var less, tree;

if (typeof environment === “object” && ({}).toString.call(environment) === “[object Environment]”) {

// Rhino
// Details on how to detect Rhino: https://github.com/ringo/ringojs/issues/88
if (typeof(window) === 'undefined') { less = {} }
else                                { less = window.less = {} }
tree = less.tree = {};
less.mode = 'rhino';

} else if (typeof(window) === 'undefined') {

// Node.js
less = exports,
tree = require('./tree');
less.mode = 'node';

} else {

// Browser
if (typeof(window.less) === 'undefined') { window.less = {} }
less = window.less,
tree = window.less.tree = {};
less.mode = 'browser';

} // // 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 `current` 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. // // less.Parser = function Parser(env) {

var input,       // LeSS input string
    i,           // current index in %xinput`
    j,           // current chunk
    temp,        // temporarily holds a chunk's state, for backtracking
    memo,        // temporarily holds `i`, when backtracking
    furthest,    // furthest index the parser has gone to
    chunks,      // chunkified input
    current,     // index of current chunk, in `input`
    parser;

var that = this;

// This function is called after all files
// have been imported through `@import`.
var finish = function () {};

var imports = this.imports = {
    paths: env && env.paths || [],  // Search paths, when importing
    queue: [],                      // Files which haven't been imported yet
    files: {},                      // Holds the imported parse trees
    contents: {},                   // Holds the imported file contents
    mime:  env && env.mime,         // MIME type of .less files
    error: null,                    // Error in parsing/evaluating an import
    push: function (path, callback) {
        var that = this;
        this.queue.push(path);

        //
        // Import a file asynchronously
        //
        less.Parser.importer(path, this.paths, function (e, root, contents) {
            that.queue.splice(that.queue.indexOf(path), 1); // Remove the path from the queue
            that.files[path] = root;                        // Store the root
            that.contents[path] = contents;

            if (e && !that.error) { that.error = e }
            callback(e, root);

            if (that.queue.length === 0) { finish() }       // Call `finish` if we're done importing
        }, env);
    }
};

function save()    { temp = chunks[j], memo = i, current = i }
function restore() { chunks[j] = temp, i = memo, current = i }

function sync() {
    if (i > current) {
        chunks[j] = chunks[j].slice(i - current);
        current = i;
    }
}
//
// Parse from a token, regexp or string, and move forward if match
//
function $(tok) {
    var match, args, length, c, index, endIndex, k, mem;

    //
    // Non-terminal
    //
    if (tok instanceof Function) {
        return tok.call(parser.parsers);
    //
    // Terminal
    //
    //     Either match a single character in the input,
    //     or match a regexp in the current chunk (chunk[j]).
    //
    } else if (typeof(tok) === 'string') {
        match = input.charAt(i) === tok ? tok : null;
        length = 1;
        sync ();
    } else {
        sync ();

        if (match = tok.exec(chunks[j])) {
            length = match[0].length;
        } else {
            return null;
        }
    }

    // The match is confirmed, add the match length to %xi`,
    // and consume any extra white-space characters (' ' || '\n')
    // which come after that. The reason for this is that LeSS's
    // grammar is mostly white-space insensitive.
    //
    if (match) {
        mem = i += length;
        endIndex = i + chunks[j].length - length;

        while (i < endIndex) {
            c = input.charCodeAt(i);
            if (! (c === 32 || c === 10 || c === 9)) { break }
            i++;
        }
        chunks[j] = chunks[j].slice(length + (i - mem));
        current = i;

        if (chunks[j].length === 0 && j < chunks.length - 1) { j++ }

        if(typeof(match) === 'string') {
            return match;
        } else {
            return match.length === 1 ? match[0] : match;
        }
    }
}

function expect(arg, msg) {
    var result = $(arg);
    if (! result) {
        error(msg || (typeof(arg) === 'string' ? "expected '" + arg + "' got '" + input.charAt(i) + "'"
                                               : "unexpected token"));
    } else {
        return result;
    }
}

function error(msg, type) {
    throw { index: i, type: type || 'Syntax', message: msg };
}

// Same as $(), but don't change the state of the parser,
// just return the match.
function peek(tok) {
    if (typeof(tok) === 'string') {
        return input.charAt(i) === tok;
    } else {
        if (tok.test(chunks[j])) {
            return true;
        } else {
            return false;
        }
    }
}

function basename(pathname) {
    if (less.mode === 'node') {
        return require('path').basename(pathname);
    } else {
        return pathname.match(/[^\/]+$/)[0];
    }
}

function getInput(e, env) {
    if (e.filename && env.filename && (e.filename !== env.filename)) {
        return parser.imports.contents[basename(e.filename)];
    } else {
        return input;
    }
}

function getLocation(index, input) {
    for (var n = index, column = -1;
             n >= 0 && input.charAt(n) !== '\n';
             n--) { column++ }

    return { line:   typeof(index) === 'number' ? (input.slice(0, index).match(/\n/g) || "").length : null,
             column: column };
}

function LessError(e, env) {
    var input = getInput(e, env),
        loc = getLocation(e.index, input),
        line = loc.line,
        col  = loc.column,
        lines = input.split('\n');

    this.type = e.type || 'Syntax';
    this.message = e.message;
    this.filename = e.filename || env.filename;
    this.index = e.index;
    this.line = typeof(line) === 'number' ? line + 1 : null;
    this.callLine = e.call && (getLocation(e.call, input).line + 1);
    this.callExtract = lines[getLocation(e.call, input).line];
    this.stack = e.stack;
    this.column = col;
    this.extract = [
        lines[line - 1],
        lines[line],
        lines[line + 1]
    ];
}

this.env = env = env || {};

// The optimization level dictates the thoroughness of the parser,
// the lower the number, the less nodes it will create in the tree.
// This could matter for debugging, or if you want to access
// the individual nodes in the tree.
this.optimization = ('optimization' in this.env) ? this.env.optimization : 1;

this.env.filename = this.env.filename || null;

//
// The Parser
//
return parser = {

    imports: imports,
    //
    // Parse an input string into an abstract syntax tree,
    // call %xcallback` when done.
    //
    parse: function (str, callback) {
        var root, start, end, zone, line, lines, buff = [], c, error = null;

        i = j = current = furthest = 0;
        input = str.replace(/\r\n/g, '\n');

        // Split the input into chunks.
        chunks = (function (chunks) {
            var j = 0,
                skip = /[^"'`\{\}\/\(\)\]+/g,
                comment = /\/\*(?:[^*]|\*+[^\  ])*\*+\/|\/\/.  g,
                string = /"((?:[^"\\\r\n]|\\.)*)"|'((?:[^'\\\r\n]|\\.)*)'|`((?:[^`\\\r\n]|\\.)*)`/g,
                level = 0,
                match,
                chunk = chunks[0],
                inParam;

            for (var i = 0, c, cc; i < input.length; i++) {
                skip.lastIndex = i;
                if (match = skip.exec(input)) {
                    if (match.index === i) {
                        i += match[0].length;
                        chunk.push(match[0]);
                    }
                }
                c = input.charAt(i);
                comment.lastIndex = string.lastIndex = i;

                if (match = string.exec(input)) {
                    if (match.index === i) {
                        i += match[0].length;
                        chunk.push(match[0]);
                        c = input.charAt(i);
                    }
                }

                if (!inParam && c === '/') {
                    cc = input.charAt(i + 1);
                    if (cc === '/' || cc === '*') {
                        if (match = comment.exec(input)) {
                            if (match.index === i) {
                                i += match[0].length;
                                chunk.push(match[0]);
                                c = input.charAt(i);
                            }
                        }
                    }
                }

                switch (c) {
                    case '{': if (! inParam) { level ++;        chunk.push(c);                           break }
                    case '}': if (! inParam) { level --;        chunk.push(c); chunks[++j] = chunk = []; break }
                    case '(': if (! inParam) { inParam = true;  chunk.push(c);                           break }
                    case ')': if (  inParam) { inParam = false; chunk.push(c);                           break }
                    default:                                    chunk.push(c);
                }
            }
            if (level > 0) {
                error = new(LessError)({
                    index: i,
                    type: 'Parse',
                    message: "missing closing %x}`",
                    filename: env.filename
                }, env);
            }

            return chunks.map(function (c) { return c.join('') });;
        })([[]]);

        if (error) {
            return callback(error);
        }

        // 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 {
            root = new(tree.Ruleset)([], $(this.parsers.primary));
            root.root = true;
        } catch (e) {
            return callback(new(LessError)(e, env));
        }

        root.toCSS = (function (evaluate) {
            var line, lines, column;

            return function (options, variables) {
                var frames = [], importError;

                options = options || {};
                //
                // Allows setting variables with a hash, so:
                //
                //   `{ color: new(tree.Color)('#f01') }` will become:
                //
                //   new(tree.Rule)('@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) {
                        var 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.Rule)('@' + k, value, false, 0);
                    });
                    frames = [new(tree.Ruleset)(null, variables)];
                }

                try {
                    var css = evaluate.call(this, { frames: frames })
                                      .toCSS([], { compress: options.compress || false });
                } catch (e) {
                    throw new(LessError)(e, env);
                }

                if ((importError = parser.imports.error)) { // Check if there was an error during importing
                    if (importError instanceof LessError) throw importError;
                    else                                  throw new(LessError)(importError, env);
                }

                if (options.yuicompress && less.mode === 'node') {
                    return require('./cssmin').compressor.cssmin(css);
                } else if (options.compress) {
                    return css.replace(/(\s)+/g, "$1");
                } else {
                    return css;
                }
            };
        })(root.eval);

        // 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 occured.
        // We split it up into two parts (the part which parsed,
        // and the part which didn't), so we can color them differently.
        if (i < input.length - 1) {
            i = furthest;
            lines = input.split('\n');
            line = (input.slice(0, i).match(/\n/g) || "").length + 1;

            for (var n = i, column = -1; n >= 0 && input.charAt(n) !== '\n'; n--) { column++ }

            error = {
                type: "Parse",
                message: "Syntax Error on line " + line,
                index: i,
                filename: env.filename,
                line: line,
                column: column,
                extract: [
                    lines[line - 2],
                    lines[line - 1],
                    lines[line]
                ]
            };
        }

        if (this.imports.queue.length > 0) {
            finish = function () { callback(error, root) };
        } else {
            callback(error, root);
        }
    },

    //
    // Here in, the parsing rules/functions
    //
    // The basic structure of the syntax tree generated is as follows:
    //
    //   Ruleset ->  Rule -> 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', [
    //         Rule ("color",  Value ([Expression [Color #fff]]))
    //         Rule ("border", Value ([Expression [Dimension 1px][Keyword "solid"][Color #000]]))
    //         Rule ("width",  Value ([Expression [Operation "+" [Variable "@w"][Dimension 4px]]]))
    //         Ruleset (Selector [Element '>', '.child'], [...])
    //     ])
    //
    //  In general, most rules will try to parse a token with the `$()` 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: {
        //
        // 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 | rule)+
        //     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 () {
            var node, root = [];

            while ((node = $(this.mixin.definition) || $(this.rule)    ||  $(this.ruleset) ||
                           $(this.mixin.call)       || $(this.comment) ||  $(this.directive))
                           || $(/^[\s\n]+/)) {
                node && root.push(node);
            }
            return root;
        },

        // We create a Comment node for CSS comments `     `,
        // but keep the LeSS comments `//` silent, by just skipping
        // over them.
        comment: function () {
            var comment;

            if (input.charAt(i) !== '/') return;

            if (input.charAt(i + 1) === '/') {
                return new(tree.Comment)($(/^\/\/.*/), true);
            } else if (comment = $(/^\/\*(?:[^*]|\*+[^\/*])*\*+\/\n?/)) {
                return new(tree.Comment)(comment);
            }
        },

        //
        // Entities are tokens which can be found inside an Expression
        //
        entities: {
            //
            // A string, which supports escaping " and '
            //
            //     "milky way" 'he\'s the one!'
            //
            quoted: function () {
                var str, j = i, e;

                if (input.charAt(j) === '~') { j++, e = true } // Escaped strings
                if (input.charAt(j) !== '"' && input.charAt(j) !== "'") return;

                e && $('~');

                if (str = $(/^"((?:[^"\\\r\n]|\\.)*)"|'((?:[^'\\\r\n]|\\.)*)'/)) {
                    return new(tree.Quoted)(str[0], str[1] || str[2], e);
                }
            },

            //
            // A catch-all word, such as:
            //
            //     black border-collapse
            //
            keyword: function () {
                var k;

                if (k = $(/^[_A-Za-z-][_A-Za-z0-9-]*/)) { 
                    if (tree.colors.hasOwnProperty(k)) {
                        // detect named color
                        return new(tree.Color)(tree.colors[k].slice(1));
                    } else {
                        return new(tree.Keyword)(k);
                    }
                }
            },

            //
            // A function call
            //
            //     rgb(255, 0, 255)
            //
            // We also try to catch IE's `alpha()`, but let the `alpha` parser
            // deal with the details.
            //
            // The arguments are parsed with the `entities.arguments` parser.
            //
            call: function () {
                var name, args, index = i;

                if (! (name = /^([\w-]+|%|progid:[\w\.]+)\(/.exec(chunks[j]))) return;

                name = name[1].toLowerCase();

                if (name === 'url') { return null }
                else                { i += name.length }

                if (name === 'alpha') { return $(this.alpha) }

                $('('); // Parse the '(' and consume whitespace.

                args = $(this.entities.arguments);

                if (! $(')')) return;

                if (name) { return new(tree.Call)(name, args, index, env.filename) }
            },
            arguments: function () {
                var args = [], arg;

                while (arg = $(this.entities.assignment) || $(this.expression)) {
                    args.push(arg);
                    if (! $(',')) { break }
                }
                return args;
            },
            literal: function () {
                return $(this.entities.dimension) ||
                       $(this.entities.color) ||
                       $(this.entities.quoted);
            },

            // 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 () {
                var key, value;
                if ((key = $(/^\w+(?=\s?=)/i)) && $('=') && (value = $(this.entity))) {
                    return new(tree.Assignment)(key, value);
                }
            },

            //
            // 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 () {
                var value;

                if (input.charAt(i) !== 'u' || !$(/^url\(/)) return;
                value = $(this.entities.quoted)  || $(this.entities.variable) ||
                        $(this.entities.dataURI) || $(/^[-\w%@$\/.&=:;#+?~]+/) || "";

                expect(')');

                return new(tree.URL)((value.value || value.data || value instanceof tree.Variable)
                                    ? value : new(tree.Anonymous)(value), imports.paths);
            },

            dataURI: function () {
                var obj;

                if ($(/^data:/)) {
                    obj         = {};
                    obj.mime    = $(/^[^\/]+\/[^,;)]+/)     || '';
                    obj.charset = $(/^;\s*charset=[^,;)]+/) || '';
                    obj.base64  = $(/^;\s*base64/)          || '';
                    obj.data    = $(/^,\s*[^)]+/);

                    if (obj.data) { return obj }
                }
            },

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

                if (input.charAt(i) === '@' && (name = $(/^@@?[\w-]+/))) {
                    return new(tree.Variable)(name, index, env.filename);
                }
            },

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

                if (input.charAt(i) === '#' && (rgb = $(/^#([a-fA-F0-9]{6}|[a-fA-F0-9]{3})/))) {
                    return new(tree.Color)(rgb[1]);
                }
            },

            //
            // A Dimension, that is, a number and a unit
            //
            //     0.5em 95%
            //
            dimension: function () {
                var value, c = input.charCodeAt(i);
                if ((c > 57 || c < 45) || c === 47) return;

                if (value = $(/^(-?\d*\.?\d+)(px|%|em|rem|pc|ex|in|deg|s|ms|pt|cm|mm|rad|grad|turn)?/)) {
                    return new(tree.Dimension)(value[1], value[2]);
                }
            },

            //
            // JavaScript code to be evaluated
            //
            //     `window.location.href`
            //
            javascript: function () {
                var str, j = i, e;

                if (input.charAt(j) === '~') { j++, e = true } // Escaped strings
                if (input.charAt(j) !== '`') { return }

                e && $('~');

                if (str = $(/^`([^`]*)`/)) {
                    return new(tree.JavaScript)(str[1], i, e);
                }
            }
        },

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

            if (input.charAt(i) === '@' && (name = $(/^(@[\w-]+)\s*:/))) { return name[1] }
        },

        //
        // A font size/line-height shorthand
        //
        //     small/12px
        //
        // We need to peek first, or we'll match on keywords and dimensions
        //
        shorthand: function () {
            var a, b;

            if (! peek(/^[@\w.%-]+\/[@\w.-]+/)) return;

            if ((a = $(this.entity)) && $('/') && (b = $(this.entity))) {
                return new(tree.Shorthand)(a, b);
            }
        },

        //
        // Mixins
        //
        mixin: {
            //
            // A Mixin call, with an optional argument list
            //
            //     #mixins > .square(#fff);
            //     .rounded(4px, black);
            //     .button;
            //
            // The `while` loop is there because mixins can be
            // namespaced, but we only support the child and descendant
            // selector for now.
            //
            call: function () {
                var elements = [], e, c, args, index = i, s = input.charAt(i), important = false;

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

                while (e = $(/^[#.](?:[\w-]|\\(?:[a-fA-F0-9]{1,6} ?|[^a-fA-F0-9]))+/)) {
                    elements.push(new(tree.Element)(c, e, i));
                    c = $('>');
                }
                $('(') && (args = $(this.entities.arguments)) && $(')');

                if ($(this.important)) {
                    important = true;
                }

                if (elements.length > 0 && ($(';') || peek('}'))) {
                    return new(tree.mixin.Call)(elements, args || [], index, env.filename, important);
                }
            },

            //
            // 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 () {
                var name, params = [], match, ruleset, param, value, cond, variadic = false;
                if ((input.charAt(i) !== '.' && input.charAt(i) !== '#') ||
                    peek(/^[^{]*(;|})/)) return;

                save();

                if (match = $(/^([#.](?:[\w-]|\\(?:[a-fA-F0-9]{1,6} ?|[^a-fA-F0-9]))+)\s*\(/)) {
                    name = match[1];

                    do {
                        if (input.charAt(i) === '.' && $(/^\.{3}/)) {
                            variadic = true;
                            break;
                        } else if (param = $(this.entities.variable) || $(this.entities.literal)
                                                                     || $(this.entities.keyword)) {
                            // Variable
                            if (param instanceof tree.Variable) {
                                if ($(':')) {
                                    value = expect(this.expression, 'expected expression');
                                    params.push({ name: param.name, value: value });
                                } else if ($(/^\.{3}/)) {
                                    params.push({ name: param.name, variadic: true });
                                    variadic = true;
                                    break;
                                } else {
                                    params.push({ name: param.name });
                                }
                            } else {
                                params.push({ value: param });
                            }
                        } else {
                            break;
                        }
                    } while ($(','))

                    expect(')');

                    if ($(/^when/)) { // Guard
                        cond = expect(this.conditions, 'expected condition');
                    }

                    ruleset = $(this.block);

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

        //
        // Entities are the smallest recognized token,
        // and can be found inside a rule's value.
        //
        entity: function () {
            return $(this.entities.literal) || $(this.entities.variable) || $(this.entities.url) ||
                   $(this.entities.call)    || $(this.entities.keyword)  || $(this.entities.javascript) ||
                   $(this.comment);
        },

        //
        // A Rule 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 ommitted.
        //
        end: function () {
            return $(';') || peek('}');
        },

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

            if (! $(/^\(opacity=/i)) return;
            if (value = $(/^\d+/) || $(this.entities.variable)) {
                expect(')');
                return new(tree.Alpha)(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 () {
            var e, t, c, v;

            c = $(this.combinator);
            e = $(/^(?:\d+\.\d+|\d+)%/) || $(/^(?:[.#]?|:*)(?:[\w-]|\\(?:[a-fA-F0-9]{1,6} ?|[^a-fA-F0-9]))+/) ||
                $('*') || $(this.attribute) || $(/^\([^)@]+\)/);

            if (! e) {
                $('(') && (v = $(this.entities.variable)) && $(')') && (e = new(tree.Paren)(v));
            }

            if (e) { return new(tree.Element)(c, e, i) }

            if (c.value && c.value.charAt(0) === '&') {
                return new(tree.Element)(c, null, i);
            }
        },

        //
        // 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 () {
            var match, c = input.charAt(i);

            if (c === '>' || c === '+' || c === '~') {
                i++;
                while (input.charAt(i) === ' ') { i++ }
                return new(tree.Combinator)(c);
            } else if (c === '&') {
                match = '&';
                i++;
                if(input.charAt(i) === ' ') {
                    match = '& ';
                }
                while (input.charAt(i) === ' ') { i++ }
                return new(tree.Combinator)(match);
            } else if (input.charAt(i - 1) === ' ') {
                return new(tree.Combinator)(" ");
            } else {
                return new(tree.Combinator)(null);
            }
        },

        //
        // A CSS Selector
        //
        //     .class > div + h1
        //     li a:hover
        //
        // Selectors are made out of one or more Elements, see above.
        //
        selector: function () {
            var sel, e, elements = [], c, match;

            if ($('(')) {
                sel = $(this.entity);
                expect(')');
                return new(tree.Selector)([new(tree.Element)('', sel, i)]);
            }

            while (e = $(this.element)) {
                c = input.charAt(i);
                elements.push(e)
                if (c === '{' || c === '}' || c === ';' || c === ',') { break }
            }

            if (elements.length > 0) { return new(tree.Selector)(elements) }
        },
        tag: function () {
            return $(/^[a-zA-Z][a-zA-Z-]*[0-9]?/) || $('*');
        },
        attribute: function () {
            var attr = '', key, val, op;

            if (! $('[')) return;

            if (key = $(/^[a-zA-Z-]+/) || $(this.entities.quoted)) {
                if ((op = $(/^[|~*$^]?=/)) &&
                    (val = $(this.entities.quoted) || $(/^[\w-]+/))) {
                    attr = [key, op, val.toCSS ? val.toCSS() : val].join('');
                } else { attr = key }
            }

            if (! $(']')) return;

            if (attr) { return "[" + attr + "]" }
        },

        //
        // The `block` rule is used by `ruleset` and `mixin.definition`.
        // It's a wrapper around the `primary` rule, with added `{}`.
        //
        block: function () {
            var content;

            if ($('{') && (content = $(this.primary)) && $('}')) {
                return content;
            }
        },

        //
        // div, .class, body > p {...}
        //
        ruleset: function () {
            var selectors = [], s, rules, match;
            save();

            while (s = $(this.selector)) {
                selectors.push(s);
                $(this.comment);
                if (! $(',')) { break }
                $(this.comment);
            }

            if (selectors.length > 0 && (rules = $(this.block))) {
                return new(tree.Ruleset)(selectors, rules, env.strictImports);
            } else {
                // Backtrack
                furthest = i;
                restore();
            }
        },
        rule: function () {
            var name, value, c = input.charAt(i), important, match;
            save();

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

            if (name = $(this.variable) || $(this.property)) {
                if ((name.charAt(0) != '@') && (match = /^([^@+\/'"*%x(;{}-]*);/.exec(chunks[j]))) {
                    i += match[0].length - 1;
                    value = new(tree.Anonymous)(match[1]);
                } else if (name === "font") {
                    value = $(this.font);
                } else {
                    value = $(this.value);
                }
                important = $(this.important);

                if (value && $(this.end)) {
                    return new(tree.Rule)(name, value, important, memo);
                } else {
                    furthest = i;
                    restore();
                }
            }
        },

        //
        // An @import directive
        //
        //     @import "lib";
        //
        // Depending on our environemnt, 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%x, which we pass to the Import constructor.
        //
        "import": function () {
            var path, features, index = i;
            if ($(/^@import\s+/) &&
                (path = $(this.entities.quoted) || $(this.entities.url))) {
                features = $(this.mediaFeatures);
                if ($(';')) {
                    return new(tree.Import)(path, imports, features, index);
                }
            }
        },

        mediaFeature: function () {
            var e, p, nodes = [];

            do {
                if (e = $(this.entities.keyword)) {
                    nodes.push(e);
                } else if ($('(')) {
                    p = $(this.property);
                    e = $(this.entity);
                    if ($(')')) {
                        if (p && e) {
                            nodes.push(new(tree.Paren)(new(tree.Rule)(p, e, null, i, true)));
                        } else if (e) {
                            nodes.push(new(tree.Paren)(e));
                        } else {
                            return null;
                        }
                    } else { return null }
                }
            } while (e);

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

        mediaFeatures: function () {
            var e, features = [];

            do {
              if (e = $(this.mediaFeature)) {
                  features.push(e);
                  if (! $(',')) { break }
              } else if (e = $(this.entities.variable)) {
                  features.push(e);
                  if (! $(',')) { break }
              }
            } while (e);

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

        media: function () {
            var features, rules;

            if ($(/^@media/)) {
                features = $(this.mediaFeatures);

                if (rules = $(this.block)) {
                    return new(tree.Media)(rules, features);
                }
            }
        },

        //
        // A CSS Directive
        //
        //     @charset "utf-8";
        //
        directive: function () {
            var name, value, rules, types, e, nodes;

            if (input.charAt(i) !== '@') return;

            if (value = $(this['import']) || $(this.media)) {
                return value;
            } else if (name = $(/^@page|@keyframes/) || $(/^@(?:-webkit-|-moz-|-o-|-ms-)[a-z0-9-]+/)) {
                types = ($(/^[^{]+/) || '').trim();
                if (rules = $(this.block)) {
                    return new(tree.Directive)(name + " " + types, rules);
                }
            } else if (name = $(/^@[-a-z]+/)) {
                if (name === '@font-face') {
                    if (rules = $(this.block)) {
                        return new(tree.Directive)(name, rules);
                    }
                } else if ((value = $(this.entity)) && $(';')) {
                    return new(tree.Directive)(name, value);
                }
            }
        },
        font: function () {
            var value = [], expression = [], weight, shorthand, font, e;

            while (e = $(this.shorthand) || $(this.entity)) {
                expression.push(e);
            }
            value.push(new(tree.Expression)(expression));

            if ($(',')) {
                while (e = $(this.expression)) {
                    value.push(e);
                    if (! $(',')) { break }
                }
            }
            return new(tree.Value)(value);
        },

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

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

            if (expressions.length > 0) {
                return new(tree.Value)(expressions);
            }
        },
        important: function () {
            if (input.charAt(i) === '!') {
                return $(/^! *important/);
            }
        },
        sub: function () {
            var e;

            if ($('(') && (e = $(this.expression)) && $(')')) {
                return e;
            }
        },
        multiplication: function () {
            var m, a, op, operation;
            if (m = $(this.operand)) {
                while (!peek(/^\/\*/) && (op = ($('/') || $('*'))) && (a = $(this.operand))) {
                    operation = new(tree.Operation)(op, [operation || m, a]);
                }
                return operation || m;
            }
        },
        addition: function () {
            var m, a, op, operation;
            if (m = $(this.multiplication)) {
                while ((op = $(/^[-+]\s+/) || (input.charAt(i - 1) != ' ' && ($('+') || $('-')))) &&
                       (a = $(this.multiplication))) {
                    operation = new(tree.Operation)(op, [operation || m, a]);
                }
                return operation || m;
            }
        },
        conditions: function () {
            var a, b, index = i, condition;

            if (a = $(this.condition)) {
                while ($(',') && (b = $(this.condition))) {
                    condition = new(tree.Condition)('or', condition || a, b, index);
                }
                return condition || a;
            }
        },
        condition: function () {
            var a, b, c, op, index = i, negate = false;

            if ($(/^not/)) { negate = true }
            expect('(');
            if (a = $(this.addition) || $(this.entities.keyword) || $(this.entities.quoted)) {
                if (op = $(/^(?:>=|=<|[<=>])/)) {
                    if (b = $(this.addition) || $(this.entities.keyword) || $(this.entities.quoted)) {
                        c = new(tree.Condition)(op, a, b, index, negate);
                    } else {
                        error('expected expression');
                    }
                } else {
                    c = new(tree.Condition)('=', a, new(tree.Keyword)('true'), index, negate);
                }
                expect(')');
                return $(/^and/) ? new(tree.Condition)('and', c, $(this.condition)) : c;
            }
        },

        //
        // An operand is anything that can be part of an operation,
        // such as a Color, or a Variable
        //
        operand: function () {
            var negate, p = input.charAt(i + 1);

            if (input.charAt(i) === '-' && (p === '@' || p === '(')) { negate = $('-') }
            var o = $(this.sub) || $(this.entities.dimension) ||
                    $(this.entities.color) || $(this.entities.variable) ||
                    $(this.entities.call);
            return negate ? new(tree.Operation)('*', [new(tree.Dimension)(-1), o])
                          : o;
        },

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

            while (e = $(this.addition) || $(this.entity)) {
                entities.push(e);
            }
            if (entities.length > 0) {
                return new(tree.Expression)(entities);
            }
        },
        property: function () {
            var name;

            if (name = $(/^(\*?-?[-a-z_0-9]+)\s*:/)) {
                return name[1];
            }
        }
    }
};

};

if (less.mode === 'browser' || less.mode === 'rhino') {

//
// Used by `@import` directives
//
less.Parser.importer = function (path, paths, callback, env) {
    if (!/^([a-z]+:)?\//.test(path) && paths.length > 0) {
        path = paths[0] + path;
    }
    // We pass `true` as 3rd argument, to force the reload of the import.
    // This is so we can get the syntax tree as opposed to just the CSS output,
    // as we need this to evaluate the current stylesheet.
    loadStyleSheet({ href: path, title: path, type: env.mime }, function (e) {
        if (e && typeof(env.errback) === "function") {
            env.errback.call(null, path, paths, callback, env);
        } else {
            callback.apply(null, arguments);
        }
    }, true);
};

}