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                            /**
                             * The selector module provides helper methods allowing CSS2 Selectors to be used with DOM elements.
                             * @module dom
                             * @submodule selector-css2
                             * @for Selector
                             */
                            
                            /*
                             * Provides helper methods for collecting and filtering DOM elements.
                             */
                            
                            var PARENT_NODE = 'parentNode',
                                TAG_NAME = 'tagName',
                                ATTRIBUTES = 'attributes',
                                COMBINATOR = 'combinator',
                                PSEUDOS = 'pseudos',
                            
                                Selector = Y.Selector,
                            
                                SelectorCSS2 = {
                                    _reRegExpTokens: /([\^\$\?\[\]\*\+\-\.\(\)\|\\])/,
                                    SORT_RESULTS: true,
                            
                                    // TODO: better detection, document specific
                                    _isXML: (function() {
                                        var isXML = (Y.config.doc.createElement('div').tagName !== 'DIV');
                                        return isXML;
                                    }()),
                            
                                    /**
                                     * Mapping of shorthand tokens to corresponding attribute selector
                                     * @property shorthand
                                     * @type object
                                     */
                                    shorthand: {
                                        '\\#(-?[_a-z0-9]+[-\\w\\uE000]*)': '[id=$1]',
                                        '\\.(-?[_a-z]+[-\\w\\uE000]*)': '[className~=$1]'
                                    },
                            
                                    /**
                                     * List of operators and corresponding boolean functions.
                                     * These functions are passed the attribute and the current node's value of the attribute.
                                     * @property operators
                                     * @type object
                                     */
                                    operators: {
                                        '': function(node, attr) { return Y.DOM.getAttribute(node, attr) !== ''; }, // Just test for existence of attribute
                                        '~=': '(?:^|\\s+){val}(?:\\s+|$)', // space-delimited
                                        '|=': '^{val}-?' // optional hyphen-delimited
                                    },
                            
                                    pseudos: {
                                       'first-child': function(node) {
                                            return Y.DOM._children(node[PARENT_NODE])[0] === node;
                                        }
                                    },
                            
                                    _bruteQuery: function(selector, root, firstOnly) {
                                        var ret = [],
                                            nodes = [],
                                            visited,
                                            tokens = Selector._tokenize(selector),
                                            token = tokens[tokens.length - 1],
                                            rootDoc = Y.DOM._getDoc(root),
                                            child,
                                            id,
                                            className,
                                            tagName,
                                            isUniversal;
                            
                                        if (token) {
                                            // prefilter nodes
                                            id = token.id;
                                            className = token.className;
                                            tagName = token.tagName || '*';
                            
                                            if (typeof root.getElementsByTagName !== "undefined") { // non-IE lacks DOM api on doc frags
                                                // try ID first, unless no root.all && root not in document
                                                // (root.all works off document, but not getElementById)
                                                if (id && (root.all || (root.nodeType === 9 || Y.DOM.inDoc(root)))) {
                                                    nodes = Y.DOM.allById(id, root);
                                                // try className
                                                } else if (className) {
                                                    nodes = root.getElementsByClassName(className);
                                                } else { // default to tagName
                                                    nodes = root.getElementsByTagName(tagName);
                                                }
                            
                                            } else { // brute getElementsByTagName()
                                                visited = [];
                                                child = root.firstChild;
                                                isUniversal = tagName === "*";
                                                while (child) {
                                                    while (child) {
                                                        // IE 6-7 considers comment nodes as element nodes, and gives them the tagName "!".
                                                        // We can filter them out by checking if its tagName is > "@".
                                                        // This also avoids a superflous nodeType === 1 check.
                                                        if (child.tagName > "@" && (isUniversal || child.tagName === tagName)) {
                                                            nodes.push(child);
                                                        }
                            
                                                        // We may need to traverse back up the tree to find more unvisited subtrees.
                                                        visited.push(child);
                                                        child = child.firstChild;
                                                    }
                            
                                                    // Find the most recently visited node who has a next sibling.
                                                    while (visited.length > 0 && !child) {
                                                        child = visited.pop().nextSibling;
                                                    }
                                                }
                                            }
                            
                                            if (nodes.length) {
                                                ret = Selector._filterNodes(nodes, tokens, firstOnly);
                                            }
                                        }
                            
                                        return ret;
                                    },
                            
                                    _filterNodes: function(nodes, tokens, firstOnly) {
                                        var i = 0,
                                            j,
                                            len = tokens.length,
                                            n = len - 1,
                                            result = [],
                                            node = nodes[0],
                                            tmpNode = node,
                                            getters = Y.Selector.getters,
                                            operator,
                                            combinator,
                                            token,
                                            path,
                                            pass,
                                            value,
                                            tests,
                                            test;
                            
                                        for (i = 0; (tmpNode = node = nodes[i++]);) {
                                            n = len - 1;
                                            path = null;
                            
                                            testLoop:
                                            while (tmpNode && tmpNode.tagName) {
                                                token = tokens[n];
                                                tests = token.tests;
                                                j = tests.length;
                                                if (j && !pass) {
                                                    while ((test = tests[--j])) {
                                                        operator = test[1];
                                                        if (getters[test[0]]) {
                                                            value = getters[test[0]](tmpNode, test[0]);
                                                        } else {
                                                            value = tmpNode[test[0]];
                                                            if (test[0] === 'tagName' && !Selector._isXML) {
                                                                value = value.toUpperCase();
                                                            }
                                                            if (typeof value != 'string' && value !== undefined && value.toString) {
                                                                value = value.toString(); // coerce for comparison
                                                            } else if (value === undefined && tmpNode.getAttribute) {
                                                                // use getAttribute for non-standard attributes
                                                                value = tmpNode.getAttribute(test[0], 2); // 2 === force string for IE
                                                            }
                                                        }
                            
                                                        if ((operator === '=' && value !== test[2]) ||  // fast path for equality
                                                            (typeof operator !== 'string' && // protect against String.test monkey-patch (Moo)
                                                            operator.test && !operator.test(value)) ||  // regex test
                                                            (!operator.test && // protect against RegExp as function (webkit)
                                                                    typeof operator === 'function' && !operator(tmpNode, test[0], test[2]))) { // function test
                            
                                                            // skip non element nodes or non-matching tags
                                                            if ((tmpNode = tmpNode[path])) {
                                                                while (tmpNode &&
                                                                    (!tmpNode.tagName ||
                                                                        (token.tagName && token.tagName !== tmpNode.tagName))
                                                                ) {
                                                                    tmpNode = tmpNode[path];
                                                                }
                                                            }
                                                            continue testLoop;
                                                        }
                                                    }
                                                }
                            
                                                n--; // move to next token
                                                // now that we've passed the test, move up the tree by combinator
                                                if (!pass && (combinator = token.combinator)) {
                                                    path = combinator.axis;
                                                    tmpNode = tmpNode[path];
                            
                                                    // skip non element nodes
                                                    while (tmpNode && !tmpNode.tagName) {
                                                        tmpNode = tmpNode[path];
                                                    }
                            
                                                    if (combinator.direct) { // one pass only
                                                        path = null;
                                                    }
                            
                                                } else { // success if we made it this far
                                                    result.push(node);
                                                    if (firstOnly) {
                                                        return result;
                                                    }
                                                    break;
                                                }
                                            }
                                        }
                                        node = tmpNode = null;
                                        return result;
                                    },
                            
                                    combinators: {
                                        ' ': {
                                            axis: 'parentNode'
                                        },
                            
                                        '>': {
                                            axis: 'parentNode',
                                            direct: true
                                        },
                            
                            
                                        '+': {
                                            axis: 'previousSibling',
                                            direct: true
                                        }
                                    },
                            
                                    _parsers: [
                                        {
                                            name: ATTRIBUTES,
                                            re: /^\uE003(-?[a-z]+[\w\-]*)+([~\|\^\$\*!=]=?)?['"]?([^\uE004'"]*)['"]?\uE004/i,
                                            fn: function(match, token) {
                                                var operator = match[2] || '',
                                                    operators = Selector.operators,
                                                    escVal = (match[3]) ? match[3].replace(/\\/g, '') : '',
                                                    test;
                            
                                                // add prefiltering for ID and CLASS
                                                if ((match[1] === 'id' && operator === '=') ||
                                                        (match[1] === 'className' &&
                                                        Y.config.doc.documentElement.getElementsByClassName &&
                                                        (operator === '~=' || operator === '='))) {
                                                    token.prefilter = match[1];
                            
                            
                                                    match[3] = escVal;
                            
                                                    // escape all but ID for prefilter, which may run through QSA (via Dom.allById)
                                                    token[match[1]] = (match[1] === 'id') ? match[3] : escVal;
                            
                                                }
                            
                                                // add tests
                                                if (operator in operators) {
                                                    test = operators[operator];
                                                    if (typeof test === 'string') {
                                                        match[3] = escVal.replace(Selector._reRegExpTokens, '\\$1');
                                                        test = new RegExp(test.replace('{val}', match[3]));
                                                    }
                                                    match[2] = test;
                                                }
                                                if (!token.last || token.prefilter !== match[1]) {
                                                    return match.slice(1);
                                                }
                                            }
                                        },
                                        {
                                            name: TAG_NAME,
                                            re: /^((?:-?[_a-z]+[\w-]*)|\*)/i,
                                            fn: function(match, token) {
                                                var tag = match[1];
                            
                                                if (!Selector._isXML) {
                                                    tag = tag.toUpperCase();
                                                }
                            
                                                token.tagName = tag;
                            
                                                if (tag !== '*' && (!token.last || token.prefilter)) {
                                                    return [TAG_NAME, '=', tag];
                                                }
                                                if (!token.prefilter) {
                                                    token.prefilter = 'tagName';
                                                }
                                            }
                                        },
                                        {
                                            name: COMBINATOR,
                                            re: /^\s*([>+~]|\s)\s*/,
                                            fn: function(match, token) {
                                            }
                                        },
                                        {
                                            name: PSEUDOS,
                                            re: /^:([\-\w]+)(?:\uE005['"]?([^\uE005]*)['"]?\uE006)*/i,
                                            fn: function(match, token) {
                                                var test = Selector[PSEUDOS][match[1]];
                                                if (test) { // reorder match array and unescape special chars for tests
                                                    if (match[2]) {
                                                        match[2] = match[2].replace(/\\/g, '');
                                                    }
                                                    return [match[2], test];
                                                } else { // selector token not supported (possibly missing CSS3 module)
                                                    return false;
                                                }
                                            }
                                        }
                                        ],
                            
                                    _getToken: function(token) {
                                        return {
                                            tagName: null,
                                            id: null,
                                            className: null,
                                            attributes: {},
                                            combinator: null,
                                            tests: []
                                        };
                                    },
                            
                                    /*
                                        Break selector into token units per simple selector.
                                        Combinator is attached to the previous token.
                                     */
                                    _tokenize: function(selector) {
                                        selector = selector || '';
                                        selector = Selector._parseSelector(Y.Lang.trim(selector));
                                        var token = Selector._getToken(),     // one token per simple selector (left selector holds combinator)
                                            query = selector, // original query for debug report
                                            tokens = [],    // array of tokens
                                            found = false,  // whether or not any matches were found this pass
                                            match,         // the regex match
                                            test,
                                            i, parser;
                            
                                        /*
                                            Search for selector patterns, store, and strip them from the selector string
                                            until no patterns match (invalid selector) or we run out of chars.
                            
                                            Multiple attributes and pseudos are allowed, in any order.
                                            for example:
                                                'form:first-child[type=button]:not(button)[lang|=en]'
                                        */
                                        outer:
                                        do {
                                            found = false; // reset after full pass
                                            for (i = 0; (parser = Selector._parsers[i++]);) {
                                                if ( (match = parser.re.exec(selector)) ) { // note assignment
                                                    if (parser.name !== COMBINATOR ) {
                                                        token.selector = selector;
                                                    }
                                                    selector = selector.replace(match[0], ''); // strip current match from selector
                                                    if (!selector.length) {
                                                        token.last = true;
                                                    }
                            
                                                    if (Selector._attrFilters[match[1]]) { // convert class to className, etc.
                                                        match[1] = Selector._attrFilters[match[1]];
                                                    }
                            
                                                    test = parser.fn(match, token);
                                                    if (test === false) { // selector not supported
                                                        found = false;
                                                        break outer;
                                                    } else if (test) {
                                                        token.tests.push(test);
                                                    }
                            
                                                    if (!selector.length || parser.name === COMBINATOR) {
                                                        tokens.push(token);
                                                        token = Selector._getToken(token);
                                                        if (parser.name === COMBINATOR) {
                                                            token.combinator = Y.Selector.combinators[match[1]];
                                                        }
                                                    }
                                                    found = true;
                                                }
                                            }
                                        } while (found && selector.length);
                            
                                        if (!found || selector.length) { // not fully parsed
                                            Y.log('query: ' + query + ' contains unsupported token in: ' + selector, 'warn', 'Selector');
                                            tokens = [];
                                        }
                                        return tokens;
                                    },
                            
                                    _replaceMarkers: function(selector) {
                                        selector = selector.replace(/\[/g, '\uE003');
                                        selector = selector.replace(/\]/g, '\uE004');
                            
                                        selector = selector.replace(/\(/g, '\uE005');
                                        selector = selector.replace(/\)/g, '\uE006');
                                        return selector;
                                    },
                            
                                    _replaceShorthand: function(selector) {
                                        var shorthand = Y.Selector.shorthand,
                                            re;
                            
                                        for (re in shorthand) {
                                            if (shorthand.hasOwnProperty(re)) {
                                                selector = selector.replace(new RegExp(re, 'gi'), shorthand[re]);
                                            }
                                        }
                            
                                        return selector;
                                    },
                            
                                    _parseSelector: function(selector) {
                                        var replaced = Y.Selector._replaceSelector(selector),
                                            selector = replaced.selector;
                            
                                        // replace shorthand (".foo, #bar") after pseudos and attrs
                                        // to avoid replacing unescaped chars
                                        selector = Y.Selector._replaceShorthand(selector);
                            
                                        selector = Y.Selector._restore('attr', selector, replaced.attrs);
                                        selector = Y.Selector._restore('pseudo', selector, replaced.pseudos);
                            
                                        // replace braces and parens before restoring escaped chars
                                        // to avoid replacing ecaped markers
                                        selector = Y.Selector._replaceMarkers(selector);
                                        selector = Y.Selector._restore('esc', selector, replaced.esc);
                            
                                        return selector;
                                    },
                            
                                    _attrFilters: {
                                        'class': 'className',
                                        'for': 'htmlFor'
                                    },
                            
                                    getters: {
                                        href: function(node, attr) {
                                            return Y.DOM.getAttribute(node, attr);
                                        },
                            
                                        id: function(node, attr) {
                                            return Y.DOM.getId(node);
                                        }
                                    }
                                };
                            
                            Y.mix(Y.Selector, SelectorCSS2, true);
                            Y.Selector.getters.src = Y.Selector.getters.rel = Y.Selector.getters.href;
                            
                            // IE wants class with native queries
                            if (Y.Selector.useNative && Y.config.doc.querySelector) {
                                Y.Selector.shorthand['\\.(-?[_a-z]+[-\\w]*)'] = '[class~=$1]';
                            }