(function (global, factory) {
    typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
    typeof define === 'function' && define.amd ? define(factory) :
    (global = global || self, global.csstree = factory());
}(this, function () { 'use strict';

    //
    //                              list
    //                            ┌──────┐
    //             ┌──────────────┼─head │
    //             │              │ tail─┼──────────────┐
    //             │              └──────┘              │
    //             ▼                                    ▼
    //            item        item        item        item
    //          ┌──────┐    ┌──────┐    ┌──────┐    ┌──────┐
    //  null ◀──┼─prev │◀───┼─prev │◀───┼─prev │◀───┼─prev │
    //          │ next─┼───▶│ next─┼───▶│ next─┼───▶│ next─┼──▶ null
    //          ├──────┤    ├──────┤    ├──────┤    ├──────┤
    //          │ data │    │ data │    │ data │    │ data │
    //          └──────┘    └──────┘    └──────┘    └──────┘
    //

    function createItem(data) {
        return {
            prev: null,
            next: null,
            data: data
        };
    }

    function allocateCursor(node, prev, next) {
        var cursor;

        if (cursors !== null) {
            cursor = cursors;
            cursors = cursors.cursor;
            cursor.prev = prev;
            cursor.next = next;
            cursor.cursor = node.cursor;
        } else {
            cursor = {
                prev: prev,
                next: next,
                cursor: node.cursor
            };
        }

        node.cursor = cursor;

        return cursor;
    }

    function releaseCursor(node) {
        var cursor = node.cursor;

        node.cursor = cursor.cursor;
        cursor.prev = null;
        cursor.next = null;
        cursor.cursor = cursors;
        cursors = cursor;
    }

    var cursors = null;
    var List = function() {
        this.cursor = null;
        this.head = null;
        this.tail = null;
    };

    List.createItem = createItem;
    List.prototype.createItem = createItem;

    List.prototype.updateCursors = function(prevOld, prevNew, nextOld, nextNew) {
        var cursor = this.cursor;

        while (cursor !== null) {
            if (cursor.prev === prevOld) {
                cursor.prev = prevNew;
            }

            if (cursor.next === nextOld) {
                cursor.next = nextNew;
            }

            cursor = cursor.cursor;
        }
    };

    List.prototype.getSize = function() {
        var size = 0;
        var cursor = this.head;

        while (cursor) {
            size++;
            cursor = cursor.next;
        }

        return size;
    };

    List.prototype.fromArray = function(array) {
        var cursor = null;

        this.head = null;

        for (var i = 0; i < array.length; i++) {
            var item = createItem(array[i]);

            if (cursor !== null) {
                cursor.next = item;
            } else {
                this.head = item;
            }

            item.prev = cursor;
            cursor = item;
        }

        this.tail = cursor;

        return this;
    };

    List.prototype.toArray = function() {
        var cursor = this.head;
        var result = [];

        while (cursor) {
            result.push(cursor.data);
            cursor = cursor.next;
        }

        return result;
    };

    List.prototype.toJSON = List.prototype.toArray;

    List.prototype.isEmpty = function() {
        return this.head === null;
    };

    List.prototype.first = function() {
        return this.head && this.head.data;
    };

    List.prototype.last = function() {
        return this.tail && this.tail.data;
    };

    List.prototype.each = function(fn, context) {
        var item;

        if (context === undefined) {
            context = this;
        }

        // push cursor
        var cursor = allocateCursor(this, null, this.head);

        while (cursor.next !== null) {
            item = cursor.next;
            cursor.next = item.next;

            fn.call(context, item.data, item, this);
        }

        // pop cursor
        releaseCursor(this);
    };

    List.prototype.forEach = List.prototype.each;

    List.prototype.eachRight = function(fn, context) {
        var item;

        if (context === undefined) {
            context = this;
        }

        // push cursor
        var cursor = allocateCursor(this, this.tail, null);

        while (cursor.prev !== null) {
            item = cursor.prev;
            cursor.prev = item.prev;

            fn.call(context, item.data, item, this);
        }

        // pop cursor
        releaseCursor(this);
    };

    List.prototype.forEachRight = List.prototype.eachRight;

    List.prototype.nextUntil = function(start, fn, context) {
        if (start === null) {
            return;
        }

        var item;

        if (context === undefined) {
            context = this;
        }

        // push cursor
        var cursor = allocateCursor(this, null, start);

        while (cursor.next !== null) {
            item = cursor.next;
            cursor.next = item.next;

            if (fn.call(context, item.data, item, this)) {
                break;
            }
        }

        // pop cursor
        releaseCursor(this);
    };

    List.prototype.prevUntil = function(start, fn, context) {
        if (start === null) {
            return;
        }

        var item;

        if (context === undefined) {
            context = this;
        }

        // push cursor
        var cursor = allocateCursor(this, start, null);

        while (cursor.prev !== null) {
            item = cursor.prev;
            cursor.prev = item.prev;

            if (fn.call(context, item.data, item, this)) {
                break;
            }
        }

        // pop cursor
        releaseCursor(this);
    };

    List.prototype.some = function(fn, context) {
        var cursor = this.head;

        if (context === undefined) {
            context = this;
        }

        while (cursor !== null) {
            if (fn.call(context, cursor.data, cursor, this)) {
                return true;
            }

            cursor = cursor.next;
        }

        return false;
    };

    List.prototype.map = function(fn, context) {
        var result = new List();
        var cursor = this.head;

        if (context === undefined) {
            context = this;
        }

        while (cursor !== null) {
            result.appendData(fn.call(context, cursor.data, cursor, this));
            cursor = cursor.next;
        }

        return result;
    };

    List.prototype.filter = function(fn, context) {
        var result = new List();
        var cursor = this.head;

        if (context === undefined) {
            context = this;
        }

        while (cursor !== null) {
            if (fn.call(context, cursor.data, cursor, this)) {
                result.appendData(cursor.data);
            }
            cursor = cursor.next;
        }

        return result;
    };

    List.prototype.clear = function() {
        this.head = null;
        this.tail = null;
    };

    List.prototype.copy = function() {
        var result = new List();
        var cursor = this.head;

        while (cursor !== null) {
            result.insert(createItem(cursor.data));
            cursor = cursor.next;
        }

        return result;
    };

    List.prototype.prepend = function(item) {
        //      head
        //    ^
        // item
        this.updateCursors(null, item, this.head, item);

        // insert to the beginning of the list
        if (this.head !== null) {
            // new item <- first item
            this.head.prev = item;

            // new item -> first item
            item.next = this.head;
        } else {
            // if list has no head, then it also has no tail
            // in this case tail points to the new item
            this.tail = item;
        }

        // head always points to new item
        this.head = item;

        return this;
    };

    List.prototype.prependData = function(data) {
        return this.prepend(createItem(data));
    };

    List.prototype.append = function(item) {
        return this.insert(item);
    };

    List.prototype.appendData = function(data) {
        return this.insert(createItem(data));
    };

    List.prototype.insert = function(item, before) {
        if (before !== undefined && before !== null) {
            // prev   before
            //      ^
            //     item
            this.updateCursors(before.prev, item, before, item);

            if (before.prev === null) {
                // insert to the beginning of list
                if (this.head !== before) {
                    throw new Error('before doesn\'t belong to list');
                }

                // since head points to before therefore list doesn't empty
                // no need to check tail
                this.head = item;
                before.prev = item;
                item.next = before;

                this.updateCursors(null, item);
            } else {

                // insert between two items
                before.prev.next = item;
                item.prev = before.prev;

                before.prev = item;
                item.next = before;
            }
        } else {
            // tail
            //      ^
            //      item
            this.updateCursors(this.tail, item, null, item);

            // insert to the ending of the list
            if (this.tail !== null) {
                // last item -> new item
                this.tail.next = item;

                // last item <- new item
                item.prev = this.tail;
            } else {
                // if list has no tail, then it also has no head
                // in this case head points to new item
                this.head = item;
            }

            // tail always points to new item
            this.tail = item;
        }

        return this;
    };

    List.prototype.insertData = function(data, before) {
        return this.insert(createItem(data), before);
    };

    List.prototype.remove = function(item) {
        //      item
        //       ^
        // prev     next
        this.updateCursors(item, item.prev, item, item.next);

        if (item.prev !== null) {
            item.prev.next = item.next;
        } else {
            if (this.head !== item) {
                throw new Error('item doesn\'t belong to list');
            }

            this.head = item.next;
        }

        if (item.next !== null) {
            item.next.prev = item.prev;
        } else {
            if (this.tail !== item) {
                throw new Error('item doesn\'t belong to list');
            }

            this.tail = item.prev;
        }

        item.prev = null;
        item.next = null;

        return item;
    };

    List.prototype.push = function(data) {
        this.insert(createItem(data));
    };

    List.prototype.pop = function() {
        if (this.tail !== null) {
            return this.remove(this.tail);
        }
    };

    List.prototype.unshift = function(data) {
        this.prepend(createItem(data));
    };

    List.prototype.shift = function() {
        if (this.head !== null) {
            return this.remove(this.head);
        }
    };

    List.prototype.prependList = function(list) {
        return this.insertList(list, this.head);
    };

    List.prototype.appendList = function(list) {
        return this.insertList(list);
    };

    List.prototype.insertList = function(list, before) {
        // ignore empty lists
        if (list.head === null) {
            return this;
        }

        if (before !== undefined && before !== null) {
            this.updateCursors(before.prev, list.tail, before, list.head);

            // insert in the middle of dist list
            if (before.prev !== null) {
                // before.prev <-> list.head
                before.prev.next = list.head;
                list.head.prev = before.prev;
            } else {
                this.head = list.head;
            }

            before.prev = list.tail;
            list.tail.next = before;
        } else {
            this.updateCursors(this.tail, list.tail, null, list.head);

            // insert to end of the list
            if (this.tail !== null) {
                // if destination list has a tail, then it also has a head,
                // but head doesn't change

                // dest tail -> source head
                this.tail.next = list.head;

                // dest tail <- source head
                list.head.prev = this.tail;
            } else {
                // if list has no a tail, then it also has no a head
                // in this case points head to new item
                this.head = list.head;
            }

            // tail always start point to new item
            this.tail = list.tail;
        }

        list.head = null;
        list.tail = null;

        return this;
    };

    List.prototype.replace = function(oldItem, newItemOrList) {
        if ('head' in newItemOrList) {
            this.insertList(newItemOrList, oldItem);
        } else {
            this.insert(newItemOrList, oldItem);
        }

        this.remove(oldItem);
    };

    var List_1 = List;

    var createCustomError = function createCustomError(name, message) {
        // use Object.create(), because some VMs prevent setting line/column otherwise
        // (iOS Safari 10 even throws an exception)
        var error = Object.create(SyntaxError.prototype);
        var errorStack = new Error();

        error.name = name;
        error.message = message;

        Object.defineProperty(error, 'stack', {
            get: function() {
                return (errorStack.stack || '').replace(/^(.+\n){1,3}/, name + ': ' + message + '\n');
            }
        });

        return error;
    };

    var MAX_LINE_LENGTH = 100;
    var OFFSET_CORRECTION = 60;
    var TAB_REPLACEMENT = '    ';

    function sourceFragment(error, extraLines) {
        function processLines(start, end) {
            return lines.slice(start, end).map(function(line, idx) {
                var num = String(start + idx + 1);

                while (num.length < maxNumLength) {
                    num = ' ' + num;
                }

                return num + ' |' + line;
            }).join('\n');
        }

        var lines = error.source.split(/\r\n?|\n|\f/);
        var line = error.line;
        var column = error.column;
        var startLine = Math.max(1, line - extraLines) - 1;
        var endLine = Math.min(line + extraLines, lines.length + 1);
        var maxNumLength = Math.max(4, String(endLine).length) + 1;
        var cutLeft = 0;

        // column correction according to replaced tab before column
        column += (TAB_REPLACEMENT.length - 1) * (lines[line - 1].substr(0, column - 1).match(/\t/g) || []).length;

        if (column > MAX_LINE_LENGTH) {
            cutLeft = column - OFFSET_CORRECTION + 3;
            column = OFFSET_CORRECTION - 2;
        }

        for (var i = startLine; i <= endLine; i++) {
            if (i >= 0 && i < lines.length) {
                lines[i] = lines[i].replace(/\t/g, TAB_REPLACEMENT);
                lines[i] =
                    (cutLeft > 0 && lines[i].length > cutLeft ? '\u2026' : '') +
                    lines[i].substr(cutLeft, MAX_LINE_LENGTH - 2) +
                    (lines[i].length > cutLeft + MAX_LINE_LENGTH - 1 ? '\u2026' : '');
            }
        }

        return [
            processLines(startLine, line),
            new Array(column + maxNumLength + 2).join('-') + '^',
            processLines(line, endLine)
        ].filter(Boolean).join('\n');
    }

    var SyntaxError$1 = function(message, source, offset, line, column) {
        var error = createCustomError('SyntaxError', message);

        error.source = source;
        error.offset = offset;
        error.line = line;
        error.column = column;

        error.sourceFragment = function(extraLines) {
            return sourceFragment(error, isNaN(extraLines) ? 0 : extraLines);
        };
        Object.defineProperty(error, 'formattedMessage', {
            get: function() {
                return (
                    'Parse error: ' + error.message + '\n' +
                    sourceFragment(error, 2)
                );
            }
        });

        // for backward capability
        error.parseError = {
            offset: offset,
            line: line,
            column: column
        };

        return error;
    };

    var _SyntaxError = SyntaxError$1;

    // CSS Syntax Module Level 3
    // https://www.w3.org/TR/css-syntax-3/
    var TYPE = {
        EOF: 0,                 // <EOF-token>
        Ident: 1,               // <ident-token>
        Function: 2,            // <function-token>
        AtKeyword: 3,           // <at-keyword-token>
        Hash: 4,                // <hash-token>
        String: 5,              // <string-token>
        BadString: 6,           // <bad-string-token>
        Url: 7,                 // <url-token>
        BadUrl: 8,              // <bad-url-token>
        Delim: 9,               // <delim-token>
        Number: 10,             // <number-token>
        Percentage: 11,         // <percentage-token>
        Dimension: 12,          // <dimension-token>
        WhiteSpace: 13,         // <whitespace-token>
        CDO: 14,                // <CDO-token>
        CDC: 15,                // <CDC-token>
        Colon: 16,              // <colon-token>     :
        Semicolon: 17,          // <semicolon-token> ;
        Comma: 18,              // <comma-token>     ,
        LeftSquareBracket: 19,  // <[-token>
        RightSquareBracket: 20, // <]-token>
        LeftParenthesis: 21,    // <(-token>
        RightParenthesis: 22,   // <)-token>
        LeftCurlyBracket: 23,   // <{-token>
        RightCurlyBracket: 24,  // <}-token>
        Comment: 25
    };

    var NAME = Object.keys(TYPE).reduce(function(result, key) {
        result[TYPE[key]] = key;
        return result;
    }, {});

    var _const = {
        TYPE: TYPE,
        NAME: NAME
    };

    var EOF = 0;

    // https://drafts.csswg.org/css-syntax-3/
    // § 4.2. Definitions

    // digit
    // A code point between U+0030 DIGIT ZERO (0) and U+0039 DIGIT NINE (9).
    function isDigit(code) {
        return code >= 0x0030 && code <= 0x0039;
    }

    // hex digit
    // A digit, or a code point between U+0041 LATIN CAPITAL LETTER A (A) and U+0046 LATIN CAPITAL LETTER F (F),
    // or a code point between U+0061 LATIN SMALL LETTER A (a) and U+0066 LATIN SMALL LETTER F (f).
    function isHexDigit(code) {
        return (
            isDigit(code) || // 0 .. 9
            (code >= 0x0041 && code <= 0x0046) || // A .. F
            (code >= 0x0061 && code <= 0x0066)    // a .. f
        );
    }

    // uppercase letter
    // A code point between U+0041 LATIN CAPITAL LETTER A (A) and U+005A LATIN CAPITAL LETTER Z (Z).
    function isUppercaseLetter(code) {
        return code >= 0x0041 && code <= 0x005A;
    }

    // lowercase letter
    // A code point between U+0061 LATIN SMALL LETTER A (a) and U+007A LATIN SMALL LETTER Z (z).
    function isLowercaseLetter(code) {
        return code >= 0x0061 && code <= 0x007A;
    }

    // letter
    // An uppercase letter or a lowercase letter.
    function isLetter(code) {
        return isUppercaseLetter(code) || isLowercaseLetter(code);
    }

    // non-ASCII code point
    // A code point with a value equal to or greater than U+0080 <control>.
    function isNonAscii(code) {
        return code >= 0x0080;
    }

    // name-start code point
    // A letter, a non-ASCII code point, or U+005F LOW LINE (_).
    function isNameStart(code) {
        return isLetter(code) || isNonAscii(code) || code === 0x005F;
    }

    // name code point
    // A name-start code point, a digit, or U+002D HYPHEN-MINUS (-).
    function isName(code) {
        return isNameStart(code) || isDigit(code) || code === 0x002D;
    }

    // non-printable code point
    // A code point between U+0000 NULL and U+0008 BACKSPACE, or U+000B LINE TABULATION,
    // or a code point between U+000E SHIFT OUT and U+001F INFORMATION SEPARATOR ONE, or U+007F DELETE.
    function isNonPrintable(code) {
        return (
            (code >= 0x0000 && code <= 0x0008) ||
            (code === 0x000B) ||
            (code >= 0x000E && code <= 0x001F) ||
            (code === 0x007F)
        );
    }

    // newline
    // U+000A LINE FEED. Note that U+000D CARRIAGE RETURN and U+000C FORM FEED are not included in this definition,
    // as they are converted to U+000A LINE FEED during preprocessing.
    // TODO: we doesn't do a preprocessing, so check a code point for U+000D CARRIAGE RETURN and U+000C FORM FEED
    function isNewline(code) {
        return code === 0x000A || code === 0x000D || code === 0x000C;
    }

    // whitespace
    // A newline, U+0009 CHARACTER TABULATION, or U+0020 SPACE.
    function isWhiteSpace(code) {
        return isNewline(code) || code === 0x0020 || code === 0x0009;
    }

    // § 4.3.8. Check if two code points are a valid escape
    function isValidEscape(first, second) {
        // If the first code point is not U+005C REVERSE SOLIDUS (\), return false.
        if (first !== 0x005C) {
            return false;
        }

        // Otherwise, if the second code point is a newline or EOF, return false.
        if (isNewline(second) || second === EOF) {
            return false;
        }

        // Otherwise, return true.
        return true;
    }

    // § 4.3.9. Check if three code points would start an identifier
    function isIdentifierStart(first, second, third) {
        // Look at the first code point:

        // U+002D HYPHEN-MINUS
        if (first === 0x002D) {
            // If the second code point is a name-start code point or a U+002D HYPHEN-MINUS,
            // or the second and third code points are a valid escape, return true. Otherwise, return false.
            return (
                isNameStart(second) ||
                second === 0x002D ||
                isValidEscape(second, third)
            );
        }

        // name-start code point
        if (isNameStart(first)) {
            // Return true.
            return true;
        }

        // U+005C REVERSE SOLIDUS (\)
        if (first === 0x005C) {
            // If the first and second code points are a valid escape, return true. Otherwise, return false.
            return isValidEscape(first, second);
        }

        // anything else
        // Return false.
        return false;
    }

    // § 4.3.10. Check if three code points would start a number
    function isNumberStart(first, second, third) {
        // Look at the first code point:

        // U+002B PLUS SIGN (+)
        // U+002D HYPHEN-MINUS (-)
        if (first === 0x002B || first === 0x002D) {
            // If the second code point is a digit, return true.
            if (isDigit(second)) {
                return 2;
            }

            // Otherwise, if the second code point is a U+002E FULL STOP (.)
            // and the third code point is a digit, return true.
            // Otherwise, return false.
            return second === 0x002E && isDigit(third) ? 3 : 0;
        }

        // U+002E FULL STOP (.)
        if (first === 0x002E) {
            // If the second code point is a digit, return true. Otherwise, return false.
            return isDigit(second) ? 2 : 0;
        }

        // digit
        if (isDigit(first)) {
            // Return true.
            return 1;
        }

        // anything else
        // Return false.
        return 0;
    }

    //
    // Misc
    //

    // detect BOM (https://en.wikipedia.org/wiki/Byte_order_mark)
    function isBOM(code) {
        // UTF-16BE
        if (code === 0xFEFF) {
            return 1;
        }

        // UTF-16LE
        if (code === 0xFFFE) {
            return 1;
        }

        return 0;
    }

    // Fast code category
    //
    // https://drafts.csswg.org/css-syntax/#tokenizer-definitions
    // > non-ASCII code point
    // >   A code point with a value equal to or greater than U+0080 <control>
    // > name-start code point
    // >   A letter, a non-ASCII code point, or U+005F LOW LINE (_).
    // > name code point
    // >   A name-start code point, a digit, or U+002D HYPHEN-MINUS (-)
    // That means only ASCII code points has a special meaning and we define a maps for 0..127 codes only
    var CATEGORY = new Array(0x80);
    charCodeCategory.Eof = 0x80;
    charCodeCategory.WhiteSpace = 0x82;
    charCodeCategory.Digit = 0x83;
    charCodeCategory.NameStart = 0x84;
    charCodeCategory.NonPrintable = 0x85;

    for (var i = 0; i < CATEGORY.length; i++) {
        switch (true) {
            case isWhiteSpace(i):
                CATEGORY[i] = charCodeCategory.WhiteSpace;
                break;

            case isDigit(i):
                CATEGORY[i] = charCodeCategory.Digit;
                break;

            case isNameStart(i):
                CATEGORY[i] = charCodeCategory.NameStart;
                break;

            case isNonPrintable(i):
                CATEGORY[i] = charCodeCategory.NonPrintable;
                break;

            default:
                CATEGORY[i] = i || charCodeCategory.Eof;
        }
    }

    function charCodeCategory(code) {
        return code < 0x80 ? CATEGORY[code] : charCodeCategory.NameStart;
    }
    var charCodeDefinitions = {
        isDigit: isDigit,
        isHexDigit: isHexDigit,
        isUppercaseLetter: isUppercaseLetter,
        isLowercaseLetter: isLowercaseLetter,
        isLetter: isLetter,
        isNonAscii: isNonAscii,
        isNameStart: isNameStart,
        isName: isName,
        isNonPrintable: isNonPrintable,
        isNewline: isNewline,
        isWhiteSpace: isWhiteSpace,
        isValidEscape: isValidEscape,
        isIdentifierStart: isIdentifierStart,
        isNumberStart: isNumberStart,

        isBOM: isBOM,
        charCodeCategory: charCodeCategory
    };

    var isDigit$1 = charCodeDefinitions.isDigit;
    var isHexDigit$1 = charCodeDefinitions.isHexDigit;
    var isUppercaseLetter$1 = charCodeDefinitions.isUppercaseLetter;
    var isName$1 = charCodeDefinitions.isName;
    var isWhiteSpace$1 = charCodeDefinitions.isWhiteSpace;
    var isValidEscape$1 = charCodeDefinitions.isValidEscape;

    function getCharCode(source, offset) {
        return offset < source.length ? source.charCodeAt(offset) : 0;
    }

    function getNewlineLength(source, offset, code) {
        if (code === 13 /* \r */ && getCharCode(source, offset + 1) === 10 /* \n */) {
            return 2;
        }

        return 1;
    }

    function cmpChar(testStr, offset, referenceCode) {
        var code = testStr.charCodeAt(offset);

        // code.toLowerCase() for A..Z
        if (isUppercaseLetter$1(code)) {
            code = code | 32;
        }

        return code === referenceCode;
    }

    function cmpStr(testStr, start, end, referenceStr) {
        if (end - start !== referenceStr.length) {
            return false;
        }

        if (start < 0 || end > testStr.length) {
            return false;
        }

        for (var i = start; i < end; i++) {
            var testCode = testStr.charCodeAt(i);
            var referenceCode = referenceStr.charCodeAt(i - start);

            // testCode.toLowerCase() for A..Z
            if (isUppercaseLetter$1(testCode)) {
                testCode = testCode | 32;
            }

            if (testCode !== referenceCode) {
                return false;
            }
        }

        return true;
    }

    function findWhiteSpaceStart(source, offset) {
        for (; offset >= 0; offset--) {
            if (!isWhiteSpace$1(source.charCodeAt(offset))) {
                break;
            }
        }

        return offset + 1;
    }

    function findWhiteSpaceEnd(source, offset) {
        for (; offset < source.length; offset++) {
            if (!isWhiteSpace$1(source.charCodeAt(offset))) {
                break;
            }
        }

        return offset;
    }

    function findDecimalNumberEnd(source, offset) {
        for (; offset < source.length; offset++) {
            if (!isDigit$1(source.charCodeAt(offset))) {
                break;
            }
        }

        return offset;
    }

    // § 4.3.7. Consume an escaped code point
    function consumeEscaped(source, offset) {
        // It assumes that the U+005C REVERSE SOLIDUS (\) has already been consumed and
        // that the next input code point has already been verified to be part of a valid escape.
        offset += 2;

        // hex digit
        if (isHexDigit$1(getCharCode(source, offset - 1))) {
            // Consume as many hex digits as possible, but no more than 5.
            // Note that this means 1-6 hex digits have been consumed in total.
            for (var maxOffset = Math.min(source.length, offset + 5); offset < maxOffset; offset++) {
                if (!isHexDigit$1(getCharCode(source, offset))) {
                    break;
                }
            }

            // If the next input code point is whitespace, consume it as well.
            var code = getCharCode(source, offset);
            if (isWhiteSpace$1(code)) {
                offset += getNewlineLength(source, offset, code);
            }
        }

        return offset;
    }

    // §4.3.11. Consume a name
    // Note: This algorithm does not do the verification of the first few code points that are necessary
    // to ensure the returned code points would constitute an <ident-token>. If that is the intended use,
    // ensure that the stream starts with an identifier before calling this algorithm.
    function consumeName(source, offset) {
        // Let result initially be an empty string.
        // Repeatedly consume the next input code point from the stream:
        for (; offset < source.length; offset++) {
            var code = source.charCodeAt(offset);

            // name code point
            if (isName$1(code)) {
                // Append the code point to result.
                continue;
            }

            // the stream starts with a valid escape
            if (isValidEscape$1(code, getCharCode(source, offset + 1))) {
                // Consume an escaped code point. Append the returned code point to result.
                offset = consumeEscaped(source, offset) - 1;
                continue;
            }

            // anything else
            // Reconsume the current input code point. Return result.
            break;
        }

        return offset;
    }

    // §4.3.12. Consume a number
    function consumeNumber(source, offset) {
        var code = source.charCodeAt(offset);

        // 2. If the next input code point is U+002B PLUS SIGN (+) or U+002D HYPHEN-MINUS (-),
        // consume it and append it to repr.
        if (code === 0x002B || code === 0x002D) {
            code = source.charCodeAt(offset += 1);
        }

        // 3. While the next input code point is a digit, consume it and append it to repr.
        if (isDigit$1(code)) {
            offset = findDecimalNumberEnd(source, offset + 1);
            code = source.charCodeAt(offset);
        }

        // 4. If the next 2 input code points are U+002E FULL STOP (.) followed by a digit, then:
        if (code === 0x002E && isDigit$1(source.charCodeAt(offset + 1))) {
            // 4.1 Consume them.
            // 4.2 Append them to repr.
            code = source.charCodeAt(offset += 2);

            // 4.3 Set type to "number".
            // TODO

            // 4.4 While the next input code point is a digit, consume it and append it to repr.

            offset = findDecimalNumberEnd(source, offset);
        }

        // 5. If the next 2 or 3 input code points are U+0045 LATIN CAPITAL LETTER E (E)
        // or U+0065 LATIN SMALL LETTER E (e), ... , followed by a digit, then:
        if (cmpChar(source, offset, 101 /* e */)) {
            var sign = 0;
            code = source.charCodeAt(offset + 1);

            // ... optionally followed by U+002D HYPHEN-MINUS (-) or U+002B PLUS SIGN (+) ...
            if (code === 0x002D || code === 0x002B) {
                sign = 1;
                code = source.charCodeAt(offset + 2);
            }

            // ... followed by a digit
            if (isDigit$1(code)) {
                // 5.1 Consume them.
                // 5.2 Append them to repr.

                // 5.3 Set type to "number".
                // TODO

                // 5.4 While the next input code point is a digit, consume it and append it to repr.
                offset = findDecimalNumberEnd(source, offset + 1 + sign + 1);
            }
        }

        return offset;
    }

    // § 4.3.14. Consume the remnants of a bad url
    // ... its sole use is to consume enough of the input stream to reach a recovery point
    // where normal tokenizing can resume.
    function consumeBadUrlRemnants(source, offset) {
        // Repeatedly consume the next input code point from the stream:
        for (; offset < source.length; offset++) {
            var code = source.charCodeAt(offset);

            // U+0029 RIGHT PARENTHESIS ())
            // EOF
            if (code === 0x0029) {
                // Return.
                offset++;
                break;
            }

            if (isValidEscape$1(code, getCharCode(source, offset + 1))) {
                // Consume an escaped code point.
                // Note: This allows an escaped right parenthesis ("\)") to be encountered
                // without ending the <bad-url-token>. This is otherwise identical to
                // the "anything else" clause.
                offset = consumeEscaped(source, offset);
            }
        }

        return offset;
    }

    var utils = {
        consumeEscaped: consumeEscaped,
        consumeName: consumeName,
        consumeNumber: consumeNumber,
        consumeBadUrlRemnants: consumeBadUrlRemnants,

        cmpChar: cmpChar,
        cmpStr: cmpStr,

        getNewlineLength: getNewlineLength,
        findWhiteSpaceStart: findWhiteSpaceStart,
        findWhiteSpaceEnd: findWhiteSpaceEnd
    };

    var TYPE$1 = _const.TYPE;
    var NAME$1 = _const.NAME;


    var cmpStr$1 = utils.cmpStr;

    var EOF$1 = TYPE$1.EOF;
    var WHITESPACE = TYPE$1.WhiteSpace;
    var COMMENT = TYPE$1.Comment;

    var OFFSET_MASK = 0x00FFFFFF;
    var TYPE_SHIFT = 24;

    var TokenStream = function() {
        this.offsetAndType = null;
        this.balance = null;

        this.reset();
    };

    TokenStream.prototype = {
        reset: function() {
            this.eof = false;
            this.tokenIndex = -1;
            this.tokenType = 0;
            this.tokenStart = this.firstCharOffset;
            this.tokenEnd = this.firstCharOffset;
        },

        lookupType: function(offset) {
            offset += this.tokenIndex;

            if (offset < this.tokenCount) {
                return this.offsetAndType[offset] >> TYPE_SHIFT;
            }

            return EOF$1;
        },
        lookupOffset: function(offset) {
            offset += this.tokenIndex;

            if (offset < this.tokenCount) {
                return this.offsetAndType[offset - 1] & OFFSET_MASK;
            }

            return this.source.length;
        },
        lookupValue: function(offset, referenceStr) {
            offset += this.tokenIndex;

            if (offset < this.tokenCount) {
                return cmpStr$1(
                    this.source,
                    this.offsetAndType[offset - 1] & OFFSET_MASK,
                    this.offsetAndType[offset] & OFFSET_MASK,
                    referenceStr
                );
            }

            return false;
        },
        getTokenStart: function(tokenIndex) {
            if (tokenIndex === this.tokenIndex) {
                return this.tokenStart;
            }

            if (tokenIndex > 0) {
                return tokenIndex < this.tokenCount
                    ? this.offsetAndType[tokenIndex - 1] & OFFSET_MASK
                    : this.offsetAndType[this.tokenCount] & OFFSET_MASK;
            }

            return this.firstCharOffset;
        },

        // TODO: -> skipUntilBalanced
        getRawLength: function(startToken, mode) {
            var cursor = startToken;
            var balanceEnd;
            var offset = this.offsetAndType[Math.max(cursor - 1, 0)] & OFFSET_MASK;
            var type;

            loop:
            for (; cursor < this.tokenCount; cursor++) {
                balanceEnd = this.balance[cursor];

                // stop scanning on balance edge that points to offset before start token
                if (balanceEnd < startToken) {
                    break loop;
                }

                type = this.offsetAndType[cursor] >> TYPE_SHIFT;

                // check token is stop type
                switch (mode(type, this.source, offset)) {
                    case 1:
                        break loop;

                    case 2:
                        cursor++;
                        break loop;

                    default:
                        offset = this.offsetAndType[cursor] & OFFSET_MASK;

                        // fast forward to the end of balanced block
                        if (this.balance[balanceEnd] === cursor) {
                            cursor = balanceEnd;
                        }
                }
            }

            return cursor - this.tokenIndex;
        },
        isBalanceEdge: function(pos) {
            return this.balance[this.tokenIndex] < pos;
        },
        isDelim: function(code, offset) {
            if (offset) {
                return (
                    this.lookupType(offset) === TYPE$1.Delim &&
                    this.source.charCodeAt(this.lookupOffset(offset)) === code
                );
            }

            return (
                this.tokenType === TYPE$1.Delim &&
                this.source.charCodeAt(this.tokenStart) === code
            );
        },

        getTokenValue: function() {
            return this.source.substring(this.tokenStart, this.tokenEnd);
        },
        getTokenLength: function() {
            return this.tokenEnd - this.tokenStart;
        },
        substrToCursor: function(start) {
            return this.source.substring(start, this.tokenStart);
        },

        skipWS: function() {
            for (var i = this.tokenIndex, skipTokenCount = 0; i < this.tokenCount; i++, skipTokenCount++) {
                if ((this.offsetAndType[i] >> TYPE_SHIFT) !== WHITESPACE) {
                    break;
                }
            }

            if (skipTokenCount > 0) {
                this.skip(skipTokenCount);
            }
        },
        skipSC: function() {
            while (this.tokenType === WHITESPACE || this.tokenType === COMMENT) {
                this.next();
            }
        },
        skip: function(tokenCount) {
            var next = this.tokenIndex + tokenCount;

            if (next < this.tokenCount) {
                this.tokenIndex = next;
                this.tokenStart = this.offsetAndType[next - 1] & OFFSET_MASK;
                next = this.offsetAndType[next];
                this.tokenType = next >> TYPE_SHIFT;
                this.tokenEnd = next & OFFSET_MASK;
            } else {
                this.tokenIndex = this.tokenCount;
                this.next();
            }
        },
        next: function() {
            var next = this.tokenIndex + 1;

            if (next < this.tokenCount) {
                this.tokenIndex = next;
                this.tokenStart = this.tokenEnd;
                next = this.offsetAndType[next];
                this.tokenType = next >> TYPE_SHIFT;
                this.tokenEnd = next & OFFSET_MASK;
            } else {
                this.tokenIndex = this.tokenCount;
                this.eof = true;
                this.tokenType = EOF$1;
                this.tokenStart = this.tokenEnd = this.source.length;
            }
        },

        dump: function() {
            var offset = this.firstCharOffset;

            return Array.prototype.slice.call(this.offsetAndType, 0, this.tokenCount).map(function(item, idx) {
                var start = offset;
                var end = item & OFFSET_MASK;

                offset = end;

                return {
                    idx: idx,
                    type: NAME$1[item >> TYPE_SHIFT],
                    chunk: this.source.substring(start, end),
                    balance: this.balance[idx]
                };
            }, this);
        }
    };

    var TokenStream_1 = TokenStream;

    function noop(value) {
        return value;
    }

    function generateMultiplier(multiplier) {
        if (multiplier.min === 0 && multiplier.max === 0) {
            return '*';
        }

        if (multiplier.min === 0 && multiplier.max === 1) {
            return '?';
        }

        if (multiplier.min === 1 && multiplier.max === 0) {
            return multiplier.comma ? '#' : '+';
        }

        if (multiplier.min === 1 && multiplier.max === 1) {
            return '';
        }

        return (
            (multiplier.comma ? '#' : '') +
            (multiplier.min === multiplier.max
                ? '{' + multiplier.min + '}'
                : '{' + multiplier.min + ',' + (multiplier.max !== 0 ? multiplier.max : '') + '}'
            )
        );
    }

    function generateTypeOpts(node) {
        switch (node.type) {
            case 'Range':
                return (
                    ' [' +
                    (node.min === null ? '-∞' : node.min) +
                    ',' +
                    (node.max === null ? '∞' : node.max) +
                    ']'
                );

            default:
                throw new Error('Unknown node type `' + node.type + '`');
        }
    }

    function generateSequence(node, decorate, forceBraces, compact) {
        var combinator = node.combinator === ' ' || compact ? node.combinator : ' ' + node.combinator + ' ';
        var result = node.terms.map(function(term) {
            return generate(term, decorate, forceBraces, compact);
        }).join(combinator);

        if (node.explicit || forceBraces) {
            result = (compact || result[0] === ',' ? '[' : '[ ') + result + (compact ? ']' : ' ]');
        }

        return result;
    }

    function generate(node, decorate, forceBraces, compact) {
        var result;

        switch (node.type) {
            case 'Group':
                result =
                    generateSequence(node, decorate, forceBraces, compact) +
                    (node.disallowEmpty ? '!' : '');
                break;

            case 'Multiplier':
                // return since node is a composition
                return (
                    generate(node.term, decorate, forceBraces, compact) +
                    decorate(generateMultiplier(node), node)
                );

            case 'Type':
                result = '<' + node.name + (node.opts ? decorate(generateTypeOpts(node.opts), node.opts) : '') + '>';
                break;

            case 'Property':
                result = '<\'' + node.name + '\'>';
                break;

            case 'Keyword':
                result = node.name;
                break;

            case 'AtKeyword':
                result = '@' + node.name;
                break;

            case 'Function':
                result = node.name + '(';
                break;

            case 'String':
            case 'Token':
                result = node.value;
                break;

            case 'Comma':
                result = ',';
                break;

            default:
                throw new Error('Unknown node type `' + node.type + '`');
        }

        return decorate(result, node);
    }

    var generate_1 = function(node, options) {
        var decorate = noop;
        var forceBraces = false;
        var compact = false;

        if (typeof options === 'function') {
            decorate = options;
        } else if (options) {
            forceBraces = Boolean(options.forceBraces);
            compact = Boolean(options.compact);
            if (typeof options.decorate === 'function') {
                decorate = options.decorate;
            }
        }

        return generate(node, decorate, forceBraces, compact);
    };

    function fromMatchResult(matchResult) {
        var tokens = matchResult.tokens;
        var longestMatch = matchResult.longestMatch;
        var node = longestMatch < tokens.length ? tokens[longestMatch].node : null;
        var mismatchOffset = -1;
        var entries = 0;
        var css = '';

        for (var i = 0; i < tokens.length; i++) {
            if (i === longestMatch) {
                mismatchOffset = css.length;
            }

            if (node !== null && tokens[i].node === node) {
                if (i <= longestMatch) {
                    entries++;
                } else {
                    entries = 0;
                }
            }

            css += tokens[i].value;
        }

        return {
            node: node,
            css: css,
            mismatchOffset: mismatchOffset === -1 ? css.length : mismatchOffset,
            last: node === null || entries > 1
        };
    }

    function getLocation(node, point) {
        var loc = node && node.loc && node.loc[point];

        if (loc) {
            return {
                offset: loc.offset,
                line: loc.line,
                column: loc.column
            };
        }

        return null;
    }

    var SyntaxReferenceError = function(type, referenceName) {
        var error = createCustomError(
            'SyntaxReferenceError',
            type + (referenceName ? ' `' + referenceName + '`' : '')
        );

        error.reference = referenceName;

        return error;
    };

    var MatchError = function(message, syntax, node, matchResult) {
        var error = createCustomError('SyntaxMatchError', message);
        var details = fromMatchResult(matchResult);
        var mismatchOffset = details.mismatchOffset || 0;
        var badNode = details.node || node;
        var end = getLocation(badNode, 'end');
        var start = details.last ? end : getLocation(badNode, 'start');
        var css = details.css;

        error.rawMessage = message;
        error.syntax = syntax ? generate_1(syntax) : '<generic>';
        error.css = css;
        error.mismatchOffset = mismatchOffset;
        error.loc = {
            source: (badNode && badNode.loc && badNode.loc.source) || '<unknown>',
            start: start,
            end: end
        };
        error.line = start ? start.line : undefined;
        error.column = start ? start.column : undefined;
        error.offset = start ? start.offset : undefined;
        error.message = message + '\n' +
            '  syntax: ' + error.syntax + '\n' +
            '   value: ' + (error.css || '<empty string>') + '\n' +
            '  --------' + new Array(error.mismatchOffset + 1).join('-') + '^';

        return error;
    };

    var error = {
        SyntaxReferenceError: SyntaxReferenceError,
        MatchError: MatchError
    };

    var hasOwnProperty = Object.prototype.hasOwnProperty;
    var keywords = Object.create(null);
    var properties = Object.create(null);
    var HYPHENMINUS = 45; // '-'.charCodeAt()

    function isCustomProperty(str, offset) {
        offset = offset || 0;

        return str.length - offset >= 2 &&
               str.charCodeAt(offset) === HYPHENMINUS &&
               str.charCodeAt(offset + 1) === HYPHENMINUS;
    }

    function getVendorPrefix(str, offset) {
        offset = offset || 0;

        // verdor prefix should be at least 3 chars length
        if (str.length - offset >= 3) {
            // vendor prefix starts with hyper minus following non-hyper minus
            if (str.charCodeAt(offset) === HYPHENMINUS &&
                str.charCodeAt(offset + 1) !== HYPHENMINUS) {
                // vendor prefix should contain a hyper minus at the ending
                var secondDashIndex = str.indexOf('-', offset + 2);

                if (secondDashIndex !== -1) {
                    return str.substring(offset, secondDashIndex + 1);
                }
            }
        }

        return '';
    }

    function getKeywordDescriptor(keyword) {
        if (hasOwnProperty.call(keywords, keyword)) {
            return keywords[keyword];
        }

        var name = keyword.toLowerCase();

        if (hasOwnProperty.call(keywords, name)) {
            return keywords[keyword] = keywords[name];
        }

        var custom = isCustomProperty(name, 0);
        var vendor = !custom ? getVendorPrefix(name, 0) : '';

        return keywords[keyword] = Object.freeze({
            basename: name.substr(vendor.length),
            name: name,
            vendor: vendor,
            prefix: vendor,
            custom: custom
        });
    }

    function getPropertyDescriptor(property) {
        if (hasOwnProperty.call(p