruleset
        function hasFakeRuleset(atRuleNode) {
            const bodyRules = atRuleNode.rules;
            return bodyRules.length === 1 && (!bodyRules[0].paths || bodyRules[0].paths.length === 0);
        }
        function getBodyRules(atRuleNode) {
            const nodeRules = atRuleNode.rules;
            if (hasFakeRuleset(atRuleNode)) {
                return nodeRules[0].rules;
            }

            return nodeRules;
        }
        // it is still true that it is only one ruleset in array
        // this is last such moment
        // process childs
        const originalRules = getBodyRules(atRuleNode);
        atRuleNode.accept(this._visitor);
        visitArgs.visitDeeper = false;

        if (!this.utils.isEmpty(atRuleNode)) {
            this._mergeRules(atRuleNode.rules[0].rules);
        }

        return this.utils.resolveVisibility(atRuleNode, originalRules);
    },

    visitAtRuleWithoutBody: function(atRuleNode, visitArgs) {
        if (atRuleNode.blocksVisibility()) {
            return;
        }

        if (atRuleNode.name === '@charset') {
            // Only output the debug info together with subsequent @charset definitions
            // a comment (or @media statement) before the actual @charset atrule would
            // be considered illegal css as it has to be on the first line
            if (this.charset) {
                if (atRuleNode.debugInfo) {
                    const comment = new tree.Comment(`/* ${atRuleNode.toCSS(this._context).replace(/\n/g, '')} */\n`);
                    comment.debugInfo = atRuleNode.debugInfo;
                    return this._visitor.visit(comment);
                }
                return;
            }
            this.charset = true;
        }

        return atRuleNode;
    },

    checkValidNodes: function(rules, isRoot) {
        if (!rules) {
            return;
        }

        for (let i = 0; i < rules.length; i++) {
            const ruleNode = rules[i];
            if (isRoot && ruleNode instanceof tree.Declaration && !ruleNode.variable) {
                throw { message: 'Properties must be inside selector blocks. They cannot be in the root',
                    index: ruleNode.getIndex(), filename: ruleNode.fileInfo() && ruleNode.fileInfo().filename};
            }
            if (ruleNode instanceof tree.Call) {
                throw { message: `Function '${ruleNode.name}' did not return a root node`,
                    index: ruleNode.getIndex(), filename: ruleNode.fileInfo() && ruleNode.fileInfo().filename};
            }
            if (ruleNode.type && !ruleNode.allowRoot) {
                throw { message: `${ruleNode.type} node returned by a function is not valid here`,
                    index: ruleNode.getIndex(), filename: ruleNode.fileInfo() && ruleNode.fileInfo().filename};
            }
        }
    },

    visitRuleset: function (rulesetNode, visitArgs) {
        // at this point rulesets are nested into each other
        let rule;

        const rulesets = [];

        this.checkValidNodes(rulesetNode.rules, rulesetNode.firstRoot);

        if (!rulesetNode.root) {
            // remove invisible paths
            this._compileRulesetPaths(rulesetNode);

            // remove rulesets from this ruleset body and compile them separately
            const nodeRules = rulesetNode.rules;

            let nodeRuleCnt = nodeRules ? nodeRules.length : 0;
            for (let i = 0; i < nodeRuleCnt; ) {
                rule = nodeRules[i];
                if (rule && rule.rules) {
                    // visit because we are moving them out from being a child
                    rulesets.push(this._visitor.visit(rule));
                    nodeRules.splice(i, 1);
                    nodeRuleCnt--;
                    continue;
                }
                i++;
            }
            // accept the visitor to remove rules and refactor itself
            // then we can decide nogw whether we want it or not
            // compile body
            if (nodeRuleCnt > 0) {
                rulesetNode.accept(this._visitor);
            } else {
                rulesetNode.rules = null;
            }
            visitArgs.visitDeeper = false;
        } else { // if (! rulesetNode.root) {
            rulesetNode.accept(this._visitor);
            visitArgs.visitDeeper = false;
        }

        if (rulesetNode.rules) {
            this._mergeRules(rulesetNode.rules);
            this._removeDuplicateRules(rulesetNode.rules);
        }

        // now decide whether we keep the ruleset
        if (this.utils.isVisibleRuleset(rulesetNode)) {
            rulesetNode.ensureVisibility();
            rulesets.splice(0, 0, rulesetNode);
        }

        if (rulesets.length === 1) {
            return rulesets[0];
        }
        return rulesets;
    },

    _compileRulesetPaths: function(rulesetNode) {
        if (rulesetNode.paths) {
            rulesetNode.paths = rulesetNode.paths
                .filter(p => {
                    let i;
                    if (p[0].elements[0].combinator.value === ' ') {
                        p[0].elements[0].combinator = new(tree.Combinator)('');
                    }
                    for (i = 0; i < p.length; i++) {
                        if (p[i].isVisible() && p[i].getIsOutput()) {
                            return true;
                        }
                    }
                    return false;
                });
        }
    },

    _removeDuplicateRules: function(rules) {
        if (!rules) { return; }

        // remove duplicates
        const ruleCache = {};

        for (let i = rules.length - 1; i >= 0 ; i--) {
            let rule = rules[i];
            if (rule instanceof tree.Declaration) {
                if (!Object.prototype.hasOwnProperty.call(ruleCache, rule.name)) {
                    ruleCache[rule.name] = rule;
                } else {
                    let ruleList = ruleCache[rule.name];
                    if (!Array.isArray(ruleList)) {
                        const prevRuleCSS = ruleList.toCSS(this._context);
                        ruleList = ruleCache[rule.name] = [prevRuleCSS];
                    }
                    const ruleCSS = rule.toCSS(this._context);
                    if (ruleList.indexOf(ruleCSS) !== -1) {
                        rules.splice(i, 1);
                    } else {
                        ruleList.push(ruleCSS);
                    }
                }
            }
        }
    },

    _mergeRules: mergeRules
};

var visitors = {
    Visitor,
    ImportVisitor,
    MarkVisibleSelectorsVisitor: SetTreeVisibilityVisitor,
    ExtendVisitor: ProcessExtendsVisitor,
    JoinSelectorVisitor,
    ToCSSVisitor
};

var getParserInput = () => {
    let // Less input string
        input;

    let // current chunk
        j;

    const // holds state for backtracking
        saveStack = [];

    let // furthest index the parser has gone to
        furthest;

    let // if this is furthest we got to, this is the probably cause
        furthestPossibleErrorMessage;

    let // chunkified input
        chunks;

    let // current chunk
        current;

    let // index of current chunk, in `input`
        currentPos;

    const parserInput = {};
    const CHARCODE_SPACE = 32;
    const CHARCODE_TAB = 9;
    const CHARCODE_LF = 10;
    const CHARCODE_CR = 13;
    const CHARCODE_PLUS = 43;
    const CHARCODE_COMMA = 44;
    const CHARCODE_FORWARD_SLASH = 47;
    const CHARCODE_9 = 57;

    function skipWhitespace(length) {
        const oldi = parserInput.i;
        const oldj = j;
        const curr = parserInput.i - currentPos;
        const endIndex = parserInput.i + current.length - curr;
        const mem = (parserInput.i += length);
        const inp = input;
        let c;
        let nextChar;
        let comment;

        for (; parserInput.i < endIndex; parserInput.i++) {
            c = inp.charCodeAt(parserInput.i);

            if (parserInput.autoCommentAbsorb && c === CHARCODE_FORWARD_SLASH) {
                nextChar = inp.charAt(parserInput.i + 1);
                if (nextChar === '/') {
                    comment = {index: parserInput.i, isLineComment: true};
                    let nextNewLine = inp.indexOf('\n', parserInput.i + 2);
                    if (nextNewLine < 0) {
                        nextNewLine = endIndex;
                    }
                    parserInput.i = nextNewLine;
                    comment.text = inp.slice(comment.index, parserInput.i);
                    parserInput.commentStore.push(comment);
                    continue;
                } else if (nextChar === '*') {
                    const nextStarSlash = inp.indexOf('*/', parserInput.i + 2);
                    if (nextStarSlash >= 0) {
                        comment = {
                            index: parserInput.i,
                            text: inp.slice(parserInput.i, nextStarSlash + 2),
                            isLineComment: false
                        };
                        parserInput.i += comment.text.length - 1;
                        parserInput.commentStore.push(comment);
                        continue;
                    }
                }
                break;
            }

            if ((c !== CHARCODE_SPACE) && (c !== CHARCODE_LF) && (c !== CHARCODE_TAB) && (c !== CHARCODE_CR)) {
                break;
            }
        }

        current = current.slice(length + parserInput.i - mem + curr);
        currentPos = parserInput.i;

        if (!current.length) {
            if (j < chunks.length - 1) {
                current = chunks[++j];
                skipWhitespace(0); // skip space at the beginning of a chunk
                return true; // things changed
            }
            parserInput.finished = true;
        }

        return oldi !== parserInput.i || oldj !== j;
    }

    parserInput.save = () => {
        currentPos = parserInput.i;
        saveStack.push( { current, i: parserInput.i, j });
    };
    parserInput.restore = possibleErrorMessage => {

        if (parserInput.i > furthest || (parserInput.i === furthest && possibleErrorMessage && !furthestPossibleErrorMessage)) {
            furthest = parserInput.i;
            furthestPossibleErrorMessage = possibleErrorMessage;
        }
        const state = saveStack.pop();
        current = state.current;
        currentPos = parserInput.i = state.i;
        j = state.j;
    };
    parserInput.forget = () => {
        saveStack.pop();
    };
    parserInput.isWhitespace = offset => {
        const pos = parserInput.i + (offset || 0);
        const code = input.charCodeAt(pos);
        return (code === CHARCODE_SPACE || code === CHARCODE_CR || code === CHARCODE_TAB || code === CHARCODE_LF);
    };

    // Specialization of $(tok)
    parserInput.$re = tok => {
        if (parserInput.i > currentPos) {
            current = current.slice(parserInput.i - currentPos);
            currentPos = parserInput.i;
        }

        const m = tok.exec(current);
        if (!m) {
            return null;
        }

        skipWhitespace(m[0].length);
        if (typeof m === 'string') {
            return m;
        }

        return m.length === 1 ? m[0] : m;
    };

    parserInput.$char = tok => {
        if (input.charAt(parserInput.i) !== tok) {
            return null;
        }
        skipWhitespace(1);
        return tok;
    };

    parserInput.$peekChar = tok => {
        if (input.charAt(parserInput.i) !== tok) {
            return null;
        }
        return tok;
    };

    parserInput.$str = tok => {
        const tokLength = tok.length;

        // https://jsperf.com/string-startswith/21
        for (let i = 0; i < tokLength; i++) {
            if (input.charAt(parserInput.i + i) !== tok.charAt(i)) {
                return null;
            }
        }

        skipWhitespace(tokLength);
        return tok;
    };

    parserInput.$quoted = loc => {
        const pos = loc || parserInput.i;
        const startChar = input.charAt(pos);

        if (startChar !== '\'' && startChar !== '"') {
            return;
        }
        const length = input.length;
        const currentPosition = pos;

        for (let i = 1; i + currentPosition < length; i++) {
            const nextChar = input.charAt(i + currentPosition);
            switch (nextChar) {
                case '\\':
                    i++;
                    continue;
                case '\r':
                case '\n':
                    break;
                case startChar: {
                    const str = input.slice(currentPosition, currentPosition + i + 1);
                    if (!loc && loc !== 0) {
                        skipWhitespace(i + 1);
                        return str
                    }
                    return [startChar, str];
                }
            }
        }
        return null;
    };

    /**
     * Permissive parsing. Ignores everything except matching {} [] () and quotes
     * until matching token (outside of blocks)
     */
    parserInput.$parseUntil = tok => {
        let quote = '';
        let returnVal = null;
        let inComment = false;
        let blockDepth = 0;
        const blockStack = [];
        const parseGroups = [];
        const length = input.length;
        const startPos = parserInput.i;
        let lastPos = parserInput.i;
        let i = parserInput.i;
        let loop = true;
        let testChar;

        if (typeof tok === 'string') {
            testChar = char => char === tok;
        } else {
            testChar = char => tok.test(char);
        }

        do {
            let nextChar = input.charAt(i);
            if (blockDepth === 0 && testChar(nextChar)) {
                returnVal = input.slice(lastPos, i);
                if (returnVal) {
                    parseGroups.push(returnVal);
                }
                else {
                    parseGroups.push(' ');
                }
                returnVal = parseGroups;
                skipWhitespace(i - startPos);
                loop = false;
            } else {
                if (inComment) {
                    if (nextChar === '*' &&
                        input.charAt(i + 1) === '/') {
                        i++;
                        blockDepth--;
                        inComment = false;
                    }
                    i++;
                    continue;
                }
                switch (nextChar) {
                    case '\\':
                        i++;
                        nextChar = input.charAt(i);
                        parseGroups.push(input.slice(lastPos, i + 1));
                        lastPos = i + 1;
                        break;
                    case '/':
                        if (input.charAt(i + 1) === '*') {
                            i++;
                            inComment = true;
                            blockDepth++;
                        }
                        break;
                    case '\'':
                    case '"':
                        quote = parserInput.$quoted(i);
                        if (quote) {
                            parseGroups.push(input.slice(lastPos, i), quote);
                            i += quote[1].length - 1;
                            lastPos = i + 1;
                        }
                        else {
                            skipWhitespace(i - startPos);
                            returnVal = nextChar;
                            loop = false;
                        }
                        break;
                    case '{':
                        blockStack.push('}');
                        blockDepth++;
                        break;
                    case '(':
                        blockStack.push(')');
                        blockDepth++;
                        break;
                    case '[':
                        blockStack.push(']');
                        blockDepth++;
                        break;
                    case '}':
                    case ')':
                    case ']': {
                        const expected = blockStack.pop();
                        if (nextChar === expected) {
                            blockDepth--;
                        } else {
                            // move the parser to the error and return expected
                            skipWhitespace(i - startPos);
                            returnVal = expected;
                            loop = false;
                        }
                    }
                }
                i++;
                if (i > length) {
                    loop = false;
                }
            }
        } while (loop);

        return returnVal ? returnVal : null;
    };

    parserInput.autoCommentAbsorb = true;
    parserInput.commentStore = [];
    parserInput.finished = false;

    // Same as $(), but don't change the state of the parser,
    // just return the match.
    parserInput.peek = tok => {
        if (typeof tok === 'string') {
            // https://jsperf.com/string-startswith/21
            for (let i = 0; i < tok.length; i++) {
                if (input.charAt(parserInput.i + i) !== tok.charAt(i)) {
                    return false;
                }
            }
            return true;
        } else {
            return tok.test(current);
        }
    };

    // Specialization of peek()
    // TODO remove or change some currentChar calls to peekChar
    parserInput.peekChar = tok => input.charAt(parserInput.i) === tok;

    parserInput.currentChar = () => input.charAt(parserInput.i);

    parserInput.prevChar = () => input.charAt(parserInput.i - 1);

    parserInput.getInput = () => input;

    parserInput.peekNotNumeric = () => {
        const c = input.charCodeAt(parserInput.i);
        // Is the first char of the dimension 0-9, '.', '+' or '-'
        return (c > CHARCODE_9 || c < CHARCODE_PLUS) || c === CHARCODE_FORWARD_SLASH || c === CHARCODE_COMMA;
    };

    parserInput.start = (str) => {
        input = str;
        parserInput.i = j = currentPos = furthest = 0;

        chunks = [str];
        current = chunks[0];

        skipWhitespace(0);
    };

    parserInput.end = () => {
        let message;
        const isFinished = parserInput.i >= input.length;

        if (parserInput.i < furthest) {
            message = furthestPossibleErrorMessage;
            parserInput.i = furthest;
        }
        return {
            isFinished,
            furthest: parserInput.i,
            furthestPossibleErrorMessage: message,
            furthestReachedEnd: parserInput.i >= input.length - 1,
            furthestChar: input[parserInput.i]
        };
    };

    return parserInput;
};

function makeRegistry( base ) {
    return {
        _data: {},
        add: function(name, func) {
            // precautionary case conversion, as later querying of
            // the registry by function-caller uses lower case as well.
            name = name.toLowerCase();

            // eslint-disable-next-line no-prototype-builtins
            if (this._data.hasOwnProperty(name)) ;
            this._data[name] = func;
        },
        addMultiple: function(functions) {
            Object.keys(functions).forEach(
                name => {
                    this.add(name, functions[name]);
                });
        },
        get: function(name) {
            return this._data[name] || ( base && base.get( name ));
        },
        getLocalFunctions: function() {
            return this._data;
        },
        inherit: function() {
            return makeRegistry( this );
        },
        create: function(base) {
            return makeRegistry(base);
        }
    };
}

var functionRegistry = makeRegistry( null );

// @ts-check
const MediaSyntaxOptions = {
    queryInParens: true
};

const ContainerSyntaxOptions = {
    queryInParens: true
};

/**
 * Deprecation registry for Less.js
 *
 * Each deprecation has a unique ID and description.
 * Repetition limiting caps warnings at 5 per deprecation type per parse.
 * Use --quiet-deprecations to suppress all deprecation warnings.
 */

const MAX_REPETITIONS = 5;

class DeprecationHandler {
    constructor() {
        /** @type {Record<string, number>} */
        this._counts = {};
    }

    /** @param {string} deprecationId */
    shouldWarn(deprecationId) {
        if (!deprecationId) { return true; }
        const count = (this._counts[deprecationId] || 0) + 1;
        this._counts[deprecationId] = count;
        return count <= MAX_REPETITIONS;
    }

    /** @param {{ warn: (msg: string) => void }} logger */
    summarize(logger) {
        for (const id of Object.keys(this._counts)) {
            const omitted = this._counts[id] - MAX_REPETITIONS;
            if (omitted > 0) {
                logger.warn(`${omitted} repetitive "${id}" deprecation warning(s) omitted.`);
            }
        }
    }
}

//
// less.js - parser
//
//    A relatively straight-forward predictive parser.
//    There is no tokenization/lexing stage, the input is parsed
//    in one sweep.
//
//    To make the parser fast enough to run in the browser, several
//    optimization had to be made:
//
//    - Matching and slicing on a huge input is often cause of slowdowns.
//      The solution is to chunkify the input into smaller strings.
//      The chunks are stored in the `chunks` var,
//      `j` holds the current chunk index, and `currentPos` holds
//      the index of the current chunk in relation to `input`.
//      This gives us an almost 4x speed-up.
//
//    - In many cases, we don't need to match individual tokens;
//      for example, if a value doesn't hold any variables, operations
//      or dynamic references, the parser can effectively 'skip' it,
//      treating it as a literal.
//      An example would be '1px solid #000' - which evaluates to itself,
//      we don't need to know what the individual components are.
//      The drawback, of course is that you don't get the benefits of
//      syntax-checking on the CSS. This gives us a 50% speed-up in the parser,
//      and a smaller speed-up in the code-gen.
//
//
//    Token matching is done with the `$` function, which either takes
//    a terminal string or regexp, or a non-terminal function to call.
//    It also takes care of moving all the indices forwards.
//

const Parser = function Parser(context, imports, fileInfo, currentIndex) {
    currentIndex = currentIndex || 0;
    let parsers;
    const parserInput = getParserInput();

    function error(msg, type) {
        throw new LessError(
            {
                index: parserInput.i,
                filename: fileInfo.filename,
                type: type || 'Syntax',
                message: msg
            },
            imports
        );
    }

    const deprecationHandler = new DeprecationHandler();

    /**
     * @param {string} msg
     * @param {number} index
     * @param {string} type
     * @param {string} [deprecationId] - stable deprecation ID for repetition limiting
     */
    function warn(msg, index, type, deprecationId) {
        if (context.quiet) { return; }
        if (deprecationId && context.quietDeprecations) { return; }
        if (deprecationId && !deprecationHandler.shouldWarn(deprecationId)) { return; }

        logger.warn(
            (new LessError(
                {
                    index: index ?? parserInput.i,
                    filename: fileInfo.filename,
                    type: type ? `${type.toUpperCase()} WARNING` : 'WARNING',
                    message: msg
                },
                imports
            )).toString()
        );
    }

    function expect(arg, msg) {
        // some older browsers return typeof 'function' for RegExp
        const result = (arg instanceof Function) ? arg.call(parsers) : parserInput.$re(arg);
        if (result) {
            return result;
        }

        error(msg || (typeof arg === 'string'
            ? `expected '${arg}' got '${parserInput.currentChar()}'`
            : 'unexpected token'));
    }

    // Specialization of expect()
    function expectChar(arg, msg) {
        if (parserInput.$char(arg)) {
            return arg;
        }
        error(msg || `expected '${arg}' got '${parserInput.currentChar()}'`);
    }

    function getDebugInfo(index) {
        const filename = fileInfo.filename;

        return {
            lineNumber: getLocation(index, parserInput.getInput()).line + 1,
            fileName: filename
        };
    }

    /**
     *  Used after initial parsing to create nodes on the fly
     *
     *  @param {String} str          - string to parse
     *  @param {Array}  parseList    - array of parsers to run input through e.g. ["value", "important"]
     *  @param {Number} currentIndex - start number to begin indexing
     *  @param {Object} fileInfo     - fileInfo to attach to created nodes
     */
    function parseNode(str, parseList, callback) {
        let result;
        const returnNodes = [];
        const parser = parserInput;

        try {
            parser.start(str);
            for (let x = 0, p; (p = parseList[x]); x++) {
                result = parsers[p]();
                returnNodes.push(result || null);
            }

            const endInfo = parser.end();
            if (endInfo.isFinished) {
                callback(null, returnNodes);
            }
            else {
                callback(true, null);
            }
        } catch (e) {
            throw new LessError({
                index: e.index + currentIndex,
                message: e.message
            }, imports, fileInfo.filename);
        }
    }

    //
    // The Parser
    //
    return {
        parserInput,
        imports,
        fileInfo,
        parseNode,
        //
        // Parse an input string into an abstract syntax tree,
        // @param str A string containing 'less' markup
        // @param callback call `callback` when done.
        // @param [additionalData] An optional map which can contains vars - a map (key, value) of variables to apply
        //
        parse: function (str, callback, additionalData) {
            let root;
            let err = null;
            let globalVars;
            let modifyVars;
            let ignored;
            let preText = '';

            // Optionally disable @plugin parsing
            if (additionalData && additionalData.disablePluginRule) {
                parsers.plugin = function() {
                    var dir = parserInput.$re(/^@plugin?\s+/);
                    if (dir) {
                        error('@plugin statements are not allowed when disablePluginRule is set to true');
                    }
                };
            }

            globalVars = (additionalData && additionalData.globalVars) ? `${Parser.serializeVars(additionalData.globalVars)}\n` : '';
            modifyVars = (additionalData && additionalData.modifyVars) ? `\n${Parser.serializeVars(additionalData.modifyVars)}` : '';

            if (context.pluginManager) {
                const preProcessors = context.pluginManager.getPreProcessors();
                for (let i = 0; i < preProcessors.length; i++) {
                    str = preProcessors[i].process(str, { context, imports, fileInfo });
                }
            }

            if (globalVars || (additionalData && additionalData.banner)) {
                preText = ((additionalData && additionalData.banner) ? additionalData.banner : '') + globalVars;
                ignored = imports.contentsIgnoredChars;
                ignored[fileInfo.filename] = ignored[fileInfo.filename] || 0;
                ignored[fileInfo.filename] += preText.length;
            }

            str = str.replace(/\r\n?/g, '\n');
            // Remove potential UTF Byte Order Mark
            str = preText + str.replace(/^\uFEFF/, '') + modifyVars;
            imports.contents[fileInfo.filename] = str;

            // Start with the primary rule.
            // The whole syntax tree is held under a Ruleset node,
            // with the `root` property set to true, so no `{}` are
            // output. The callback is called when the input is parsed.
            try {
                parserInput.start(str);

                tree.Node.prototype.parse = this;
                root = new tree.Ruleset(null, this.parsers.primary());
                tree.Node.prototype.rootNode = root;
                root.root = true;
                root.firstRoot = true;
                root.functionRegistry = functionRegistry.inherit();

            } catch (e) {
                return callback(new LessError(e, imports, fileInfo.filename));
            }

            // If `i` is smaller than the `input.length - 1`,
            // it means the parser wasn't able to parse the whole
            // string, so we've got a parsing error.
            //
            // We try to extract a \n delimited string,
            // showing the line where the parse error occurred.
            // We split it up into two parts (the part which parsed,
            // and the part which didn't), so we can color them differently.
            const endInfo = parserInput.end();
            if (!endInfo.isFinished) {

                let message = endInfo.furthestPossibleErrorMessage;

                if (!message) {
                    message = 'Unrecognised input';
                    if (endInfo.furthestChar === '}') {
                        message += '. Possibly missing opening \'{\'';
                    } else if (endInfo.furthestChar === ')') {
                        message += '. Possibly missing opening \'(\'';
                    } else if (endInfo.furthestReachedEnd) {
                        message += '. Possibly missing something';
                    }
                }

                err = new LessError({
                    type: 'Parse',
                    message,
                    index: endInfo.furthest,
                    filename: fileInfo.filename
                }, imports);
            }

            const finish = e => {
                e = err || e || imports.error;

                if (e) {
                    if (!(e instanceof LessError)) {
                        e = new LessError(e, imports, fileInfo.filename);
                    }

                    return callback(e);
                }
                else {
                    return callback(null, root);
                }
            };

            if (context.processImports !== false) {
                new visitors.ImportVisitor(imports, finish)
                    .run(root);
            } else {
                return finish();
            }
        },

        //
        // Here in, the parsing rules/functions
        //
        // The basic structure of the syntax tree generated is as follows:
        //
        //   Ruleset ->  Declaration -> Value -> Expression -> Entity
        //
        // Here's some Less code:
        //
        //    .class {
        //      color: #fff;
        //      border: 1px solid #000;
        //      width: @w + 4px;
        //      > .child {...}
        //    }
        //
        // And here's what the parse tree might look like:
        //
        //     Ruleset (Selector '.class', [
        //         Declaration ("color",  Value ([Expression [Color #fff]]))
        //         Declaration ("border", Value ([Expression [Dimension 1px][Keyword "solid"][Color #000]]))
        //         Declaration ("width",  Value ([Expression [Operation " + " [Variable "@w"][Dimension 4px]]]))
        //         Ruleset (Selector [Element '>', '.child'], [...])
        //     ])
        //
        //  In general, most rules will try to parse a token with the `$re()` function, and if the return
        //  value is truly, will return a new node, of the relevant type. Sometimes, we need to check
        //  first, before parsing, that's when we use `peek()`.
        //
        parsers: parsers = {
            //
            // The `primary` rule is the *entry* and *exit* point of the parser.
            // The rules here can appear at any level of the parse tree.
            //
            // The recursive nature of the grammar is an interplay between the `block`
            // rule, which represents `{ ... }`, the `ruleset` rule, and this `primary` rule,
            // as represented by this simplified grammar:
            //
            //     primary  →  (ruleset | declaration)+
            //     ruleset  →  selector+ block
            //     block    →  '{' primary '}'
            //
            // Only at one point is the primary rule not called from the
            // block rule: at the root level.
            //
            primary: function () {
                const mixin = this.mixin;
                let root = [];
                let node;

                while (true) {
                    while (true) {
                        node = this.comment();
                        if (!node) { break; }
                        root.push(node);
                    }
                    // always process comments before deciding if finished
                    if (parserInput.finished) {
                        break;
                    }
                    if (parserInput.peek('}')) {
                        break;
                    }

                    node = this.extendRule();
                    if (node) {
                        root = root.concat(node);
                        continue;
                    }

                    node = mixin.definition() || this.declaration() || mixin.call(false, false) ||
                        this.ruleset() || this.variableCall() || this.entities.call() || this.atrule();
                    if (node) {
                        root.push(node);
                    } else {
                        let foundSemiColon = false;
                        while (parserInput.$char(';')) {
                            foundSemiColon = true;
                        }
                        if (!foundSemiColon) {
                            break;
                        }
                    }
                }

                return root;
            },

            // comments are collected by the main parsing mechanism and then assigned to nodes
            // where the current structure allows it
            comment: function () {
                if (parserInput.commentStore.length) {
                    const comment = parserInput.commentStore.shift();
                    return new(tree.Comment)(comment.text, comment.isLineComment, comment.index + currentIndex, fileInfo);
                }
            },

            //
            // Entities are tokens which can be found inside an Expression
            //
            entities: {
                mixinLookup: function() {
                    return parsers.mixin.call(true, true);
                },
                //
                // A string, which supports escaping " and '
                //
                //     "milky way" 'he\'s the one!'
                //
                quoted: function (forceEscaped) {
                    let str;
                    const index = parserInput.i;
                    let isEscaped = false;

                    parserInput.save();
                    if (parserInput.$char('~')) {
                        isEscaped = true;
                    } else if (forceEscaped) {
                        parserInput.restore();
                        return;
                    }

                    str = parserInput.$quoted();
                    if (!str) {
                        parserInput.restore();
                        return;
                    }
                    parserInput.forget();

                    return new(tree.Quoted)(str.charAt(0), str.slice(1, -1), isEscaped, index + currentIndex, fileInfo);
                },

                //
                // A catch-all word, such as:
                //
                //     black border-collapse
                //
                keyword: function () {
                    const k = parserInput.$char('%') || parserInput.$re(/^\[?(?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+\]?/);
                    if (k) {
                        return tree.Color.fromKeyword(k) || new(tree.Keyword)(k);
                    }
                },

                //
                // A function call
                //
                //     rgb(255, 0, 255)
                //
                // The arguments are parsed with the `entities.arguments` parser.
                //
                call: function () {
                    let name;
                    let args;
                    let func;
                    const index = parserInput.i;

                    // http://jsperf.com/case-insensitive-regex-vs-strtolower-then-regex/18
                    if (parserInput.peek(/^url\(/i)) {
                        return;
                    }

                    parserInput.save();

                    name = parserInput.$re(/^([\w-]+|%|~|progid:[\w.]+)\(/);
                    if (!name) {
                        parserInput.forget();
                        return;
                    }

                    name = name[1];
                    func = this.customFuncCall(name);
                    if (func) {
                        args = func.parse();
                        if (args && func.stop) {
                            parserInput.forget();
                            return args;
                        }
                    }

                    args = this.arguments(args);

                    if (!parserInput.$char(')')) {
                        parserInput.restore('Could not parse call arguments or missing \')\'');
                        return;
                    }

                    parserInput.forget();

                    return new(tree.Call)(name, args, index + currentIndex, fileInfo);
                },

                declarationCall: function () {
                    let validCall;
                    let args;
                    const index = parserInput.i;

                    parserInput.save();

                    validCall = parserInput.$re(/^[\w]+\(/);
                    if (!validCall) {
                        parserInput.forget();
                        return;
                    }

                    validCall = validCall.substring(0, validCall.length - 1);

                    // CSS at-rule keywords should never be parsed as declaration calls
                    if (/^(and|or|not|only|layer)$/i.test(validCall)) {
                        parserInput.restore();
                        return;
                    }

                    let rule = this.ruleProperty();
                    let value;
                  
                    if (rule) {
                        value = this.value();
                    }
                    
                    if (rule && value) {
                        args = [new (tree.Declaration)(rule, value, null, null, parserInput.i + currentIndex, fileInfo, true)];
                    }

                    if (!parserInput.$char(')')) {
                        parserInput.restore('Could not parse call arguments or missing \')\'');
                        return;
                    }

                    parserInput.forget();

                    return new(tree.Call)(validCall, args, index + currentIndex, fileInfo);
                },

                //
                // Parsing rules for functions with non-standard args, e.g.:
                //
                //     boolean(not(2 > 1))
                //
                //     This is a quick prototype, to be modified/improved when
                //     more custom-parsed funcs come (e.g. `selector(...)`)
                //

                customFuncCall: function (name) {
                    /* Ideally the table is to be moved out of here for faster perf.,
                       but it's quite tricky since it relies on all these `parsers`
                       and `expect` available only here */
                    return {
                        alpha:   f(parsers.ieAlpha, true),
                        boolean: f(condition),
                        'if':    f(condition)
                    }[name.toLowerCase()];

                    function f(parse, stop) {
                        return {
                            parse, // parsing function
                            stop   // when true - stop after parse() and return its result,
                            // otherwise continue for plain args
                        };
                    }

                    function condition() {
                        return [expect(parsers.condition, 'expected condition')];
                    }
                },

                arguments: function (prevArgs) {
                    let argsComma = prevArgs || [];
                    const argsSemiColon = [];
                    let isSemiColonSeparated;
                    let value;

                    parserInput.save();

                    while (true) {
                        if (prevArgs) {
                            prevArgs = false;
                        } else {
                            value = parsers.detachedRuleset() || this.assignment() || parsers.expression();
                            if (!value) {
                                break;
                            }

                            if (value.value && value.value.length == 1) {
                                value = value.value[0];
                            }

                            argsComma.push(value);
                        }

                        if (parserInput.$char(',')) {
                            continue;
                        }

                        if (parserInput.$char(';') || isSemiColonSeparated) {
                            isSemiColonSeparated = true;
                            value = (argsComma.length < 1) ? argsComma[0]
                                : new tree.Value(argsComma);
                            argsSemiColon.push(value);
                            argsComma = [];
                        }
                    }

                    parserInput.forget();
                    return isSemiColonSeparated ? argsSemiColon : argsComma;
                },
                literal: function () {
                    return this.dimension() ||
                           this.color() ||
                           this.quoted() ||
                           this.unicodeDescriptor();
                },

                // Assignments are argument entities for calls.
                // They are present in ie filter properties as shown below.
                //
                //     filter: progid:DXImageTransform.Microsoft.Alpha( *opacity=50* )
                //

                assignment: function () {
                    let key;
                    let value;
                    parserInput.save();
                    key = parserInput.$re(/^\w+(?=\s?=)/i);
                    if (!key) {
                        parserInput.restore();
                        return;
                    }
                    if (!parserInput.$char('=')) {
                        parserInput.restore();
                        return;
                    }
                    value = parsers.entity();
                    if (value) {
                        parserInput.forget();
                        return new(tree.Assignment)(key, value);
                    } else {
                        parserInput.restore();
                    }
                },

                //
                // Parse url() tokens
                //
                // We use a specific rule for urls, because they don't really behave like
                // standard function calls. The difference is that the argument doesn't have
                // to be enclosed within a string, so it can't be parsed as an Expression.
                //
                url: function () {
                    let value;
                    const index = parserInput.i;

                    parserInput.autoCommentAbsorb = false;

                    if (!parserInput.$str('url(')) {
                        parserInput.autoCommentAbsorb = true;
                        return;
                    }

                    value = this.quoted() || this.variable() || this.property() ||
                            parserInput.$re(/^(?:(?:\\[()'"])|[^()'"])+/) || '';

                    parserInput.autoCommentAbsorb = true;

                    expectChar(')');

                    return new(tree.URL)((value.value !== undefined ||
                        value instanceof tree.Variable ||
                        value instanceof tree.Property) ?
                        value : new(tree.Anonymous)(value, index), index + currentIndex, fileInfo);
                },

                //
                // A Variable entity, such as `@fink`, in
                //
                //     width: @fink + 2px
                //
                // We use a different parser for variable definitions,
                // see `parsers.variable`.
                //
                variable: function () {
                    let ch;
                    let name;
                    const index = parserInput.i;

                    parserInput.save();
                    if (parserInput.currentChar() === '@' && (name = parserInput.$re(/^@@?[\w-]+/))) {
                        ch = parserInput.currentChar();
                        if ((ch === '(' && !parserInput.prevChar().match(/^\s/))
                            || (ch === '[' && !parserInput.prevChar().match(/^\s/))) {
                            // this may be a VariableCall lookup
                            const result = parsers.variableCall(name);
                            if (result) {
                                parserInput.forget();
                                return result;
                            }
                        }
                        parserInput.forget();
                        return new(tree.Variable)(name, index + currentIndex, fileInfo);
                    }
                    parserInput.restore();
                },

                // A variable entity using the protective {} e.g. @{var}
                variableCurly: function () {
                    let curly;
                    const index = parserInput.i;

                    if (parserInput.currentChar() === '@' && (curly = parserInput.$re(/^@\{([\w-]+)\}/))) {
                        return new(tree.Variable)(`@${curly[1]}`, index + currentIndex, fileInfo);
                    }
                },
                //
                // A Property accessor, such as `$color`, in
                //
                //     background-color: $color
                //
                property: function () {
                    let name;
                    const index = parserInput.i;

                    if (parserInput.currentChar() === '$' && (name = parserInput.$re(/^\$[\w-]+/))) {
                        return new(tree.Property)(name, index + currentIndex, fileInfo);
                    }
                },

                //
                // A Hexadecimal color
                //
                //     #4F3C2F
                //
                // `rgb` and `hsl` colors are parsed through the `entities.call` parser.
                //
                color: function () {
                    let rgb;
                    parserInput.save();

                    if (parserInput.currentChar() === '#' && (rgb = parserInput.$re(/^#([A-Fa-f0-9]{8}|[A-Fa-f0-9]{6}|[A-Fa-f0-9]{3,4})([\w.#[])?/))) {
                        if (!rgb[2]) {
                            parserInput.forget();
                            return new(tree.Color)(rgb[1], undefined, rgb[0]);
                        }
                    }
                    parserInput.restore();
                },

                colorKeyword: function () {
                    parserInput.save();
                    const autoCommentAbsorb = parserInput.autoCommentAbsorb;
                    parserInput.autoCommentAbsorb = false;
                    const k = parserInput.$re(/^[_A-Za-z-][_A-Za-z0-9-]+/);
                    parserInput.autoCommentAbsorb = autoCommentAbsorb;
                    if (!k) {
                        parserInput.forget();
                        return;
                    }
                    parserInput.restore();
                    const color = tree.Color.fromKeyword(k);
                    if (color) {
                        parserInput.$str(k);
                        return color;
                    }
                },

                //
                // A Dimension, that is, a number and a unit
                //
                //     0.5em 95%
                //
                dimension: function () {
                    if (parserInput.peekNotNumeric()) {
                        return;
                    }

                    const value = parserInput.$re(/^([+-]?\d*\.?\d+)(%|[a-z_]+)?/i);
                    if (value) {
                        return new(tree.Dimension)(value[1], value[2]);
                    }
                },

                //
                // A unicode descriptor, as is used in unicode-range
                //
                // U+0??  or U+00A1-00A9
                //
                unicodeDescriptor: function () {
                    let ud;

                    ud = parserInput.$re(/^U\+[0-9a-fA-F?]+(-[0-9a-fA-F?]+)?/);
                    if (ud) {
                        return new(tree.UnicodeDescriptor)(ud[0]);
                    }
                },

                //
                // JavaScript code to be evaluated
                //
                //     `window.location.href`
                //
                javascript: function () {
                    let js;
                    const index = parserInput.i;

                    parserInput.save();

                    const escape = parserInput.$char('~');
                    const jsQuote = parserInput.$char('`');

                    if (!jsQuote) {
                        parserInput.restore();
                        return;
                    }

                    js = parserInput.$re(/^[^`]*`/);
                    if (js) {
                        warn('Inline JavaScript evaluation (backtick expressions) is deprecated and will be removed in Less 5.x. Use Less functions or custom plugins instead.', index, 'DEPRECATED', 'js-eval');
                        parserInput.forget();
                        return new(tree.JavaScript)(js.slice(0, -1), Boolean(escape), index + currentIndex, fileInfo);
                    }
                    parserInput.restore('invalid javascript definition');
                }
            },

            //
            // The variable part of a variable definition. Used in the `rule` parser
            //
            //     @fink:
            //
            variable: function () {
                let name;

                if (parserInput.currentChar() === '@' && (name = parserInput.$re(/^(@[\w-]+)\s*:/))) { return name[1]; }
            },

            //
            // Call a variable value to retrieve a detached ruleset
            // or a value from a detached ruleset's rules.
            //
            //     @fink();
            //     @fink;
            //     color: @fink[@color];
            //
            variableCall: function (parsedName) {
                let lookups;
                const i = parserInput.i;
                const inValue = !!parsedName;
                let name = parsedName;

                parserInput.save();

                if (name || (parserInput.currentChar() === '@'
                    && (name = parserInput.$re(/^(@[\w-]+)(\(\s*\))?/)))) {

                    lookups = this.mixin.ruleLookups();

                    if (!lookups && ((inValue && parserInput.$str('()') !== '()') || (name[2] !== '()'))) {
                        parserInput.restore('Missing \'[...]\' lookup in variable call');
                        return;
                    }

                    if (!inValue) {
                        name = name[1];
                    }

                    const call = new tree.VariableCall(name, i, fileInfo);
                    if (!inValue && parsers.end()) {
                        parserInput.forget();
                        return call;
                    }
                    else {
                        parserInput.forget();
                        return new tree.NamespaceValue(call, lookups, i, fileInfo);
                    }
                }

                parserInput.restore();
            },

            //
            // extend syntax - used to extend selectors
            //
            extend: function(isRule) {
                let elements;
                let e;
                const index = parserInput.i;
                let option;
                let extendList;
                let extend;

                if (!parserInput.$str(isRule ? '&:extend(' : ':extend(')) {
                    return;
                }

                do {
                    option = null;
                    elements = null;
                    let first = true;
                    while (!(option = parserInput.$re(/^(!?all)(?=\s*(\)|,))/))) {
                        e = this.element();

                        if (!e) {
                            break;
                        }
                        /**
                         * @note - This will not catch selectors in pseudos like :is() and :where() because
                         * they don't currently parse their contents as selectors.
                         */
                        if (!first && e.combinator.value) {
                            warn('Targeting complex selectors can have unexpected behavior, and this behavior may change in the future.', index);
                        }

                        first = false;
                        if (elements) {
                            elements.push(e);
                        } else {
                            elements = [ e ];
                        }
                    }

                    option = option && option[1];
                    if (!elements) {
                        error('Missing target selector for :extend().');
                    }
                    extend = new(tree.Extend)(new(tree.Selector)(elements), option, index + currentIndex, fileInfo);
                    if (extendList) {
                        extendList.push(extend);
                    } else {
                        extendList = [ extend ];
                    }
                } while (parserInput.$char(','));

                expect(/^\)/);

                if (isRule) {
                    expect(/^;/);
                }

                return extendList;
            },

            //
            // extendRule - used in a rule to extend all the parent selectors
            //
            extendRule: function() {
                return this.extend(true);
            },

            //
            // Mixins
            //
            mixin: {
                //
                // A Mixin call, with an optional argument list
                //
                //     #mixins > .square(#fff);
                //     #mixins.square(#fff);
                //     .rounded(4px, black);
                //     .button;
                //
                // We can lookup / return a value using the lookup syntax:
                //
                //     color: #mixin.square(#fff)[@color];
                //
                // The `while` loop is there because mixins can be
                // namespaced, but we only support the child and descendant
                // selector for now.
                //
                call: function (inValue, getLookup) {
                    const s = parserInput.currentChar();
                    let important = false;
                    let lookups;
                    const index = parserInput.i;
                    let elements;
                    let args;
                    let hasParens;
                    let parensIndex;
                    let parensWS = false;

                    if (s !== '.' && s !== '#') { return; }

                    parserInput.save(); // stop us absorbing part of an invalid selector

                    elements = this.elements();

                    if (elements) {
                        parensIndex = parserInput.i;
                        parensWS = parserInput.isWhitespace(-1);
                        if (parserInput.$char('(')) { 
                            args = this.args(true).args;
                            expectChar(')');
                            hasParens = true;
                            if (parensWS) {
                                warn('Whitespace between a mixin name and parentheses for a mixin call is deprecated', parensIndex, 'DEPRECATED', 'mixin-call-whitespace');
                            }
                        }

                        if (getLookup !== false) {
                            lookups = this.ruleLookups();
                        }
                        if (getLookup === true && !lookups) {
                            parserInput.restore();
                            return;
                        }

                        if (inValue && !lookups && !hasParens) {
                            // This isn't a valid in-value mixin call
                            parserInput.restore();
                            return;
                        }

                        if (!inValue && parsers.important()) {
                            important = true;
                        }

                        if (inValue || parsers.end()) {
                            parserInput.forget();
                            const mixin = new(tree.mixin.Call)(elements, args, index + currentIndex, fileInfo, !lookups && important);
                            if (lookups) {
                                return new tree.NamespaceValue(mixin, lookups);
                            }
                            else {
                                if (!hasParens) {
                                    warn('Calling a mixin without parentheses is deprecated', parensIndex, 'DEPRECATED', 'mixin-call-no-parens');
                                }
                                return mixin;
                            }
                        }
                    }

                    parserInput.restore();
                },
                /**
                 * Matching elements for mixins
                 * (Start with . or # and can have > )
                 */
                elements: function() {
                    let elements;
                    let e;
                    let c;
                    let elem;
                    let elemIndex;
                    const re = /^[#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/;
                    while (true) {
                        elemIndex = parserInput.i;
                        e = parserInput.$re(re);

                        if (!e) {
                            break;
                        }
                        elem = new(tree.Element)(c, e, false, elemIndex + currentIndex, fileInfo);
                        if (elements) {
                            elements.push(elem);
                        } else {
                            elements = [ elem ];
                        }
                        c = parserInput.$char('>');
                    }
                    return elements;
                },
                args: function (isCall) {
                    const entities = parsers.entities;
                    const returner = { args:null, variadic: false };
                    let expressions = [];
                    const argsSemiColon = [];
                    const argsComma = [];
                    let isSemiColonSeparated;
                    let expressionContainsNamed;
                    let name;
                    let nameLoop;
                    let value;
                    let arg;
                    let expand;
                    let hasSep = true;

                    parserInput.save();

                    while (true) {
                        if (isCall) {
                            arg = parsers.detachedRuleset() || parsers.expression();
                        } else {
                            parserInput.commentStore.length = 0;
                            if (parserInput.$str('...')) {
                                returner.variadic = true;
                                if (parserInput.$char(';') && !isSemiColonSeparated) {
                                    isSemiColonSeparated = true;
                                }
                                (isSemiColonSeparated ? argsSemiColon : argsComma)
                                    .push({ variadic: true });
                                break;
                            }
                            arg = entities.variable() || entities.property() || entities.literal() || entities.keyword() || this.call(true);
                        }

                        if (!arg || !hasSep) {
                            break;
                        }

                        nameLoop = null;
                        if (arg.throwAwayComments) {
                            arg.throwAwayComments();
                        }
                        value = arg;
                        let val = null;

                        if (isCall) {
                            // Variable
                            if (arg.value && arg.value.length == 1) {
                                val = arg.value[0];
                            }
                        } else {
                            val = arg;
                        }

                        if (val && (val instanceof tree.Variable || val instanceof tree.Property)) {
                            if (parserInput.$char(':')) {
                                if (expressions.length > 0) {
                                    if (isSemiColonSeparated) {
                                        error('Cannot mix ; and , as delimiter types');
                                    }
                                    expressionContainsNamed = true;
                                }

                                value = parsers.detachedRuleset() || parsers.expression();

                                if (!value) {
                                    if (isCall) {
                                        error('could not understand value for named argument');
                                    } else {
                                        parserInput.restore();
                                        returner.args = [];
                                        return returner;
                                    }
                                }
                                nameLoop = (name = val.name);
                            } else if (parserInput.$str('...')) {
                                if (!isCall) {
                                    returner.variadic = true;
                                    if (parserInput.$char(';') && !isSemiColonSeparated) {
                                        isSemiColonSeparated = true;
                                    }
                                    (isSemiColonSeparated ? argsSemiColon : argsComma)
                                        .push({ name: arg.name, variadic: true });
                                    break;
                                } else {
                                    expand = true;
                                }
                            } else if (!isCall) {
                                name = nameLoop = val.name;
                                value = null;
                            }
                        }

                        if (value) {
                            expressions.push(value);
                        }

                        argsComma.push({ name:nameLoop, value, expand });

                        if (parserInput.$char(',')) {
                            hasSep = true;
                            continue;
                        }
                        hasSep = parserInput.$char(';') === ';';

                        if (hasSep || isSemiColonSeparated) {

                            if (expressionContainsNamed) {
                                error('Cannot mix ; and , as delimiter types');
                            }

                            isSemiColonSeparated = true;

                            if (expressions.length > 1) {
                                value = new(tree.Value)(expressions);
                            }
                            argsSemiColon.push({ name, value, expand });

                            name = null;
                            expressions = [];
                            expressionContainsNamed = false;
                        }
                    }

                    parserInput.forget();
                    returner.args = isSemiColonSeparated ? argsSemiColon : argsComma;
                    return returner;
                },
                //
                // A Mixin definition, with a list of parameters
                //
                //     .rounded (@radius: 2px, @color) {
                //        ...
                //     }
                //
                // Until we have a finer grained state-machine, we have to
                // do a look-ahead, to make sure we don't have a mixin call.
                // See the `rule` function for more information.
                //
                // We start by matching `.rounded (`, and then proceed on to
                // the argument list, which has optional default values.
                // We store the parameters in `params`, with a `value` key,
                // if there is a value, such as in the case of `@radius`.
                //
                // Once we've got our params list, and a closing `)`, we parse
                // the `{...}` block.
                //
                definition: function () {
                    let name;
                    let params = [];
                    let match;
                    let ruleset;
                    let cond;
                    let variadic = false;
                    if ((parserInput.currentChar() !== '.' && parserInput.currentChar() !== '#') ||
                        parserInput.peek(/^[^{]*\}/)) {
                        return;
                    }

                    parserInput.save();

                    match = parserInput.$re(/^([#.](?:[\w-]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+)\s*\(/);
                    if (match) {
                        name = match[1];

                        const argInfo = this.args(false);
                        params = argInfo.args;
                        variadic = argInfo.variadic;

                        // .mixincall("@{a}");
                        // looks a bit like a mixin definition..
                        // also
                        // .mixincall(@a: {rule: set;});
                        // so we have to be nice and restore
                        if (!parserInput.$char(')')) {
                            parserInput.restore('Missing closing \')\'');
                            return;
                        }

                        parserInput.commentStore.length = 0;

                        if (parserInput.$str('when')) { // Guard
                            cond = expect(parsers.conditions, 'expected condition');
                        }

                        ruleset = parsers.block();

                        if (ruleset) {
                            parserInput.forget();
                            return new(tree.mixin.Definition)(name, params, ruleset, cond, variadic);
                        } else {
                            parserInput.restore();
                        }
                    } else {
                        parserInput.restore();
                    }
                },

                ruleLookups: function() {
                    let rule;
                    const lookups = [];

                    if (parserInput.currentChar() !== '[') {
                        return;
                    }

                    while (true) {
                        parserInput.save();
                        rule = this.lookupValue();
                        if (!rule && rule !== '') {
                            parserInput.restore();
                            break;
                        }
                        lookups.push(rule);
                        parserInput.forget();
                    }
                    if (lookups.length > 0) {
                        return lookups;
                    }
                },

                lookupValue: function() {
                    parserInput.save();

                    if (!parserInput.$char('[')) {
                        parserInput.restore();
                        return;
                    }

                    const name = parserInput.$re(/^(?:[@$]{0,2})[_a-zA-Z0-9-]*/);

                    if (!parserInput.$char(']')) {
                        parserInput.restore();
                        return;
                    }

                    if (name || name === '') {
                        parserInput.forget();
                        return name;
                    }

                    parserInput.restore();
                }
            },
            //
            // Entities are the smallest recognized token,
            // and can be found inside a rule's value.
            //
            entity: function () {
                const entities = this.entities;

                return this.comment() || entities.literal() || entities.variable() || entities.url() ||
                    entities.property() || entities.call() || entities.keyword() || this.mixin.call(true) ||
                    entities.javascript();
            },

            //
            // A Declaration terminator. Note that we use `peek()` to check for '}',
            // because the `block` rule will be expecting it, but we still need to make sure
            // it's there, if ';' was omitted.
            //
            end: function () {
                return parserInput.$char(';') || parserInput.peek('}');
            },

            //
            // IE's alpha function
            //
            //     alpha(opacity=88)
            //
            ieAlpha: function () {
                let value;

                // http://jsperf.com/case-insensitive-regex-vs-strtolower-then-regex/18
                if (!parserInput.$re(/^opacity=/i)) { return; }
                value = parserInput.$re(/^\d+/);
                if (!value) {
                    value = expect(parsers.entities.variable, 'Could not parse alpha');
                    value = `@{${value.name.slice(1)}}`;
                }
                expectChar(')');
                return new tree.Quoted('', `alpha(opacity=${value})`);
            },

            /** 
             * A Selector Element
             *
             *   div
             *   + h1
             *   #socks
             *   input[type="text"]
             *
             * Elements are the building blocks for Selectors,
             * they are made out of a `Combinator` (see combinator rule),
             * and an element name, such as a tag a class, or `*`.
             */
            element: function () {
                let e;
                let c;
                let v;
                const index = parserInput.i;

                c = this.combinator();

                /** This selector parser is quite simplistic and will pass a number of invalid selectors. */
                e = parserInput.$re(/^(?:\d+\.\d+|\d+)%/) ||
                    // eslint-disable-next-line no-control-regex
                    parserInput.$re(/^(?:[.#]?|:*)(?:[\w-]|[^\x00-\x9f]|\\(?:[A-Fa-f0-9]{1,6} ?|[^A-Fa-f0-9]))+/) ||
                    parserInput.$char('*') || parserInput.$char('&') || this.attribute() ||
                    parserInput.$re(/^\([^&()@]+\)/) ||  parserInput.$re(/^[.#:](?=@)/) ||
                    this.entities.variableCurly();

                if (!e) {
                    parserInput.save();
                    if (parserInput.$char('(')) {
                        if ((v = this.selector(false))) {
                            let selectors = [];
                            while (parserInput.$char(',')) {
                                selectors.push(v);
                                selectors.push(new Anonymous(','));
                                v = this.selector(false);
                            }
                            selectors.push(v);
                                                        
                            if (parserInput.$char(')')) {
                                if (selectors.length > 1) {
                                    e = new (tree.Paren)(new Selector(selectors));
                                } else {
                                    e = new(tree.Paren)(v);
                                }
                                parserInput.forget();
                            } else {
                                parserInput.restore('Missing closing \')\'');
                            }
                        } else {
                            parserInput.restore('Missing closing \')\'');
                        }
                    } else {
                        parserInput.forget();
                    }
                }

                if (e) { return new(tree.Element)(c, e, e instanceof tree.Variable, index + currentIndex, fileInfo); }
            },

            //
            // Combinators combine elements together, in a Selector.
            //
            // Because our parser isn't white-space sensitive, special care
            // has to be taken, when parsing the descendant combinator, ` `,
            // as it's an empty space. We have to check the previous character
            // in the input, to see if it's a ` ` character. More info on how
            // we deal with this in *combinator.js*.
            //
            combinator: function () {
                let c = parserInput.currentChar();

                if (c === '/') {
                    parserInput.save();
                    const slashedCombinator = parserInput.$re(/^\/[a-z]+\//i);
                    if (slashedCombinator) {
                        parserInput.forget();
                        return new(tree.Combinator)(slashedCombinator);
                    }
                    parserInput.restore();
                }

                if (c === '>' || c === '+' || c === '~' || c === '|' || c === '^') {
                    parserInput.i++;
                    if (c === '^' && parserInput.currentChar() === '^') {
                        c = '^^';
                        parserInput.i++;
                    }
                    while (parserInput.isWhitespace()) { parserInput.i++; }
                    return new(tree.Combinator)(c);
                } else if (parserInput.isWhitespace(-1)) {
                    return new(tree.Combinator)(' ');
                } else {
                    return new(tree.Combinator)(null);
                }
            },
            //
            // A CSS Selector
            // with less extensions e.g. the ability to extend and guard
            //
            //     .class > div + h1
            //     li a:hover
            //
            // Selectors are made out of one or more Elements, see above.
            //
            selector: function (isLess) {
                const index = parserInput.i;
                let elements;
                let extendList;
                let c;
                let e;
                let allExtends;
                let when;
                let condition;
                isLess = isLess !== false;
                while ((isLess && (extendList = this.extend())) || (isLess && (when = parserInput.$str('when'))) || (e = this.element())) {
                    if (when) {
                        condition = expect(this.conditions, 'expected condition');
                    } else if (condition) {
                        error('CSS guard can only be used at the end of selector');
                    } else if (extendList) {
                        if (allExtends) {
                            allExtends = allExtends.concat(extendList);
                        } else {
                            allExtends = extendList;
                        }
                    } else {
                        if (allExtends) { error('Extend can only be used at the end of selector'); }
                        c = parserInput.currentChar();
                        if (Array.isArray(e)){
                            e.forEach(ele => elements.push(ele));
                        } if (elements) {
                            elements.push(e);
                        } else {
                            elements = [ e ];
                        }
                        e = null;
                    }
                    if (c === '{' || c === '}' || c === ';' || c === ',' || c === ')') {
                        break;
                    }
                }

                if (elements) { return new(tree.Selector)(elements, allExtends, condition, index + currentIndex, fileInfo); }
                if (allExtends) { error('Extend must be used to extend a selector, it cannot be used on its own'); }
            },
            selectors: function () {
                let s;
                let selectors;
                while (true) {
                    s = this.selector();
                    if (!s) {
                        break;
                    }
                    if (selectors) {
                        selectors.push(s);
                    } else {
                        selectors = [ s ];
                    }
                    parserInput.commentStore.length = 0;
                    if (s.condition && selectors.length > 1) {
                        error('Guards are only currently allowed on a single selector.');
                    }
                    if (!parserInput.$char(',')) { break; }
                    if (s.condition) {
                        error('Guards are only currently allowed on a single selector.');
                    }
                    parserInput.commentStore.length = 0;
                }
                return selectors;
            },
            attribute: function () {
                if (!parserInput.$char('[')) { return; }

                const entities = this.entities;
                let key;
                let val;
                let op;
                //
                // case-insensitive flag
                // e.g. [attr operator value i]
                //
                let cif;

                if (!(key = entities.variableCurly())) {
                    key = expect(/^(?:[_A-Za-z0-9-*]*\|)?(?:[_A-Za-z0-9-]|\\.)+/);
                }

                op = parserInput.$re(/^[|~*$^]?=/);
                if (op) {
                    val = entities.quoted() || parserInput.$re(/^[0-9]+%/) || parserInput.$re(/^[\w-]+/) || entities.variableCurly();
                    if (val) {
                        cif = parserInput.$re(/^[iIsS]/);
                    }
                }

                expectChar(']');

                return new(tree.Attribute)(key, op, val, cif);
            },

            //
            // The `block` rule is used by `ruleset` and `mixin.definition`.
            // It's a wrapper around the `primary` rule, with added `{}`.
            //
            block: function () {
                let content;
                if (parserInput.$char('{') && (content = this.primary()) && parserInput.$char('}')) {
                    return content;
                }
            },

            blockRuleset: function() {
                let block = this.block();
                if (block) {
                    return new tree.Ruleset(null, block);
                }
            },

            detachedRuleset: function() {
                let argInfo;
                let params;
                let variadic;

                parserInput.save();
                if (parserInput.$re(/^[.#]\(/)) {
                    /**
                     * DR args currently only implemented for each() function, and not
                     * yet settable as `@dr: #(@arg) {}`
                     * This should be done when DRs are merged with mixins.
                     * See: https://github.com/less/less-meta/issues/16
                     */
                    argInfo = this.mixin.args(false);
                    params = argInfo.args;
                    variadic = argInfo.variadic;
                    if (!parserInput.$char(')')) {
                        parserInput.restore();
                        return;
                    }
                }
                const blockRuleset = this.blockRuleset();
                if (blockRuleset) {
                    parserInput.forget();
                    if (params) {
                        return new tree.mixin.Definition(null, params, blockRuleset, null, variadic);
                    }
                    return new tree.DetachedRuleset(blockRuleset);
                }
                parserInput.restore();
            },

            //
            // div, .class, body > p {...}
            //
            ruleset: function () {
                let selectors;
                let rules;
                let debugInfo;

                parserInput.save();

                if (context.dumpLineNumbers) {
                    debugInfo = getDebugInfo(parserInput.i);
                }

                selectors = this.selectors();

                if (selectors && (rules = this.block())) {
                    parserInput.forget();
                    const ruleset = new(tree.Ruleset)(selectors, rules, context.strictImports);
                    if (context.dumpLineNumbers) {
                        ruleset.debugInfo = debugInfo;
                    }
                    return ruleset;
                } else {
                    parserInput.restore();
                }
            },
            declaration: function () {
                let name;
                let value;
                const index = parserInput.i;
                let hasDR;
                const c = parserInput.currentChar();
                let important;
                let merge;
                let isVariable;

                if (c === '.' || c === '#' || c === '&' || c === ':') { return; }

                parserInput.save();

                name = this.variable() || this.ruleProperty();
                if (name) {
                    isVariable = typeof name === 'string';

                    if (isVariable) {
                        value = this.detachedRuleset();
                        if (value) {
                            hasDR = true;
                        }
                    }

                    parserInput.commentStore.length = 0;
                    if (!value) {
                        // a name returned by this.ruleProperty() is always an array of the form:
                        // [string-1, ..., string-n, ""] or [string-1, ..., string-n, "+"]
                        // where each item is a tree.Keyword or tree.Variable
                        merge = !isVariable && name.length > 1 && name.pop().value;

                        // Custom property values get permissive parsing
                        if (name[0].value && name[0].value.slice(0, 2) === '--') {
                            if (parserInput.$char(';')) {
                                value = new Anonymous('');
                            } else {
                                value = this.permissiveValue(/[;}]/, true);
                            }
                        }
                        // Try to store values as anonymous
                        // If we need the value later we'll re-parse it in ruleset.parseValue
                        else {
                            value = this.anonymousValue();
                        }
                        if (value) {
                            parserInput.forget();
                            // anonymous values absorb the end ';' which is required for them to work
                            return new(tree.Declaration)(name, value, false, merge, index + currentIndex, fileInfo);
                        }

                        if (!value) {
                            value = this.value();
                        }

                        if (value) {
                            important = this.important();
                        } else if (isVariable) {
                            /**
                             * As a last resort, try permissiveValue
                             *
                             * @todo - This has created some knock-on problems of not
                             * flagging incorrect syntax or detecting user intent.
                             */
                            value = this.permissiveValue();
                        }
                    }

                    if (value && (this.end() || hasDR)) {
                        parserInput.forget();
                        return new(tree.Declaration)(name, value, important, merge, index + currentIndex, fileInfo);
                    }
                    else {
                        parserInput.restore();
                    }
                } else {
                    parserInput.restore();
                }
            },
            anonymousValue: function () {
                const index = parserInput.i;
                const match = parserInput.$re(/^([^.#@$+/'"*`(;{}-]*);/);
                if (match) {
                    return new(tree.Anonymous)(match[1], index + currentIndex);
                }
            },
            /**
             * Used for custom properties, at-rules, and variables (as fallback)
             * Parses almost anything inside of {} [] () "" blocks
             * until it reaches outer-most tokens.
             *
             * First, it will try to parse comments and entities to reach
             * the end. This is mostly like the Expression parser except no
             * math is allowed.
             * 
             * @param {RexExp} untilTokens - Characters to stop parsing at
             */
            permissiveValue: function (untilTokens) {
                let i;
                let e;
                let done;
                let value;
                const tok = untilTokens || ';';
                const index = parserInput.i;
                const result = [];

                function testCurrentChar() {
                    const char = parserInput.currentChar();
                    if (typeof tok === 'string') {
                        return char === tok;
                    } else {
                        return tok.test(char);
                    }
                }
                if (testCurrentChar()) {
                    return;
                }
                value = [];
                do {
                    e = this.comment();
                    if (e) {
                        value.push(e);
                        continue;
                    }
                    e = this.entity();
                    if (e) {
                        value.push(e);
                    }
                    if (parserInput.peek(',')) {
                        value.push(new (tree.Anonymous)(',', parserInput.i));
                        parserInput.$char(',');
                    }
                } while (e);

                done = testCurrentChar();

                if (value.length > 0) {
                    value = new(tree.Expression)(value);
                    if (done) {
                        return value;
                    }
                    else {
                        result.push(value);
                    }
                    // Preserve space before $parseUntil as it will not
                    if (parserInput.prevChar() === ' ') {
                        result.push(new tree.Anonymous(' ', index));
                    }
                }
                parserInput.save();

                value = parserInput.$parseUntil(tok);

                if (value) {
                    if (typeof value === 'string') {
                        error(`Expected '${value}'`, 'Parse');
                    }
                    if (value.length === 1 && value[0] === ' ') {
                        parserInput.forget();
                        return new tree.Anonymous('', index);
                    }
                    /** @type {string} */
                    let item;
                    for (i = 0; i < value.length; i++) {
                        item = value[i];
                        if (Array.isArray(item)) {
                            // Treat actual quotes as normal quoted values
                            result.push(new tree.Quoted(item[0], item[1], true, index, fileInfo));
                        }
                        else {
                            if (i === value.length - 1) {
                                item = item.trim();
                            }
                            // Treat like quoted values, but replace vars like unquoted expressions
                            const quote = new tree.Quoted('\'', item, true, index, fileInfo);
                            const variableRegex = /@([\w-]+)/g;
                            const propRegex = /\$([\w-]+)/g;
                            if (variableRegex.test(item)) {
                                warn('@[ident] in unknown values will not be evaluated as variables in the future. Use @{[ident]}', index, 'DEPRECATED', 'variable-in-unknown-value');
                            }
                            if (propRegex.test(item)) {
                                warn('$[ident] in unknown values will not be evaluated as property references in the future. Use ${[ident]}', index, 'DEPRECATED', 'property-in-unknown-value');
                            }
                            quote.variableRegex = /@([\w-]+)|@{([\w-]+)}/g;
                            quote.propRegex = /\$([\w-]+)|\${([\w-]+)}/g;
                            result.push(quote);
                        }
                    }
                    parserInput.forget();
                    return new tree.Expression(result, true);
                }
                parserInput.restore();
            },

            //
            // An @import atrule
            //
            //     @import "lib";
            //
            // Depending on our environment, importing is done differently:
            // In the browser, it's an XHR request, in Node, it would be a
            // file-system operation. The function used for importing is
            // stored in `import`, which we pass to the Import constructor.
            //
            'import': function () {
                let path;
                let features;
                const index = parserInput.i;

                const dir = parserInput.$re(/^@import\s+/);

                if (dir) {
                    const options = (dir ? this.importOptions() : null) || {};

                    if ((path = this.entities.quoted() || this.entities.url())) {
                        features = this.mediaFeatures({});

                        if (!parserInput.$char(';')) {
                            parserInput.i = index;
                            error('missing semi-colon or unrecognised media features on import');
                        }
                        features = features && new(tree.Value)(features);
                        return new(tree.Import)(path, features, options, index + currentIndex, fileInfo);
                    }
                    else {
                        parserInput.i = index;
                        error('malformed import statement');
                    }
                }
            },

            importOptions: function() {
                let o;
                const options = {};
                let optionName;
                let value;

                // list of options, surrounded by parens
                if (!parserInput.$char('(')) { return null; }
                do {
                    o = this.importOption();
                    if (o) {
                        optionName = o;
                        value = true;
                        switch (optionName) {
                            case 'css':
                                optionName = 'less';
                                value = false;
                                break;
                            case 'once':
                                optionName = 'multiple';
                                value = false;
                                break;
                        }
                        options[optionName] = value;
                        if (!parserInput.$char(',')) { break; }
                    }
                } while (o);
                expectChar(')');
                return options;
            },

            importOption: function() {
                const opt = parserInput.$re(/^(less|css|multiple|once|inline|reference|optional)/);
                if (opt) {
                    return opt[1];
                }
            },

            mediaFeature: function (syntaxOptions) {
                const entities = this.entities;
                const nodes = [];
                let e;
                let p;
                let rangeP;
                let spacing = false;
                parserInput.save();
                do {
                    parserInput.save();
                    if (parserInput.$re(/^[0-9a-z-]*\s+\(/)) {
                        spacing = true;
                    }
                    parserInput.restore();

                    e = entities.declarationCall.bind(this)() || entities.keyword() || entities.variable() || entities.mixinLookup();
                    if (e) {
                        nodes.push(e);
                        if (e.type === 'Variable' ||
                            (e.type === 'Keyword' && /^(and|or|not|only)$/i.test(e.value))) {
                            spacing = true;
                        }
                    } else if (parserInput.$char('(')) {
                        p = this.property();
                        parserInput.save();
                        if (!p && syntaxOptions.queryInParens && parserInput.$re(/^[0-9a-z-]*\s*([<>]=|<=|>=|[<>]|=)/)) {
                            parserInput.restore();
                            p = this.condition();

                            parserInput.save();
                            rangeP = this.atomicCondition(null, p.rvalue);
                            if (!rangeP) {
                                parserInput.restore();
                            }
                        } else {
                            parserInput.restore();
                            e = this.value();
                        }
                        if (parserInput.$char(')')) {
                            if (p && !e) {
                                nodes.push(new (tree.Paren)(new (tree.QueryInParens)(p.op, p.lvalue, p.rvalue, rangeP ? rangeP.op : null, rangeP ? rangeP.rvalue : null, p._index)));
                                e = p;
                            } else if (p && e) {
                                nodes.push(new (tree.Paren)(new (tree.Declaration)(p, e, null, null, parserInput.i + currentIndex, fileInfo, true)));
                                if (!spacing) {
                                    nodes[nodes.length - 1].noSpacing = true;
                                }
                                spacing = false;
                            } else if (e) {
                                nodes.push(new(tree.Paren)(e));
                                spacing = false;
                            } else {
                                error('badly formed media feature definition');
                            }
                        } else {
                            error('Missing closing \')\'', 'Parse');
                        }
                    }
                } while (e);

                parserInput.forget();
                if (nodes.length > 0) {
                    return new(tree.Expression)(nodes);
                }
            },

            mediaFeatures: function (syntaxOptions) {
                const entities = this.entities;
                const features = [];
                let e;
                do {
                    e = this.mediaFeature(syntaxOptions);
                    if (e) {
                        features.push(e);
                        if (!parserInput.$char(',')) { break; }
                        else if (!features[features.length - 1].noSpacing) {
                            features[features.length - 1].noSpacing = false;
                        }
                    } else {
                        e = entities.variable() || entities.mixinLookup();
                        if (e) {
                            features.push(e);
                            if (!parserInput.$char(',')) { break; }
                            else if (!features[features.length - 1].noSpacing) {
                                features[features.length - 1].noSpacing = false;
                            }
                        }
                    }
                } while (e);

                return features.length > 0 ? features : null;
            },

            prepareAndGetNestableAtRule: function (treeType, index, debugInfo, syntaxOptions) {
                const features = this.mediaFeatures(syntaxOptions);

                const rules = this.block();

                if (!rules) {
                    error('media definitions require block statements after any features');
                }

                parserInput.forget();

                const atRule = new (treeType)(rules, features, index + currentIndex, fileInfo);
                if (context.dumpLineNumbers) {
                    atRule.debugInfo = debugInfo;
                }

                return atRule;
            },

            nestableAtRule: function () {
                let debugInfo;
                const index = parserInput.i;

                if (context.dumpLineNumbers) {
                    debugInfo = getDebugInfo(index);
                }
                parserInput.save();

                if (parserInput.$peekChar('@')) {
                    if (parserInput.$str('@media')) {
                        return this.prepareAndGetNestableAtRule(tree.Media, index, debugInfo, MediaSyntaxOptions);
                    }

                    if (parserInput.$str('@container')) {
                        return this.prepareAndGetNestableAtRule(tree.Container, index, debugInfo, ContainerSyntaxOptions);
                    }
                }

                parserInput.restore();
            },

            //

            // A @plugin directive, used to import plugins dynamically.
            //
            //     @plugin (args) "lib";
            //
            plugin: function () {
                let path;
                let args;
                let options;
                const index = parserInput.i;
                const dir   = parserInput.$re(/^@plugin\s+/);

                if (dir) {
                    warn('The @plugin directive is deprecated and will be replaced in Less 5.x. Use --plugin CLI option or the programmatic plugin API instead.', index, 'DEPRECATED', 'at-plugin');
                    args = this.pluginArgs();

                    if (args) {
                        options = {
                            pluginArgs: args,
                            isPlugin: true
                        };
                    }
                    else {
                        options = { isPlugin: true };
                    }

                    if ((path = this.entities.quoted() || this.entities.url())) {

                        if (!parserInput.$char(';')) {
                            parserInput.i = index;
                            error('missing semi-colon on @plugin');
                        }
                        return new(tree.Import)(path, null, options, index + currentIndex, fileInfo);
                    }
                    else {
                        parserInput.i = index;
                        error('malformed @plugin statement');
                    }
                }
            },

            pluginArgs: function() {
                // list of options, surrounded by parens
                parserInput.save();
                if (!parserInput.$char('(')) {
                    parserInput.restore();
                    return null;
                }
                const args = parserInput.$re(/^\s*([^);]+)\)\s*/);
                if (args[1]) {
                    parserInput.forget();
                    return args[1].trim();
                }
                else {
                    parserInput.restore();
                    return null;
                }
            },
            atruleUnknown: function (value, name, hasBlock) {
                value = this.permissiveValue(/^[{;]/);
                hasBlock = (parserInput.currentChar() === '{');
                if (!value) {
                    if (!hasBlock && parserInput.currentChar() !== ';') {
                        error(''.concat(name, ' rule is missing block or ending semi-colon'));
                    }
                }
                else if (!value.value) {
                    value = null;
                }
                return [value, hasBlock];
            },
            atruleBlock: function (rules, value, isRooted, isKeywordList) {
                rules = this.blockRuleset();
                parserInput.save();
                if (!rules && !isRooted) {
                    value = this.entity();
                    rules = this.blockRuleset();
                }
                if (!rules && !isRooted) {
                    parserInput.restore();
                    var e = [];
                    value = this.entity();
                    while (parserInput.$char(',')) {
                        e.push(value);
                        value = this.entity();
                    }
                    if (value && e.length > 0) {
                        e.push(value);
                        value = e;
                        isKeywordList = true;
                    }
                    else {
                        rules = this.blockRuleset();
                    }
                }
                else {
                    parserInput.forget();
                }
                    
                return [rules, value, isKeywordList];
            },
            //
            // A CSS AtRule
            //
            //     @charset "utf-8";
            //
            atrule: function () {
                const index = parserInput.i;
                let name;
                let value;
                let rules;
                let nonVendorSpecificName;
                let hasIdentifier;
                let hasExpression;
                let hasUnknown;
                let hasBlock = true;
                let isRooted = true;
                let isKeywordList = false;

                if (parserInput.currentChar() !== '@') { return; }

                value = this['import']() || this.plugin() || this.nestableAtRule();
                if (value) {
                    return value;
                }

                parserInput.save();

                name = parserInput.$re(/^@[a-z-]+/);

                if (!name) { return; }

                nonVendorSpecificName = name;
                if (name.charAt(1) == '-' && name.indexOf('-', 2) > 0) {
                    nonVendorSpecificName = `@${name.slice(name.indexOf('-', 2) + 1)}`;
                }

                switch (nonVendorSpecificName) {
                    case '@charset':
                        hasIdentifier = true;
                        hasBlock = false;
                        break;
                    case '@namespace':
                        hasExpression = true;
                        hasBlock = false;
                        break;
                    case '@keyframes':
                    case '@counter-style':
                        hasIdentifier = true;
                        break;
                    case '@document':
                    case '@supports':
                        hasUnknown = true;
                        isRooted = false;
                        break;
                    case '@starting-style':
                        isRooted = false;
                        break;
                    case '@layer':
                        isRooted = false;
                        break;
                    default:
                        hasUnknown = true;
                        break;
                }

                parserInput.commentStore.length = 0;

                if (hasIdentifier) {
                    value = this.entity();
                    if (!value) {
                        error(`expected ${name} identifier`);
                    }
                } else if (hasExpression) {
                    value = this.expression();
                    if (!value) {
                        error(`expected ${name} expression`);
                    }
                } else if (hasUnknown) {
                    const unknownPackage = this.atruleUnknown(value, name, hasBlock);
                    value = unknownPackage[0];
                    hasBlock = unknownPackage[1];
                }
                    
                if (hasBlock) {
                    let blockPackage = this.atruleBlock(rules, value, isRooted, isKeywordList);
                    rules = blockPackage[0];
                    value = blockPackage[1];
                    isKeywordList = blockPackage[2];

                    if (!rules && !hasUnknown) {
                        parserInput.restore();
                        name = parserInput.$re(/^@[a-z-]+/);
                        const unknownPackage = this.atruleUnknown(value, name, hasBlock);
                        value = unknownPackage[0];
                        hasBlock = unknownPackage[1];
                        if (hasBlock) {
                            blockPackage = this.atruleBlock(rules, value, isRooted, isKeywordList);
                            rules = blockPackage[0];
                            value = blockPackage[1];
                            isKeywordList = blockPackage[2];
                        }
                    }
                }

                if (rules || isKeywordList || (!hasBlock && value && parserInput.$char(';'))) {
                    parserInput.forget();
                    return new(tree.AtRule)(name, value, rules, index + currentIndex, fileInfo,
                        context.dumpLineNumbers ? getDebugInfo(index) : null,
                        isRooted
                    );
                }

                parserInput.restore('at-rule options not recognised');
            },

            //
            // A Value is a comma-delimited list of Expressions
            //
            //     font-family: Baskerville, Georgia, serif;
            //
            // In a Rule, a Value represents everything after the `:`,
            // and before the `;`.
            //
            value: function () {
                let e;
                const expressions = [];
                const index = parserInput.i;

                do {
                    e = this.expression();
                    if (e) {
                        expressions.push(e);
                        if (!parserInput.$char(',')) { break; }
                    }
                } while (e);

                if (expressions.length > 0) {
                    return new(tree.Value)(expressions, index + currentIndex);
                }
            },
            important: function () {
                if (parserInput.currentChar() === '!') {
                    return parserInput.$re(/^! *important/);
                }
            },
            sub: function () {
                let a;
                let e;

                parserInput.save();
                if (parserInput.$char('(')) {
                    a = this.addition();
                    if (a && parserInput.$char(')')) {
                        parserInput.forget();
                        e = new(tree.Expression)([a]);
                        e.parens = true;
                        return e;
                    }
                    parserInput.restore('Expected \')\'');
                    return;
                }
                parserInput.restore();
            },
            colorOperand: function () {
                parserInput.save();

                // hsl or rgb or lch operand
                const match = parserInput.$re(/^[lchrgbs]\s+/);
                if (match) {
                    parserInput.forget();
                    return new tree.Keyword(match[0]);
                }

                parserInput.restore();
            },
            multiplication: function () {
                let m;
                let a;
                let op;
                let operation;
                let isSpaced;
                m = this.operand();
                if (m) {
                    isSpaced = parserInput.isWhitespace(-1);
                    while (true) {
                        if (parserInput.peek(/^\/[*/]/)) {
                            break;
                        }

                        parserInput.save();

                        op = parserInput.$char('/') || parserInput.$char('*');
                        if (!op) {
                            let index = parserInput.i;
                            op = parserInput.$str('./');
                            if (op) {
                                warn('./ operator is deprecated', index, 'DEPRECATED', 'dot-slash-operator');
                            }
                        }

                        if (!op) { parserInput.forget(); break; }

                        a = this.operand();

                        if (!a) { parserInput.restore(); break; }
                        parserInput.forget();

                        m.parensInOp = true;
                        a.parensInOp = true;
                        operation = new(tree.Operation)(op, [operation || m, a], isSpaced);
                        isSpaced = parserInput.isWhitespace(-1);
                    }
                    return operation || m;
                }
            },
            addition: function () {
                let m;
                let a;
                let op;
                let operation;
                let isSpaced;
                m = this.multiplication();
                if (m) {
                    isSpaced = parserInput.isWhitespace(-1);
                    while (true) {
                        op = parserInput.$re(/^[-+]\s+/) || (!isSpaced && (parserInput.$char('+') || parserInput.$char('-')));
                        if (!op) {
                            break;
                        }
                        a = this.multiplication();
                        if (!a) {
                            break;
                        }

                        m.parensInOp = true;
                        a.parensInOp = true;
                        operation = new(tree.Operation)(op, [operation || m, a], isSpaced);
                        isSpaced = parserInput.isWhitespace(-1);
                    }
                    return operation || m;
                }
            },
            conditions: function () {
                let a;
                let b;
                const index = parserInput.i;
                let condition;

                a = this.condition(true);
                if (a) {
                    while (true) {
                        if (!parserInput.peek(/^,\s*(not\s*)?\(/) || !parserInput.$char(',')) {
                            break;
                        }
                        b = this.condition(true);
                        if (!b) {
                            break;
                        }
                        condition = new(tree.Condition)('or', condition || a, b, index + currentIndex);
                    }
                    return condition || a;
                }
            },
            condition: function (needsParens) {
                let result;
                let logical;
                let next;
                function or() {
                    return parserInput.$str('or');
                }

                result = this.conditionAnd(needsParens);
                if (!result) {
                    return ;
                }
                logical = or();
                if (logical) {
                    next = this.condition(needsParens);
                    if (next) {
                        result = new(tree.Condition)(logical, result, next);
                    } else {
                        return ;
                    }
                }
                return result;
            },
            conditionAnd: function (needsParens) {
                let result;
                let logical;
                let next;
                const self = this;
                function insideCondition() {
                    const cond = self.negatedCondition(needsParens) || self.parenthesisCondition(needsParens);
                    if (!cond && !needsParens) {
                        return self.atomicCondition(needsParens);
                    }
                    return cond;
                }
                function and() {
                    return parserInput.$str('and');
                }

                result = insideCondition();
                if (!result) {
                    return ;
                }
                logical = and();
                if (logical) {
                    next = this.conditionAnd(needsParens);
                    if (next) {
                        result = new(tree.Condition)(logical, result, next);
                    } else {
                        return ;
                    }
                }
                return result;
            },
            negatedCondition: function (needsParens) {
                if (parserInput.$str('not')) {
                    const result = this.parenthesisCondition(needsParens);
                    if (result) {
                        result.negate = !result.negate;
                    }
                    return result;
                }
            },
            parenthesisCondition: function (needsParens) {
                function tryConditionFollowedByParenthesis(me) {
                    let body;
                    parserInput.save();
                    body = me.condition(needsParens);
                    if (!body) {
                        parserInput.restore();
                        return ;
                    }
                    if (!parserInput.$char(')')) {
                        parserInput.restore();
                        return ;
                    }
                    parserInput.forget();
                    return body;
                }

                let body;
                parserInput.save();
                if (!parserInput.$str('(')) {
                    parserInput.restore();
                    return ;
                }
                body = tryConditionFollowedByParenthesis(this);
                if (body) {
                    parserInput.forget();
                    return body;
                }

                body = this.atomicCondition(needsParens);
                if (!body) {
                    parserInput.restore();
                    return ;
                }
                if (!parserInput.$char(')')) {
                    parserInput.restore(`expected ')' got '${parserInput.currentChar()}'`);
                    return ;
                }
                parserInput.forget();
                return body;
            },
            atomicCondition: function (needsParens, preparsedCond) {
                const entities = this.entities;
                const index = parserInput.i;
                let a;
                let b;
                let c;
                let op;

                const cond = (function() {
                    return this.addition() || entities.keyword() || entities.quoted() || entities.mixinLookup();
                }).bind(this);

                if (preparsedCond) {
                    a = preparsedCond;
                } else {
                    a = cond();
                }

                if (a) {
                    if (parserInput.$char('>')) {
                        if (parserInput.$char('=')) {
                            op = '>=';
                        } else {
                            op = '>';
                        }
                    } else
                    if (parserInput.$char('<')) {
                        if (parserInput.$char('=')) {
                            op = '<=';
                        } else {
                            op = '<';
                        }
                    } else
                    if (parserInput.$char('=')) {
                        if (parserInput.$char('>')) {
                            op = '=>';
                        } else if (parserInput.$char('<')) {
                            op = '=<';
                        } else {
                            op = '=';
                        }
                    }
                    if (op) {
                        b = cond();
                        if (b) {
                            c = new(tree.Condition)(op, a, b, index + currentIndex, false);
                        } else {
                            error('expected expression');
                        }
                    } else if (!preparsedCond) {
                        c = new(tree.Condition)('=', a, new(tree.Keyword)('true'), index + currentIndex, false);
                    }
                    return c;
                }
            },

            //
            // An operand is anything that can be part of an operation,
            // such as a Color, or a Variable
            //
            operand: function () {
                const entities = this.entities;
                let negate;

                if (parserInput.peek(/^-[@$(]/)) {
                    negate = parserInput.$char('-');
                }

                let o = this.sub() || entities.dimension() ||
                        entities.color() || entities.variable() ||
                        entities.property() || entities.call() ||
                        entities.quoted(true) || entities.colorKeyword() ||
                        this.colorOperand() || entities.mixinLookup();

                if (negate) {
                    o.parensInOp = true;
                    o = new(tree.Negative)(o);
                }

                return o;
            },

            //
            // Expressions either represent mathematical operations,
            // or white-space delimited Entities.
            //
            //     1px solid black
            //     @var * 2
            //
            expression: function () {
                const entities = [];
                let e;
                let delim;
                const index = parserInput.i;

                do {
                    e = this.comment();
                    if (e && !e.isLineComment) {
                        entities.push(e);
                        continue;
                    }
                    e = this.addition() || this.entity();

                    if (e instanceof tree.Comment) {
                        e = null;
                    }

                    if (e) {
                        entities.push(e);
                        // operations do not allow keyword "/" dimension (e.g. small/20px) so we support that here
                        if (!parserInput.peek(/^\/[/*]/)) {
                            delim = parserInput.$char('/');
                            if (delim) {
                                entities.push(new(tree.Anonymous)(delim, index + currentIndex));
                            }
                        }
                    }
                } while (e);
                if (entities.length > 0) {
                    return new(tree.Expression)(entities);
                }
            },
            property: function () {
                const name = parserInput.$re(/^(\*?-?[_a-zA-Z0-9-]+)\s*:/);
                if (name) {
                    return name[1];
                }
            },
            ruleProperty: function () {
                let name = [];
                const index = [];
                let s;
                let k;

                parserInput.save();

                const simpleProperty = parserInput.$re(/^([_a-zA-Z0-9-]+)\s*:/);
                if (simpleProperty) {
                    name = [new(tree.Keyword)(simpleProperty[1])];
                    parserInput.forget();
                    return name;
                }

                function match(re) {
                    const i = parserInput.i;
                    const chunk = parserInput.$re(re);
                    if (chunk) {
                        index.push(i);
                        return name.push(chunk[1]);
                    }
                }

                match(/^(\*?)/);
                while (true) {
                    if (!match(/^((?:[\w-]+)|(?:[@$]\{[\w-]+\}))/)) {
                        break;
                    }
                }

                if ((name.length > 1) && match(/^((?:\+_|\+)?)\s*:/)) {
                    parserInput.forget();

                    // at last, we have the complete match now. move forward,
                    // convert name particles to tree objects and return:
                    if (name[0] === '') {
                        name.shift();
                        index.shift();
                    }
                    for (k = 0; k < name.length; k++) {
                        s = name[k];
                        name[k] = (s.charAt(0) !== '@' && s.charAt(0) !== '$') ?
                            new(tree.Keyword)(s) :
                            (s.charAt(0) === '@' ?
                                new(tree.Variable)(`@${s.slice(2, -1)}`, index[k] + currentIndex, fileInfo) :
                                new(tree.Property)(`$${s.slice(2, -1)}`, index[k] + currentIndex, fileInfo));
                    }
                    return name;
                }
                parserInput.restore();
            }
        }
    };
};
Parser.serializeVars = vars => {
    let s = '';

    for (const name in vars) {
        if (Object.hasOwnProperty.call(vars, name)) {
            const value = vars[name];
            s += `${((name[0] === '@') ? '' : '@') + name}: ${value}${(String(value).slice(-1) === ';') ? '' : ';'}`;
        }
    }

    return s;
};

// @ts-check

/** @import { EvalContext, CSSOutput, FileInfo, VisibilityInfo, TreeVisitor } from './node.js' */

class Selector extends Node {
    get type() { return 'Selector'; }

    /**
     * @param {(Element | Selector)[] | string} [elements]
     * @param {Node[] | null} [extendList]
     * @param {Node | null} [condition]
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(elements, extendList, condition, index, currentFileInfo, visibilityInfo) {
        super();
        /** @type {Node[] | null | undefined} */
        this.extendList = extendList;
        /** @type {Node | null | undefined} */
        this.condition = condition;
        /** @type {boolean | Node} */
        this.evaldCondition = !condition;
        this._index = index;
        this._fileInfo = currentFileInfo;
        /** @type {Element[]} */
        this.elements = this.getElements(elements);
        /** @type {string[] | undefined} */
        this.mixinElements_ = undefined;
        /** @type {boolean | undefined} */
        this.mediaEmpty = undefined;
        this.copyVisibilityInfo(visibilityInfo);
        this.setParent(this.elements, this);
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        if (this.elements) {
            this.elements = /** @type {Element[]} */ (visitor.visitArray(this.elements));
        }
        if (this.extendList) {
            this.extendList = visitor.visitArray(this.extendList);
        }
        if (this.condition) {
            this.condition = visitor.visit(this.condition);
        }
    }

    /**
     * @param {Element[]} elements
     * @param {Node[] | null} [extendList]
     * @param {boolean | Node} [evaldCondition]
     */
    createDerived(elements, extendList, evaldCondition) {
        elements = this.getElements(elements);
        const newSelector = new Selector(elements, extendList || this.extendList,
            null, this.getIndex(), this.fileInfo(), this.visibilityInfo());
        newSelector.evaldCondition = (!isNullOrUndefined(evaldCondition)) ? evaldCondition : this.evaldCondition;
        newSelector.mediaEmpty = this.mediaEmpty;
        return newSelector;
    }

    /**
     * @param {(Element | Selector)[] | string | null | undefined} els
     * @returns {Element[]}
     */
    getElements(els) {
        if (!els) {
            return [new Element('', '&', false, this._index, this._fileInfo)];
        }
        if (typeof els === 'string') {
            const fileInfo = this._fileInfo;
            const parse = this.parse;
            new (/** @type {new (...args: unknown[]) => { parseNode: Function }} */ (/** @type {unknown} */ (Parser)))(parse.context, parse.importManager, fileInfo, this._index).parseNode(
                els,
                ['selector'],
                function(/** @type {{ index: number, message: string } | null} */ err, /** @type {Selector[]} */ result) {
                    if (err) {
                        throw new LessError({
                            index: err.index,
                            message: err.message
                        }, parse.imports, /** @type {string} */ (/** @type {FileInfo} */ (fileInfo).filename));
                    }
                    els = result[0].elements;
                });
        }
        return /** @type {Element[]} */ (els);
    }

    createEmptySelectors() {
        const el = new Element('', '&', false, this._index, this._fileInfo), sels = [new Selector([el], null, null, this._index, this._fileInfo)];
        sels[0].mediaEmpty = true;
        return sels;
    }

    /**
     * @param {Selector} other
     * @returns {number}
     */
    match(other) {
        const elements = this.elements;
        const len = elements.length;
        let olen;
        let i;

        /** @type {string[]} */
        const mixinEls = other.mixinElements();
        olen = mixinEls.length;
        if (olen === 0 || len < olen) {
            return 0;
        } else {
            for (i = 0; i < olen; i++) {
                if (elements[i].value !== mixinEls[i]) {
                    return 0;
                }
            }
        }

        return olen; // return number of matched elements
    }

    /** @returns {string[]} */
    mixinElements() {
        if (this.mixinElements_) {
            return this.mixinElements_;
        }

        /** @type {string[] | null} */
        let elements = this.elements.map( function(v) {
            return /** @type {string} */ (v.combinator.value) + (/** @type {{ value: string }} */ (v.value).value || v.value);
        }).join('').match(/[,&#*.\w-]([\w-]|(\\.))*/g);

        if (elements) {
            if (elements[0] === '&') {
                elements.shift();
            }
        } else {
            elements = [];
        }

        return (this.mixinElements_ = elements);
    }

    isJustParentSelector() {
        return !this.mediaEmpty &&
            this.elements.length === 1 &&
            this.elements[0].value === '&' &&
            (this.elements[0].combinator.value === ' ' || this.elements[0].combinator.value === '');
    }

    /** @param {EvalContext} context */
    eval(context) {
        const evaldCondition = this.condition && this.condition.eval(context);
        let elements = this.elements;
        /** @type {Node[] | null | undefined} */
        let extendList = this.extendList;

        if (elements) {
            const evaldElements = new Array(elements.length);
            for (let i = 0; i < elements.length; i++) {
                evaldElements[i] = elements[i].eval(context);
            }
            elements = evaldElements;
        }
        if (extendList) {
            const evaldExtends = new Array(extendList.length);
            for (let i = 0; i < extendList.length; i++) {
                evaldExtends[i] = extendList[i].eval(context);
            }
            extendList = evaldExtends;
        }

        return this.createDerived(elements, extendList, evaldCondition);
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        let i, element;
        if ((!context || !/** @type {EvalContext & { firstSelector?: boolean }} */ (context).firstSelector) && this.elements[0].combinator.value === '') {
            output.add(' ', this.fileInfo(), this.getIndex());
        }
        for (i = 0; i < this.elements.length; i++) {
            element = this.elements[i];
            element.genCSS(context, output);
        }
    }

    getIsOutput() {
        return this.evaldCondition;
    }
}

// @ts-check

/** @import { EvalContext, CSSOutput } from './node.js' */

class Keyword extends Node {
    get type() { return 'Keyword'; }

    /** @param {string} value */
    constructor(value) {
        super();
        this.value = value;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        if (this.value === '%') { throw { type: 'Syntax', message: 'Invalid % without number' }; }
        output.add(/** @type {string} */ (this.value));
    }
}

Keyword.True = new Keyword('true');
Keyword.False = new Keyword('false');

// @ts-check
const MATH$1 = Math$1;

/**
 * @param {EvalContext} context
 * @param {Node[]} name
 * @returns {string}
 */
function evalName(context, name) {
    let value = '';
    let i;
    const n = name.length;
    /** @type {CSSOutput} */
    const output = {add: function (s) {value += s;}, isEmpty: function() { return value === ''; }};
    for (i = 0; i < n; i++) {
        name[i].eval(context).genCSS(context, output);
    }
    return value;
}

class Declaration extends Node {
    get type() { return 'Declaration'; }

    /**
     * @param {string | Node[]} name
     * @param {Node | string | null} value
     * @param {string} [important]
     * @param {string} [merge]
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     * @param {boolean} [inline]
     * @param {boolean} [variable]
     */
    constructor(name, value, important, merge, index, currentFileInfo, inline, variable) {
        super();
        this.name = name;
        this.value = (value instanceof Node) ? value : new Value([value ? new Anonymous(value) : null]);
        this.important = important ? ` ${important.trim()}` : '';
        /** @type {string | undefined} */
        this.merge = merge;
        this._index = index;
        this._fileInfo = currentFileInfo;
        /** @type {boolean} */
        this.inline = inline || false;
        /** @type {boolean} */
        this.variable = (variable !== undefined) ? variable
            : (typeof name === 'string' && name.charAt(0) === '@');
        /** @type {boolean} */
        this.allowRoot = true;
        this.setParent(this.value, this);
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add(/** @type {string} */ (this.name) + (context.compress ? ':' : ': '), this.fileInfo(), this.getIndex());
        try {
            /** @type {Node} */ (this.value).genCSS(context, output);
        }
        catch (e) {
            const err = /** @type {{ index?: number, filename?: string }} */ (e);
            err.index = this._index;
            err.filename = this._fileInfo && this._fileInfo.filename;
            throw e;
        }
        output.add(this.important + ((this.inline || (context.lastRule && context.compress)) ? '' : ';'), this._fileInfo, this._index);
    }

    /** @param {EvalContext} context */
    eval(context) {
        let mathBypass = false, prevMath, name = this.name, evaldValue, variable = this.variable;
        if (typeof name !== 'string') {
            // expand 'primitive' name directly to get
            // things faster (~10% for benchmark.less):
            name = (/** @type {Node[]} */ (name).length === 1) && (/** @type {Node[]} */ (name)[0] instanceof Keyword) ?
                /** @type {string} */ (/** @type {Node[]} */ (name)[0].value) : evalName(context, /** @type {Node[]} */ (name));
            variable = false; // never treat expanded interpolation as new variable name
        }

        // @todo remove when parens-division is default
        if (name === 'font' && context.math === MATH$1.ALWAYS) {
            mathBypass = true;
            prevMath = context.math;
            context.math = MATH$1.PARENS_DIVISION;
        }
        try {
            context.importantScope.push({});
            evaldValue = /** @type {Node} */ (this.value).eval(context);

            if (!this.variable && evaldValue.type === 'DetachedRuleset') {
                throw { message: 'Rulesets cannot be evaluated on a property.',
                    index: this.getIndex(), filename: this.fileInfo().filename };
            }
            let important = this.important;
            const importantResult = context.importantScope.pop();
            if (!important && importantResult && importantResult.important) {
                important = importantResult.important;
            }

            return new Declaration(/** @type {string} */ (name),
                evaldValue,
                important,
                this.merge,
                this.getIndex(), this.fileInfo(), this.inline,
                variable);
        }
        catch (e) {
            const err = /** @type {{ index?: number, filename?: string }} */ (e);
            if (typeof err.index !== 'number') {
                err.index = this.getIndex();
                err.filename = this.fileInfo().filename;
            }
            throw e;
        }
        finally {
            if (mathBypass) {
                context.math = prevMath;
            }
        }
    }

    makeImportant() {
        return new Declaration(this.name,
            /** @type {Node} */ (this.value),
            '!important',
            this.merge,
            this.getIndex(), this.fileInfo(), this.inline);
    }
}

const defaultFunc = {
    eval: function () {
        const v = this.value_;
        const e = this.error_;
        if (e) {
            throw e;
        }
        if (!isNullOrUndefined(v)) {
            return v ? Keyword.True : Keyword.False;
        }
    },
    value: function (v) {
        this.value_ = v;
    },
    error: function (e) {
        this.error_ = e;
    },
    reset: function () {
        this.value_ = this.error_ = null;
    }
};

// @ts-check

/**
 * @typedef {Node & {
 *   rules?: Node[],
 *   selectors?: Selector[],
 *   root?: boolean,
 *   firstRoot?: boolean,
 *   allowImports?: boolean,
 *   functionRegistry?: FunctionRegistry,
 *   originalRuleset?: Node,
 *   debugInfo?: { lineNumber: number, fileName: string },
 *   evalFirst?: boolean,
 *   isRuleset?: boolean,
 *   isCharset?: () => boolean,
 *   merge?: boolean | string,
 *   multiMedia?: boolean,
 *   parse?: { context: EvalContext, importManager: object },
 *   bubbleSelectors?: (selectors: Selector[]) => void
 * }} RuleNode
 */

class Ruleset extends Node {
    get type() { return 'Ruleset'; }

    /**
     * @param {Selector[] | null} selectors
     * @param {Node[] | null} rules
     * @param {boolean} [strictImports]
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(selectors, rules, strictImports, visibilityInfo) {
        super();
        /** @type {Selector[] | null} */
        this.selectors = selectors;
        /** @type {Node[] | null} */
        this.rules = rules;
        /** @type {Object<string, { rule: Node, path: Node[] }[]>} */
        this._lookups = {};
        /** @type {Object<string, Declaration> | null} */
        this._variables = null;
        /** @type {Object<string, Declaration[]> | null} */
        this._properties = null;
        /** @type {boolean | undefined} */
        this.strictImports = strictImports;
        this.copyVisibilityInfo(visibilityInfo);
        this.allowRoot = true;
        /** @type {boolean} */
        this.isRuleset = true;

        /** @type {boolean | undefined} */
        this.root = undefined;
        /** @type {boolean | undefined} */
        this.firstRoot = undefined;
        /** @type {boolean | undefined} */
        this.allowImports = undefined;
        /** @type {FunctionRegistry | undefined} */
        this.functionRegistry = undefined;
        /** @type {Node | undefined} */
        this.originalRuleset = undefined;
        /** @type {{ lineNumber: number, fileName: string } | undefined} */
        this.debugInfo = undefined;
        /** @type {Selector[][] | undefined} */
        this.paths = undefined;
        /** @type {Ruleset[] | null | undefined} */
        this._rulesets = undefined;
        /** @type {boolean | undefined} */
        this.evalFirst = undefined;
        this.setParent(this.selectors, this);
        this.setParent(this.rules, this);
    }

    isRulesetLike() { return true; }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        if (this.paths) {
            this.paths = /** @type {Selector[][]} */ (/** @type {unknown} */ (visitor.visitArray(/** @type {Node[]} */ (/** @type {unknown} */ (this.paths)), true)));
        } else if (this.selectors) {
            this.selectors = /** @type {Selector[]} */ (visitor.visitArray(this.selectors));
        }
        if (this.rules && this.rules.length) {
            this.rules = visitor.visitArray(this.rules);
        }
    }

    /** @param {EvalContext} context */
    eval(context) {
        /** @type {Selector[] | undefined} */
        let selectors;
        /** @type {number} */
        let selCnt;
        /** @type {Selector} */
        let selector;
        /** @type {number} */
        let i;
        /** @type {boolean | undefined} */
        let hasVariable;
        let hasOnePassingSelector = false;

        if (this.selectors && (selCnt = this.selectors.length)) {
            selectors = new Array(selCnt);
            defaultFunc.error({
                type: 'Syntax',
                message: 'it is currently only allowed in parametric mixin guards,'
            });

            for (i = 0; i < selCnt; i++) {
                selector = /** @type {Selector} */ (this.selectors[i].eval(context));
                for (let j = 0; j < selector.elements.length; j++) {
                    if (selector.elements[j].isVariable) {
                        hasVariable = true;
                        break;
                    }
                }
                selectors[i] = selector;
                if (selector.evaldCondition) {
                    hasOnePassingSelector = true;
                }
            }

            if (hasVariable) {
                const toParseSelectors = new Array(selCnt);
                for (i = 0; i < selCnt; i++) {
                    selector = selectors[i];
                    toParseSelectors[i] = selector.toCSS(context);
                }
                const startingIndex = selectors[0].getIndex();
                const selectorFileInfo = selectors[0].fileInfo();
                new (/** @type {new (...args: [EvalContext, object, FileInfo, number]) => { parseNode: Function }} */ (/** @type {unknown} */ (Parser)))(context, /** @type {{ context: EvalContext, importManager: object }} */ (this.parse).importManager, selectorFileInfo, startingIndex).parseNode(
                    toParseSelectors.join(','),
                    ['selectors'],
                    function(/** @type {Error | null} */ err, /** @type {Node[]} */ result) {
                        if (result) {
                            selectors = /** @type {Selector[]} */ (flattenArray(result));
                        }
                    });
            }

            defaultFunc.reset();
        } else {
            hasOnePassingSelector = true;
        }

        let rules = this.rules ? copyArray(this.rules) : null;
        const ruleset = new Ruleset(selectors, rules, this.strictImports, this.visibilityInfo());
        /** @type {Node} */
        let rule;
        /** @type {Node} */
        let subRule;

        ruleset.originalRuleset = this;
        ruleset.root = this.root;
        ruleset.firstRoot = this.firstRoot;
        ruleset.allowImports = this.allowImports;

        if (this.debugInfo) {
            ruleset.debugInfo = this.debugInfo;
        }

        if (!hasOnePassingSelector) {
            /** @type {Node[]} */ (rules).length = 0;
        }

        // push the current ruleset to the frames stack
        const ctxFrames = context.frames;

        // inherit a function registry from the frames stack when possible;
        // otherwise from the global registry
        /** @type {FunctionRegistry | undefined} */
        let foundRegistry;
        for (let fi = 0, fn = ctxFrames.length; fi !== fn; ++fi) {
            foundRegistry = /** @type {RuleNode} */ (ctxFrames[fi]).functionRegistry;
            if (foundRegistry) { break; }
        }
        ruleset.functionRegistry = (foundRegistry || functionRegistry).inherit();
        ctxFrames.unshift(ruleset);

        // currrent selectors
        /** @type {Selector[][] | undefined} */
        let ctxSelectors = /** @type {EvalContext & { selectors?: Selector[][] }} */ (context).selectors;
        if (!ctxSelectors) {
            /** @type {EvalContext & { selectors?: Selector[][] }} */ (context).selectors = ctxSelectors = [];
        }
        ctxSelectors.unshift(this.selectors);

        // Evaluate imports
        if (ruleset.root || ruleset.allowImports || !ruleset.strictImports) {
            ruleset.evalImports(context);
        }

        // Store the frames around mixin definitions,
        // so they can be evaluated like closures when the time comes.
        const rsRules = /** @type {Node[]} */ (ruleset.rules);
        for (i = 0; (rule = rsRules[i]); i++) {
            if (/** @type {RuleNode} */ (rule).evalFirst) {
                rsRules[i] = rule.eval(context);
            }
        }

        const mediaBlockCount = (context.mediaBlocks && context.mediaBlocks.length) || 0;

        // Evaluate mixin calls.
        for (i = 0; (rule = rsRules[i]); i++) {
            if (rule.type === 'MixinCall') {
                /* jshint loopfunc:true */
                rules = /** @type {Node[]} */ (/** @type {unknown} */ (rule.eval(context))).filter(function(/** @type {Node & { variable?: boolean }} */ r) {
                    if ((r instanceof Declaration) && r.variable) {
                        // do not pollute the scope if the variable is
                        // already there. consider returning false here
                        // but we need a way to "return" variable from mixins
                        return !(ruleset.variable(/** @type {string} */ (r.name)));
                    }
                    return true;
                });
                rsRules.splice.apply(rsRules, /** @type {[number, number, ...Node[]]} */ ([i, 1].concat(rules)));
                i += rules.length - 1;
                ruleset.resetCache();
            } else if (rule.type ===  'VariableCall') {
                /* jshint loopfunc:true */
                rules = /** @type {Node[]} */ (/** @type {RuleNode} */ (rule.eval(context)).rules).filter(function(/** @type {Node & { variable?: boolean }} */ r) {
                    if ((r instanceof Declaration) && r.variable) {
                        // do not pollute the scope at all
                        return false;
                    }
                    return true;
                });
                rsRules.splice.apply(rsRules, /** @type {[number, number, ...Node[]]} */ ([i, 1].concat(rules)));
                i += rules.length - 1;
                ruleset.resetCache();
            }
        }

        // Evaluate everything else
        for (i = 0; (rule = rsRules[i]); i++) {
            if (!/** @type {RuleNode} */ (rule).evalFirst) {
                rsRules[i] = rule = rule.eval ? rule.eval(context) : rule;
            }
        }

        // Evaluate everything else
        for (i = 0; (rule = rsRules[i]); i++) {
            // for rulesets, check if it is a css guard and can be removed
            if (rule instanceof Ruleset && rule.selectors && rule.selectors.length === 1) {
                // check if it can be folded in (e.g. & where)
                if (rule.selectors[0] && rule.selectors[0].isJustParentSelector()) {
                    rsRules.splice(i--, 1);

                    for (let j = 0; (subRule = rule.rules[j]); j++) {
                        if (subRule instanceof Node) {
                            subRule.copyVisibilityInfo(rule.visibilityInfo());
                            if (!(subRule instanceof Declaration) || !subRule.variable) {
                                rsRules.splice(++i, 0, subRule);
                            }
                        }
                    }
                }
            }
        }

        // Pop the stack
        ctxFrames.shift();
        ctxSelectors.shift();

        if (context.mediaBlocks) {
            for (i = mediaBlockCount; i < context.mediaBlocks.length; i++) {
                /** @type {RuleNode} */ (context.mediaBlocks[i]).bubbleSelectors(selectors);
            }
        }

        return ruleset;
    }

    /** @param {EvalContext} context */
    evalImports(context) {
        const rules = this.rules;
        /** @type {number} */
        let i;
        /** @type {Node | Node[]} */
        let importRules;
        if (!rules) { return; }

        for (i = 0; i < rules.length; i++) {
            if (rules[i].type === 'Import') {
                importRules = rules[i].eval(context);
                if (importRules && (/** @type {Node[]} */ (/** @type {unknown} */ (importRules)).length || /** @type {Node[]} */ (/** @type {unknown} */ (importRules)).length === 0)) {
                    const importArr = /** @type {Node[]} */ (/** @type {unknown} */ (importRules));
                    rules.splice(i, 1, ...importArr);
                    i += importArr.length - 1;
                } else {
                    rules.splice(i, 1, importRules);
                }
                this.resetCache();
            }
        }
    }

    makeImportant() {
        const result = new Ruleset(this.selectors, /** @type {Node[]} */ (this.rules).map(function (/** @type {Node & { makeImportant?: () => Node }} */ r) {
            if (r.makeImportant) {
                return r.makeImportant();
            } else {
                return r;
            }
        }), this.strictImports, this.visibilityInfo());

        return result;
    }

    /** @param {Node[] | object[] | null} [args] */
    matchArgs(args) {
        return !args || args.length === 0;
    }

    /**
     * @param {Node[] | object[] | null} args
     * @param {EvalContext} context
     */
    matchCondition(args, context) {
        const lastSelector = /** @type {Selector[]} */ (this.selectors)[/** @type {Selector[]} */ (this.selectors).length - 1];
        if (!lastSelector.evaldCondition) {
            return false;
        }
        if (lastSelector.condition &&
            !lastSelector.condition.eval(
                new contexts.Eval(context,
                    context.frames))) {
            return false;
        }
        return true;
    }

    resetCache() {
        this._rulesets = null;
        this._variables = null;
        this._properties = null;
        this._lookups = {};
    }

    variables() {
        if (!this._variables) {
            this._variables = !this.rules ? {} : this.rules.reduce(function (/** @type {Object<string, Declaration>} */ hash, /** @type {Node} */ r) {
                if (r instanceof Declaration && r.variable === true) {
                    hash[/** @type {string} */ (r.name)] = r;
                }
                // when evaluating variables in an import statement, imports have not been eval'd
                // so we need to go inside import statements.
                // guard against root being a string (in the case of inlined less)
                if (r.type === 'Import' && /** @type {RuleNode} */ (r).root && /** @type {RuleNode & { root: Ruleset }} */ (r).root.variables) {
                    const vars = /** @type {RuleNode & { root: Ruleset }} */ (r).root.variables();
                    for (const name in vars) {
                        if (Object.prototype.hasOwnProperty.call(vars, name)) {
                            hash[name] = /** @type {Declaration} */ (/** @type {RuleNode & { root: Ruleset }} */ (r).root.variable(name));
                        }
                    }
                }
                return hash;
            }, {});
        }
        return this._variables;
    }

    properties() {
        if (!this._properties) {
            this._properties = !this.rules ? {} : this.rules.reduce(function (/** @type {Object<string, Declaration[]>} */ hash, /** @type {Node} */ r) {
                if (r instanceof Declaration && r.variable !== true) {
                    const name = (/** @type {Node[]} */ (r.name).length === 1) && (/** @type {Node[]} */ (r.name)[0] instanceof Keyword) ?
                        /** @type {string} */ (/** @type {Node[]} */ (r.name)[0].value) : /** @type {string} */ (r.name);
                    // Properties don't overwrite as they can merge
                    if (!hash[`$${name}`]) {
                        hash[`$${name}`] = [ r ];
                    }
                    else {
                        hash[`$${name}`].push(r);
                    }
                }
                return hash;
            }, {});
        }
        return this._properties;
    }

    /** @param {string} name */
    variable(name) {
        const decl = this.variables()[name];
        if (decl) {
            return this.parseValue(decl);
        }
    }

    /** @param {string} name */
    property(name) {
        const decl = this.properties()[name];
        if (decl) {
            return this.parseValue(decl);
        }
    }

    lastDeclaration() {
        for (let i = /** @type {Node[]} */ (this.rules).length; i > 0; i--) {
            const decl = /** @type {Node[]} */ (this.rules)[i - 1];
            if (decl instanceof Declaration) {
                return this.parseValue(decl);
            }
        }
    }

    /** @param {Declaration | Declaration[]} toParse */
    parseValue(toParse) {
        const self = this;
        /** @param {Declaration} decl */
        function transformDeclaration(decl) {
            if (decl.value instanceof Anonymous && !/** @type {Declaration & { parsed?: boolean }} */ (decl).parsed) {
                if (typeof decl.value.value === 'string') {
                    new (/** @type {new (...args: [EvalContext, object, FileInfo, number]) => { parseNode: Function }} */ (/** @type {unknown} */ (Parser)))(/** @type {{ context: EvalContext, importManager: object }} */ (/** @type {Ruleset} */ (this).parse).context, /** @type {{ context: EvalContext, importManager: object }} */ (/** @type {Ruleset} */ (this).parse).importManager, decl.fileInfo(), decl.value.getIndex()).parseNode(
                        decl.value.value,
                        ['value', 'important'],
                        function(/** @type {Error | null} */ err, /** @type {Node[]} */ result) {
                            if (err) {
                                decl.parsed = /** @type {Node} */ (/** @type {unknown} */ (true));
                            }
                            if (result) {
                                decl.value = result[0];
                                /** @type {Declaration & { important?: string }} */ (decl).important = /** @type {string} */ (/** @type {unknown} */ (result[1])) || '';
                                decl.parsed = /** @type {Node} */ (/** @type {unknown} */ (true));
                            }
                        });
                } else {
                    decl.parsed = /** @type {Node} */ (/** @type {unknown} */ (true));
                }

                return decl;
            }
            else {
                return decl;
            }
        }
        if (!Array.isArray(toParse)) {
            return transformDeclaration.call(self, toParse);
        }
        else {
            /** @type {Declaration[]} */
            const nodes = [];
            for (let ti = 0; ti < toParse.length; ti++) {
                nodes.push(transformDeclaration.call(self, toParse[ti]));
            }
            return nodes;
        }
    }

    rulesets() {
        if (!this.rules) { return []; }

        /** @type {Node[]} */
        const filtRules = [];
        const rules = this.rules;
        /** @type {number} */
        let i;
        /** @type {Node} */
        let rule;

        for (i = 0; (rule = rules[i]); i++) {
            if (/** @type {RuleNode} */ (rule).isRuleset) {
                filtRules.push(rule);
            }
        }

        return filtRules;
    }

    /** @param {Node} rule */
    prependRule(rule) {
        const rules = this.rules;
        if (rules) {
            rules.unshift(rule);
        } else {
            this.rules = [ rule ];
        }
        this.setParent(rule, this);
    }

    /**
     * @param {Selector} selector
     * @param {Ruleset | null} [self]
     * @param {((rule: Node) => boolean)} [filter]
     * @returns {{ rule: Node, path: Node[] }[]}
     */
    find(selector, self, filter) {
        self = self || this;
        /** @type {{ rule: Node, path: Node[] }[]} */
        const rules = [];
        /** @type {number | undefined} */
        let match;
        /** @type {{ rule: Node, path: Node[] }[]} */
        let foundMixins;
        const key = selector.toCSS(/** @type {EvalContext} */ ({}));

        if (key in this._lookups) { return /** @type {{ rule: Node, path: Node[] }[]} */ (this._lookups[key]); }

        this.rulesets().forEach(function (rule) {
            if (rule !== self) {
                for (let j = 0; j < /** @type {RuleNode} */ (rule).selectors.length; j++) {
                    match = selector.match(/** @type {RuleNode} */ (rule).selectors[j]);
                    if (match) {
                        if (selector.elements.length > match) {
                            if (!filter || filter(rule)) {
                                foundMixins = /** @type {Ruleset} */ (/** @type {unknown} */ (rule)).find(new Selector(selector.elements.slice(match)), self, filter);
                                for (let i = 0; i < foundMixins.length; ++i) {
                                    foundMixins[i].path.push(rule);
                                }
                                Array.prototype.push.apply(rules, foundMixins);
                            }
                        } else {
                            rules.push({ rule, path: []});
                        }
                        break;
                    }
                }
            }
        });
        this._lookups[key] = rules;
        return rules;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        /** @type {number} */
        let i;
        /** @type {number} */
        let j;
        /** @type {Node[]} */
        const charsetRuleNodes = [];
        /** @type {Node[]} */
        let ruleNodes = [];

        let // Line number debugging
            debugInfo$1;

        /** @type {Node} */
        let rule;
        /** @type {Selector[]} */
        let path;

        context.tabLevel = (context.tabLevel || 0);

        if (!this.root) {
            context.tabLevel++;
        }

        const tabRuleStr = context.compress ? '' : Array(context.tabLevel + 1).join('  ');
        const tabSetStr = context.compress ? '' : Array(context.tabLevel).join('  ');
        /** @type {string} */
        let sep;

        let charsetNodeIndex = 0;
        let importNodeIndex = 0;
        for (i = 0; (rule = /** @type {Node[]} */ (this.rules)[i]); i++) {
            if (rule instanceof Comment) {
                if (importNodeIndex === i) {
                    importNodeIndex++;
                }
                ruleNodes.push(rule);
            } else if (/** @type {RuleNode} */ (rule).isCharset && /** @type {RuleNode} */ (rule).isCharset()) {
                ruleNodes.splice(charsetNodeIndex, 0, rule);
                charsetNodeIndex++;
                importNodeIndex++;
            } else if (rule.type === 'Import') {
                ruleNodes.splice(importNodeIndex, 0, rule);
                importNodeIndex++;
            } else {
                ruleNodes.push(rule);
            }
        }
        ruleNodes = charsetRuleNodes.concat(ruleNodes);

        // If this is the root node, we don't render
        // a selector, or {}.
        if (!this.root) {
            debugInfo$1 = debugInfo(context, /** @type {{ debugInfo: { lineNumber: number, fileName: string } }} */ (/** @type {unknown} */ (this)), tabSetStr);

            if (debugInfo$1) {
                output.add(debugInfo$1);
                output.add(tabSetStr);
            }

            const paths = /** @type {Selector[][]} */ (this.paths);
            const pathCnt = paths.length;
            /** @type {number} */
            let pathSubCnt;

            sep = context.compress ? ',' : (`,\n${tabSetStr}`);

            for (i = 0; i < pathCnt; i++) {
                path = paths[i];
                if (!(pathSubCnt = path.length)) { continue; }
                if (i > 0) { output.add(sep); }

                /** @type {EvalContext & { firstSelector?: boolean }} */ (context).firstSelector = true;
                path[0].genCSS(context, output);

                /** @type {EvalContext & { firstSelector?: boolean }} */ (context).firstSelector = false;
                for (j = 1; j < pathSubCnt; j++) {
                    path[j].genCSS(context, output);
                }
            }

            output.add((context.compress ? '{' : ' {\n') + tabRuleStr);
        }

        // Compile rules and rulesets
        for (i = 0; (rule = ruleNodes[i]); i++) {

            if (i + 1 === ruleNodes.length) {
                context.lastRule = true;
            }

            const currentLastRule = context.lastRule;
            if (rule.isRulesetLike()) {
                context.lastRule = false;
            }

            if (rule.genCSS) {
                rule.genCSS(context, output);
            } else if (rule.value) {
                output.add(/** @type {string} */ (rule.value).toString());
            }

            context.lastRule = currentLastRule;

            if (!context.lastRule && rule.isVisible()) {
                output.add(context.compress ? '' : (`\n${tabRuleStr}`));
            } else {
                context.lastRule = false;
            }
        }

        if (!this.root) {
            output.add((context.compress ? '}' : `\n${tabSetStr}}`));
            context.tabLevel--;
        }

        if (!output.isEmpty() && !context.compress && this.firstRoot) {
            output.add('\n');
        }
    }

    /**
     * @param {Selector[][]} paths
     * @param {Selector[][]} context
     * @param {Selector[]} selectors
     */
    joinSelectors(paths, context, selectors) {
        for (let s = 0; s < selectors.length; s++) {
            this.joinSelector(paths, context, selectors[s]);
        }
    }

    /**
     * @param {Selector[][]} paths
     * @param {Selector[][]} context
     * @param {Selector} selector
     */
    joinSelector(paths, context, selector) {

        /**
         * @param {Selector[]} elementsToPak
         * @param {Element} originalElement
         * @returns {Paren}
         */
        function createParenthesis(elementsToPak, originalElement) {
            /** @type {Paren} */
            let replacementParen;
            /** @type {number} */
            let j;
            if (elementsToPak.length === 0) {
                replacementParen = new Paren(elementsToPak[0]);
            } else {
                const insideParent = new Array(elementsToPak.length);
                for (j = 0; j < elementsToPak.length; j++) {
                    insideParent[j] = new Element(
                        null,
                        elementsToPak[j],
                        originalElement.isVariable,
                        originalElement._index,
                        originalElement._fileInfo
                    );
                }
                replacementParen = new Paren(new Selector(insideParent));
            }
            return replacementParen;
        }

        /**
         * @param {Paren | Selector} containedElement
         * @param {Element} originalElement
         * @returns {Selector}
         */
        function createSelector(containedElement, originalElement) {
            /** @type {Element} */
            let element;
            /** @type {Selector} */
            let selector;
            element = new Element(null, containedElement, originalElement.isVariable, originalElement._index, originalElement._fileInfo);
            selector = new Selector([element]);
            return selector;
        }

        /**
         * @param {Selector[]} beginningPath
         * @param {Selector[]} addPath
         * @param {Element} replacedElement
         * @param {Selector} originalSelector
         * @returns {Selector[]}
         */
        function addReplacementIntoPath(beginningPath, addPath, replacedElement, originalSelector) {
            /** @type {Selector[]} */
            let newSelectorPath;
            /** @type {Selector} */
            let lastSelector;
            /** @type {Selector} */
            let newJoinedSelector;
            // our new selector path
            newSelectorPath = [];

            // construct the joined selector - if & is the first thing this will be empty,
            // if not newJoinedSelector will be the last set of elements in the selector
            if (beginningPath.length > 0) {
                newSelectorPath = copyArray(beginningPath);
                lastSelector = newSelectorPath.pop();
                newJoinedSelector = originalSelector.createDerived(copyArray(lastSelector.elements));
            }
            else {
                newJoinedSelector = originalSelector.createDerived([]);
            }

            if (addPath.length > 0) {
                // /deep/ is a CSS4 selector - (removed, so should deprecate)
                // that is valid without anything in front of it
                // so if the & does not have a combinator that is "" or " " then
                // and there is a combinator on the parent, then grab that.
                // this also allows + a { & .b { .a & { ... though not sure why you would want to do that
                let combinator = replacedElement.combinator;

                const parentEl = addPath[0].elements[0];
                if (combinator.emptyOrWhitespace && !parentEl.combinator.emptyOrWhitespace) {
                    combinator = parentEl.combinator;
                }
                // join the elements so far with the first part of the parent
                newJoinedSelector.elements.push(new Element(
                    combinator,
                    parentEl.value,
                    replacedElement.isVariable,
                    replacedElement._index,
                    replacedElement._fileInfo
                ));
                newJoinedSelector.elements = newJoinedSelector.elements.concat(addPath[0].elements.slice(1));
            }

            // now add the joined selector - but only if it is not empty
            if (newJoinedSelector.elements.length !== 0) {
                newSelectorPath.push(newJoinedSelector);
            }

            // put together the parent selectors after the join (e.g. the rest of the parent)
            if (addPath.length > 1) {
                let restOfPath = addPath.slice(1);
                restOfPath = restOfPath.map(function (/** @type {Selector} */ selector) {
                    return selector.createDerived(selector.elements, []);
                });
                newSelectorPath = newSelectorPath.concat(restOfPath);
            }
            return newSelectorPath;
        }

        /**
         * @param {Selector[][]} beginningPath
         * @param {Selector[]} addPaths
         * @param {Element} replacedElement
         * @param {Selector} originalSelector
         * @param {Selector[][]} result
         * @returns {Selector[][]}
         */
        function addAllReplacementsIntoPath( beginningPath, addPaths, replacedElement, originalSelector, result) {
            /** @type {number} */
            let j;
            for (j = 0; j < beginningPath.length; j++) {
                const newSelectorPath = addReplacementIntoPath(beginningPath[j], addPaths, replacedElement, originalSelector);
                result.push(newSelectorPath);
            }
            return result;
        }

        /**
         * @param {Element[]} elements
         * @param {Selector[][]} selectors
         */
        function mergeElementsOnToSelectors(elements, selectors) {
            /** @type {number} */
            let i;
            /** @type {Selector[]} */
            let sel;

            if (elements.length === 0) {
                return ;
            }
            if (selectors.length === 0) {
                selectors.push([ new Selector(elements) ]);
                return;
            }

            for (i = 0; (sel = selectors[i]); i++) {
                // if the previous thing in sel is a parent this needs to join on to it
                if (sel.length > 0) {
                    sel[sel.length - 1] = sel[sel.length - 1].createDerived(sel[sel.length - 1].elements.concat(elements));
                }
                else {
                    sel.push(new Selector(elements));
                }
            }
        }

        /**
         * @param {Selector[][]} paths
         * @param {Selector[][]} context
         * @param {Selector} inSelector
         * @returns {boolean}
         */
        function replaceParentSelector(paths, context, inSelector) {
            // The paths are [[Selector]]
            // The first list is a list of comma separated selectors
            // The inner list is a list of inheritance separated selectors
            // e.g.
            // .a, .b {
            //   .c {
            //   }
            // }
            // == [[.a] [.c]] [[.b] [.c]]
            //
            /** @type {number} */
            let i;
            /** @type {number} */
            let j;
            /** @type {number} */
            let k;
            /** @type {Element[]} */
            let currentElements;
            /** @type {Selector[][]} */
            let newSelectors;
            /** @type {Selector[][]} */
            let selectorsMultiplied;
            /** @type {Selector[]} */
            let sel;
            /** @type {Element} */
            let el;
            let hadParentSelector = false;
            /** @type {number} */
            let length;
            /** @type {Selector} */
            let lastSelector;

            /**
             * @param {Element} element
             * @returns {Selector | null}
             */
            function findNestedSelector(element) {
                /** @type {Node} */
                let maybeSelector;
                if (!(element.value instanceof Paren)) {
                    return null;
                }

                maybeSelector = /** @type {Node} */ (element.value.value);
                if (!(maybeSelector instanceof Selector)) {
                    return null;
                }

                return maybeSelector;
            }

            // the elements from the current selector so far
            currentElements = [];
            // the current list of new selectors to add to the path.
            // We will build it up. We initiate it with one empty selector as we "multiply" the new selectors
            // by the parents
            newSelectors = [
                []
            ];

            for (i = 0; (el = inSelector.elements[i]); i++) {
                // non parent reference elements just get added
                if (el.value !== '&') {
                    const nestedSelector = findNestedSelector(el);
                    if (nestedSelector !== null) {
                        // merge the current list of non parent selector elements
                        // on to the current list of selectors to add
                        mergeElementsOnToSelectors(currentElements, newSelectors);

                        /** @type {Selector[][]} */
                        const nestedPaths = [];
                        /** @type {boolean | undefined} */
                        let replaced;
                        /** @type {Selector[][]} */
                        const replacedNewSelectors = [];

                        // Check if this is a comma-separated selector list inside the paren
                        // e.g. :not(&.a, &.b) produces Selector([Selector, Anonymous(','), Selector])
                        const hasSubSelectors = nestedSelector.elements.some(e => e instanceof Selector);

                        if (hasSubSelectors) {
                            // Process each sub-selector individually
                            /** @type {(Element | Selector)[]} */
                            const resolvedElements = [];
                            for (const subEl of nestedSelector.elements) {
                                if (subEl instanceof Selector) {
                                    /** @type {Selector[][]} */
                                    const subPaths = [];
                                    const subReplaced = replaceParentSelector(subPaths, context, subEl);
                                    replaced = replaced || subReplaced;
                                    if (subPaths.length > 0 && subPaths[0].length > 0) {
                                        resolvedElements.push(subPaths[0][0]);
                                    } else {
                                        resolvedElements.push(subEl);
                                    }
                                } else {
                                    resolvedElements.push(subEl);
                                }
                            }
                            hadParentSelector = hadParentSelector || /** @type {boolean} */ (replaced);
                            const resolvedNestedSelector = new Selector(resolvedElements);
                            const replacementSelector = createSelector(createParenthesis([resolvedNestedSelector], el), el);
                            addAllReplacementsIntoPath(newSelectors, [replacementSelector], el, inSelector, replacedNewSelectors);
                        } else {
                            replaced = replaceParentSelector(nestedPaths, context, nestedSelector);
                            hadParentSelector = hadParentSelector || replaced;
                            // the nestedPaths array should have only one member - replaceParentSelector does not multiply selectors
                            for (k = 0; k < nestedPaths.length; k++) {
                                const replacementSelector = createSelector(createParenthesis(nestedPaths[k], el), el);
                                addAllReplacementsIntoPath(newSelectors, [replacementSelector], el, inSelector, replacedNewSelectors);
                            }
                        }
                        newSelectors = replacedNewSelectors;
                        currentElements = [];
                    } else {
                        currentElements.push(el);
                    }

                } else {
                    hadParentSelector = true;
                    // the new list of selectors to add
                    selectorsMultiplied = [];

                    // merge the current list of non parent selector elements
                    // on to the current list of selectors to add
                    mergeElementsOnToSelectors(currentElements, newSelectors);

                    // loop through our current selectors
                    for (j = 0; j < newSelectors.length; j++) {
                        sel = newSelectors[j];
                        // if we don't have any parent paths, the & might be in a mixin so that it can be used
                        // whether there are parents or not
                        if (context.length === 0) {
                            // the combinator used on el should now be applied to the next element instead so that
                            // it is not lost
                            if (sel.length > 0) {
                                sel[0].elements.push(new Element(el.combinator, '', el.isVariable, el._index, el._fileInfo));
                            }
                            selectorsMultiplied.push(sel);
                        }
                        else {
                            // and the parent selectors
                            for (k = 0; k < context.length; k++) {
                                // We need to put the current selectors
                                // then join the last selector's elements on to the parents selectors
                                const newSelectorPath = addReplacementIntoPath(sel, context[k], el, inSelector);
                                // add that to our new set of selectors
                                selectorsMultiplied.push(newSelectorPath);
                            }
                        }
                    }

                    // our new selectors has been multiplied, so reset the state
                    newSelectors = selectorsMultiplied;
                    currentElements = [];
                }
            }

            // if we have any elements left over (e.g. .a& .b == .b)
            // add them on to all the current selectors
            mergeElementsOnToSelectors(currentElements, newSelectors);

            for (i = 0; i < newSelectors.length; i++) {
                length = newSelectors[i].length;
                if (length > 0) {
                    paths.push(newSelectors[i]);
                    lastSelector = newSelectors[i][length - 1];
                    newSelectors[i][length - 1] = lastSelector.createDerived(lastSelector.elements, inSelector.extendList);
                }
            }

            return hadParentSelector;
        }

        /**
         * @param {VisibilityInfo} visibilityInfo
         * @param {Selector} deriveFrom
         */
        function deriveSelector(visibilityInfo, deriveFrom) {
            const newSelector = deriveFrom.createDerived(deriveFrom.elements, deriveFrom.extendList, deriveFrom.evaldCondition);
            newSelector.copyVisibilityInfo(visibilityInfo);
            return newSelector;
        }

        // joinSelector code follows
        /** @type {number} */
        let i;
        /** @type {Selector[][]} */
        let newPaths;
        /** @type {boolean} */
        let hadParentSelector;

        newPaths = [];
        hadParentSelector = replaceParentSelector(newPaths, context, selector);

        if (!hadParentSelector) {
            if (context.length > 0) {
                newPaths = [];
                for (i = 0; i < context.length; i++) {

                    const concatenated = context[i].map(deriveSelector.bind(this, selector.visibilityInfo()));

                    concatenated.push(selector);
                    newPaths.push(concatenated);
                }
            }
            else {
                newPaths = [[selector]];
            }
        }

        for (i = 0; i < newPaths.length; i++) {
            paths.push(newPaths[i]);
        }

    }
}

// @ts-check

/**
 * @typedef {object} FunctionRegistry
 * @property {(name: string, func: Function) => void} add
 * @property {(functions: Object) => void} addMultiple
 * @property {(name: string) => Function} get
 * @property {() => Object} getLocalFunctions
 * @property {() => FunctionRegistry} inherit
 * @property {(base: FunctionRegistry) => FunctionRegistry} create
 */

/**
 * @typedef {Node & {
 *   features: Value,
 *   rules: Ruleset[],
 *   type: string,
 *   functionRegistry?: FunctionRegistry,
 *   multiMedia?: boolean,
 *   debugInfo?: { lineNumber: number, fileName: string },
 *   allowRoot?: boolean,
 *   _evaluated?: boolean,
 *   evalFunction: () => void,
 *   evalTop: (context: EvalContext) => Node | Ruleset,
 *   evalNested: (context: EvalContext) => Node | Ruleset,
 *   permute: (arr: Node[][]) => Node[][],
 *   bubbleSelectors: (selectors: Selector[] | undefined) => void,
 *   outputRuleset: (context: EvalContext, output: CSSOutput, rules: Node[]) => void
 * }} NestableAtRuleThis
 */

const NestableAtRulePrototype = {

    isRulesetLike() {
        return true;
    },

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        /** @type {NestableAtRuleThis} */
        const self = /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (this));
        if (self.features) {
            self.features = /** @type {Value} */ (visitor.visit(self.features));
        }
        if (self.rules) {
            self.rules = /** @type {Ruleset[]} */ (visitor.visitArray(self.rules));
        }
    },

    evalFunction: function () {
        /** @type {NestableAtRuleThis} */
        const self = /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (this));
        if (!self.features || !Array.isArray(self.features.value) || self.features.value.length < 1) {
            return;
        }

        const exprValues = /** @type {Node[]} */ (self.features.value);
        /** @type {Node | undefined} */
        let expr;
        /** @type {Node | undefined} */
        let paren;

        for (let index = 0; index < exprValues.length; ++index) {
            expr = exprValues[index];

            if ((expr.type === 'Keyword' || expr.type === 'Variable')
                && index + 1 < exprValues.length
                && (/** @type {Node & { noSpacing?: boolean }} */ (expr).noSpacing || /** @type {Node & { noSpacing?: boolean }} */ (expr).noSpacing == null)) {
                paren =  exprValues[index + 1];

                if (paren.type ===  'Paren' && /** @type {Node & { noSpacing?: boolean }} */ (paren).noSpacing) {
                    exprValues[index]= new Expression([expr, paren]);
                    exprValues.splice(index + 1, 1);
                    /** @type {Node & { noSpacing?: boolean }} */ (exprValues[index]).noSpacing = true;
                }
            }
        }
    },

    /** @param {EvalContext} context */
    evalTop(context) {
        /** @type {NestableAtRuleThis} */
        const self = /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (this));
        self.evalFunction();

        /** @type {Node | Ruleset} */
        let result = self;

        // Render all dependent Media blocks.
        if (context.mediaBlocks.length > 1) {
            const selectors = (new Selector([], null, null, self.getIndex(), self.fileInfo())).createEmptySelectors();
            result = new Ruleset(selectors, context.mediaBlocks);
            /** @type {Ruleset & { multiMedia?: boolean }} */ (result).multiMedia = true;
            result.copyVisibilityInfo(self.visibilityInfo());
            self.setParent(result, self);
        }

        delete context.mediaBlocks;
        delete context.mediaPath;

        return result;
    },

    /** @param {EvalContext} context */
    evalNested(context) {
        /** @type {NestableAtRuleThis} */
        const self = /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (this));
        self.evalFunction();

        let i;
        /** @type {Node | Node[]} */
        let value;
        const path = context.mediaPath.concat([self]);

        // Extract the media-query conditions separated with `,` (OR).
        for (i = 0; i < path.length; i++) {
            if (path[i].type !== self.type) {
                const blockIndex = context.mediaBlocks.indexOf(self);
                if (blockIndex > -1) {
                    context.mediaBlocks.splice(blockIndex, 1);
                }
                return self;
            }

            value = /** @type {NestableAtRuleThis} */ (path[i]).features instanceof Value ?
                /** @type {Node[]} */ (/** @type {NestableAtRuleThis} */ (path[i]).features.value) : /** @type {NestableAtRuleThis} */ (path[i]).features;
            path[i] = /** @type {Node} */ (/** @type {unknown} */ (Array.isArray(value) ? value : [value]));
        }

        // Trace all permutations to generate the resulting media-query.
        //
        // (a, b and c) with nested (d, e) ->
        //    a and d
        //    a and e
        //    b and c and d
        //    b and c and e
        self.features = new Value(self.permute(/** @type {Node[][]} */ (/** @type {unknown} */ (path))).map(
            /** @param {Node | Node[]} path */
            path => {
            path = /** @type {Node[]} */ (path).map(
                /** @param {Node & { toCSS?: Function }} fragment */
                fragment => fragment.toCSS ? fragment : new Anonymous(/** @type {string} */ (/** @type {unknown} */ (fragment))));

            for (i = /** @type {Node[]} */ (path).length - 1; i > 0; i--) {
                /** @type {Node[]} */ (path).splice(i, 0, new Anonymous('and'));
            }

            return new Expression(/** @type {Node[]} */ (path));
        }));
        self.setParent(self.features, self);

        // Fake a tree-node that doesn't output anything.
        return new Ruleset([], []);
    },

    /**
     * @param {Node[][]} arr
     * @returns {Node[][]}
     */
    permute(arr) {
        if (arr.length === 0) {
            return [];
        } else if (arr.length === 1) {
            return /** @type {Node[][]} */ (/** @type {unknown} */ (arr[0]));
        } else {
            /** @type {Node[][]} */
            const result = [];
            const rest = this.permute(arr.slice(1));
            for (let i = 0; i < rest.length; i++) {
                for (let j = 0; j < arr[0].length; j++) {
                    result.push([arr[0][j]].concat(rest[i]));
                }
            }
            return result;
        }
    },

    /** @param {Selector[] | undefined} selectors */
    bubbleSelectors(selectors) {
        /** @type {NestableAtRuleThis} */
        const self = /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (this));
        if (!selectors) {
            return;
        }
        self.rules = [new Ruleset(copyArray(selectors), [self.rules[0]])];
        self.setParent(self.rules, self);
    }
};

// @ts-check

/**
 * @typedef {Node & {
 *   rules?: Node[],
 *   selectors?: Selector[],
 *   root?: boolean,
 *   allowImports?: boolean,
 *   functionRegistry?: FunctionRegistry,
 *   merge?: boolean,
 *   debugInfo?: { lineNumber: number, fileName: string },
 *   elements?: import('./element.js').default[]
 * }} RulesetLikeNode
 */

class AtRule extends Node {
    get type() { return 'AtRule'; }

    /**
     * @param {string} [name]
     * @param {Node | string} [value]
     * @param {Node[] | Ruleset} [rules]
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     * @param {{ lineNumber: number, fileName: string }} [debugInfo]
     * @param {boolean} [isRooted]
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(
        name,
        value,
        rules,
        index,
        currentFileInfo,
        debugInfo,
        isRooted,
        visibilityInfo
    ) {
        super();
        let i;
        (new Selector([], null, null, index, currentFileInfo)).createEmptySelectors();

        /** @type {string | undefined} */
        this.name  = name;
        this.value = (value instanceof Node) ? value : (value ? new Anonymous(value) : value);
        /** @type {boolean | undefined} */
        this.simpleBlock = undefined;
        /** @type {RulesetLikeNode[] | undefined} */
        this.declarations = undefined;
        /** @type {RulesetLikeNode[] | undefined} */
        this.rules = undefined;
        if (rules) {
            if (Array.isArray(rules)) {
                const allDeclarations = this.declarationsBlock(rules);

                let allRulesetDeclarations = true;
                rules.forEach(rule => {
                    if (rule.type === 'Ruleset' && /** @type {RulesetLikeNode} */ (rule).rules) allRulesetDeclarations = allRulesetDeclarations && this.declarationsBlock(/** @type {Node[]} */ (/** @type {RulesetLikeNode} */ (rule).rules), true);
                });

                if (allDeclarations && !isRooted) {
                    this.simpleBlock = true;
                    this.declarations = rules;
                } else if (allRulesetDeclarations && rules.length === 1 && !isRooted && !value) {
                    this.simpleBlock = true;
                    this.declarations = /** @type {RulesetLikeNode} */ (rules[0]).rules ? /** @type {RulesetLikeNode} */ (rules[0]).rules : rules;
                } else {
                    this.rules = rules;
                }
            } else {
                const allDeclarations = this.declarationsBlock(/** @type {Node[]} */ (rules.rules));

                if (allDeclarations && !isRooted && !value) {
                    this.simpleBlock = true;
                    this.declarations = rules.rules;
                } else {
                    this.rules = [rules];
                    /** @type {RulesetLikeNode} */ (this.rules[0]).selectors = (new Selector([], null, null, index, currentFileInfo)).createEmptySelectors();
                }
            }
            if (!this.simpleBlock) {
                for (i = 0; i < this.rules.length; i++) {
                    /** @type {RulesetLikeNode} */ (this.rules[i]).allowImports = true;
                }
            }
            if (this.declarations) {
                this.setParent(this.declarations, /** @type {Node} */ (/** @type {unknown} */ (this)));
            }
            if (this.rules) {
                this.setParent(this.rules, /** @type {Node} */ (/** @type {unknown} */ (this)));
            }
        }
        this._index = index;
        this._fileInfo = currentFileInfo;
        /** @type {{ lineNumber: number, fileName: string } | undefined} */
        this.debugInfo = debugInfo;
        /** @type {boolean} */
        this.isRooted = isRooted || false;
        this.copyVisibilityInfo(visibilityInfo);
        this.allowRoot = true;
    }

    /**
     * @param {Node[]} rules
     * @param {boolean} [mergeable]
     * @returns {boolean}
     */
    declarationsBlock(rules, mergeable = false) {
        if (!mergeable) {
            return rules.filter(function (/** @type {Node & { merge?: boolean }} */ node) { return (node.type === 'Declaration' || node.type === 'Comment') && !node.merge}).length === rules.length;
        } else {
            return rules.filter(function (/** @type {Node} */ node) { return (node.type === 'Declaration' || node.type === 'Comment'); }).length === rules.length;
        }
    }

    /**
     * @param {Node[]} rules
     * @returns {boolean}
     */
    keywordList(rules) {
        if (!Array.isArray(rules)) {
            return false;
        } else {
            return rules.filter(function (/** @type {Node} */ node) { return (node.type === 'Keyword' || node.type === 'Comment'); }).length === rules.length;
        }
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        const value = this.value, rules = this.rules, declarations = this.declarations;

        if (rules) {
            this.rules = visitor.visitArray(rules);
        } else if (declarations) {
            this.declarations = visitor.visitArray(declarations);
        }
        if (value) {
            this.value = visitor.visit(/** @type {Node} */ (value));
        }
    }

    /** @override @returns {boolean} */
    isRulesetLike() {
        return /** @type {boolean} */ (/** @type {unknown} */ (this.rules || !this.isCharset()));
    }

    isCharset() {
        return '@charset' === this.name;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        const value = this.value, rules = this.rules || this.declarations;
        output.add(/** @type {string} */ (this.name), this.fileInfo(), this.getIndex());
        if (value) {
            output.add(' ');
            /** @type {Node} */ (value).genCSS(context, output);
        }
        if (this.simpleBlock) {
            this.outputRuleset(context, output, /** @type {Node[]} */ (this.declarations));
        } else if (rules) {
            this.outputRuleset(context, output, rules);
        } else {
            output.add(';');
        }
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        let mediaPathBackup, mediaBlocksBackup, value = this.value, rules = this.rules || this.declarations;

        // media stored inside other atrule should not bubble over it
        // backpup media bubbling information
        mediaPathBackup = context.mediaPath;
        mediaBlocksBackup = context.mediaBlocks;
        // deleted media bubbling information
        context.mediaPath = [];
        context.mediaBlocks = [];

        if (value) {
            value = /** @type {Node} */ (value).eval(context);
        }

        if (rules) {
            rules = this.evalRoot(context, rules);
        }
        if (Array.isArray(rules) && /** @type {RulesetLikeNode} */ (rules[0]).rules && Array.isArray(/** @type {RulesetLikeNode} */ (rules[0]).rules) && /** @type {Node[]} */ (/** @type {RulesetLikeNode} */ (rules[0]).rules).length) {
            const allMergeableDeclarations = this.declarationsBlock(/** @type {Node[]} */ (/** @type {RulesetLikeNode} */ (rules[0]).rules), true);
            if (allMergeableDeclarations && !this.isRooted && !value) {
                mergeRules(/** @type {Node[]} */ (/** @type {RulesetLikeNode} */ (rules[0]).rules));
                rules = /** @type {RulesetLikeNode[]} */ (/** @type {RulesetLikeNode} */ (rules[0]).rules);
                rules.forEach(/** @param {RulesetLikeNode} rule */ rule => { rule.merge = false; });
            }
        }
        if (this.simpleBlock && rules) {
            /** @type {RulesetLikeNode} */ (rules[0]).functionRegistry = /** @type {RulesetLikeNode} */ (context.frames[0]).functionRegistry.inherit();
            rules = rules.map(function (/** @type {Node} */ rule) { return rule.eval(context); });
        }

        // restore media bubbling information
        context.mediaPath = mediaPathBackup;
        context.mediaBlocks = mediaBlocksBackup;
        return /** @type {Node} */ (/** @type {unknown} */ (new AtRule(this.name, value, rules, this.getIndex(), this.fileInfo(), this.debugInfo, this.isRooted, this.visibilityInfo())));
    }

    /**
     * @param {EvalContext} context
     * @param {Node[]} rules
     * @returns {Node[]}
     */
    evalRoot(context, rules) {
        let ampersandCount = 0;
        let noAmpersandCount = 0;
        let noAmpersands = true;

        if (!this.simpleBlock) {
            rules = [rules[0].eval(context)];
        }

        /** @type {Selector[]} */
        let precedingSelectors = [];
        if (context.frames.length > 0) {
            for (let index = 0; index < context.frames.length; index++) {
                const frame = /** @type {RulesetLikeNode} */ (context.frames[index]);
                if (
                    frame.type === 'Ruleset' &&
                    frame.rules &&
                    frame.rules.length > 0
                ) {
                    if (frame && !frame.root && frame.selectors && frame.selectors.length > 0) {
                        precedingSelectors = precedingSelectors.concat(frame.selectors);
                    }
                }
                if (precedingSelectors.length > 0) {
                    const allAmpersandElements = precedingSelectors.every(
                        sel => sel.elements && sel.elements.length > 0 && sel.elements.every(
                            /** @param {import('./element.js').default} el */
                            el => el.value === '&'
                        )
                    );
                    if (allAmpersandElements) {
                        noAmpersands = false;
                        noAmpersandCount++;
                    } else {
                        ampersandCount++;
                    }
                }
            }
        }

        const mixedAmpersands = ampersandCount > 0 && noAmpersandCount > 0 && !noAmpersands;
        if (
            (this.isRooted && ampersandCount > 0 && noAmpersandCount === 0 && noAmpersands)
            || !mixedAmpersands
        ) {
            /** @type {RulesetLikeNode} */ (rules[0]).root = true;
        }
        return rules;
    }

    /** @param {string} name */
    variable(name) {
        if (this.rules) {
            // assuming that there is only one rule at this point - that is how parser constructs the rule
            return Ruleset.prototype.variable.call(this.rules[0], name);
        }
    }

    find() {
        if (this.rules) {
            // assuming that there is only one rule at this point - that is how parser constructs the rule
            return Ruleset.prototype.find.apply(this.rules[0], arguments);
        }
    }

    rulesets() {
        if (this.rules) {
            // assuming that there is only one rule at this point - that is how parser constructs the rule
            return Ruleset.prototype.rulesets.apply(this.rules[0]);
        }
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     * @param {Node[]} rules
     */
    outputRuleset(context, output, rules) {
        const ruleCnt = rules.length;
        let i;
        context.tabLevel = (context.tabLevel | 0) + 1;

        // Compressed
        if (context.compress) {
            output.add('{');
            for (i = 0; i < ruleCnt; i++) {
                rules[i].genCSS(context, output);
            }
            output.add('}');
            context.tabLevel--;
            return;
        }

        // Non-compressed
        const tabSetStr = `\n${Array(context.tabLevel).join('  ')}`, tabRuleStr = `${tabSetStr}  `;
        if (!ruleCnt) {
            output.add(` {${tabSetStr}}`);
        } else {
            output.add(` {${tabRuleStr}`);
            rules[0].genCSS(context, output);
            for (i = 1; i < ruleCnt; i++) {
                output.add(tabRuleStr);
                rules[i].genCSS(context, output);
            }
            output.add(`${tabSetStr}}`);
        }

        context.tabLevel--;
    }
}

// Apply shared methods from NestableAtRulePrototype that AtRule doesn't override
const { evalFunction, evalTop, evalNested, permute, bubbleSelectors } = NestableAtRulePrototype;
Object.assign(AtRule.prototype, { evalFunction, evalTop, evalNested, permute, bubbleSelectors });

// @ts-check

class DetachedRuleset extends Node {
    get type() { return 'DetachedRuleset'; }

    /**
     * @param {Node} ruleset
     * @param {Node[]} [frames]
     */
    constructor(ruleset, frames) {
        super();
        this.ruleset = ruleset;
        this.frames = frames;
        this.evalFirst = true;
        this.setParent(this.ruleset, this);
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        this.ruleset = visitor.visit(this.ruleset);
    }

    /**
     * @param {EvalContext} context
     * @returns {DetachedRuleset}
     */
    eval(context) {
        const frames = this.frames || copyArray(context.frames);
        return new DetachedRuleset(this.ruleset, frames);
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    callEval(context) {
        return this.ruleset.eval(this.frames ? new contexts.Eval(context, this.frames.concat(context.frames)) : context);
    }
}

// @ts-check
const MATH = Math$1;

class Operation extends Node {
    get type() { return 'Operation'; }

    /**
     * @param {string} op
     * @param {Node[]} operands
     * @param {boolean} isSpaced
     */
    constructor(op, operands, isSpaced) {
        super();
        this.op = op.trim();
        this.operands = operands;
        this.isSpaced = isSpaced;
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        this.operands = visitor.visitArray(this.operands);
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        let a = this.operands[0].eval(context), b = this.operands[1].eval(context), op;

        if (context.isMathOn(this.op)) {
            op = this.op === './' ? '/' : this.op;
            if (a instanceof Dimension && b instanceof Color) {
                a = /** @type {Dimension} */ (a).toColor();
            }
            if (b instanceof Dimension && a instanceof Color) {
                b = /** @type {Dimension} */ (b).toColor();
            }
            if (!/** @type {Dimension | Color} */ (a).operate || !/** @type {Dimension | Color} */ (b).operate) {
                if (
                    (a instanceof Operation || b instanceof Operation)
                    && /** @type {Operation} */ (a).op === '/' && context.math === MATH.PARENS_DIVISION
                ) {
                    return new Operation(this.op, [a, b], this.isSpaced);
                }
                throw { type: 'Operation',
                    message: 'Operation on an invalid type' };
            }

            if (a instanceof Dimension) {
                return a.operate(context, op, /** @type {Dimension} */ (b));
            }
            return /** @type {Color} */ (a).operate(context, op, /** @type {Color} */ (b));
        } else {
            return new Operation(this.op, [a, b], this.isSpaced);
        }
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        this.operands[0].genCSS(context, output);
        if (this.isSpaced) {
            output.add(' ');
        }
        output.add(this.op);
        if (this.isSpaced) {
            output.add(' ');
        }
        this.operands[1].genCSS(context, output);
    }
}

class functionCaller {
    constructor(name, context, index, currentFileInfo) {
        this.name = name.toLowerCase();
        this.index = index;
        this.context = context;
        this.currentFileInfo = currentFileInfo;

        this.func = context.frames[0].functionRegistry.get(this.name);
    }

    isValid() {
        return Boolean(this.func);
    }

    call(args) {
        if (!(Array.isArray(args))) {
            args = [args];
        }
        const evalArgs = this.func.evalArgs;
        if (evalArgs !== false) {
            args = args.map(a => a.eval(this.context));
        }
        const commentFilter = item => !(item.type === 'Comment');

        // This code is terrible and should be replaced as per this issue...
        // https://github.com/less/less.js/issues/2477
        args = args
            .filter(commentFilter)
            .map(item => {
                if (item.type === 'Expression') {
                    const subNodes = item.value.filter(commentFilter);
                    if (subNodes.length === 1) {
                        // https://github.com/less/less.js/issues/3616
                        if (item.parens && subNodes[0].op === '/') {
                            return item;
                        }
                        return subNodes[0];
                    } else {
                        return new Expression(subNodes);
                    }
                }
                return item;
            });

        if (evalArgs === false) {
            return this.func(this.context, ...args);
        }

        return this.func(...args);
    }
}

// @ts-check

//
// A function call node.
//
class Call extends Node {
    get type() { return 'Call'; }

    /**
     * @param {string} name
     * @param {Node[]} args
     * @param {number} index
     * @param {FileInfo} currentFileInfo
     */
    constructor(name, args, index, currentFileInfo) {
        super();
        this.name = name;
        this.args = args;
        this.calc = name === 'calc';
        this._index = index;
        this._fileInfo = currentFileInfo;
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        if (this.args) {
            this.args = visitor.visitArray(this.args);
        }
    }

    //
    // When evaluating a function call,
    // we either find the function in the functionRegistry,
    // in which case we call it, passing the  evaluated arguments,
    // if this returns null or we cannot find the function, we
    // simply print it out as it appeared originally [2].
    //
    // The reason why we evaluate the arguments, is in the case where
    // we try to pass a variable to a function, like: `saturate(@color)`.
    // The function should receive the value, not the variable.
    //
    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        /**
         * Turn off math for calc(), and switch back on for evaluating nested functions
         */
        const currentMathContext = context.mathOn;
        context.mathOn = !this.calc;
        if (this.calc || context.inCalc) {
            context.enterCalc();
        }

        const exitCalc = () => {
            if (this.calc || context.inCalc) {
                context.exitCalc();
            }
            context.mathOn = currentMathContext;
        };

        /** @type {Node | string | boolean | null | undefined} */
        let result;
        const funcCaller = new functionCaller(this.name, context, this.getIndex(), this.fileInfo());

        if (funcCaller.isValid()) {
            try {
                result = funcCaller.call(this.args);
                exitCalc();
            } catch (e) {
                // eslint-disable-next-line no-prototype-builtins
                if (/** @type {Record<string, unknown>} */ (e).hasOwnProperty('line') && /** @type {Record<string, unknown>} */ (e).hasOwnProperty('column')) {
                    throw e;
                }
                throw {
                    type: /** @type {Record<string, string>} */ (e).type || 'Runtime',
                    message: `Error evaluating function \`${this.name}\`${/** @type {Error} */ (e).message ? `: ${/** @type {Error} */ (e).message}` : ''}`,
                    index: this.getIndex(),
                    filename: this.fileInfo().filename,
                    line: /** @type {Record<string, number>} */ (e).lineNumber,
                    column: /** @type {Record<string, number>} */ (e).columnNumber
                };
            }
        }

        if (result !== null && result !== undefined) {
            // Results that that are not nodes are cast as Anonymous nodes
            // Falsy values or booleans are returned as empty nodes
            if (!(result instanceof Node)) {
                if (!result || result === true) {
                    result = new Anonymous(null);
                }
                else {
                    result = new Anonymous(result.toString());
                }

            }
            result._index = this._index;
            result._fileInfo = this._fileInfo;
            return result;
        }

        const args = this.args.map(a => a.eval(context));
        exitCalc();

        return new Call(this.name, args, this.getIndex(), this.fileInfo());
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add(`${this.name}(`, this.fileInfo(), this.getIndex());

        for (let i = 0; i < this.args.length; i++) {
            this.args[i].genCSS(context, output);
            if (i + 1 < this.args.length) {
                output.add(', ');
            }
        }

        output.add(')');
    }
}

// @ts-check

class Variable extends Node {
    get type() { return 'Variable'; }

    /**
     * @param {string} name
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     */
    constructor(name, index, currentFileInfo) {
        super();
        this.name = name;
        this._index = index;
        this._fileInfo = currentFileInfo;
        /** @type {boolean | undefined} */
        this.evaluating = undefined;
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        let variable, name = this.name;

        if (name.indexOf('@@') === 0) {
            name = `@${new Variable(name.slice(1), this.getIndex(), this.fileInfo()).eval(context).value}`;
        }

        if (this.evaluating) {
            throw { type: 'Name',
                message: `Recursive variable definition for ${name}`,
                filename: this.fileInfo().filename,
                index: this.getIndex() };
        }

        this.evaluating = true;

        variable = this.find(context.frames, function (frame) {
            const v = /** @type {Ruleset} */ (frame).variable(name);
            if (v) {
                if (v.important) {
                    const importantScope = context.importantScope[context.importantScope.length - 1];
                    importantScope.important = v.important;
                }
                // If in calc, wrap vars in a function call to cascade evaluate args first
                if (context.inCalc) {
                    return (new Call('_SELF', [v.value], 0, undefined)).eval(context);
                }
                else {
                    return v.value.eval(context);
                }
            }
        });
        if (variable) {
            this.evaluating = false;
            return variable;
        } else {
            throw { type: 'Name',
                message: `variable ${name} is undefined`,
                filename: this.fileInfo().filename,
                index: this.getIndex() };
        }
    }

    /**
     * @param {Node[]} obj
     * @param {(frame: Node) => Node | undefined} fun
     * @returns {Node | null}
     */
    find(obj, fun) {
        for (let i = 0, r; i < obj.length; i++) {
            r = fun.call(obj, obj[i]);
            if (r) { return r; }
        }
        return null;
    }
}

// @ts-check

class Property extends Node {
    get type() { return 'Property'; }

    /**
     * @param {string} name
     * @param {number} index
     * @param {FileInfo} currentFileInfo
     */
    constructor(name, index, currentFileInfo) {
        super();
        this.name = name;
        this._index = index;
        this._fileInfo = currentFileInfo;
        /** @type {boolean | undefined} */
        this.evaluating = undefined;
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        let property;
        const name = this.name;
        // TODO: shorten this reference
        const mergeRules = /** @type {{ less: { visitors: { ToCSSVisitor: { prototype: { _mergeRules: (rules: Declaration[]) => void } } } } }} */ (context.pluginManager).less.visitors.ToCSSVisitor.prototype._mergeRules;

        if (this.evaluating) {
            throw { type: 'Name',
                message: `Recursive property reference for ${name}`,
                filename: this.fileInfo().filename,
                index: this.getIndex() };
        }

        this.evaluating = true;

        property = this.find(context.frames, function (/** @type {Node} */ frame) {
            let v;
            const vArr = /** @type {Ruleset} */ (frame).property(name);
            if (vArr) {
                for (let i = 0; i < vArr.length; i++) {
                    v = vArr[i];

                    vArr[i] = new Declaration(v.name,
                        v.value,
                        v.important,
                        v.merge,
                        v.index,
                        v.currentFileInfo,
                        v.inline,
                        v.variable
                    );
                }
                mergeRules(vArr);

                v = vArr[vArr.length - 1];
                if (v.important) {
                    const importantScope = context.importantScope[context.importantScope.length - 1];
                    importantScope.important = v.important;
                }
                v = v.value.eval(context);
                return v;
            }
        });
        if (property) {
            this.evaluating = false;
            return property;
        } else {
            throw { type: 'Name',
                message: `Property '${name}' is undefined`,
                filename: this.currentFileInfo.filename,
                index: this.index };
        }
    }

    /**
     * @param {Node[]} obj
     * @param {(frame: Node) => Node | undefined} fun
     * @returns {Node | null}
     */
    find(obj, fun) {
        for (let i = 0, r; i < obj.length; i++) {
            r = fun.call(obj, obj[i]);
            if (r) { return r; }
        }
        return null;
    }
}

// @ts-check

class Attribute extends Node {
    get type() { return 'Attribute'; }

    /**
     * @param {string | Node} key
     * @param {string} op
     * @param {string | Node} value
     * @param {string} cif
     */
    constructor(key, op, value, cif) {
        super();
        this.key = key;
        this.op = op;
        this.value = value;
        this.cif = cif;
    }

    /**
     * @param {EvalContext} context
     * @returns {Attribute}
     */
    eval(context) {
        return new Attribute(
            /** @type {Node} */ (this.key).eval ? /** @type {Node} */ (this.key).eval(context) : /** @type {string} */ (this.key),
            this.op,
            (this.value && /** @type {Node} */ (this.value).eval) ? /** @type {Node} */ (this.value).eval(context) : this.value,
            this.cif
        );
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add(this.toCSS(context));
    }

    /**
     * @param {EvalContext} context
     * @returns {string}
     */
    toCSS(context) {
        let value = /** @type {Node} */ (this.key).toCSS ? /** @type {Node} */ (this.key).toCSS(context) : /** @type {string} */ (this.key);

        if (this.op) {
            value += this.op;
            value += (/** @type {Node} */ (this.value).toCSS ? /** @type {Node} */ (this.value).toCSS(context) : /** @type {string} */ (this.value));
        }

        if (this.cif) {
            value = value + ' ' + this.cif;
        }

        return `[${value}]`;
    }
}

// @ts-check

class Quoted extends Node {
    get type() { return 'Quoted'; }

    /**
     * @param {string} str
     * @param {string} [content]
     * @param {boolean} [escaped]
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     */
    constructor(str, content, escaped, index, currentFileInfo) {
        super();
        /** @type {boolean} */
        this.escaped = (escaped === undefined) ? true : escaped;
        /** @type {string} */
        this.value = content || '';
        /** @type {string} */
        this.quote = str.charAt(0);
        this._index = index;
        this._fileInfo = currentFileInfo;
        /** @type {RegExp} */
        this.variableRegex = /@\{([\w-]+)\}/g;
        /** @type {RegExp} */
        this.propRegex = /\$\{([\w-]+)\}/g;
        /** @type {boolean | undefined} */
        this.allowRoot = escaped;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        if (!this.escaped) {
            output.add(this.quote, this.fileInfo(), this.getIndex());
        }
        output.add(/** @type {string} */ (this.value));
        if (!this.escaped) {
            output.add(this.quote);
        }
    }

    /** @returns {RegExpMatchArray | null} */
    containsVariables() {
        return /** @type {string} */ (this.value).match(this.variableRegex);
    }

    /** @param {EvalContext} context */
    eval(context) {
        const that = this;
        let value = /** @type {string} */ (this.value);
        /**
         * @param {string} _
         * @param {string} name1
         * @param {string} name2
         * @returns {string}
         */
        const variableReplacement = function (_, name1, name2) {
            const v = new Variable(`@${name1 ?? name2}`, that.getIndex(), that.fileInfo()).eval(context);
            return (v instanceof Quoted) ? /** @type {string} */ (v.value) : v.toCSS(context);
        };
        /**
         * @param {string} _
         * @param {string} name1
         * @param {string} name2
         * @returns {string}
         */
        const propertyReplacement = function (_, name1, name2) {
            const v = new Property(`$${name1 ?? name2}`, that.getIndex(), that.fileInfo()).eval(context);
            return (v instanceof Quoted) ? /** @type {string} */ (v.value) : v.toCSS(context);
        };
        /**
         * @param {string} value
         * @param {RegExp} regexp
         * @param {(substring: string, ...args: string[]) => string} replacementFnc
         * @returns {string}
         */
        function iterativeReplace(value, regexp, replacementFnc) {
            let evaluatedValue = value;
            do {
                value = evaluatedValue.toString();
                evaluatedValue = value.replace(regexp, replacementFnc);
            } while (value !== evaluatedValue);
            return evaluatedValue;
        }
        value = iterativeReplace(value, this.variableRegex, variableReplacement);
        value = iterativeReplace(value, this.propRegex, propertyReplacement);
        return new Quoted(this.quote + value + this.quote, value, this.escaped, this.getIndex(), this.fileInfo());
    }

    /**
     * @param {Node} other
     * @returns {number | undefined}
     */
    compare(other) {
        // when comparing quoted strings allow the quote to differ
        if (other.type === 'Quoted' && !this.escaped && !/** @type {Quoted} */ (other).escaped) {
            return Node.numericCompare(
                /** @type {string} */ (this.value),
                /** @type {string} */ (other.value)
            );
        } else {
            return other.toCSS && this.toCSS(/** @type {EvalContext} */ ({})) === other.toCSS(/** @type {EvalContext} */ ({})) ? 0 : undefined;
        }
    }
}

// @ts-check

/**
 * @param {string} path
 * @returns {string}
 */
function escapePath(path) {
    return path.replace(/[()'"\s]/g, function(match) { return `\\${match}`; });
}

class URL extends Node {
    get type() { return 'Url'; }

    /**
     * @param {Node} val
     * @param {number} index
     * @param {FileInfo} currentFileInfo
     * @param {boolean} [isEvald]
     */
    constructor(val, index, currentFileInfo, isEvald) {
        super();
        this.value = val;
        this._index = index;
        this._fileInfo = currentFileInfo;
        /** @type {boolean | undefined} */
        this.isEvald = isEvald;
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        this.value = visitor.visit(/** @type {Node} */ (this.value));
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add('url(');
        /** @type {Node} */ (this.value).genCSS(context, output);
        output.add(')');
    }

    /** @param {EvalContext} context */
    eval(context) {
        const val = /** @type {Node} */ (this.value).eval(context);
        let rootpath;

        if (!this.isEvald) {
            // Add the rootpath if the URL requires a rewrite
            rootpath = this.fileInfo() && this.fileInfo().rootpath;
            if (typeof rootpath === 'string' &&
                typeof val.value === 'string' &&
                context.pathRequiresRewrite(/** @type {string} */ (val.value))) {
                if (!/** @type {import('./quoted.js').default} */ (val).quote) {
                    rootpath = escapePath(rootpath);
                }
                val.value = context.rewritePath(/** @type {string} */ (val.value), rootpath);
            } else {
                val.value = context.normalizePath(/** @type {string} */ (val.value));
            }

            // Add url args if enabled
            if (context.urlArgs) {
                if (!/** @type {string} */ (val.value).match(/^\s*data:/)) {
                    const delimiter = /** @type {string} */ (val.value).indexOf('?') === -1 ? '?' : '&';
                    const urlArgs = delimiter + context.urlArgs;
                    if (/** @type {string} */ (val.value).indexOf('#') !== -1) {
                        val.value = /** @type {string} */ (val.value).replace('#', `${urlArgs}#`);
                    } else {
                        val.value += urlArgs;
                    }
                }
            }
        }

        return new URL(val, this.getIndex(), this.fileInfo(), true);
    }
}

// @ts-check

class Media extends AtRule {
    get type() { return 'Media'; }

    /**
     * @param {Node[] | null} value
     * @param {Node[]} features
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(value, features, index, currentFileInfo, visibilityInfo) {
        super();
        this._index = index;
        this._fileInfo = currentFileInfo;

        const selectors = (new Selector([], null, null, this._index, this._fileInfo)).createEmptySelectors();

        /** @type {Value} */
        this.features = new Value(features);
        /** @type {RulesetLikeNode[]} */
        this.rules = [new Ruleset(selectors, value)];
        /** @type {RulesetLikeNode} */ (this.rules[0]).allowImports = true;
        this.copyVisibilityInfo(visibilityInfo);
        this.allowRoot = true;
        this.setParent(selectors, /** @type {Node} */ (/** @type {unknown} */ (this)));
        this.setParent(this.features, /** @type {Node} */ (/** @type {unknown} */ (this)));
        this.setParent(this.rules, /** @type {Node} */ (/** @type {unknown} */ (this)));
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add('@media ', this._fileInfo, this._index);
        this.features.genCSS(context, output);
        this.outputRuleset(context, output, this.rules);
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        if (!context.mediaBlocks) {
            context.mediaBlocks = [];
            context.mediaPath = [];
        }

        const media = new Media(null, [], this._index, this._fileInfo, this.visibilityInfo());
        if (this.debugInfo) {
            /** @type {RulesetLikeNode} */ (this.rules[0]).debugInfo = this.debugInfo;
            media.debugInfo = this.debugInfo;
        }

        media.features = /** @type {Value} */ (this.features.eval(context));

        context.mediaPath.push(/** @type {Node} */ (/** @type {unknown} */ (media)));
        context.mediaBlocks.push(/** @type {Node} */ (/** @type {unknown} */ (media)));

        const fr = /** @type {RulesetLikeNode} */ (context.frames[0]).functionRegistry;
        if (fr) {
            /** @type {RulesetLikeNode} */ (this.rules[0]).functionRegistry = fr.inherit();
        }
        context.frames.unshift(this.rules[0]);
        media.rules = [/** @type {RulesetLikeNode} */ (this.rules[0].eval(context))];
        context.frames.shift();

        context.mediaPath.pop();

        return context.mediaPath.length === 0 ? /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (media)).evalTop(context) :
            /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (media)).evalNested(context);
    }
}

// Apply NestableAtRulePrototype methods (accept, isRulesetLike override AtRule's versions)
Object.assign(Media.prototype, NestableAtRulePrototype);

// @ts-check

/**
 * @typedef {object} ImportOptions
 * @property {boolean} [less]
 * @property {boolean} [inline]
 * @property {boolean} [isPlugin]
 * @property {boolean} [reference]
 */

//
// CSS @import node
//
// The general strategy here is that we don't want to wait
// for the parsing to be completed, before we start importing
// the file. That's because in the context of a browser,
// most of the time will be spent waiting for the server to respond.
//
// On creation, we push the import path to our import queue, though
// `import,push`, we also pass it a callback, which it'll call once
// the file has been fetched, and parsed.
//
class Import extends Node {
    get type() { return 'Import'; }

    /**
     * @param {Node} path
     * @param {Node | null} features
     * @param {ImportOptions} options
     * @param {number} index
     * @param {FileInfo} [currentFileInfo]
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(path, features, options, index, currentFileInfo, visibilityInfo) {
        super();
        /** @type {ImportOptions} */
        this.options = options;
        this._index = index;
        this._fileInfo = currentFileInfo;
        this.path = path;
        /** @type {Node | null} */
        this.features = features;
        /** @type {boolean} */
        this.allowRoot = true;

        /** @type {boolean | undefined} */
        this.css = undefined;
        /** @type {boolean | undefined} */
        this.layerCss = undefined;
        /** @type {(Ruleset & { imports?: object, filename?: string, functions?: object, functionRegistry?: { addMultiple: (fns: object) => void } }) | undefined} */
        this.root = undefined;
        /** @type {string | undefined} */
        this.importedFilename = undefined;
        /** @type {boolean | (() => boolean) | undefined} */
        this.skip = undefined;
        /** @type {{ message: string, index: number, filename: string } | undefined} */
        this.error = undefined;

        if (this.options.less !== undefined || this.options.inline) {
            this.css = !this.options.less || this.options.inline;
        } else {
            const pathValue = this.getPath();
            if (pathValue && /[#.&?]css([?;].*)?$/.test(pathValue)) {
                this.css = true;
            }
        }
        this.copyVisibilityInfo(visibilityInfo);
        if (this.features) {
            this.setParent(this.features, /** @type {Node} */ (this));
        }
        this.setParent(this.path, /** @type {Node} */ (this));
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        if (this.features) {
            this.features = visitor.visit(this.features);
        }
        this.path = visitor.visit(this.path);
        if (!this.options.isPlugin && !this.options.inline && this.root) {
            this.root = /** @type {Ruleset} */ (visitor.visit(this.root));
        }
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        if (this.css && this.path._fileInfo.reference === undefined) {
            output.add('@import ', this._fileInfo, this._index);
            this.path.genCSS(context, output);
            if (this.features) {
                output.add(' ');
                this.features.genCSS(context, output);
            }
            output.add(';');
        }
    }

    /** @returns {string | undefined} */
    getPath() {
        return (this.path instanceof URL) ?
            /** @type {string} */ (/** @type {Node} */ (this.path.value).value) :
            /** @type {string | undefined} */ (this.path.value);
    }

    /** @returns {boolean | RegExpMatchArray | null} */
    isVariableImport() {
        let path = this.path;
        if (path instanceof URL) {
            path = /** @type {Node} */ (path.value);
        }
        if (path instanceof Quoted) {
            return path.containsVariables();
        }

        return true;
    }

    /** @param {EvalContext} context */
    evalForImport(context) {
        let path = this.path;

        if (path instanceof URL) {
            path = /** @type {Node} */ (path.value);
        }

        return new Import(path.eval(context), this.features, this.options, this._index || 0, this._fileInfo, this.visibilityInfo());
    }

    /** @param {EvalContext} context */
    evalPath(context) {
        const path = this.path.eval(context);
        const fileInfo = this._fileInfo;

        if (!(path instanceof URL)) {
            // Add the rootpath if the URL requires a rewrite
            const pathValue = /** @type {string} */ (path.value);
            if (fileInfo &&
                pathValue &&
                context.pathRequiresRewrite(pathValue)) {
                path.value = context.rewritePath(pathValue, fileInfo.rootpath);
            } else {
                path.value = context.normalizePath(/** @type {string} */ (path.value));
            }
        }

        return path;
    }

    /** @param {EvalContext} context */
    // @ts-ignore - Import.eval returns Node | Node[] | Import (wider than Node.eval's Node return)
    eval(context) {
        const result = this.doEval(context);
        if (this.options.reference || this.blocksVisibility()) {
            if (Array.isArray(result)) {
                result.forEach(function (node) {
                    node.addVisibilityBlock();
                });
            } else {
                /** @type {Node} */ (result).addVisibilityBlock();
            }
        }
        return result;
    }

    /** @param {EvalContext} context */
    doEval(context) {
        /** @type {Ruleset | undefined} */
        let ruleset;
        const features = this.features && this.features.eval(context);

        if (this.options.isPlugin) {
            if (this.root && this.root.eval) {
                try {
                    this.root.eval(context);
                }
                catch (e) {
                    const err = /** @type {{ message: string }} */ (e);
                    err.message = 'Plugin error during evaluation';
                    throw new LessError(
                        /** @type {{ message: string, index?: number, filename?: string }} */ (e),
                        /** @type {{ imports: object }} */ (/** @type {unknown} */ (this.root)).imports,
                        /** @type {{ filename: string }} */ (/** @type {unknown} */ (this.root)).filename
                    );
                }
            }
            const frame0 = /** @type {Ruleset & { functionRegistry?: { addMultiple: (fns: object) => void } }} */ (context.frames[0]);
            const registry = frame0 && frame0.functionRegistry;
            if (registry && this.root && this.root.functions) {
                registry.addMultiple(this.root.functions);
            }

            return [];
        }

        if (this.skip) {
            if (typeof this.skip === 'function') {
                this.skip = this.skip();
            }
            if (this.skip) {
                return [];
            }
        }
        if (this.features) {
            let featureValue = /** @type {Node[]} */ (this.features.value);
            if (Array.isArray(featureValue) && featureValue.length >= 1) {
                const expr = featureValue[0];
                if (expr.type === 'Expression' && Array.isArray(expr.value) && /** @type {Node[]} */ (expr.value).length >= 2) {
                    featureValue = /** @type {Node[]} */ (expr.value);
                    const isLayer = featureValue[0].type === 'Keyword' && featureValue[0].value === 'layer'
                        && featureValue[1].type === 'Paren';
                    if (isLayer) {
                        this.css = false;
                    }
                }
            }
        }
        if (this.options.inline) {
            const contents = new Anonymous(
                /** @type {string} */ (/** @type {unknown} */ (this.root)),
                0,
                {
                    filename: this.importedFilename,
                    reference: this.path._fileInfo && this.path._fileInfo.reference
                },
                true,
                true
            );

            return this.features ? new Media([contents], /** @type {Node[]} */ (this.features.value)) : [contents];
        } else if (this.css || this.layerCss) {
            const newImport = new Import(this.evalPath(context), features, this.options, this._index || 0);
            if (this.layerCss) {
                newImport.css = this.layerCss;
                newImport.path._fileInfo = this._fileInfo;
            }
            if (!newImport.css && this.error) {
                throw this.error;
            }
            return newImport;
        } else if (this.root) {
            if (this.features) {
                let featureValue = /** @type {Node[]} */ (this.features.value);
                if (Array.isArray(featureValue) && featureValue.length === 1) {
                    const expr = featureValue[0];
                    if (expr.type === 'Expression' && Array.isArray(expr.value) && /** @type {Node[]} */ (expr.value).length >= 2) {
                        featureValue = /** @type {Node[]} */ (expr.value);
                        const isLayer = featureValue[0].type === 'Keyword' && featureValue[0].value === 'layer'
                            && featureValue[1].type === 'Paren';
                        if (isLayer) {
                            this.layerCss = true;
                            featureValue[0] = new Expression(/** @type {Node[]} */ (featureValue.slice(0, 2)));
                            featureValue.splice(1, 1);
                            /** @type {Expression} */ (featureValue[0]).noSpacing = true;
                            return this;
                        }
                    }
                }
            }
            ruleset = new Ruleset(null, copyArray(this.root.rules));
            ruleset.evalImports(context);

            return this.features ? new Media(ruleset.rules, /** @type {Node[]} */ (this.features.value)) : ruleset.rules;
        } else {
            if (this.features) {
                let featureValue = /** @type {Node[]} */ (this.features.value);
                if (Array.isArray(featureValue) && featureValue.length >= 1) {
                    featureValue = /** @type {Node[]} */ (featureValue[0].value);
                    if (Array.isArray(featureValue) && featureValue.length >= 2) {
                        const isLayer = featureValue[0].type === 'Keyword' && featureValue[0].value === 'layer'
                            && featureValue[1].type === 'Paren';
                        if (isLayer) {
                            this.css = true;
                            featureValue[0] = new Expression(/** @type {Node[]} */ (featureValue.slice(0, 2)));
                            featureValue.splice(1, 1);
                            /** @type {Expression} */ (featureValue[0]).noSpacing = true;
                            return this;
                        }
                    }
                }
            }
            return [];
        }
    }
}

// @ts-check

class JsEvalNode extends Node {
    /**
     * @param {string} expression
     * @param {EvalContext} context
     * @returns {string | number | boolean}
     */
    evaluateJavaScript(expression, context) {
        let result;
        const that = this;
        /** @type {Record<string, { value: Node, toJS: () => string }>} */
        const evalContext = {};

        if (!context.javascriptEnabled) {
            throw { message: 'Inline JavaScript is not enabled. Is it set in your options?',
                filename: this.fileInfo().filename,
                index: this.getIndex() };
        }

        expression = expression.replace(/@\{([\w-]+)\}/g, function (_, name) {
            return that.jsify(new Variable(`@${name}`, that.getIndex(), that.fileInfo()).eval(context));
        });

        /** @type {Function} */
        let expressionFunc;
        try {
            expressionFunc = new Function(`return (${expression})`);
        } catch (e) {
            throw { message: `JavaScript evaluation error: ${/** @type {Error} */ (e).message} from \`${expression}\`` ,
                filename: this.fileInfo().filename,
                index: this.getIndex() };
        }

        const variables = /** @type {Node & { variables: () => Record<string, { value: Node }> }} */ (context.frames[0]).variables();
        for (const k in variables) {
            // eslint-disable-next-line no-prototype-builtins
            if (variables.hasOwnProperty(k)) {
                evalContext[k.slice(1)] = {
                    value: variables[k].value,
                    toJS: function () {
                        return this.value.eval(context).toCSS(context);
                    }
                };
            }
        }

        try {
            result = expressionFunc.call(evalContext);
        } catch (e) {
            throw { message: `JavaScript evaluation error: '${/** @type {Error} */ (e).name}: ${/** @type {Error} */ (e).message.replace(/["]/g, '\'')}'` ,
                filename: this.fileInfo().filename,
                index: this.getIndex() };
        }
        return result;
    }

    /**
     * @param {Node} obj
     * @returns {string}
     */
    jsify(obj) {
        if (Array.isArray(obj.value) && (obj.value.length > 1)) {
            return `[${obj.value.map(function (v) { return v.toCSS(/** @type {EvalContext} */ (undefined)); }).join(', ')}]`;
        } else {
            return obj.toCSS(/** @type {EvalContext} */ (undefined));
        }
    }
}

// @ts-check

class JavaScript extends JsEvalNode {
    get type() { return 'JavaScript'; }

    /**
     * @param {string} string
     * @param {boolean} escaped
     * @param {number} index
     * @param {FileInfo} currentFileInfo
     */
    constructor(string, escaped, index, currentFileInfo) {
        super();
        this.escaped = escaped;
        this.expression = string;
        this._index = index;
        this._fileInfo = currentFileInfo;
    }

    /**
     * @param {EvalContext} context
     * @returns {Dimension | Quoted | Anonymous}
     */
    eval(context) {
        const result = this.evaluateJavaScript(this.expression, context);
        const type = typeof result;

        if (type === 'number' && !isNaN(/** @type {number} */ (result))) {
            return new Dimension(/** @type {number} */ (result));
        } else if (type === 'string') {
            return new Quoted(`"${result}"`, /** @type {string} */ (result), this.escaped, this._index);
        } else if (Array.isArray(result)) {
            return new Anonymous(/** @type {string[]} */ (result).join(', '));
        } else {
            return new Anonymous(/** @type {string} */ (result));
        }
    }
}

// @ts-check

class Assignment extends Node {
    get type() { return 'Assignment'; }

    /**
     * @param {string} key
     * @param {Node} val
     */
    constructor(key, val) {
        super();
        this.key = key;
        this.value = val;
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        this.value = visitor.visit(/** @type {Node} */ (this.value));
    }

    /**
     * @param {EvalContext} context
     * @returns {Assignment}
     */
    eval(context) {
        if (/** @type {Node} */ (this.value).eval) {
            return new Assignment(this.key, /** @type {Node} */ (this.value).eval(context));
        }
        return this;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add(`${this.key}=`);
        if (/** @type {Node} */ (this.value).genCSS) {
            /** @type {Node} */ (this.value).genCSS(context, output);
        } else {
            output.add(/** @type {string} */ (/** @type {unknown} */ (this.value)));
        }
    }
}

// @ts-check

class Condition extends Node {
    get type() { return 'Condition'; }

    /**
     * @param {string} op
     * @param {Node} l
     * @param {Node} r
     * @param {number} i
     * @param {boolean} negate
     */
    constructor(op, l, r, i, negate) {
        super();
        this.op = op.trim();
        this.lvalue = l;
        this.rvalue = r;
        this._index = i;
        this.negate = negate;
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        this.lvalue = visitor.visit(this.lvalue);
        this.rvalue = visitor.visit(this.rvalue);
    }

    /**
     * @param {EvalContext} context
     * @returns {boolean}
     * @suppress {checkTypes}
     */
    // @ts-ignore - Condition.eval returns boolean, not Node (used as guard condition)
    eval(context) {
        const a = this.lvalue.eval(context);
        const b = this.rvalue.eval(context);
        /** @type {boolean} */
        let result;

        switch (this.op) {
            case 'and': result = Boolean(a && b); break;
            case 'or':  result = Boolean(a || b); break;
            default:
                switch (Node.compare(a, b)) {
                    case -1:
                        result = this.op === '<' || this.op === '=<' || this.op === '<=';
                        break;
                    case 0:
                        result = this.op === '=' || this.op === '>=' || this.op === '=<' || this.op === '<=';
                        break;
                    case 1:
                        result = this.op === '>' || this.op === '>=';
                        break;
                    default:
                        result = false;
                }
        }

        return this.negate ? !result : result;
    }
}

// @ts-check

class QueryInParens extends Node {
    get type() { return 'QueryInParens'; }

    /**
     * @param {string} op
     * @param {Node} l
     * @param {Node} m
     * @param {string | null} op2
     * @param {Node | null} r
     * @param {number} i
     */
    constructor(op, l, m, op2, r, i) {
        super();
        this.op = op.trim();
        this.lvalue = l;
        this.mvalue = m;
        this.op2 = op2 ? op2.trim() : null;
        /** @type {Node | null} */
        this.rvalue = r;
        this._index = i;
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        this.lvalue = visitor.visit(this.lvalue);
        this.mvalue = visitor.visit(this.mvalue);
        if (this.rvalue) {
            this.rvalue = visitor.visit(this.rvalue);
        }
    }

    /** @param {EvalContext} context */
    eval(context) {
        const node = new QueryInParens(
            this.op,
            this.lvalue.eval(context),
            this.mvalue.eval(context),
            this.op2,
            this.rvalue ? this.rvalue.eval(context) : null,
            this._index || 0
        );
        return node;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        this.lvalue.genCSS(context, output);
        output.add(' ' + this.op + ' ');
        this.mvalue.genCSS(context, output);
        if (this.rvalue) {
            output.add(' ' + this.op2 + ' ');
            this.rvalue.genCSS(context, output);
        }
    }
}

// @ts-check

/**
 * @typedef {Ruleset & {
 *   allowImports?: boolean,
 *   debugInfo?: { lineNumber: number, fileName: string },
 *   functionRegistry?: FunctionRegistry
 * }} RulesetWithExtras
 */

class Container extends AtRule {
    get type() { return 'Container'; }

    /**
     * @param {Node[] | null} value
     * @param {Node[]} features
     * @param {number} index
     * @param {FileInfo} currentFileInfo
     * @param {VisibilityInfo} visibilityInfo
     */
    constructor(value, features, index, currentFileInfo, visibilityInfo) {
        super();
        this._index = index;
        this._fileInfo = currentFileInfo;

        const selectors = (new Selector([], null, null, this._index, this._fileInfo)).createEmptySelectors();

        /** @type {Value} */
        this.features = new Value(features);
        /** @type {RulesetWithExtras[]} */
        this.rules = [new Ruleset(selectors, value)];
        this.rules[0].allowImports = true;
        this.copyVisibilityInfo(visibilityInfo);
        this.allowRoot = true;
        this.setParent(selectors, /** @type {Node} */ (/** @type {unknown} */ (this)));
        this.setParent(this.features, /** @type {Node} */ (/** @type {unknown} */ (this)));
        this.setParent(this.rules, /** @type {Node} */ (/** @type {unknown} */ (this)));

        /** @type {boolean | undefined} */
        this._evaluated = undefined;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add('@container ', this._fileInfo, this._index);
        this.features.genCSS(context, output);
        this.outputRuleset(context, output, this.rules);
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        if (this._evaluated) {
            return /** @type {Node} */ (/** @type {unknown} */ (this));
        }
        if (!context.mediaBlocks) {
            context.mediaBlocks = [];
            context.mediaPath = [];
        }

        const media = new Container(null, [], this._index, this._fileInfo, this.visibilityInfo());
        media._evaluated = true;
        if (this.debugInfo) {
            this.rules[0].debugInfo = this.debugInfo;
            media.debugInfo = this.debugInfo;
        }

        media.features = /** @type {Value} */ (this.features.eval(context));

        context.mediaPath.push(/** @type {Node} */ (/** @type {unknown} */ (media)));
        context.mediaBlocks.push(/** @type {Node} */ (/** @type {unknown} */ (media)));

        const fr = /** @type {RulesetWithExtras} */ (context.frames[0]).functionRegistry;
        if (fr) {
            this.rules[0].functionRegistry = fr.inherit();
        }
        context.frames.unshift(this.rules[0]);
        media.rules = [/** @type {RulesetWithExtras} */ (this.rules[0].eval(context))];
        context.frames.shift();

        context.mediaPath.pop();

        return context.mediaPath.length === 0 ? /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (media)).evalTop(context) :
            /** @type {NestableAtRuleThis} */ (/** @type {unknown} */ (media)).evalNested(context);
    }
}

// Apply NestableAtRulePrototype methods (accept, isRulesetLike override AtRule's versions)
Object.assign(Container.prototype, NestableAtRulePrototype);

// @ts-check

class UnicodeDescriptor extends Node {
    get type() { return 'UnicodeDescriptor'; }

    /** @param {string} value */
    constructor(value) {
        super();
        this.value = value;
    }
}

// @ts-check

class Negative extends Node {
    get type() { return 'Negative'; }

    /** @param {Node} node */
    constructor(node) {
        super();
        this.value = node;
    }

    /**
     * @param {EvalContext} context
     * @param {CSSOutput} output
     */
    genCSS(context, output) {
        output.add('-');
        /** @type {Node} */ (this.value).genCSS(context, output);
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        if (context.isMathOn('*')) {
            return (new Operation('*', [new Dimension(-1), /** @type {Node} */ (this.value)], false)).eval(context);
        }
        return new Negative(/** @type {Node} */ (this.value).eval(context));
    }
}

// @ts-check

class Extend extends Node {
    get type() { return 'Extend'; }

    /**
     * @param {Selector} selector
     * @param {string} option
     * @param {number} index
     * @param {FileInfo} currentFileInfo
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(selector, option, index, currentFileInfo, visibilityInfo) {
        super();
        this.selector = selector;
        this.option = option;
        this.object_id = Extend.next_id++;
        /** @type {number[]} */
        this.parent_ids = [this.object_id];
        this._index = index;
        this._fileInfo = currentFileInfo;
        this.copyVisibilityInfo(visibilityInfo);
        /** @type {boolean} */
        this.allowRoot = true;
        /** @type {boolean} */
        this.allowBefore = false;
        /** @type {boolean} */
        this.allowAfter = false;

        switch (option) {
            case '!all':
            case 'all':
                this.allowBefore = true;
                this.allowAfter = true;
                break;
            default:
                this.allowBefore = false;
                this.allowAfter = false;
                break;
        }
        this.setParent(this.selector, this);
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        this.selector = /** @type {Selector} */ (visitor.visit(this.selector));
    }

    /** @param {EvalContext} context */
    eval(context) {
        return new Extend(/** @type {Selector} */ (this.selector.eval(context)), this.option, this.getIndex(), this.fileInfo(), this.visibilityInfo());
    }

    // remove when Nodes have JSDoc types
    // eslint-disable-next-line no-unused-vars
    /** @param {EvalContext} [context] */
    clone(context) {
        return new Extend(this.selector, this.option, this.getIndex(), this.fileInfo(), this.visibilityInfo());
    }

    // it concatenates (joins) all selectors in selector array
    /** @param {Selector[]} selectors */
    findSelfSelectors(selectors) {
        /** @type {import('./element.js').default[]} */
        let selfElements = [];
        let i, selectorElements;

        for (i = 0; i < selectors.length; i++) {
            selectorElements = selectors[i].elements;
            // duplicate the logic in genCSS function inside the selector node.
            // future TODO - move both logics into the selector joiner visitor
            if (i > 0 && selectorElements.length && selectorElements[0].combinator.value === '') {
                selectorElements[0].combinator.value = ' ';
            }
            selfElements = selfElements.concat(selectors[i].elements);
        }

        /** @type {Selector[]} */
        this.selfSelectors = [new Selector(selfElements)];
        this.selfSelectors[0].copyVisibilityInfo(this.visibilityInfo());
    }
}

Extend.next_id = 0;

// @ts-check

class VariableCall extends Node {
    get type() { return 'VariableCall'; }

    /**
     * @param {string} variable
     * @param {number} index
     * @param {FileInfo} currentFileInfo
     */
    constructor(variable, index, currentFileInfo) {
        super();
        this.variable = variable;
        this._index = index;
        this._fileInfo = currentFileInfo;
        this.allowRoot = true;
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        let rules;
        /** @type {DetachedRuleset | Node} */
        let detachedRuleset = new Variable(this.variable, this.getIndex(), this.fileInfo()).eval(context);
        const error = new LessError({message: `Could not evaluate variable call ${this.variable}`});

        if (!(/** @type {DetachedRuleset} */ (detachedRuleset)).ruleset) {
            const dr = /** @type {Node & { rules?: Node[] }} */ (detachedRuleset);
            if (dr.rules) {
                rules = detachedRuleset;
            }
            else if (Array.isArray(detachedRuleset)) {
                rules = new Ruleset(null, detachedRuleset);
            }
            else if (Array.isArray(detachedRuleset.value)) {
                rules = new Ruleset(null, detachedRuleset.value);
            }
            else {
                throw error;
            }
            detachedRuleset = new DetachedRuleset(rules);
        }

        const dr = /** @type {DetachedRuleset} */ (detachedRuleset);
        if (dr.ruleset) {
            return dr.callEval(context);
        }
        throw error;
    }
}

// @ts-check

class NamespaceValue extends Node {
    get type() { return 'NamespaceValue'; }

    /**
     * @param {Node} ruleCall
     * @param {string[]} lookups
     * @param {number} index
     * @param {FileInfo} fileInfo
     */
    constructor(ruleCall, lookups, index, fileInfo) {
        super();
        this.value = ruleCall;
        this.lookups = lookups;
        this._index = index;
        this._fileInfo = fileInfo;
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        let i, name;
        /** @type {Ruleset | Node | Node[]} */
        let rules = this.value.eval(context);

        for (i = 0; i < this.lookups.length; i++) {
            name = this.lookups[i];

            if (Array.isArray(rules)) {
                rules = new Ruleset([new Selector()], rules);
            }

            const rs = /** @type {Ruleset} */ (rules);

            if (name === '') {
                rules = rs.lastDeclaration();
            }
            else if (name.charAt(0) === '@') {
                if (name.charAt(1) === '@') {
                    name = `@${new Variable(name.slice(1)).eval(context).value}`;
                }
                if (rs.variables) {
                    rules = rs.variable(name);
                }

                if (!rules) {
                    throw { type: 'Name',
                        message: `variable ${name} not found`,
                        filename: this.fileInfo().filename,
                        index: this.getIndex() };
                }
            }
            else {
                if (name.substring(0, 2) === '$@') {
                    name = `$${new Variable(name.slice(1)).eval(context).value}`;
                }
                else {
                    name = name.charAt(0) === '$' ? name : `$${name}`;
                }
                if (rs.properties) {
                    rules = rs.property(name);
                }

                if (!rules) {
                    throw { type: 'Name',
                        message: `property "${name.slice(1)}" not found`,
                        filename: this.fileInfo().filename,
                        index: this.getIndex() };
                }
                const rulesArr = /** @type {Node[]} */ (rules);
                rules = rulesArr[rulesArr.length - 1];
            }

            const current = /** @type {Node} */ (rules);
            if (current.value) {
                rules = /** @type {Node} */ (current.eval(context).value);
            }
            const currentNode = /** @type {Node & { ruleset?: Node }} */ (rules);
            if (currentNode.ruleset) {
                rules = currentNode.ruleset.eval(context);
            }
        }
        return /** @type {Node} */ (rules);
    }
}

// @ts-check

/**
 * @typedef {object} MixinParam
 * @property {string} [name]
 * @property {Node} [value]
 * @property {boolean} [variadic]
 */

/**
 * @typedef {Ruleset & {
 *   functionRegistry?: FunctionRegistry,
 *   originalRuleset?: Node
 * }} RulesetWithRegistry
 */

class Definition extends Ruleset {
    get type() { return 'MixinDefinition'; }

    /**
     * @param {string | undefined} name
     * @param {MixinParam[]} params
     * @param {Node[]} rules
     * @param {Node | null} [condition]
     * @param {boolean} [variadic]
     * @param {Node[] | null} [frames]
     * @param {VisibilityInfo} [visibilityInfo]
     */
    constructor(name, params, rules, condition, variadic, frames, visibilityInfo) {
        super(null, null);
        /** @type {string} */
        this.name = name || 'anonymous mixin';
        this.selectors = [new Selector([new Element(null, name, false, this._index, this._fileInfo)])];
        /** @type {MixinParam[]} */
        this.params = params;
        /** @type {Node | null | undefined} */
        this.condition = condition;
        /** @type {boolean | undefined} */
        this.variadic = variadic;
        /** @type {number} */
        this.arity = params.length;
        this.rules = rules;
        this._lookups = {};
        /** @type {string[]} */
        const optionalParameters = [];
        /** @type {number} */
        this.required = params.reduce(function (/** @type {number} */ count, /** @type {MixinParam} */ p) {
            if (!p.name || (p.name && !p.value)) {
                return count + 1;
            }
            else {
                optionalParameters.push(p.name);
                return count;
            }
        }, 0);
        /** @type {string[]} */
        this.optionalParameters = optionalParameters;
        /** @type {Node[] | null | undefined} */
        this.frames = frames;
        this.copyVisibilityInfo(visibilityInfo);
        this.allowRoot = true;
        /** @type {boolean} */
        this.evalFirst = true;
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        if (this.params && this.params.length) {
            this.params = /** @type {MixinParam[]} */ (/** @type {unknown} */ (visitor.visitArray(/** @type {Node[]} */ (/** @type {unknown} */ (this.params)))));
        }
        this.rules = visitor.visitArray(this.rules);
        if (this.condition) {
            this.condition = visitor.visit(this.condition);
        }
    }

    /**
     * @param {EvalContext} context
     * @param {EvalContext} mixinEnv
     * @param {MixinArg[] | null} args
     * @param {Node[]} evaldArguments
     * @returns {Ruleset}
     */
    evalParams(context, mixinEnv, args, evaldArguments) {
        /* jshint boss:true */
        const frame = new Ruleset(null, null);

        /** @type {Node[] | undefined} */
        let varargs;
        /** @type {MixinArg | undefined} */
        let arg;
        const params = /** @type {MixinParam[]} */ (copyArray(this.params));
        /** @type {number} */
        let i;
        /** @type {number} */
        let j;
        /** @type {Node | undefined} */
        let val;
        /** @type {string | undefined} */
        let name;
        /** @type {boolean} */
        let isNamedFound;
        /** @type {number} */
        let argIndex;
        let argsLength = 0;

        if (mixinEnv.frames && mixinEnv.frames[0] && /** @type {RulesetWithRegistry} */ (mixinEnv.frames[0]).functionRegistry) {
            /** @type {RulesetWithRegistry} */ (frame).functionRegistry = /** @type {FunctionRegistry} */ (/** @type {RulesetWithRegistry} */ (mixinEnv.frames[0]).functionRegistry).inherit();
        }
        mixinEnv = new contexts.Eval(mixinEnv, /** @type {Node[]} */ ([frame]).concat(/** @type {Node[]} */ (mixinEnv.frames)));

        if (args) {
            args = /** @type {MixinArg[]} */ (copyArray(args));
            argsLength = args.length;

            for (i = 0; i < argsLength; i++) {
                arg = args[i];
                if (name = (arg && arg.name)) {
                    isNamedFound = false;
                    for (j = 0; j < params.length; j++) {
                        if (!evaldArguments[j] && name === params[j].name) {
                            evaldArguments[j] = arg.value.eval(context);
                            frame.prependRule(new Declaration(name, arg.value.eval(context)));
                            isNamedFound = true;
                            break;
                        }
                    }
                    if (isNamedFound) {
                        args.splice(i, 1);
                        i--;
                        continue;
                    } else {
                        throw { type: 'Runtime', message: `Named argument for ${this.name} ${args[i].name} not found` };
                    }
                }
            }
        }
        argIndex = 0;
        for (i = 0; i < params.length; i++) {
            if (evaldArguments[i]) { continue; }

            arg = args && args[argIndex];

            if (name = params[i].name) {
                if (params[i].variadic) {
                    varargs = [];
                    for (j = argIndex; j < argsLength; j++) {
                        varargs.push(/** @type {MixinArg[]} */ (args)[j].value.eval(context));
                    }
                    frame.prependRule(new Declaration(name, new Expression(varargs).eval(context)));
                } else {
                    val = arg && arg.value;
                    if (val) {
                        // This was a mixin call, pass in a detached ruleset of it's eval'd rules
                        if (Array.isArray(val)) {
                            val = /** @type {Node} */ (/** @type {unknown} */ (new DetachedRuleset(new Ruleset(null, /** @type {Node[]} */ (val)))));
                        }
                        else {
                            val = val.eval(context);
                        }
                    } else if (params[i].value) {
                        val = /** @type {Node} */ (params[i].value).eval(mixinEnv);
                        frame.resetCache();
                    } else {
                        throw { type: 'Runtime', message: `wrong number of arguments for ${this.name} (${argsLength} for ${this.arity})` };
                    }

                    frame.prependRule(new Declaration(name, val));
                    evaldArguments[i] = val;
                }
            }

            if (params[i].variadic && args) {
                for (j = argIndex; j < argsLength; j++) {
                    evaldArguments[j] = args[j].value.eval(context);
                }
            }
            argIndex++;
        }

        return frame;
    }

    /** @returns {Ruleset} */
    makeImportant() {
        const rules = !this.rules ? this.rules : this.rules.map(function (/** @type {Node & { makeImportant?: (important?: boolean) => Node }} */ r) {
            if (r.makeImportant) {
                return r.makeImportant(true);
            } else {
                return r;
            }
        });
        const result = new Definition(this.name, this.params, rules, this.condition, this.variadic, this.frames);
        return /** @type {Ruleset} */ (/** @type {unknown} */ (result));
    }

    /**
     * @param {EvalContext} context
     * @returns {Definition}
     */
    eval(context) {
        return new Definition(this.name, this.params, this.rules, this.condition, this.variadic, this.frames || copyArray(context.frames));
    }

    /**
     * @param {EvalContext} context
     * @param {MixinArg[]} args
     * @param {string | undefined} important
     * @returns {Ruleset}
     */
    evalCall(context, args, important) {
        /** @type {Node[]} */
        const _arguments = [];
        const mixinFrames = this.frames ? /** @type {Node[]} */ (this.frames).concat(/** @type {Node[]} */ (context.frames)) : /** @type {Node[]} */ (context.frames);
        const frame = this.evalParams(context, new contexts.Eval(context, mixinFrames), args, _arguments);
        /** @type {Node[]} */
        let rules;
        /** @type {Ruleset} */
        let ruleset;

        frame.prependRule(new Declaration('@arguments', new Expression(_arguments).eval(context)));

        rules = copyArray(this.rules);

        ruleset = new Ruleset(null, rules);
        /** @type {RulesetWithRegistry} */ (ruleset).originalRuleset = this;
        ruleset = /** @type {Ruleset} */ (ruleset.eval(new contexts.Eval(context, /** @type {Node[]} */ ([this, frame]).concat(mixinFrames))));
        if (important) {
            ruleset = /** @type {Ruleset} */ (ruleset.makeImportant());
        }
        return ruleset;
    }

    /**
     * @param {MixinArg[] | null} args
     * @param {EvalContext} context
     * @returns {boolean}
     */
    matchCondition(args, context) {
        if (this.condition && !this.condition.eval(
            new contexts.Eval(context,
                /** @type {Node[]} */ ([this.evalParams(context, /* the parameter variables */
                    new contexts.Eval(context, this.frames ? /** @type {Node[]} */ (this.frames).concat(/** @type {Node[]} */ (context.frames)) : context.frames), args, [])])
                    .concat(/** @type {Node[]} */ (this.frames || [])) // the parent namespace/mixin frames
                    .concat(/** @type {Node[]} */ (context.frames))))) { // the current environment frames
            return false;
        }
        return true;
    }

    /**
     * @param {MixinArg[] | null} args
     * @param {EvalContext} [context]
     * @returns {boolean}
     */
    matchArgs(args, context) {
        const allArgsCnt = (args && args.length) || 0;
        let len;
        const optionalParameters = this.optionalParameters;
        const requiredArgsCnt = !args ? 0 : args.reduce(function (/** @type {number} */ count, /** @type {MixinArg} */ p) {
            if (optionalParameters.indexOf(p.name) < 0) {
                return count + 1;
            } else {
                return count;
            }
        }, 0);

        if (!this.variadic) {
            if (requiredArgsCnt < this.required) {
                return false;
            }
            if (allArgsCnt > this.params.length) {
                return false;
            }
        } else {
            if (requiredArgsCnt < (this.required - 1)) {
                return false;
            }
        }

        // check patterns
        len = Math.min(requiredArgsCnt, this.arity);

        for (let i = 0; i < len; i++) {
            if (!this.params[i].name && !this.params[i].variadic) {
                if (/** @type {MixinArg[]} */ (args)[i].value.eval(context).toCSS(/** @type {EvalContext} */ ({})) != /** @type {Node} */ (this.params[i].value).eval(context).toCSS(/** @type {EvalContext} */ ({}))) {
                    return false;
                }
            }
        }
        return true;
    }
}

// @ts-check

/**
 * @typedef {{ name?: string, value: Node, expand?: boolean }} MixinArg
 */

/**
 * @typedef {Node & {
 *   rules?: Node[],
 *   selectors?: Selector[],
 *   originalRuleset?: Node,
 *   matchArgs: (args: MixinArg[] | null, context: EvalContext) => boolean,
 *   matchCondition?: (args: MixinArg[] | null, context: EvalContext) => boolean,
 *   find: (selector: Selector, self?: Node | null, filter?: (rule: Node) => boolean) => Array<{ rule: Node & { rules?: Node[], originalRuleset?: Node, matchArgs: Function, matchCondition?: Function, evalCall?: Function }, path: Node[] }>,
 *   functionRegistry?: FunctionRegistry
 * }} MixinSearchFrame
 */

class MixinCall extends Node {
    get type() { return 'MixinCall'; }

    /**
     * @param {import('./element.js').default[]} elements
     * @param {MixinArg[]} [args]
     * @param {number} [index]
     * @param {FileInfo} [currentFileInfo]
     * @param {string} [important]
     */
    constructor(elements, args, index, currentFileInfo, important) {
        super();
        /** @type {Selector} */
        this.selector = new Selector(elements);
        /** @type {MixinArg[]} */
        this.arguments = args || [];
        this._index = index;
        this._fileInfo = currentFileInfo;
        /** @type {string | undefined} */
        this.important = important;
        this.allowRoot = true;
        this.setParent(this.selector, /** @type {Node} */ (/** @type {unknown} */ (this)));
    }

    /** @param {TreeVisitor} visitor */
    accept(visitor) {
        if (this.selector) {
            this.selector = /** @type {Selector} */ (visitor.visit(this.selector));
        }
        if (this.arguments.length) {
            this.arguments = /** @type {MixinArg[]} */ (/** @type {unknown} */ (visitor.visitArray(/** @type {Node[]} */ (/** @type {unknown} */ (this.arguments)))));
        }
    }

    /**
     * @param {EvalContext} context
     * @returns {Node}
     */
    eval(context) {
        /** @type {{ rule: Node & { rules?: Node[], originalRuleset?: Node, matchArgs: Function, matchCondition?: Function, evalCall?: Function }, path: Node[] }[] | undefined} */
        let mixins;
        /** @type {Node & { rules?: Node[], originalRuleset?: Node, matchArgs: Function, matchCondition?: Function, evalCall?: Function }} */
        let mixin;
        /** @type {Node[]} */
        let mixinPath;
        /** @type {MixinArg[]} */
        const args = [];
        /** @type {MixinArg} */
        let arg;
        /** @type {Node} */
        let argValue;
        /** @type {Node[]} */
        const rules = [];
        let match = false;
        /** @type {number} */
        let i;
        /** @type {number} */
        let m;
        /** @type {number} */
        let f;
        /** @type {boolean} */
        let isRecursive;
        /** @type {boolean | undefined} */
        let isOneFound;
        /** @type {{ mixin: Node & { rules?: Node[], originalRuleset?: Node, matchArgs: Function, matchCondition?: Function, evalCall?: Function }, group: number }[]} */
        const candidates = [];
        /** @type {{ mixin: Node & { rules?: Node[], originalRuleset?: Node, matchArgs: Function, matchCondition?: Function, evalCall?: Function }, group: number } | number} */
        let candidate;
        /** @type {boolean[]} */
        const conditionResult = [];
        /** @type {number | undefined} */
        let defaultResult;
        const defFalseEitherCase = -1;
        const defNone = 0;
        const defTrue = 1;
        const defFalse = 2;
        /** @type {number[]} */
        let count;
        /** @type {Node | undefined} */
        let originalRuleset;
        /** @type {((rule: MixinSearchFrame) => boolean) | undefined} */
        let noArgumentsFilter;

        this.selector = /** @type {Selector} */ (this.selector.eval(context));

        /**
         * @param {Node & { matchCondition?: Function }} mixin
         * @param {Node[]} mixinPath
         */
        function calcDefGroup(mixin, mixinPath) {
            /** @type {number} */
            let f;
            /** @type {number} */
            let p;
            /** @type {Node & { matchCondition?: Function }} */
            let namespace;

            for (f = 0; f < 2; f++) {
                conditionResult[f] = true;
                defaultFunc.value(f);
                for (p = 0; p < mixinPath.length && conditionResult[f]; p++) {
                    namespace = mixinPath[p];
                    if (namespace.matchCondition) {
                        conditionResult[f] = conditionResult[f] && namespace.matchCondition(null, context);
                    }
                }
                if (mixin.matchCondition) {
                    conditionResult[f] = conditionResult[f] && mixin.matchCondition(args, context);
                }
            }
            if (conditionResult[0] || conditionResult[1]) {
                if (conditionResult[0] != conditionResult[1]) {
                    return conditionResult[1] ?
                        defTrue : defFalse;
                }

                return defNone;
            }
            return defFalseEitherCase;
        }

        for (i = 0; i < this.arguments.length; i++) {
            arg = this.arguments[i];
            argValue = arg.value.eval(context);
            if (arg.expand && Array.isArray(argValue.value)) {
                const expandedValues = /** @type {Node[]} */ (argValue.value);
                for (m = 0; m < expandedValues.length; m++) {
                    args.push({value: expandedValues[m]});
                }
            } else {
                args.push({name: arg.name, value: argValue});
            }
        }

        noArgumentsFilter = function(/** @type {MixinSearchFrame} */ rule) {return rule.matchArgs(null, context);};

        for (i = 0; i < context.frames.length; i++) {
            if ((mixins = /** @type {MixinSearchFrame} */ (context.frames[i]).find(this.selector, null, /** @type {(rule: Node) => boolean} */ (/** @type {unknown} */ (noArgumentsFilter)))).length > 0) {
                isOneFound = true;

                // To make `default()` function independent of definition order we have two "subpasses" here.
                // At first we evaluate each guard *twice* (with `default() == true` and `default() == false`),
                // and build candidate list with corresponding flags. Then, when we know all possible matches,
                // we make a final decision.

                for (m = 0; m < mixins.length; m++) {
                    mixin = mixins[m].rule;
                    mixinPath = mixins[m].path;
                    isRecursive = false;
                    for (f = 0; f < context.frames.length; f++) {
                        if ((!(mixin instanceof Definition)) && mixin === (/** @type {Node & { originalRuleset?: Node }} */ (context.frames[f]).originalRuleset || context.frames[f])) {
                            isRecursive = true;
                            break;
                        }
                    }
                    if (isRecursive) {
                        continue;
                    }

                    if (mixin.matchArgs(args, context)) {
                        candidate = {mixin, group: calcDefGroup(mixin, mixinPath)};

                        if (/** @type {{ mixin: Node, group: number }} */ (candidate).group !== defFalseEitherCase) {
                            candidates.push(/** @type {{ mixin: Node & { rules?: Node[], originalRuleset?: Node, matchArgs: Function, matchCondition?: Function, evalCall?: Function }, group: number }} */ (candidate));
                        }

                        match = true;
                    }
                }

                defaultFunc.reset();

                count = [0, 0, 0];
                for (m = 0; m < candidates.length; m++) {
                    count[candidates[m].group]++;
                }

                if (count[defNone] > 0) {
                    defaultResult = defFalse;
                } else {
                    defaultResult = defTrue;
                    if ((count[defTrue] + count[defFalse]) > 1) {
                        throw { type: 'Runtime',
                            message: `Ambiguous use of \`default()\` found when matching for \`${this.format(args)}\``,
                            index: this.getIndex(), filename: this.fileInfo().filename };
                    }
                }

                for (m = 0; m < candidates.length; m++) {
                    candidate = candidates[m].group;
                    if ((candidate === defNone) || (candidate === defaultResult)) {
                        try {
                            mixin = candidates[m].mixin;
                            if (!(mixin instanceof Definition)) {
                                originalRuleset = /** @type {Node & { originalRuleset?: Node }} */ (mixin).originalRuleset || mixin;
                                mixin = new Definition('', [], mixin.rules, null, false, null, originalRuleset.visibilityInfo());
                                /** @type {Node & { originalRuleset?: Node }} */ (mixin).originalRuleset = originalRuleset;
                            }
                            const newRules = /** @type {MixinDefinition} */ (mixin).evalCall(context, args, this.important).rules;
                            this._setVisibilityToReplacement(newRules);
                            Array.prototype.push.apply(rules, newRules);
                        } catch (e) {
                            throw { .../** @type {object} */ (e), index: this.getIndex(), filename: this.fileInfo().filename };
                        }
                    }
                }

                if (match) {
                    return /** @type {Node} */ (/** @type {unknown} */ (rules));
                }
            }
        }
        if (isOneFound) {
            throw { type:    'Runtime',
                message: `No matching definition was found for \`${this.format(args)}\``,
                index:   this.getIndex(), filename: this.fileInfo().filename };
        } else {
            throw { type:    'Name',
                message: `${this.selector.toCSS(/** @type {EvalContext} */ ({})).trim()} is undefined`,
                index:   this.getIndex(), filename: this.fileInfo().filename };
        }
    }

    /** @param {Node[]} replacement */
    _setVisibilityToReplacement(replacement) {
        /** @type {number} */
        let i;
        /** @type {Node} */
        let rule;
        if (this.blocksVisibility()) {
            for (i = 0; i < replacement.length; i++) {
                rule = replacement[i];
                rule.addVisibilityBlock();
            }
        }
    }

    /** @param {MixinArg[]} args */
    format(args) {
        return `${this.selector.toCSS(/** @type {EvalContext} */ ({})).trim()}(${args ? args.map(function (/** @type {MixinArg} */ a) {
            let argValue = '';
            if (a.name) {
                argValue += `${a.name}:`;
            }
            if (a.value.toCSS) {
                argValue += a.value.toCSS(/** @type {EvalContext} */ ({}));
            } else {
                argValue += '???';
            }
            return argValue;
        }).join(', ') : ''})`;
    }
}

// @ts-check

var tree = {
    Node, Color, AtRule, DetachedRuleset, Operation,
    Dimension, Unit, Keyword, Variable, Property,
    Ruleset, Element, Attribute, Combinator, Selector,
    Quoted, Expression, Declaration, Call, URL, Import,
    Comment, Anonymous, Value, JavaScript, Assignment,
    Condition, Paren, Media, Container, QueryInParens,
    UnicodeDescriptor, Negative, Extend, VariableCall,
    NamespaceValue,
    mixin: {
        Call: MixinCall,
        Definition: Definition
    }
};

class AbstractPluginLoader {
    constructor() {
        // Implemented by Node.js plugin loader
        this.require = function() {
            return null;
        };
    }

    evalPlugin(contents, context, imports, pluginOptions, fileInfo) {

        let loader, registry, pluginObj, localModule, pluginManager, filename, result;

        pluginManager = context.pluginManager;

        if (fileInfo) {
            if (typeof fileInfo === 'string') {
                filename = fileInfo;
            }
            else {
                filename = fileInfo.filename;
            }
        }
        const shortname = (new this.less.FileManager()).extractUrlParts(filename).filename;

        if (filename) {
            pluginObj = pluginManager.get(filename);

            if (pluginObj) {
                result = this.trySetOptions(pluginObj, filename, shortname, pluginOptions);
                if (result) {
                    return result;
                }
                try {
                    if (pluginObj.use) {
                        pluginObj.use.call(this.context, pluginObj);
                    }
                }
                catch (e) {
                    e.message = e.message || 'Error during @plugin call';
                    return new LessError(e, imports, filename);
                }
                return pluginObj;
            }
        }
        localModule = {
            exports: {},
            pluginManager,
            fileInfo
        };
        registry = functionRegistry.create();

        const registerPlugin = function(obj) {
            pluginObj = obj;
        };

        try {
            loader = new Function('module', 'require', 'registerPlugin', 'functions', 'tree', 'less', 'fileInfo', contents);
            loader(localModule, this.require(filename), registerPlugin, registry, this.less.tree, this.less, fileInfo);
        }
        catch (e) {
            return new LessError(e, imports, filename);
        }

        if (!pluginObj) {
            pluginObj = localModule.exports;
        }
        pluginObj = this.validatePlugin(pluginObj, filename, shortname);

        if (pluginObj instanceof LessError) {
            return pluginObj;
        }

        if (pluginObj) {
            pluginObj.imports = imports;
            pluginObj.filename = filename;

            // For < 3.x (or unspecified minVersion) - setOptions() before install()
            if (!pluginObj.minVersion || this.compareVersion('3.0.0', pluginObj.minVersion) < 0) {
                result = this.trySetOptions(pluginObj, filename, shortname, pluginOptions);

                if (result) {
                    return result;
                }
            }

            // Run on first load
            pluginManager.addPlugin(pluginObj, fileInfo.filename, registry);
            pluginObj.functions = registry.getLocalFunctions();

            // Need to call setOptions again because the pluginObj might have functions
            result = this.trySetOptions(pluginObj, filename, shortname, pluginOptions);
            if (result) {
                return result;
            }

            // Run every @plugin call
            try {
                if (pluginObj.use) {
                    pluginObj.use.call(this.context, pluginObj);
                }
            }
            catch (e) {
                e.message = e.message || 'Error during @plugin call';
                return new LessError(e, imports, filename);
            }

        }
        else {
            return new LessError({ message: 'Not a valid plugin' }, imports, filename);
        }

        return pluginObj;

    }

    trySetOptions(plugin, filename, name, options) {
        if (options && !plugin.setOptions) {
            return new LessError({
                message: `Options have been provided but the plugin ${name} does not support any options.`
            });
        }
        try {
            plugin.setOptions && plugin.setOptions(options);
        }
        catch (e) {
            return new LessError(e);
        }
    }

    validatePlugin(plugin, filename, name) {
        if (plugin) {
            // support plugins being a function
            // so that the plugin can be more usable programmatically
            if (typeof plugin === 'function') {
                plugin = new plugin();
            }

            if (plugin.minVersion) {
                if (this.compareVersion(plugin.minVersion, this.less.version) < 0) {
                    return new LessError({
                        message: `Plugin ${name} requires version ${this.versionToString(plugin.minVersion)}`
                    });
                }
            }
            return plugin;
        }
        return null;
    }

    compareVersion(aVersion, bVersion) {
        if (typeof aVersion === 'string') {
            aVersion = aVersion.match(/^(\d+)\.?(\d+)?\.?(\d+)?/);
            aVersion.shift();
        }
        for (let i = 0; i < aVersion.length; i++) {
            if (aVersion[i] !== bVersion[i]) {
                return parseInt(aVersion[i]) > parseInt(bVersion[i]) ? -1 : 1;
            }
        }
        return 0;
    }

    versionToString(version) {
        let versionString = '';
        for (let i = 0; i < version.length; i++) {
            versionString += (versionString ? '.' : '') + version[i];
        }
        return versionString;
    }

    printUsage(plugins) {
        for (let i = 0; i < plugins.length; i++) {
            const plugin = plugins[i];
            if (plugin.printUsage) {
                plugin.printUsage();
            }
        }
    }
}

function boolean(condition) {
    return condition ? Keyword.True : Keyword.False;
}

/**
 * Functions with evalArgs set to false are sent context
 * as the first argument.
 */
function If(context, condition, trueValue, falseValue) {
    return condition.eval(context) ? trueValue.eval(context)
        : (falseValue ? falseValue.eval(context) : new Anonymous);
}
If.evalArgs = false;

function isdefined(context, variable) {
    try {
        variable.eval(context);
        return Keyword.True;
    } catch (e) {
        return Keyword.False;
    }
}

isdefined.evalArgs = false;

var boolean$1 = { isdefined, boolean, 'if': If };

let colorFunctions;

function clamp(val) {
    return Math.min(1, Math.max(0, val));
}
function hsla(origColor, hsl) {
    const color = colorFunctions.hsla(hsl.h, hsl.s, hsl.l, hsl.a);
    if (color) {
        if (origColor.value && 
            /^(rgb|hsl)/.test(origColor.value)) {
            color.value = origColor.value;
        } else {
            color.value = 'rgb';
        }
        return color;
    }
}
function toHSL(color) {
    if (color.toHSL) {
        return color.toHSL();
    } else {
        throw new Error('Argument cannot be evaluated to a color');
    }
}

function toHSV(color) {
    if (color.toHSV) {
        return color.toHSV();
    } else {
        throw new Error('Argument cannot be evaluated to a color');
    }
}

function number$1(n) {
    if (n instanceof Dimension) {
        return parseFloat(n.unit.is('%') ? n.value / 100 : n.value);
    } else if (typeof n === 'number') {
        return n;
    } else {
        throw {
            type: 'Argument',
            message: 'color functions take numbers as parameters'
        };
    }
}
function scaled(n, size) {
    if (n instanceof Dimension && n.unit.is('%')) {
        return parseFloat(n.value * size / 100);
    } else {
        return number$1(n);
    }
}
colorFunctions = {
    rgb: function (r, g, b) {
        let a = 1;
        /**
         * Comma-less syntax
         *   e.g. rgb(0 128 255 / 50%)
         */
        if (r instanceof Expression) {
            const val = r.value;
            r = val[0];
            g = val[1];
            b = val[2];
            /** 
             * @todo - should this be normalized in
             *   function caller? Or parsed differently?
             */
            if (b instanceof Operation) {
                const op = b;
                b = op.operands[0];
                a = op.operands[1];
            }
        }
        const color = colorFunctions.rgba(r, g, b, a);
        if (color) {
            color.value = 'rgb';
            return color;
        }
    },
    rgba: function (r, g, b, a) {
        try {
            if (r instanceof Color) {
                if (g) {
                    a = number$1(g);
                } else {
                    a = r.alpha;
                }
                return new Color(r.rgb, a, 'rgba');
            }
            const rgb = [r, g, b].map(c => scaled(c, 255));
            a = number$1(a);
            return new Color(rgb, a, 'rgba');
        }
        catch (e) {}
    },
    hsl: function (h, s, l) {
        let a = 1;
        if (h instanceof Expression) {
            const val = h.value;
            h = val[0];
            s = val[1];
            l = val[2];

            if (l instanceof Operation) {
                const op = l;
                l = op.operands[0];
                a = op.operands[1];
            }
        }
        const color = colorFunctions.hsla(h, s, l, a);
        if (color) {
            color.value = 'hsl';
            return color;
        }
    },
    hsla: function (h, s, l, a) {
        let m1;
        let m2;

        function hue(h) {
            h = h < 0 ? h + 1 : (h > 1 ? h - 1 : h);
            if (h * 6 < 1) {
                return m1 + (m2 - m1) * h * 6;
            }
            else if (h * 2 < 1) {
                return m2;
            }
            else if (h * 3 < 2) {
                return m1 + (m2 - m1) * (2 / 3 - h) * 6;
            }
            else {
                return m1;
            }
        }

        try {
            if (h instanceof Color) {
                if (s) {
                    a = number$1(s);
                } else {
                    a = h.alpha;
                }
                return new Color(h.rgb, a, 'hsla');
            }

            h = (number$1(h) % 360) / 360;
            s = clamp(number$1(s));l = clamp(number$1(l));a = clamp(number$1(a));

            m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s;
            m1 = l * 2 - m2;

            const rgb = [
                hue(h + 1 / 3) * 255,
                hue(h)       * 255,
                hue(h - 1 / 3) * 255
            ];
            a = number$1(a);
            return new Color(rgb, a, 'hsla');
        }
        catch (e) {}
    },

    hsv: function(h, s, v) {
        return colorFunctions.hsva(h, s, v, 1.0);
    },

    hsva: function(h, s, v, a) {
        h = ((number$1(h) % 360) / 360) * 360;
        s = number$1(s);v = number$1(v);a = number$1(a);

        let i;
        let f;
        i = Math.floor((h / 60) % 6);
        f = (h / 60) - i;

        const vs = [v,
            v * (1 - s),
            v * (1 - f * s),
            v * (1 - (1 - f) * s)];
        const perm = [[0, 3, 1],
            [2, 0, 1],
            [1, 0, 3],
            [1, 2, 0],
            [3, 1, 0],
            [0, 1, 2]];

        return colorFunctions.rgba(vs[perm[i][0]] * 255,
            vs[perm[i][1]] * 255,
            vs[perm[i][2]] * 255,
            a);
    },

    hue: function (color) {
        return new Dimension(toHSL(color).h);
    },
    saturation: function (color) {
        return new Dimension(toHSL(color).s * 100, '%');
    },
    lightness: function (color) {
        return new Dimension(toHSL(color).l * 100, '%');
    },
    hsvhue: function(color) {
        return new Dimension(toHSV(color).h);
    },
    hsvsaturation: function (color) {
        return new Dimension(toHSV(color).s * 100, '%');
    },
    hsvvalue: function (color) {
        return new Dimension(toHSV(color).v * 100, '%');
    },
    red: function (color) {
        return new Dimension(color.rgb[0]);
    },
    green: function (color) {
        return new Dimension(color.rgb[1]);
    },
    blue: function (color) {
        return new Dimension(color.rgb[2]);
    },
    alpha: function (color) {
        return new Dimension(toHSL(color).a);
    },
    luma: function (color) {
        return new Dimension(color.luma() * color.alpha * 100, '%');
    },
    luminance: function (color) {
        const luminance =
            (0.2126 * color.rgb[0] / 255) +
                (0.7152 * color.rgb[1] / 255) +
                (0.0722 * color.rgb[2] / 255);

        return new Dimension(luminance * color.alpha * 100, '%');
    },
    saturate: function (color, amount, method) {
        // filter: saturate(3.2);
        // should be kept as is, so check for color
        if (!color.rgb) {
            return null;
        }
        const hsl = toHSL(color);

        if (typeof method !== 'undefined' && method.value === 'relative') {
            hsl.s +=  hsl.s * amount.value / 100;
        }
        else {
            hsl.s += amount.value / 100;
        }
        hsl.s = clamp(hsl.s);
        return hsla(color, hsl);
    },
    desaturate: function (color, amount, method) {
        const hsl = toHSL(color);

        if (typeof method !== 'undefined' && method.value === 'relative') {
            hsl.s -=  hsl.s * amount.value / 100;
        }
        else {
            hsl.s -= amount.value / 100;
        }
        hsl.s = clamp(hsl.s);
        return hsla(color, hsl);
    },
    lighten: function (color, amount, method) {
        const hsl = toHSL(color);

        if (typeof method !== 'undefined' && method.value === 'relative') {
            hsl.l +=  hsl.l * amount.value / 100;
        }
        else {
            hsl.l += amount.value / 100;
        }
        hsl.l = clamp(hsl.l);
        return hsla(color, hsl);
    },
    darken: function (color, amount, method) {
        const hsl = toHSL(color);

        if (typeof method !== 'undefined' && method.value === 'relative') {
            hsl.l -=  hsl.l * amount.value / 100;
        }
        else {
            hsl.l -= amount.value / 100;
        }
        hsl.l = clamp(hsl.l);
        return hsla(color, hsl);
    },
    fadein: function (color, amount, method) {
        const hsl = toHSL(color);

        if (typeof method !== 'undefined' && method.value === 'relative') {
            hsl.a +=  hsl.a * amount.value / 100;
        }
        else {
            hsl.a += amount.value / 100;
        }
        hsl.a = clamp(hsl.a);
        return hsla(color, hsl);
    },
    fadeout: function (color, amount, method) {
        const hsl = toHSL(color);

        if (typeof method !== 'undefined' && method.value === 'relative') {
            hsl.a -=  hsl.a * amount.value / 100;
        }
        else {
            hsl.a -= amount.value / 100;
        }
        hsl.a = clamp(hsl.a);
        return hsla(color, hsl);
    },
    fade: function (color, amount) {
        const hsl = toHSL(color);

        hsl.a = amount.value / 100;
        hsl.a = clamp(hsl.a);
        return hsla(color, hsl);
    },
    spin: function (color, amount) {
        const hsl = toHSL(color);
        const hue = (hsl.h + amount.value) % 360;

        hsl.h = hue < 0 ? 360 + hue : hue;

        return hsla(color, hsl);
    },
    //
    // Copyright (c) 2006-2009 Hampton Catlin, Natalie Weizenbaum, and Chris Eppstein
    // http://sass-lang.com
    //
    mix: function (color1, color2, weight) {
        if (!weight) {
            weight = new Dimension(50);
        }
        const p = weight.value / 100.0;
        const w = p * 2 - 1;
        const a = toHSL(color1).a - toHSL(color2).a;

        const w1 = (((w * a == -1) ? w : (w + a) / (1 + w * a)) + 1) / 2.0;
        const w2 = 1 - w1;

        const rgb = [color1.rgb[0] * w1 + color2.rgb[0] * w2,
            color1.rgb[1] * w1 + color2.rgb[1] * w2,
            color1.rgb[2] * w1 + color2.rgb[2] * w2];

        const alpha = color1.alpha * p + color2.alpha * (1 - p);

        return new Color(rgb, alpha);
    },
    greyscale: function (color) {
        return colorFunctions.desaturate(color, new Dimension(100));
    },
    contrast: function (color, dark, light, threshold) {
        // filter: contrast(3.2);
        // should be kept as is, so check for color
        if (!color.rgb) {
            return null;
        }
        if (typeof light === 'undefined') {
            light = colorFunctions.rgba(255, 255, 255, 1.0);
        }
        if (typeof dark === 'undefined') {
            dark = colorFunctions.rgba(0, 0, 0, 1.0);
        }
        // Figure out which is actually light and dark:
        if (dark.luma() > light.luma()) {
            const t = light;
            light = dark;
            dark = t;
        }
        if (typeof threshold === 'undefined') {
            threshold = 0.43;
        } else {
            threshold = number$1(threshold);
        }
        if (color.luma() < threshold) {
            return light;
        } else {
            return dark;
        }
    },
    // Changes made in 2.7.0 - Reverted in 3.0.0
    // contrast: function (color, color1, color2, threshold) {
    //     // Return which of `color1` and `color2` has the greatest contrast with `color`
    //     // according to the standard WCAG contrast ratio calculation.
    //     // http://www.w3.org/TR/WCAG20/#contrast-ratiodef
    //     // The threshold param is no longer used, in line with SASS.
    //     // filter: contrast(3.2);
    //     // should be kept as is, so check for color
    //     if (!color.rgb) {
    //         return null;
    //     }
    //     if (typeof color1 === 'undefined') {
    //         color1 = colorFunctions.rgba(0, 0, 0, 1.0);
    //     }
    //     if (typeof color2 === 'undefined') {
    //         color2 = colorFunctions.rgba(255, 255, 255, 1.0);
    //     }
    //     var contrast1, contrast2;
    //     var luma = color.luma();
    //     var luma1 = color1.luma();
    //     var luma2 = color2.luma();
    //     // Calculate contrast ratios for each color
    //     if (luma > luma1) {
    //         contrast1 = (luma + 0.05) / (luma1 + 0.05);
    //     } else {
    //         contrast1 = (luma1 + 0.05) / (luma + 0.05);
    //     }
    //     if (luma > luma2) {
    //         contrast2 = (luma + 0.05) / (luma2 + 0.05);
    //     } else {
    //         contrast2 = (luma2 + 0.05) / (luma + 0.05);
    //     }
    //     if (contrast1 > contrast2) {
    //         return color1;
    //     } else {
    //         return color2;
    //     }
    // },
    argb: function (color) {
        return new Anonymous(color.toARGB());
    },
    color: function(c) {
        if ((c instanceof Quoted) &&
            (/^#([A-Fa-f0-9]{8}|[A-Fa-f0-9]{6}|[A-Fa-f0-9]{3,4})$/i.test(c.value))) {
            const val = c.value.slice(1);
            return new Color(val, undefined, `#${val}`);
        }
        if ((c instanceof Color) || (c = Color.fromKeyword(c.value))) {
            c.value = undefined;
            return c;
        }
        throw {
            type:    'Argument',
            message: 'argument must be a color keyword or 3|4|6|8 digit hex e.g. #FFF'
        };
    },
    tint: function(color, amount) {
        return colorFunctions.mix(colorFunctions.rgb(255, 255, 255), color, amount);
    },
    shade: function(color, amount) {
        return colorFunctions.mix(colorFunctions.rgb(0, 0, 0), color, amount);
    }
};

var color = colorFunctions;

// Color Blending
// ref: http://www.w3.org/TR/compositing-1

function colorBlend(mode, color1, color2) {
    const ab = color1.alpha;        // result

    let // backdrop
        cb;

    const as = color2.alpha;

    let // source
        cs;

    let ar;
    let cr;
    const r = [];

    ar = as + ab * (1 - as);
    for (let i = 0; i < 3; i++) {
        cb = color1.rgb[i] / 255;
        cs = color2.rgb[i] / 255;
        cr = mode(cb, cs);
        if (ar) {
            cr = (as * cs + ab * (cb -
                  as * (cb + cs - cr))) / ar;
        }
        r[i] = cr * 255;
    }

    return new Color(r, ar);
}

const colorBlendModeFunctions = {
    multiply: function(cb, cs) {
        return cb * cs;
    },
    screen: function(cb, cs) {
        return cb + cs - cb * cs;
    },
    overlay: function(cb, cs) {
        cb *= 2;
        return (cb <= 1) ?
            colorBlendModeFunctions.multiply(cb, cs) :
            colorBlendModeFunctions.screen(cb - 1, cs);
    },
    softlight: function(cb, cs) {
        let d = 1;
        let e = cb;
        if (cs > 0.5) {
            e = 1;
            d = (cb > 0.25) ? Math.sqrt(cb)
                : ((16 * cb - 12) * cb + 4) * cb;
        }
        return cb - (1 - 2 * cs) * e * (d - cb);
    },
    hardlight: function(cb, cs) {
        return colorBlendModeFunctions.overlay(cs, cb);
    },
    difference: function(cb, cs) {
        return Math.abs(cb - cs);
    },
    exclusion: function(cb, cs) {
        return cb + cs - 2 * cb * cs;
    },

    // non-w3c functions:
    average: function(cb, cs) {
        return (cb + cs) / 2;
    },
    negation: function(cb, cs) {
        return 1 - Math.abs(cb + cs - 1);
    }
};

for (const f in colorBlendModeFunctions) {
    // eslint-disable-next-line no-prototype-builtins
    if (colorBlendModeFunctions.hasOwnProperty(f)) {
        colorBlend[f] = colorBlend.bind(null, colorBlendModeFunctions[f]);
    }
}

var dataUri = environment => {
    
    const fallback = (functionThis, node) => new URL(node, functionThis.index, functionThis.currentFileInfo).eval(functionThis.context);    

    return { 'data-uri': function(mimetypeNode, filePathNode) {

        if (!filePathNode) {
            filePathNode = mimetypeNode;
            mimetypeNode = null;
        }

        let mimetype = mimetypeNode && mimetypeNode.value;
        let filePath = filePathNode.value;
        const currentFileInfo = this.currentFileInfo;
        const currentDirectory = currentFileInfo.rewriteUrls ?
            currentFileInfo.currentDirectory : currentFileInfo.entryPath;

        const fragmentStart = filePath.indexOf('#');
        let fragment = '';
        if (fragmentStart !== -1) {
            fragment = filePath.slice(fragmentStart);
            filePath = filePath.slice(0, fragmentStart);
        }
        const context = clone(this.context);
        context.rawBuffer = true;

        const fileManager = environment.getFileManager(filePath, currentDirectory, context, environment, true);

        if (!fileManager) {
            return fallback(this, filePathNode);
        }

        let useBase64 = false;

        // detect the mimetype if not given
        if (!mimetypeNode) {

            mimetype = environment.mimeLookup(filePath);

            if (mimetype === 'image/svg+xml') {
                useBase64 = false;
            } else {
                // use base 64 unless it's an ASCII or UTF-8 format
                const charset = environment.charsetLookup(mimetype);
                useBase64 = ['US-ASCII', 'UTF-8'].indexOf(charset) < 0;
            }
            if (useBase64) { mimetype += ';base64'; }
        }
        else {
            useBase64 = /;base64$/.test(mimetype);
        }

        const fileSync = fileManager.loadFileSync(filePath, currentDirectory, context, environment);
        if (!fileSync.contents) {
            logger.warn(`Skipped data-uri embedding of ${filePath} because file not found`);
            return fallback(this, filePathNode || mimetypeNode);
        }
        let buf = fileSync.contents;
        if (useBase64 && !environment.encodeBase64) {
            return fallback(this, filePathNode);
        }

        buf = useBase64 ? environment.encodeBase64(buf) : encodeURIComponent(buf);

        const uri = `data:${mimetype},${buf}${fragment}`;

        return new URL(new Quoted(`"${uri}"`, uri, false, this.index, this.currentFileInfo), this.index, this.currentFileInfo);
    }};
};

const getItemsFromNode = node => {
    // handle non-array values as an array of length 1
    // return 'undefined' if index is invalid
    const items = Array.isArray(node.value) ?
        node.value : Array(node);

    return items;
};

var list = {
    _SELF: function(n) {
        return n;
    },
    '~': function(...expr) {
        if (expr.length === 1) {
            return expr[0];
        }
        return new Value(expr);
    },
    extract: function(values, index) {
        // (1-based index)
        index = index.value - 1;

        return getItemsFromNode(values)[index];
    },
    length: function(values) {
        return new Dimension(getItemsFromNode(values).length);
    },
    /**
     * Creates a Less list of incremental values.
     * Modeled after Lodash's range function, also exists natively in PHP
     * 
     * @param {Dimension} [start=1]
     * @param {Dimension} end  - e.g. 10 or 10px - unit is added to output
     * @param {Dimension} [step=1] 
     */
    range: function(start, end, step) {
        let from;
        let to;
        let stepValue = 1;
        const list = [];
        if (end) {
            to = end;
            from = start.value;
            if (step) {
                stepValue = step.value;
            }
        }
        else {
            from = 1;
            to = start;
        }

        for (let i = from; i <= to.value; i += stepValue) {
            list.push(new Dimension(i, to.unit));
        }

        return new Expression(list);
    },
    each: function(list, rs) {
        const rules = [];
        let newRules;
        let iterator;

        const tryEval = val => {
            if (val instanceof Node) {
                return val.eval(this.context);
            }
            return val;
        };

        if (list.value && !(list instanceof Quoted)) {
            if (Array.isArray(list.value)) {
                iterator = list.value.map(tryEval);
            } else {
                iterator = [tryEval(list.value)];
            }
        } else if (list.ruleset) {
            iterator = tryEval(list.ruleset).rules;
        } else if (list.rules) {
            iterator = list.rules.map(tryEval);
        } else if (Array.isArray(list)) {
            iterator = list.map(tryEval);
        } else {
            iterator = [tryEval(list)];
        }

        let valueName = '@value';
        let keyName = '@key';
        let indexName = '@index';

        if (rs.params) {
            valueName = rs.params[0] && rs.params[0].name;
            keyName = rs.params[1] && rs.params[1].name;
            indexName = rs.params[2] && rs.params[2].name;
            rs = rs.rules;
        } else {
            rs = rs.ruleset;
        }

        for (let i = 0; i < iterator.length; i++) {
            let key;
            let value;
            const item = iterator[i];
            if (item instanceof Declaration) {
                key = typeof item.name === 'string' ? item.name : item.name[0].value;
                value = item.value;
            } else {
                key = new Dimension(i + 1);
                value = item;
            }

            if (item instanceof Comment) {
                continue;
            }

            newRules = rs.rules.slice(0);
            if (valueName) {
                newRules.push(new Declaration(valueName,
                    value,
                    false, false, this.index, this.currentFileInfo));
            }
            if (indexName) {
                newRules.push(new Declaration(indexName,
                    new Dimension(i + 1),
                    false, false, this.index, this.currentFileInfo));
            }
            if (keyName) {
                newRules.push(new Declaration(keyName,
                    key,
                    false, false, this.index, this.currentFileInfo));
            }

            rules.push(new Ruleset([ new(Selector)([ new Element('', '&') ]) ],
                newRules,
                rs.strictImports,
                rs.visibilityInfo()
            ));
        }

        return new Ruleset([ new(Selector)([ new Element('', '&') ]) ],
            rules,
            rs.strictImports,
            rs.visibilityInfo()
        ).eval(this.context);
    }
};

const MathHelper = (fn, unit, n) => {
    if (!(n instanceof Dimension)) {
        throw { type: 'Argument', message: 'argument must be a number' };
    }
    if (unit === null) {
        unit = n.unit;
    } else {
        n = n.unify();
    }
    return new Dimension(fn(parseFloat(n.value)), unit);
};

const mathFunctions = {
    // name,  unit
    ceil:  null,
    floor: null,
    sqrt:  null,
    abs:   null,
    tan:   '',
    sin:   '',
    cos:   '',
    atan:  'rad',
    asin:  'rad',
    acos:  'rad'
};

for (const f in mathFunctions) {
    // eslint-disable-next-line no-prototype-builtins
    if (mathFunctions.hasOwnProperty(f)) {
        mathFunctions[f] = MathHelper.bind(null, Math[f], mathFunctions[f]);
    }
}

mathFunctions.round = (n, f) => {
    const fraction = typeof f === 'undefined' ? 0 : f.value;
    return MathHelper(num => num.toFixed(fraction), null, n);
};

const minMax = function (isMin, args) {
    args = Array.prototype.slice.call(args);
    switch (args.length) {
        case 0: throw { type: 'Argument', message: 'one or more arguments required' };
    }
    let i; // key is the unit.toString() for unified Dimension values,
    let j;
    let current;
    let currentUnified;
    let referenceUnified;
    let unit;
    let unitStatic;
    let unitClone;

    const // elems only contains original argument values.
        order  = [];

    const values = {};
    // value is the index into the order array.
    for (i = 0; i < args.length; i++) {
        current = args[i];
        if (!(current instanceof Dimension)) {
            if (Array.isArray(args[i].value)) {
                Array.prototype.push.apply(args, Array.prototype.slice.call(args[i].value));
                continue;
            } else {
                throw { type: 'Argument', message: 'incompatible types' };
            }
        }
        currentUnified = current.unit.toString() === '' && unitClone !== undefined ? new Dimension(current.value, unitClone).unify() : current.unify();
        unit = currentUnified.unit.toString() === '' && unitStatic !== undefined ? unitStatic : currentUnified.unit.toString();
        unitStatic = unit !== '' && unitStatic === undefined || unit !== '' && order[0].unify().unit.toString() === '' ? unit : unitStatic;
        unitClone = unit !== '' && unitClone === undefined ? current.unit.toString() : unitClone;
        j = values[''] !== undefined && unit !== '' && unit === unitStatic ? values[''] : values[unit];
        if (j === undefined) {
            if (unitStatic !== undefined && unit !== unitStatic) {
                throw { type: 'Argument', message: 'incompatible types' };
            }
            values[unit] = order.length;
            order.push(current);
            continue;
        }
        referenceUnified = order[j].unit.toString() === '' && unitClone !== undefined ? new Dimension(order[j].value, unitClone).unify() : order[j].unify();
        if ( isMin && currentUnified.value < referenceUnified.value ||
            !isMin && currentUnified.value > referenceUnified.value) {
            order[j] = current;
        }
    }
    if (order.length == 1) {
        return order[0];
    }
    args = order.map(a => { return a.toCSS(this.context); }).join(this.context.compress ? ',' : ', ');
    return new Anonymous(`${isMin ? 'min' : 'max'}(${args})`);
};

var number = {
    min: function(...args) {
        try {
            return minMax.call(this, true, args);
        } catch (e) {}
    },
    max: function(...args) {
        try {
            return minMax.call(this, false, args);
        } catch (e) {}
    },
    convert: function (val, unit) {
        return val.convertTo(unit.value);
    },
    pi: function () {
        return new Dimension(Math.PI);
    },
    mod: function(a, b) {
        return new Dimension(a.value % b.value, a.unit);
    },
    pow: function(x, y) {
        if (typeof x === 'number' && typeof y === 'number') {
            x = new Dimension(x);
            y = new Dimension(y);
        } else if (!(x instanceof Dimension) || !(y instanceof Dimension)) {
            throw { type: 'Argument', message: 'arguments must be numbers' };
        }

        return new Dimension(Math.pow(x.value, y.value), x.unit);
    },
    percentage: function (n) {
        const result = MathHelper(num => num * 100, '%', n);

        return result;
    }
};

var string = {
    e: function (str) {
        return new Quoted('"', str instanceof JavaScript ? str.evaluated : str.value, true);
    },
    escape: function (str) {
        return new Anonymous(
            encodeURI(str.value).replace(/=/g, '%3D').replace(/:/g, '%3A').replace(/#/g, '%23').replace(/;/g, '%3B')
                .replace(/\(/g, '%28').replace(/\)/g, '%29'));
    },
    replace: function (string, pattern, replacement, flags) {
        let result = string.value;
        replacement = (replacement.type === 'Quoted') ?
            replacement.value : replacement.toCSS();
        result = result.replace(new RegExp(pattern.value, flags ? flags.value : ''), replacement);
        return new Quoted(string.quote || '', result, string.escaped);
    },
    '%': function (string /* arg, arg, ... */) {
        const args = Array.prototype.slice.call(arguments, 1);
        let result = string.value;

        for (let i = 0; i < args.length; i++) {
            /* jshint loopfunc:true */
            result = result.replace(/%[sda]/i, token => {
                const value = ((args[i].type === 'Quoted') &&
                    token.match(/s/i)) ? args[i].value : args[i].toCSS();
                return token.match(/[A-Z]$/) ? encodeURIComponent(value) : value;
            });
        }
        result = result.replace(/%%/g, '%');
        return new Quoted(string.quote || '', result, string.escaped);
    }
};

var svg = () => {
    return { 'svg-gradient': function(direction) {
        let stops;
        let gradientDirectionSvg;
        let gradientType = 'linear';
        let rectangleDimension = 'x="0" y="0" width="1" height="1"';
        const renderEnv = {compress: false};
        let returner;
        const directionValue = direction.toCSS(renderEnv);
        let i;
        let color;
        let position;
        let positionValue;
        let alpha;

        function throwArgumentDescriptor() {
            throw { type: 'Argument',
                message: 'svg-gradient expects direction, start_color [start_position], [color position,]...,' +
                            ' end_color [end_position] or direction, color list' };
        }

        if (arguments.length == 2) {
            if (arguments[1].value.length < 2) {
                throwArgumentDescriptor();
            }
            stops = arguments[1].value;
        } else if (arguments.length < 3) {
            throwArgumentDescriptor();
        } else {
            stops = Array.prototype.slice.call(arguments, 1);
        }

        switch (directionValue) {
            case 'to bottom':
                gradientDirectionSvg = 'x1="0%" y1="0%" x2="0%" y2="100%"';
                break;
            case 'to right':
                gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="0%"';
                break;
            case 'to bottom right':
                gradientDirectionSvg = 'x1="0%" y1="0%" x2="100%" y2="100%"';
                break;
            case 'to top right':
                gradientDirectionSvg = 'x1="0%" y1="100%" x2="100%" y2="0%"';
                break;
            case 'ellipse':
            case 'ellipse at center':
                gradientType = 'radial';
                gradientDirectionSvg = 'cx="50%" cy="50%" r="75%"';
                rectangleDimension = 'x="-50" y="-50" width="101" height="101"';
                break;
            default:
                throw { type: 'Argument', message: 'svg-gradient direction must be \'to bottom\', \'to right\',' +
                    ' \'to bottom right\', \'to top right\' or \'ellipse at center\'' };
        }
        returner = `<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1 1"><${gradientType}Gradient id="g" ${gradientDirectionSvg}>`;

        for (i = 0; i < stops.length; i += 1) {
            if (stops[i] instanceof Expression) {
                color = stops[i].value[0];
                position = stops[i].value[1];
            } else {
                color = stops[i];
                position = undefined;
            }

            if (!(color instanceof Color) || (!((i === 0 || i + 1 === stops.length) && position === undefined) && !(position instanceof Dimension))) {
                throwArgumentDescriptor();
            }
            positionValue = position ? position.toCSS(renderEnv) : i === 0 ? '0%' : '100%';
            alpha = color.alpha;
            returner += `<stop offset="${positionValue}" stop-color="${color.toRGB()}"${alpha < 1 ? ` stop-opacity="${alpha}"` : ''}/>`;
        }
        returner += `</${gradientType}Gradient><rect ${rectangleDimension} fill="url(#g)" /></svg>`;

        returner = encodeURIComponent(returner);

        returner = `data:image/svg+xml,${returner}`;
        return new URL(new Quoted(`'${returner}'`, returner, false, this.index, this.currentFileInfo), this.index, this.currentFileInfo);
    }};
};

const isa = (n, Type) => (n instanceof Type) ? Keyword.True : Keyword.False;
const isunit = (n, unit) => {
    if (unit === undefined) {
        throw { type: 'Argument', message: 'missing the required second argument to isunit.' };
    }
    unit = typeof unit.value === 'string' ? unit.value : unit;
    if (typeof unit !== 'string') {
        throw { type: 'Argument', message: 'Second argument to isunit should be a unit or a string.' };
    }
    return (n instanceof Dimension) && n.unit.is(unit) ? Keyword.True : Keyword.False;
};

var types = {
    isruleset: function (n) {
        return isa(n, DetachedRuleset);
    },
    iscolor: function (n) {
        return isa(n, Color);
    },
    isnumber: function (n) {
        return isa(n, Dimension);
    },
    isstring: function (n) {
        return isa(n, Quoted);
    },
    iskeyword: function (n) {
        return isa(n, Keyword);
    },
    isurl: function (n) {
        return isa(n, URL);
    },
    ispixel: function (n) {
        return isunit(n, 'px');
    },
    ispercentage: function (n) {
        return isunit(n, '%');
    },
    isem: function (n) {
        return isunit(n, 'em');
    },
    isunit,
    unit: function (val, unit) {
        if (!(val instanceof Dimension)) {
            throw { type: 'Argument',
                message: `the first argument to unit must be a number${val instanceof Operation ? '. Have you forgotten parenthesis?' : ''}` };
        }
        if (unit) {
            if (unit instanceof Keyword) {
                unit = unit.value;
            } else {
                unit = unit.toCSS();
            }
        } else {
            unit = '';
        }
        return new Dimension(val.value, unit);
    },
    'get-unit': function (n) {
        return new Anonymous(n.unit);
    }
};

/** @param {*[]} args */
const styleExpression = function (args) {
    args = Array.prototype.slice.call(args);
    if (args.length === 0) {
        throw { type: 'Argument', message: 'one or more arguments required' };
    }

    const entityList = [new Variable(args[0].value, this.index, this.currentFileInfo).eval(this.context)];

    const result = entityList.map(a => { return a.toCSS(this.context); }).join(this.context.compress ? ',' : ', ');

    return new Anonymous(`style(${result})`);
};

var style = {
    /** @param {...*} args */
    style: function(...args) {
        try {
            return styleExpression.call(this, args);
        } catch (e) {
            // When style() is used as a CSS function (e.g. @container style(--responsive: true)),
            // arguments won't be valid Less variables. Return undefined to let the
            // parser fall through and treat it as plain CSS.
        }
    },
};

var functions = environment => {
    const functions = { functionRegistry, functionCaller };

    // register functions
    functionRegistry.addMultiple(boolean$1);
    functionRegistry.add('default', defaultFunc.eval.bind(defaultFunc));
    functionRegistry.addMultiple(color);
    functionRegistry.addMultiple(colorBlend);
    functionRegistry.addMultiple(dataUri(environment));
    functionRegistry.addMultiple(list);
    functionRegistry.addMultiple(mathFunctions);
    functionRegistry.addMultiple(number);
    functionRegistry.addMultiple(string);
    functionRegistry.addMultiple(svg());
    functionRegistry.addMultiple(types);
    functionRegistry.addMultiple(style);

    return functions;
};

/**
 * @param {import('./tree/node.js').default} root
 * @param {{ variables?: Record<string, *>, compress?: boolean, pluginManager?: *, frames?: *[] }} options
 * @returns {import('./tree/node.js').default}
 */
function transformTree(root, options) {
    options = options || {};
    let evaldRoot;
    let variables = options.variables;
    const evalEnv = new contexts.Eval(options);

    //
    // Allows setting variables with a hash, so:
    //
    //   `{ color: new tree.Color('#f01') }` will become:
    //
    //   new tree.Declaration('@color',
    //     new tree.Value([
    //       new tree.Expression([
    //         new tree.Color('#f01')
    //       ])
    //     ])
    //   )
    //
    if (typeof variables === 'object' && !Array.isArray(variables)) {
        variables = Object.keys(variables).map(function (k) {
            let value = variables[k];

            if (!(value instanceof tree.Value)) {
                if (!(value instanceof tree.Expression)) {
                    value = new tree.Expression([value]);
                }
                value = new tree.Value([value]);
            }
            return new tree.Declaration(`@${k}`, value, false, null, 0);
        });
        evalEnv.frames = [new tree.Ruleset(null, variables)];
    }

    const visitors$1 = [
        new visitors.JoinSelectorVisitor(),
        new visitors.MarkVisibleSelectorsVisitor(true),
        new visitors.ExtendVisitor(),
        new visitors.ToCSSVisitor({compress: Boolean(options.compress)})
    ];

    const preEvalVisitors = [];
    let v;
    let visitorIterator;

    /**
     * first() / get() allows visitors to be added while visiting
     * 
     * @todo Add scoping for visitors just like functions for @plugin; right now they're global
     */
    if (options.pluginManager) {
        visitorIterator = options.pluginManager.visitor();
        for (let i = 0; i < 2; i++) {
            visitorIterator.first();
            while ((v = visitorIterator.get())) {
                if (v.isPreEvalVisitor) {
                    if (i === 0 || preEvalVisitors.indexOf(v) === -1) {
                        preEvalVisitors.push(v);
                        v.run(root);
                    }
                }
                else {
                    if (i === 0 || visitors$1.indexOf(v) === -1) {
                        if (v.isPreVisitor) {
                            visitors$1.unshift(v);
                        }
                        else {
                            visitors$1.push(v);
                        }
                    }
                }
            }
        }
    }

    evaldRoot = root.eval(evalEnv);

    for (let i = 0; i < visitors$1.length; i++) {
        visitors$1[i].run(evaldRoot);
    }

    // Run any remaining visitors added after eval pass
    if (options.pluginManager) {
        visitorIterator.first();
        while ((v = visitorIterator.get())) {
            if (visitors$1.indexOf(v) === -1 && preEvalVisitors.indexOf(v) === -1) {
                v.run(evaldRoot);
            }
        }
    }

    return evaldRoot;
}

/**
 * Plugin Manager
 */
class PluginManager {
    constructor(less) {
        this.less = less;
        this.visitors = [];
        this.preProcessors = [];
        this.postProcessors = [];
        this.installedPlugins = [];
        this.fileManagers = [];
        this.iterator = -1;
        this.pluginCache = {};
        this.Loader = new less.PluginLoader(less);
    }

    /**
     * Adds all the plugins in the array
     * @param {Array} plugins
     */
    addPlugins(plugins) {
        if (plugins) {
            for (let i = 0; i < plugins.length; i++) {
                this.addPlugin(plugins[i]);
            }
        }
    }

    /**
     *
     * @param plugin
     * @param {String} filename
     */
    addPlugin(plugin, filename, functionRegistry) {
        this.installedPlugins.push(plugin);
        if (filename) {
            this.pluginCache[filename] = plugin;
        }
        if (plugin.install) {
            plugin.install(this.less, this, functionRegistry || this.less.functions.functionRegistry);
        }
    }

    /**
     *
     * @param filename
     */
    get(filename) {
        return this.pluginCache[filename];
    }

    /**
     * Adds a visitor. The visitor object has options on itself to determine
     * when it should run.
     * @param visitor
     */
    addVisitor(visitor) {
        this.visitors.push(visitor);
    }

    /**
     * Adds a pre processor object
     * @param {object} preProcessor
     * @param {number} priority - guidelines 1 = before import, 1000 = import, 2000 = after import
     */
    addPreProcessor(preProcessor, priority) {
        let indexToInsertAt;
        for (indexToInsertAt = 0; indexToInsertAt < this.preProcessors.length; indexToInsertAt++) {
            if (this.preProcessors[indexToInsertAt].priority >= priority) {
                break;
            }
        }
        this.preProcessors.splice(indexToInsertAt, 0, {preProcessor, priority});
    }

    /**
     * Adds a post processor object
     * @param {object} postProcessor
     * @param {number} priority - guidelines 1 = before compression, 1000 = compression, 2000 = after compression
     */
    addPostProcessor(postProcessor, priority) {
        let indexToInsertAt;
        for (indexToInsertAt = 0; indexToInsertAt < this.postProcessors.length; indexToInsertAt++) {
            if (this.postProcessors[indexToInsertAt].priority >= priority) {
                break;
            }
        }
        this.postProcessors.splice(indexToInsertAt, 0, {postProcessor, priority});
    }

    /**
     *
     * @param manager
     */
    addFileManager(manager) {
        this.fileManagers.push(manager);
    }

    /**
     *
     * @returns {Array}
     * @private
     */
    getPreProcessors() {
        const preProcessors = [];
        for (let i = 0; i < this.preProcessors.length; i++) {
            preProcessors.push(this.preProcessors[i].preProcessor);
        }
        return preProcessors;
    }

    /**
     *
     * @returns {Array}
     * @private
     */
    getPostProcessors() {
        const postProcessors = [];
        for (let i = 0; i < this.postProcessors.length; i++) {
            postProcessors.push(this.postProcessors[i].postProcessor);
        }
        return postProcessors;
    }

    /**
     *
     * @returns {Array}
     * @private
     */
    getVisitors() {
        return this.visitors;
    }

    visitor() {
        const self = this;
        return {
            first: function() {
                self.iterator = -1;
                return self.visitors[self.iterator];
            },
            get: function() {
                self.iterator += 1;
                return self.visitors[self.iterator];
            }
        };
    }

    /**
     *
     * @returns {Array}
     * @private
     */
    getFileManagers() {
        return this.fileManagers;
    }
}

let pm;

const PluginManagerFactory = function(less, newFactory) {
    if (newFactory || !pm) {
        pm = new PluginManager(less);
    }
    return pm;
};

function SourceMapOutput (environment) {
    class SourceMapOutput {
        constructor(options) {
            this._css = [];
            this._rootNode = options.rootNode;
            this._contentsMap = options.contentsMap;
            this._contentsIgnoredCharsMap = options.contentsIgnoredCharsMap;
            if (options.sourceMapFilename) {
                this._sourceMapFilename = options.sourceMapFilename.replace(/\\/g, '/');
            }
            this._outputFilename = options.outputFilename ? options.outputFilename.replace(/\\/g, '/') : options.outputFilename;
            this.sourceMapURL = options.sourceMapURL;
            if (options.sourceMapBasepath) {
                this._sourceMapBasepath = options.sourceMapBasepath.replace(/\\/g, '/');
            }
            if (options.sourceMapRootpath) {
                this._sourceMapRootpath = options.sourceMapRootpath.replace(/\\/g, '/');
                if (this._sourceMapRootpath.charAt(this._sourceMapRootpath.length - 1) !== '/') {
                    this._sourceMapRootpath += '/';
                }
            } else {
                this._sourceMapRootpath = '';
            }
            this._outputSourceFiles = options.outputSourceFiles;
            this._sourceMapGeneratorConstructor = environment.getSourceMapGenerator();

            this._lineNumber = 0;
            this._column = 0;
        }

        removeBasepath(path) {
            if (this._sourceMapBasepath && path.indexOf(this._sourceMapBasepath) === 0) {
                path = path.substring(this._sourceMapBasepath.length);
                if (path.charAt(0) === '\\' || path.charAt(0) === '/') {
                    path = path.substring(1);
                }
            }

            return path;
        }

        normalizeFilename(filename) {
            filename = filename.replace(/\\/g, '/');
            filename = this.removeBasepath(filename);
            return (this._sourceMapRootpath || '') + filename;
        }

        add(chunk, fileInfo, index, mapLines) {

            // ignore adding empty strings
            if (!chunk) {
                return;
            }

            let lines, sourceLines, columns, sourceColumns, i;

            if (fileInfo && fileInfo.filename) {
                let inputSource = this._contentsMap[fileInfo.filename];

                // remove vars/banner added to the top of the file
                if (this._contentsIgnoredCharsMap[fileInfo.filename]) {
                    // adjust the index
                    index -= this._contentsIgnoredCharsMap[fileInfo.filename];
                    if (index < 0) { index = 0; }
                    // adjust the source
                    inputSource = inputSource.slice(this._contentsIgnoredCharsMap[fileInfo.filename]);
                }

                /** 
                 * ignore empty content, or failsafe
                 * if contents map is incorrect
                 */
                if (inputSource === undefined) {
                    this._css.push(chunk);
                    return;
                }

                inputSource = inputSource.substring(0, index);
                sourceLines = inputSource.split('\n');
                sourceColumns = sourceLines[sourceLines.length - 1];
            }

            lines = chunk.split('\n');
            columns = lines[lines.length - 1];

            if (fileInfo && fileInfo.filename) {
                if (!mapLines) {
                    this._sourceMapGenerator.addMapping({ generated: { line: this._lineNumber + 1, column: this._column},
                        original: { line: sourceLines.length, column: sourceColumns.length},
                        source: this.normalizeFilename(fileInfo.filename)});
                } else {
                    for (i = 0; i < lines.length; i++) {
                        this._sourceMapGenerator.addMapping({ generated: { line: this._lineNumber + i + 1, column: i === 0 ? this._column : 0},
                            original: { line: sourceLines.length + i, column: i === 0 ? sourceColumns.length : 0},
                            source: this.normalizeFilename(fileInfo.filename)});
                    }
                }
            }

            if (lines.length === 1) {
                this._column += columns.length;
            } else {
                this._lineNumber += lines.length - 1;
                this._column = columns.length;
            }

            this._css.push(chunk);
        }

        isEmpty() {
            return this._css.length === 0;
        }

        toCSS(context) {
            this._sourceMapGenerator = new this._sourceMapGeneratorConstructor({ file: this._outputFilename, sourceRoot: null });

            if (this._outputSourceFiles) {
                for (const filename in this._contentsMap) {
                    // eslint-disable-next-line no-prototype-builtins
                    if (this._contentsMap.hasOwnProperty(filename)) {
                        let source = this._contentsMap[filename];
                        if (this._contentsIgnoredCharsMap[filename]) {
                            source = source.slice(this._contentsIgnoredCharsMap[filename]);
                        }
                        this._sourceMapGenerator.setSourceContent(this.normalizeFilename(filename), source);
                    }
                }
            }

            this._rootNode.genCSS(context, this);

            if (this._css.length > 0) {
                let sourceMapURL;
                const sourceMapContent = JSON.stringify(this._sourceMapGenerator.toJSON());

                if (this.sourceMapURL) {
                    sourceMapURL = this.sourceMapURL;
                } else if (this._sourceMapFilename) {
                    sourceMapURL = this._sourceMapFilename;
                }
                this.sourceMapURL = sourceMapURL;

                this.sourceMap = sourceMapContent;
            }

            return this._css.join('');
        }
    }

    return SourceMapOutput;
}

function SourceMapBuilder (SourceMapOutput, environment) {
    class SourceMapBuilder {
        constructor(options) {
            this.options = options;
        }

        toCSS(rootNode, options, imports) {
            const sourceMapOutput = new SourceMapOutput(
                {
                    contentsIgnoredCharsMap: imports.contentsIgnoredChars,
                    rootNode,
                    contentsMap: imports.contents,
                    sourceMapFilename: this.options.sourceMapFilename,
                    sourceMapURL: this.options.sourceMapURL,
                    outputFilename: this.options.sourceMapOutputFilename,
                    sourceMapBasepath: this.options.sourceMapBasepath,
                    sourceMapRootpath: this.options.sourceMapRootpath,
                    outputSourceFiles: this.options.outputSourceFiles,
                    sourceMapGenerator: this.options.sourceMapGenerator,
                    sourceMapFileInline: this.options.sourceMapFileInline,    
                    disableSourcemapAnnotation: this.options.disableSourcemapAnnotation
                });

            const css = sourceMapOutput.toCSS(options);
            this.sourceMap = sourceMapOutput.sourceMap;
            this.sourceMapURL = sourceMapOutput.sourceMapURL;
            if (this.options.sourceMapInputFilename) {
                this.sourceMapInputFilename = sourceMapOutput.normalizeFilename(this.options.sourceMapInputFilename);
            }
            if (this.options.sourceMapBasepath !== undefined && this.sourceMapURL !== undefined) {
                this.sourceMapURL = sourceMapOutput.removeBasepath(this.sourceMapURL);
            }
            return css + this.getCSSAppendage();
        }

        getCSSAppendage() {

            let sourceMapURL = this.sourceMapURL;
            if (this.options.sourceMapFileInline) {
                if (this.sourceMap === undefined) {
                    return '';
                }
                sourceMapURL = `data:application/json;base64,${environment.encodeBase64(this.sourceMap)}`;
            }

            if (this.options.disableSourcemapAnnotation) {
                return '';
            }

            if (sourceMapURL) {
                return `/*# sourceMappingURL=${sourceMapURL} */`;
            }
            return '';
        }

        getExternalSourceMap() {
            return this.sourceMap;
        }

        setExternalSourceMap(sourceMap) {
            this.sourceMap = sourceMap;
        }

        isInline() {
            return this.options.sourceMapFileInline;
        }

        getSourceMapURL() {
            return this.sourceMapURL;
        }

        getOutputFilename() {
            return this.options.sourceMapOutputFilename;
        }

        getInputFilename() {
            return this.sourceMapInputFilename;
        }
    }

    return SourceMapBuilder;
}

function ParseTree(SourceMapBuilder) {
    class ParseTree {
        constructor(root, imports) {
            this.root = root;
            this.imports = imports;
        }

        toCSS(options) {
            let evaldRoot;
            const result = {};
            let sourceMapBuilder;
            try {
                evaldRoot = transformTree(this.root, options);
            } catch (e) {
                throw new LessError(e, this.imports);
            }

            try {
                const compress = Boolean(options.compress);
                if (compress) {
                    logger.warn('The compress option has been deprecated. ' + 
                        'We recommend you use a dedicated css minifier, for instance see less-plugin-clean-css.');
                }

                const toCSSOptions = {
                    compress,
                    // @deprecated The dumpLineNumbers option is deprecated. Use sourcemaps instead. All modes will be removed in a future version.
                    dumpLineNumbers: options.dumpLineNumbers,
                    strictUnits: Boolean(options.strictUnits),
                    numPrecision: 8};

                if (options.sourceMap) {
                    // Normalize sourceMap option: if it's just true, convert to object
                    if (options.sourceMap === true) {
                        options.sourceMap = {};
                    }
                    const sourceMapOpts = options.sourceMap;
                    
                    // Set sourceMapInputFilename if not set and filename is available
                    if (!sourceMapOpts.sourceMapInputFilename && options.filename) {
                        sourceMapOpts.sourceMapInputFilename = options.filename;
                    }
                    
                    // Default sourceMapBasepath to the input file's directory if not set
                    // This matches the behavior documented and implemented in bin/lessc
                    if (sourceMapOpts.sourceMapBasepath === undefined && options.filename) {
                        // Get directory from filename using string manipulation (works cross-platform)
                        const lastSlash = Math.max(options.filename.lastIndexOf('/'), options.filename.lastIndexOf('\\'));
                        if (lastSlash >= 0) {
                            sourceMapOpts.sourceMapBasepath = options.filename.substring(0, lastSlash);
                        } else {
                            // No directory separator found, use current directory
                            sourceMapOpts.sourceMapBasepath = '.';
                        }
                    }
                    
                    // Handle sourceMapFullFilename (CLI-specific: --source-map=filename)
                    // This is converted to sourceMapFilename and sourceMapOutputFilename
                    if (sourceMapOpts.sourceMapFullFilename && !sourceMapOpts.sourceMapFileInline) {
                        // This case is handled by lessc before calling render
                        // We just need to ensure sourceMapFilename is set if sourceMapFullFilename is provided
                        if (!sourceMapOpts.sourceMapFilename && !sourceMapOpts.sourceMapURL) {
                            // Extract just the basename for the sourceMappingURL comment
                            const mapBase = sourceMapOpts.sourceMapFullFilename.split(/[/\\]/).pop();
                            sourceMapOpts.sourceMapFilename = mapBase;
                        }
                    } else if (!sourceMapOpts.sourceMapFilename && !sourceMapOpts.sourceMapURL) {
                        // If sourceMapFilename is not set and sourceMapURL is not set,
                        // derive it from the output filename (if available) or input filename
                        if (sourceMapOpts.sourceMapOutputFilename) {
                            // Use output filename + .map
                            sourceMapOpts.sourceMapFilename = sourceMapOpts.sourceMapOutputFilename + '.map';
                        } else if (options.filename) {
                            // Fallback to input filename + .css.map (basename only)
                            const inputBasename = options.filename.split(/[/\\]/).pop().replace(/\.[^/.]+$/, '');
                            sourceMapOpts.sourceMapFilename = inputBasename + '.css.map';
                        }
                    }
                    
                    // Default sourceMapOutputFilename if not set
                    if (!sourceMapOpts.sourceMapOutputFilename) {
                        if (options.filename) {
                            const inputBasename = options.filename.split(/[/\\]/).pop().replace(/\.[^/.]+$/, '');
                            sourceMapOpts.sourceMapOutputFilename = inputBasename + '.css';
                        } else {
                            sourceMapOpts.sourceMapOutputFilename = 'output.css';
                        }
                    }
                    
                    sourceMapBuilder = new SourceMapBuilder(sourceMapOpts);
                    result.css = sourceMapBuilder.toCSS(evaldRoot, toCSSOptions, this.imports);
                } else {
                    result.css = evaldRoot.toCSS(toCSSOptions);
                }
            } catch (e) {
                throw new LessError(e, this.imports);
            }

            if (options.pluginManager) {
                const postProcessors = options.pluginManager.getPostProcessors();
                for (let i = 0; i < postProcessors.length; i++) {
                    result.css = postProcessors[i].process(result.css, { sourceMap: sourceMapBuilder, options, imports: this.imports });
                }
            }
            if (options.sourceMap) {
                result.map = sourceMapBuilder.getExternalSourceMap();
            }

            result.imports = [];
            for (const file in this.imports.files) {
                if (Object.prototype.hasOwnProperty.call(this.imports.files, file) && file !== this.imports.rootFilename) {
                    result.imports.push(file);
                }
            }
            return result;
        }
    }

    return ParseTree;
}

function ImportManager(environment) {
    // FileInfo = {
    //  'rewriteUrls' - option - whether to adjust URL's to be relative
    //  'filename' - full resolved filename of current file
    //  'rootpath' - path to append to normal URLs for this node
    //  'currentDirectory' - path to the current file, absolute
    //  'rootFilename' - filename of the base file
    //  'entryPath' - absolute path to the entry file
    //  'reference' - whether the file should not be output and only output parts that are referenced

    class ImportManager {
        constructor(less, context, rootFileInfo) {
            this.less = less;
            this.rootFilename = rootFileInfo.filename;
            this.paths = context.paths || [];  // Search paths, when importing
            this.contents = {};             // map - filename to contents of all the files
            this.contentsIgnoredChars = {}; // map - filename to lines at the beginning of each file to ignore
            this.mime = context.mime;
            this.error = null;
            this.context = context;
            // Deprecated? Unused outside of here, could be useful.
            this.queue = [];        // Files which haven't been imported yet
            this.files = {};        // Holds the imported parse trees.
        }

        /**
         * Add an import to be imported
         * @param path - the raw path
         * @param tryAppendExtension - whether to try appending a file extension (.less or .js if the path has no extension)
         * @param currentFileInfo - the current file info (used for instance to work out relative paths)
         * @param importOptions - import options
         * @param callback - callback for when it is imported
         */
        push(path, tryAppendExtension, currentFileInfo, importOptions, callback) {
            const importManager = this, pluginLoader = this.context.pluginManager.Loader;

            this.queue.push(path);

            const fileParsedFunc = function (e, root, fullPath) {
                importManager.queue.splice(importManager.queue.indexOf(path), 1); // Remove the path from the queue

                const importedEqualsRoot = fullPath === importManager.rootFilename;
                if (importOptions.optional && e) {
                    callback(null, {rules:[]}, false, null);
                    logger.info(`The file ${fullPath} was skipped because it was not found and the import was marked optional.`);
                }
                else {
                    // Inline imports aren't cached here.
                    // If we start to cache them, please make sure they won't conflict with non-inline imports of the
                    // same name as they used to do before this comment and the condition below have been added.
                    if (!importManager.files[fullPath] && !importOptions.inline) {
                        importManager.files[fullPath] = { root, options: importOptions };
                    }
                    if (e && !importManager.error) { importManager.error = e; }
                    callback(e, root, importedEqualsRoot, fullPath);
                }
            };

            const newFileInfo = {
                rewriteUrls: this.context.rewriteUrls,
                entryPath: currentFileInfo.entryPath,
                rootpath: currentFileInfo.rootpath,
                rootFilename: currentFileInfo.rootFilename
            };

            const fileManager = environment.getFileManager(path, currentFileInfo.currentDirectory, this.context, environment);

            if (!fileManager) {
                fileParsedFunc({ message: `Could not find a file-manager for ${path}` });
                return;
            }

            const loadFileCallback = function(loadedFile) {
                let plugin;
                const resolvedFilename = loadedFile.filename;
                const contents = loadedFile.contents.replace(/^\uFEFF/, '');

                // Pass on an updated rootpath if path of imported file is relative and file
                // is in a (sub|sup) directory
                //
                // Examples:
                // - If path of imported file is 'module/nav/nav.less' and rootpath is 'less/',
                //   then rootpath should become 'less/module/nav/'
                // - If path of imported file is '../mixins.less' and rootpath is 'less/',
                //   then rootpath should become 'less/../'
                newFileInfo.currentDirectory = fileManager.getPath(resolvedFilename);
                if (newFileInfo.rewriteUrls) {
                    newFileInfo.rootpath = fileManager.join(
                        (importManager.context.rootpath || ''),
                        fileManager.pathDiff(newFileInfo.currentDirectory, newFileInfo.entryPath));

                    if (!fileManager.isPathAbsolute(newFileInfo.rootpath) && fileManager.alwaysMakePathsAbsolute()) {
                        newFileInfo.rootpath = fileManager.join(newFileInfo.entryPath, newFileInfo.rootpath);
                    }
                }
                newFileInfo.filename = resolvedFilename;

                const newEnv = new contexts.Parse(importManager.context);

                newEnv.processImports = false;
                importManager.contents[resolvedFilename] = contents;

                if (currentFileInfo.reference || importOptions.reference) {
                    newFileInfo.reference = true;
                }

                if (importOptions.isPlugin) {
                    plugin = pluginLoader.evalPlugin(contents, newEnv, importManager, importOptions.pluginArgs, newFileInfo);
                    if (plugin instanceof LessError) {
                        fileParsedFunc(plugin, null, resolvedFilename);
                    }
                    else {
                        fileParsedFunc(null, plugin, resolvedFilename);
                    }
                } else if (importOptions.inline) {
                    fileParsedFunc(null, contents, resolvedFilename);
                } else {
                    // import (multiple) parse trees apparently get altered and can't be cached.
                    // TODO: investigate why this is
                    if (importManager.files[resolvedFilename]
                        && !importManager.files[resolvedFilename].options.multiple
                        && !importOptions.multiple) {

                        fileParsedFunc(null, importManager.files[resolvedFilename].root, resolvedFilename);
                    }
                    else {
                        new Parser(newEnv, importManager, newFileInfo).parse(contents, function (e, root) {
                            fileParsedFunc(e, root, resolvedFilename);
                        });
                    }
                }
            };
            let loadedFile;
            let promise;
            const context = clone(this.context);

            if (tryAppendExtension) {
                context.ext = importOptions.isPlugin ? '.js' : '.less';
            }

            if (importOptions.isPlugin) {
                context.mime = 'application/javascript';

                if (context.syncImport) {
                    loadedFile = pluginLoader.loadPluginSync(path, currentFileInfo.currentDirectory, context, environment, fileManager);
                } else {
                    promise = pluginLoader.loadPlugin(path, currentFileInfo.currentDirectory, context, environment, fileManager);
                }
            }
            else {
                if (context.syncImport) {
                    loadedFile = fileManager.loadFileSync(path, currentFileInfo.currentDirectory, context, environment);
                } else {
                    promise = fileManager.loadFile(path, currentFileInfo.currentDirectory, context, environment,
                        (err, loadedFile) => {
                            if (err) {
                                fileParsedFunc(err);
                            } else {
                                loadFileCallback(loadedFile);
                            }
                        });
                }
            }
            if (loadedFile) {
                if (!loadedFile.filename) {
                    fileParsedFunc(loadedFile);
                } else {
                    loadFileCallback(loadedFile);
                }
            } else if (promise) {
                promise.then(loadFileCallback, fileParsedFunc);
            }
        }
    }

    return ImportManager;
}

function Parse(environment, ParseTree, ImportManager) {
    const parse = function (input, options, callback) {

        if (typeof options === 'function') {
            callback = options;
            options = copyOptions(this.options, {});
        }
        else {
            options = copyOptions(this.options, options || {});
        }

        if (!callback) {
            const self = this;
            return new Promise(function (resolve, reject) {
                parse.call(self, input, options, function(err, output) {
                    if (err) {
                        reject(err);
                    } else {
                        resolve(output);
                    }
                });
            });
        } else {
            let context;
            let rootFileInfo;
            const pluginManager = new PluginManagerFactory(this, !options.reUsePluginManager);

            options.pluginManager = pluginManager;

            context = new contexts.Parse(options);

            if (options.rootFileInfo) {
                rootFileInfo = options.rootFileInfo;
            } else {
                const filename = options.filename || 'input';
                const entryPath = filename.replace(/[^/\\]*$/, '');
                rootFileInfo = {
                    filename,
                    rewriteUrls: context.rewriteUrls,
                    rootpath: context.rootpath || '',
                    currentDirectory: entryPath,
                    entryPath,
                    rootFilename: filename
                };
                // add in a missing trailing slash
                if (rootFileInfo.rootpath && rootFileInfo.rootpath.slice(-1) !== '/') {
                    rootFileInfo.rootpath += '/';
                }
            }

            const imports = new ImportManager(this, context, rootFileInfo);
            this.importManager = imports;

            // TODO: allow the plugins to be just a list of paths or names
            // Do an async plugin queue like lessc

            if (options.plugins) {
                options.plugins.forEach(function(plugin) {
                    let evalResult, contents;
                    if (plugin.fileContent) {
                        contents = plugin.fileContent.replace(/^\uFEFF/, '');
                        evalResult = pluginManager.Loader.evalPlugin(contents, context, imports, plugin.options, plugin.filename);
                        if (evalResult instanceof LessError) {
                            return callback(evalResult);
                        }
                    }
                    else {
                        pluginManager.addPlugin(plugin);
                    }
                });
            }

            new Parser(context, imports, rootFileInfo)
                .parse(input, function (e, root) {
                    if (e) { return callback(e); }
                    callback(null, root, imports, options);
                }, options);
        }
    };
    return parse;
}

function Render(environment, ParseTree) {
    const render = function (input, options, callback) {
        if (typeof options === 'function') {
            callback = options;
            options = copyOptions(this.options, {});
        }
        else {
            options = copyOptions(this.options, options || {});
        }

        if (!callback) {
            const self = this;
            return new Promise(function (resolve, reject) {
                render.call(self, input, options, function(err, output) {
                    if (err) {
                        reject(err);
                    } else {
                        resolve(output);
                    }
                });
            });
        } else {
            this.parse(input, options, function(err, root, imports, options) {
                if (err) { return callback(err); }

                let result;
                try {
                    const parseTree = new ParseTree(root, imports);
                    result = parseTree.toCSS(options);
                }
                catch (err) { return callback(err); }

                callback(null, result);
            });
        }
    };

    return render;
}

function parseNodeVersion(version) {
  var match = version.match(/^v(\d{1,2})\.(\d{1,2})\.(\d{1,2})(?:-([0-9A-Za-z-.]+))?(?:\+([0-9A-Za-z-.]+))?$/); // eslint-disable-line max-len
  if (!match) {
    throw new Error('Unable to parse: ' + version);
  }

  var res = {
    major: parseInt(match[1], 10),
    minor: parseInt(match[2], 10),
    patch: parseInt(match[3], 10),
    pre: match[4] || '',
    build: match[5] || '',
  };

  return res;
}

var parseNodeVersion_1 = parseNodeVersion;

function createFromEnvironment(environment, fileManagers, version = '0.0.0') {
    let sourceMapOutput, sourceMapBuilder, parseTree, importManager;

    environment = new Environment(environment, fileManagers);
    sourceMapOutput = SourceMapOutput(environment);
    sourceMapBuilder = SourceMapBuilder(sourceMapOutput, environment);
    parseTree = ParseTree(sourceMapBuilder);
    importManager = ImportManager(environment);

    const render = Render(environment, parseTree);
    const parse = Parse(environment, parseTree, importManager);

    const v = parseNodeVersion_1(`v${version}`);
    const initial = {
        version: [v.major, v.minor, v.patch],
        data,
        tree,
        Environment,
        AbstractFileManager,
        AbstractPluginLoader,
        environment,
        visitors,
        Parser,
        functions: functions(environment),
        contexts,
        SourceMapOutput: sourceMapOutput,
        SourceMapBuilder: sourceMapBuilder,
        ParseTree: parseTree,
        ImportManager: importManager,
        render,
        parse,
        LessError,
        transformTree,
        utils,
        PluginManager: PluginManagerFactory,
        logger
    };

    // Create a public API

    const ctor = function(t) {
        return function(...args) {
            return new t(...args);
        };
    };
    let t;
    const api = Object.create(initial);
    for (const n in initial.tree) {
        /* eslint guard-for-in: 0 */
        t = initial.tree[n];
        if (typeof t === 'function') {
            api[n.toLowerCase()] = ctor(t);
        }
        else {
            api[n] = Object.create(null);
            for (const o in t) {
                /* eslint guard-for-in: 0 */
                api[n][o.toLowerCase()] = ctor(t[o]);
            }
        }
    }

    /**
     * Some of the functions assume a `this` context of the API object,
     * which causes it to fail when wrapped for ES6 imports.
     * 
     * An assumed `this` should be removed in the future.
     */
    initial.parse = initial.parse.bind(api);
    initial.render = initial.render.bind(api);

    return api;
}

// lessc_helper.js
//
//      helper functions for lessc
const lessc_helper = {

    // Stylize a string
    stylize : function(str, style) {
        const styles = {
            'reset'     : [0,   0],
            'bold'      : [1,  22],
            'inverse'   : [7,  27],
            'underline' : [4,  24],
            'yellow'    : [33, 39],
            'green'     : [32, 39],
            'red'       : [31, 39],
            'grey'      : [90, 39]
        };
        return `\x1b[${styles[style][0]}m${str}\x1b[${styles[style][1]}m`;
    },

    // Print command line options
    printUsage: function() {
        console.log('usage: lessc [option option=parameter ...] <source> [destination]');
        console.log('');
        console.log('If source is set to `-\' (dash or hyphen-minus), input is read from stdin.');
        console.log('');
        console.log('options:');
        console.log('  -h, --help                   Prints help (this message) and exit.');
        console.log('  --include-path=PATHS         Sets include paths. Separated by `:\'. `;\' also supported on windows.');
        console.log('  -M, --depends                Outputs a makefile import dependency list to stdout.');
        console.log('  --no-color                   Disables colorized output.');
        console.log('  --ie-compat                  Enables IE8 compatibility checks.');
        console.log('  --js                         Enables inline JavaScript in less files');
        console.log('  -l, --lint                   Syntax check only (lint).');
        console.log('  -s, --silent                 Suppresses output of error messages.');
        console.log('  --quiet                      Suppresses output of warnings.');
        console.log('  --strict-imports             (DEPRECATED) Ignores .less imports inside selector blocks. Has confusing behavior.');
        console.log('  --insecure                   Allows imports from insecure https hosts.');
        console.log('  -v, --version                Prints version number and exit.');
        console.log('  --verbose                    Be verbose.');
        console.log('  --source-map[=FILENAME]      Outputs a v3 sourcemap to the filename (or output filename.map).');
        console.log('  --source-map-rootpath=X      Adds this path onto the sourcemap filename and less file paths.');
        console.log('  --source-map-basepath=X      Sets sourcemap base path, defaults to current working directory.');
        console.log('  --source-map-include-source  Puts the less files into the map instead of referencing them.');
        console.log('  --source-map-inline          Puts the map (and any less files) as a base64 data uri into the output css file.');
        console.log('  --source-map-url=URL         Sets a custom URL to map file, for sourceMappingURL comment');
        console.log('                               in generated CSS file.');
        console.log('  --source-map-no-annotation   Excludes the sourceMappingURL comment from the output css file.');
        console.log('  -rp, --rootpath=URL          Sets rootpath for url rewriting in relative imports and urls');
        console.log('                               Works with or without the relative-urls option.');
        console.log('  -ru=, --rewrite-urls=        Rewrites URLs to make them relative to the base less file.');
        console.log('    all|local|off              \'all\' rewrites all URLs, \'local\' just those starting with a \'.\'');
        console.log('');
        console.log('  -m=, --math=');
        console.log('     always                    Less will eagerly perform math operations always.');
        console.log('     parens-division           Math performed except for division (/) operator');
        console.log('     parens | strict           Math only performed inside parentheses');
        console.log('     strict-legacy             Parens required in very strict terms (legacy --strict-math)');
        console.log('');
        console.log('  -su=on|off                   Allows mixed units, e.g. 1px+1em or 1px*1px which have units');
        console.log('  --strict-units=on|off        that cannot be represented.');
        console.log('  --global-var=\'VAR=VALUE\'     Defines a variable that can be referenced by the file.');
        console.log('  --modify-var=\'VAR=VALUE\'     Modifies a variable already declared in the file.');
        console.log('  --url-args=\'QUERYSTRING\'     Adds params into url tokens (e.g. 42, cb=42 or \'a=1&b=2\')');
        console.log('  --plugin=PLUGIN=OPTIONS      Loads a plugin. You can also omit the --plugin= if the plugin begins');
        console.log('                               less-plugin. E.g. the clean css plugin is called less-plugin-clean-css');
        console.log('                               once installed (npm install less-plugin-clean-css), use either with');
        console.log('                               --plugin=less-plugin-clean-css or just --clean-css');
        console.log('                               specify options afterwards e.g. --plugin=less-plugin-clean-css="advanced"');
        console.log('                               or --clean-css="advanced"');
        console.log('  --disable-plugin-rule        Disallow @plugin statements');
        console.log('');
        console.log('  --quiet-deprecations         Suppress deprecation warnings only (keeps other warnings).');
        console.log('');
        console.log('-------------------------- Deprecated ----------------');
        console.log('  -sm=on|off               Legacy parens-only math. Use --math');
        console.log('  --strict-math=on|off     ');
        console.log('');
        console.log('  --line-numbers=TYPE      (DEPRECATED) Outputs filename and line numbers.');
        console.log('                           TYPE can be either \'comments\', \'mediaquery\', or \'all\'.');
        console.log('                           The entire dumpLineNumbers option is deprecated.');
        console.log('                           Use sourcemaps (--source-map) instead.');
        console.log('                           All modes will be removed in a future version.');
        console.log('                           Note: \'mediaquery\' and \'all\' modes generate @media -sass-debug-info');
        console.log('                           which had short-lived usage and is no longer recommended.');
        console.log('  -x, --compress           Compresses output by removing some whitespaces.');
        console.log('                           We recommend you use a dedicated minifer like less-plugin-clean-css');
        console.log('');
        console.log('Report bugs to: http://github.com/less/less.js/issues');
        console.log('Home page: <http://lesscss.org/>');
    }
};

const require$2 = createRequire();

/**
 * Node Plugin Loader
 */
const PluginLoader = function(less) {
    this.less = less;
    this.require = prefix => {
        prefix = path__default["default"].dirname(prefix);
        return id => {
            const str = id.slice(0, 2);
            if (str === '..' || str === './') {
                return require$2(path__default["default"].join(prefix, id));
            }
            else {
                return require$2(id);
            }
        };
    };
};

PluginLoader.prototype = Object.assign(new AbstractPluginLoader(), {
    loadPlugin(filename, basePath, context, environment, fileManager) {
        const prefix = filename.slice(0, 1);
        const explicit = prefix === '.' || prefix === '/' || filename.slice(-3).toLowerCase() === '.js';
        if (!explicit) {
            context.prefixes = ['less-plugin-', ''];
        }

        if (context.syncImport) {
            return fileManager.loadFileSync(filename, basePath, context, environment);
        }

        return new Promise((fulfill, reject) => {
            fileManager.loadFile(filename, basePath, context, environment).then(
                data => {
                    try {
                        fulfill(data);
                    }
                    catch (e) {
                        console.log(e);
                        reject(e);
                    }
                }
            ).catch(err => {
                reject(err);
            });
        });
    },

    loadPluginSync(filename, basePath, context, environment, fileManager) {
        context.syncImport = true;
        return this.loadPlugin(filename, basePath, context, environment, fileManager);
    }
});

// Export a new default each time
function defaultOptions() {
    return {
        /* Inline Javascript - @plugin still allowed */
        javascriptEnabled: false,

        /* Outputs a makefile import dependency list to stdout. */
        depends: false,

        /* (DEPRECATED) Compress using less built-in compression. 
         * This does an okay job but does not utilise all the tricks of 
         * dedicated css compression. */
        compress: false,

        /* Runs the less parser and just reports errors without any output. */
        lint: false,

        /* Sets available include paths.
         * If the file in an @import rule does not exist at that exact location, 
         * less will look for it at the location(s) passed to this option. 
         * You might use this for instance to specify a path to a library which 
         * you want to be referenced simply and relatively in the less files. */
        paths: [],

        /* color output in the terminal */
        color: true,

        /**
         * @deprecated This option has confusing behavior and may be removed in a future version.
         * 
         * When true, prevents @import statements for .less files from being evaluated inside
         * selector blocks (rulesets). The imports are silently ignored and not output.
         * 
         * Behavior:
         * - @import at root level: Always processed
         * - @import inside @-rules (@media, @supports, etc.): Processed (these are not selector blocks)
         * - @import inside selector blocks (.class, #id, etc.): NOT processed (silently ignored)
         * 
         * When false (default): All @import statements are processed regardless of context.
         * 
         * Note: Despite the name "strict", this option does NOT throw an error when imports
         * are used in selector blocks - it silently ignores them. This is confusing
         * behavior that may catch users off guard.
         * 
         * Note: Only affects .less file imports. CSS imports (url(...) or .css files) are
         * always output as CSS @import statements regardless of this setting.
         * 
         * @see https://github.com/less/less.js/issues/656
         */
        strictImports: false,

        /* Allow Imports from Insecure HTTPS Hosts */
        insecure: false,

        /* Allows you to add a path to every generated import and url in your css. 
         * This does not affect less import statements that are processed, just ones 
         * that are left in the output css. */
        rootpath: '',

        /* By default URLs are kept as-is, so if you import a file in a sub-directory 
         * that references an image, exactly the same URL will be output in the css. 
         * This option allows you to re-write URL's in imported files so that the 
         * URL is always relative to the base imported file */
        rewriteUrls: false,

        /* How to process math 
         *   0 always           - eagerly try to solve all operations
         *   1 parens-division  - require parens for division "/"
         *   2 parens | strict  - require parens for all operations
         *   3 strict-legacy    - legacy strict behavior (super-strict)
         */
        math: 1,

        /* Without this option, less attempts to guess at the output unit when it does maths. */
        strictUnits: false,

        /* Effectively the declaration is put at the top of your base Less file, 
         * meaning it can be used but it also can be overridden if this variable 
         * is defined in the file. */
        globalVars: null,

        /* As opposed to the global variable option, this puts the declaration at the
         * end of your base file, meaning it will override anything defined in your Less file. */
        modifyVars: null,

        /* This option allows you to specify a argument to go on to every URL.  */
        urlArgs: ''
    }
}

const require$1 = createRequire();

var imageSize = environment => {

    function imageSize(functionContext, filePathNode) {
        let filePath = filePathNode.value;
        const currentFileInfo = functionContext.currentFileInfo;
        const currentDirectory = currentFileInfo.rewriteUrls ?
            currentFileInfo.currentDirectory : currentFileInfo.entryPath;

        const fragmentStart = filePath.indexOf('#');
        if (fragmentStart !== -1) {
            filePath = filePath.slice(0, fragmentStart);
        }

        const fileManager = environment.getFileManager(filePath, currentDirectory, functionContext.context, environment, true);

        if (!fileManager) {
            throw {
                type: 'File',
                message: `Can not set up FileManager for ${filePathNode}`
            };
        }

        const fileSync = fileManager.loadFileSync(filePath, currentDirectory, functionContext.context, environment);

        if (fileSync.error) {
            throw fileSync.error;
        }

        const sizeOf = require$1('image-size');
        return sizeOf ? sizeOf(fileSync.filename) : {width: 0, height: 0};
    }

    const imageFunctions = {
        'image-size': function(filePathNode) {
            const size = imageSize(this, filePathNode);
            return new Expression([
                new Dimension(size.width, 'px'),
                new Dimension(size.height, 'px')
            ]);
        },
        'image-width': function(filePathNode) {
            const size = imageSize(this, filePathNode);
            return new Dimension(size.width, 'px');
        },
        'image-height': function(filePathNode) {
            const size = imageSize(this, filePathNode);
            return new Dimension(size.height, 'px');
        }
    };

    functionRegistry.addMultiple(imageFunctions);
};

createRequire();
const version = "4.6.4";

const less = createFromEnvironment(environment, [new FileManager(), new UrlFileManager()], version);

// allow people to create less with their own environment
less.createFromEnvironment = createFromEnvironment;
less.lesscHelper = lessc_helper;
less.PluginLoader = PluginLoader;
less.fs = fs$1;
less.FileManager = FileManager;
less.UrlFileManager = UrlFileManager;

// Set up options
less.options = defaultOptions();

// provide image-size functionality
imageSize(less.environment);

module.exports = less;