/**
 * A CSS3 parser.
 * @namespace parserlib.css
 * @class Parser
 * @constructor
 * @param {Object} options (Optional) Various options for the parser:
 *      starHack (true|false) to allow IE6 star hack as valid,
 *      underscoreHack (true|false) to interpret leading underscores
 *      as IE6-7 targeting for known properties, ieFilters (true|false)
 *      to indicate that IE < 8 filters should be accepted and not throw
 *      syntax errors.
 */
function Parser(options){

    //inherit event functionality
    EventTarget.call(this);


    this.options = options || {};

    this._tokenStream = null;
}

//Static constants
Parser.DEFAULT_TYPE = 0;
Parser.COMBINATOR_TYPE = 1;
Parser.MEDIA_FEATURE_TYPE = 2;
Parser.MEDIA_QUERY_TYPE = 3;
Parser.PROPERTY_NAME_TYPE = 4;
Parser.PROPERTY_VALUE_TYPE = 5;
Parser.PROPERTY_VALUE_PART_TYPE = 6;
Parser.SELECTOR_TYPE = 7;
Parser.SELECTOR_PART_TYPE = 8;
Parser.SELECTOR_SUB_PART_TYPE = 9;

Parser.prototype = function(){

    var proto = new EventTarget(),  //new prototype
        prop,
        additions =  {
        
            //restore constructor
            constructor: Parser,
                        
            //instance constants - yuck
            DEFAULT_TYPE : 0,
            COMBINATOR_TYPE : 1,
            MEDIA_FEATURE_TYPE : 2,
            MEDIA_QUERY_TYPE : 3,
            PROPERTY_NAME_TYPE : 4,
            PROPERTY_VALUE_TYPE : 5,
            PROPERTY_VALUE_PART_TYPE : 6,
            SELECTOR_TYPE : 7,
            SELECTOR_PART_TYPE : 8,
            SELECTOR_SUB_PART_TYPE : 9,            
        
            //-----------------------------------------------------------------
            // Grammar
            //-----------------------------------------------------------------
        
            _stylesheet: function(){
            
                /*
                 * stylesheet
                 *  : [ CHARSET_SYM S* STRING S* ';' ]?
                 *    [S|CDO|CDC]* [ import [S|CDO|CDC]* ]*
                 *    [ namespace [S|CDO|CDC]* ]*
                 *    [ [ ruleset | media | page | font_face | keyframes ] [S|CDO|CDC]* ]*
                 *  ;
                 */ 
               
                var tokenStream = this._tokenStream,
                    charset     = null,
                    token,
                    tt;
                    
                this.fire("startstylesheet");
            
                //try to read character set
                this._charset();
                
                this._skipCruft();

                //try to read imports - may be more than one
                while (tokenStream.peek() == Tokens.IMPORT_SYM){
                    this._import();
                    this._skipCruft();
                }
                
                //try to read namespaces - may be more than one
                while (tokenStream.peek() == Tokens.NAMESPACE_SYM){
                    this._namespace();
                    this._skipCruft();
                }
                
                //get the next token
                tt = tokenStream.peek();
                
                //try to read the rest
                while(tt > Tokens.EOF){
                
                    try {
                
                        switch(tt){
                            case Tokens.MEDIA_SYM:
                                this._media();
                                this._skipCruft();
                                break;
                            case Tokens.PAGE_SYM:
                                this._page(); 
                                this._skipCruft();
                                break;                   
                            case Tokens.FONT_FACE_SYM:
                                this._font_face(); 
                                this._skipCruft();
                                break;  
                            case Tokens.KEYFRAMES_SYM:
                                this._keyframes(); 
                                this._skipCruft();
                                break;  
                            case Tokens.S:
                                this._readWhitespace();
                                break;
                            default:                            
                                if(!this._ruleset()){
                                
                                    //error handling for known issues
                                    switch(tt){
                                        case Tokens.CHARSET_SYM:
                                            token = tokenStream.LT(1);
                                            this._charset(false);
                                            throw new SyntaxError("@charset not allowed here.", token.startLine, token.startCol);
                                        case Tokens.IMPORT_SYM:
                                            token = tokenStream.LT(1);
                                            this._import(false);
                                            throw new SyntaxError("@import not allowed here.", token.startLine, token.startCol);
                                        case Tokens.NAMESPACE_SYM:
                                            token = tokenStream.LT(1);
                                            this._namespace(false);
                                            throw new SyntaxError("@namespace not allowed here.", token.startLine, token.startCol);
                                        default:
                                            tokenStream.get();  //get the last token
                                            this._unexpectedToken(tokenStream.token());
                                    }
                                
                                }
                        }
                    } catch(ex) {
                        if (ex instanceof SyntaxError && !this.options.strict){
                            this.fire({
                                type:       "error",
                                error:      ex,
                                message:    ex.message,
                                line:       ex.line,
                                col:        ex.col
                            });                     
                        } else {
                            throw ex;
                        }
                    }
                    
                    tt = tokenStream.peek();
                }
                
                if (tt != Tokens.EOF){
                    this._unexpectedToken(tokenStream.token());
                }
            
                this.fire("endstylesheet");
            },
            
            _charset: function(emit){
                var tokenStream = this._tokenStream,
                    charset,
                    token,
                    line,
                    col;
                    
                if (tokenStream.match(Tokens.CHARSET_SYM)){
                    line = tokenStream.token().startLine;
                    col = tokenStream.token().startCol;
                
                    this._readWhitespace();
                    tokenStream.mustMatch(Tokens.STRING);
                    
                    token = tokenStream.token();
                    charset = token.value;
                    
                    this._readWhitespace();
                    tokenStream.mustMatch(Tokens.SEMICOLON);
                    
                    if (emit !== false){
                        this.fire({ 
                            type:   "charset",
                            charset:charset,
                            line:   line,
                            col:    col
                        });
                    }
                }            
            },
            
            _import: function(emit){
                /*
                 * import
                 *   : IMPORT_SYM S*
                 *    [STRING|URI] S* media_query_list? ';' S*
                 */    
            
                var tokenStream = this._tokenStream,
                    tt,
                    uri,
                    importToken,
                    mediaList   = [];
                
                //read import symbol
                tokenStream.mustMatch(Tokens.IMPORT_SYM);
                importToken = tokenStream.token();
                this._readWhitespace();
                
                tokenStream.mustMatch([Tokens.STRING, Tokens.URI]);
                
                //grab the URI value
                uri = tokenStream.token().value.replace(/(?:url\()?["']([^"']+)["']\)?/, "$1");                

                this._readWhitespace();
                
                mediaList = this._media_query_list();
                
                //must end with a semicolon
                tokenStream.mustMatch(Tokens.SEMICOLON);
                this._readWhitespace();
                
                if (emit !== false){
                    this.fire({
                        type:   "import",
                        uri:    uri,
                        media:  mediaList,
                        line:   importToken.startLine,
                        col:    importToken.startCol
                    });
                }
        
            },
            
            _namespace: function(emit){
                /*
                 * namespace
                 *   : NAMESPACE_SYM S* [namespace_prefix S*]? [STRING|URI] S* ';' S*
                 */    
            
                var tokenStream = this._tokenStream,
                    line,
                    col,
                    prefix,
                    uri;
                
                //read import symbol
                tokenStream.mustMatch(Tokens.NAMESPACE_SYM);
                line = tokenStream.token().startLine;
                col = tokenStream.token().startCol;
                this._readWhitespace();
                
                //it's a namespace prefix - no _namespace_prefix() method because it's just an IDENT
                if (tokenStream.match(Tokens.IDENT)){
                    prefix = tokenStream.token().value;
                    this._readWhitespace();
                }
                
                tokenStream.mustMatch([Tokens.STRING, Tokens.URI]);
                /*if (!tokenStream.match(Tokens.STRING)){
                    tokenStream.mustMatch(Tokens.URI);
                }*/
                
                //grab the URI value
                uri = tokenStream.token().value.replace(/(?:url\()?["']([^"']+)["']\)?/, "$1");                

                this._readWhitespace();

                //must end with a semicolon
                tokenStream.mustMatch(Tokens.SEMICOLON);
                this._readWhitespace();
                
                if (emit !== false){
                    this.fire({
                        type:   "namespace",
                        prefix: prefix,
                        uri:    uri,
                        line:   line,
                        col:    col
                    });
                }
        
            },            
                       
            _media: function(){
                /*
                 * media
                 *   : MEDIA_SYM S* media_query_list S* '{' S* ruleset* '}' S*
                 *   ;
                 */
                var tokenStream     = this._tokenStream,
                    line,
                    col,
                    mediaList;//       = [];
                
                //look for @media
                tokenStream.mustMatch(Tokens.MEDIA_SYM);
                line = tokenStream.token().startLine;
                col = tokenStream.token().startCol;
                
                this._readWhitespace();               

                mediaList = this._media_query_list();

                tokenStream.mustMatch(Tokens.LBRACE);
                this._readWhitespace();
                
                this.fire({
                    type:   "startmedia",
                    media:  mediaList,
                    line:   line,
                    col:    col
                });
                
                while(true) {
                    if (tokenStream.peek() == Tokens.PAGE_SYM){
                        this._page();
                    } else if (!this._ruleset()){
                        break;
                    }                
                }
                
                tokenStream.mustMatch(Tokens.RBRACE);
                this._readWhitespace();
        
                this.fire({
                    type:   "endmedia",
                    media:  mediaList,
                    line:   line,
                    col:    col
                });
            },                           
        

            //CSS3 Media Queries
            _media_query_list: function(){
                /*
                 * media_query_list
                 *   : S* [media_query [ ',' S* media_query ]* ]?
                 *   ;
                 */
                var tokenStream = this._tokenStream,
                    mediaList   = [];
                
                
                this._readWhitespace();
                
                if (tokenStream.peek() == Tokens.IDENT || tokenStream.peek() == Tokens.LPAREN){
                    mediaList.push(this._media_query());
                }
                
                while(tokenStream.match(Tokens.COMMA)){
                    this._readWhitespace();
                    mediaList.push(this._media_query());
                }
                
                return mediaList;
            },
            
            /*
             * Note: "expression" in the grammar maps to the _media_expression
             * method.
             
             */
            _media_query: function(){
                /*
                 * media_query
                 *   : [ONLY | NOT]? S* media_type S* [ AND S* expression ]*
                 *   | expression [ AND S* expression ]*
                 *   ;
                 */
                var tokenStream = this._tokenStream,
                    type        = null,
                    ident       = null,
                    token       = null,
                    expressions = [];
                    
                if (tokenStream.match(Tokens.IDENT)){
                    ident = tokenStream.token().value.toLowerCase();
                    
                    //since there's no custom tokens for these, need to manually check
                    if (ident != "only" && ident != "not"){
                        tokenStream.unget();
                        ident = null;
                    } else {
                        token = tokenStream.token();
                    }
                }
                                
                this._readWhitespace();
                
                if (tokenStream.peek() == Tokens.IDENT){
                    type = this._media_type();
                    if (token === null){
                        token = tokenStream.token();
                    }
                } else if (tokenStream.peek() == Tokens.LPAREN){
                    if (token === null){
                        token = tokenStream.LT(1);
                    }
                    expressions.push(this._media_expression());
                }                               
                
                if (type === null && expressions.length === 0){
                    return null;
                } else {                
                    this._readWhitespace();
                    while (tokenStream.match(Tokens.IDENT)){
                        if (tokenStream.token().value.toLowerCase() != "and"){
                            this._unexpectedToken(tokenStream.token());
                        }
                        
                        this._readWhitespace();
                        expressions.push(this._media_expression());
                    }
                }

                return new MediaQuery(ident, type, expressions, token.startLine, token.startCol);
            },

            //CSS3 Media Queries
            _media_type: function(){
                /*
                 * media_type
                 *   : IDENT
                 *   ;
                 */
                return this._media_feature();           
            },

            /**
             * Note: in CSS3 Media Queries, this is called "expression".
             * Renamed here to avoid conflict with CSS3 Selectors
             * definition of "expression". Also note that "expr" in the
             * grammar now maps to "expression" from CSS3 selectors.
             * @method _media_expression
             * @private
             */
            _media_expression: function(){
                /*
                 * expression
                 *  : '(' S* media_feature S* [ ':' S* expr ]? ')' S*
                 *  ;
                 */
                var tokenStream = this._tokenStream,
                    feature     = null,
                    token,
                    expression  = null;
                
                tokenStream.mustMatch(Tokens.LPAREN);
                
                feature = this._media_feature();
                this._readWhitespace();
                
                if (tokenStream.match(Tokens.COLON)){
                    this._readWhitespace();
                    token = tokenStream.LT(1);
                    expression = this._expression();
                }
                
                tokenStream.mustMatch(Tokens.RPAREN);
                this._readWhitespace();

                return new MediaFeature(feature, (expression ? new SyntaxUnit(expression, token.startLine, token.startCol) : null));            
            },

            //CSS3 Media Queries
            _media_feature: function(){
                /*
                 * media_feature
                 *   : IDENT
                 *   ;
                 */
                var tokenStream = this._tokenStream;
                    
                tokenStream.mustMatch(Tokens.IDENT);
                
                return SyntaxUnit.fromToken(tokenStream.token());            
            },
            
            //CSS3 Paged Media
            _page: function(){
                /*
                 * page:
                 *    PAGE_SYM S* IDENT? pseudo_page? S* 
                 *    '{' S* [ declaration | margin ]? [ ';' S* [ declaration | margin ]? ]* '}' S*
                 *    ;
                 */            
                var tokenStream = this._tokenStream,
                    line,
                    col,
                    identifier  = null,
                    pseudoPage  = null;
                
                //look for @page
                tokenStream.mustMatch(Tokens.PAGE_SYM);
                line = tokenStream.token().startLine;
                col = tokenStream.token().startCol;
                
                this._readWhitespace();
                
                if (tokenStream.match(Tokens.IDENT)){
                    identifier = tokenStream.token().value;

                    //The value 'auto' may not be used as a page name and MUST be treated as a syntax error.
                    if (identifier.toLowerCase() === "auto"){
                        this._unexpectedToken(tokenStream.token());
                    }
                }                
                
                //see if there's a colon upcoming
                if (tokenStream.peek() == Tokens.COLON){
                    pseudoPage = this._pseudo_page();
                }
            
                this._readWhitespace();
                
                this.fire({
                    type:   "startpage",
                    id:     identifier,
                    pseudo: pseudoPage,
                    line:   line,
                    col:    col
                });                   

                this._readDeclarations(true, true);                
                
                this.fire({
                    type:   "endpage",
                    id:     identifier,
                    pseudo: pseudoPage,
                    line:   line,
                    col:    col
                });             
            
            },
            
            //CSS3 Paged Media
            _margin: function(){
                /*
                 * margin :
                 *    margin_sym S* '{' declaration [ ';' S* declaration? ]* '}' S*
                 *    ;
                 */
                var tokenStream = this._tokenStream,
                    line,
                    col,
                    marginSym   = this._margin_sym();

                if (marginSym){
                    line = tokenStream.token().startLine;
                    col = tokenStream.token().startCol;
                
                    this.fire({
                        type: "startpagemargin",
                        margin: marginSym,
                        line:   line,
                        col:    col
                    });    
                    
                    this._readDeclarations(true);

                    this.fire({
                        type: "endpagemargin",
                        margin: marginSym,
                        line:   line,
                        col:    col
                    });    
                    return true;
                } else {
                    return false;
                }
            },

            //CSS3 Paged Media
            _margin_sym: function(){
            
                /*
                 * margin_sym :
                 *    TOPLEFTCORNER_SYM | 
                 *    TOPLEFT_SYM | 
                 *    TOPCENTER_SYM | 
                 *    TOPRIGHT_SYM | 
                 *    TOPRIGHTCORNER_SYM |
                 *    BOTTOMLEFTCORNER_SYM | 
                 *    BOTTOMLEFT_SYM | 
                 *    BOTTOMCENTER_SYM | 
                 *    BOTTOMRIGHT_SYM |
                 *    BOTTOMRIGHTCORNER_SYM |
                 *    LEFTTOP_SYM |
                 *    LEFTMIDDLE_SYM |
                 *    LEFTBOTTOM_SYM |
                 *    RIGHTTOP_SYM |
                 *    RIGHTMIDDLE_SYM |
                 *    RIGHTBOTTOM_SYM 
                 *    ;
                 */
            
                var tokenStream = this._tokenStream;
            
                if(tokenStream.match([Tokens.TOPLEFTCORNER_SYM, Tokens.TOPLEFT_SYM,
                        Tokens.TOPCENTER_SYM, Tokens.TOPRIGHT_SYM, Tokens.TOPRIGHTCORNER_SYM,
                        Tokens.BOTTOMLEFTCORNER_SYM, Tokens.BOTTOMLEFT_SYM, 
                        Tokens.BOTTOMCENTER_SYM, Tokens.BOTTOMRIGHT_SYM,
                        Tokens.BOTTOMRIGHTCORNER_SYM, Tokens.LEFTTOP_SYM, 
                        Tokens.LEFTMIDDLE_SYM, Tokens.LEFTBOTTOM_SYM, Tokens.RIGHTTOP_SYM,
                        Tokens.RIGHTMIDDLE_SYM, Tokens.RIGHTBOTTOM_SYM]))
                {
                    return SyntaxUnit.fromToken(tokenStream.token());                
                } else {
                    return null;
                }
            
            },
            
            _pseudo_page: function(){
                /*
                 * pseudo_page
                 *   : ':' IDENT
                 *   ;    
                 */
        
                var tokenStream = this._tokenStream;
                
                tokenStream.mustMatch(Tokens.COLON);
                tokenStream.mustMatch(Tokens.IDENT);
                
                //TODO: CSS3 Paged Media says only "left", "center", and "right" are allowed
                
                return tokenStream.token().value;
            },
            
            _font_face: function(){
                /*
                 * font_face
                 *   : FONT_FACE_SYM S* 
                 *     '{' S* declaration [ ';' S* declaration ]* '}' S*
                 *   ;
                 */     
                var tokenStream = this._tokenStream,
                    line,
                    col;
                
                //look for @page
                tokenStream.mustMatch(Tokens.FONT_FACE_SYM);
                line = tokenStream.token().startLine;
                col = tokenStream.token().startCol;
                
                this._readWhitespace();

                this.fire({
                    type:   "startfontface",
                    line:   line,
                    col:    col
                });                    
                
                this._readDeclarations(true);
                
                this.fire({
                    type:   "endfontface",
                    line:   line,
                    col:    col
                });              
            },

            _operator: function(){
            
                /*
                 * operator
                 *  : '/' S* | ',' S* | /( empty )/
                 *  ;
                 */    
                 
                var tokenStream = this._tokenStream,
                    token       = null;
                
                if (tokenStream.match([Tokens.SLASH, Tokens.COMMA])){
                    token =  tokenStream.token();
                    this._readWhitespace();
                } 
                return token ? PropertyValuePart.fromToken(token) : null;
                
            },
            
            _combinator: function(){
            
                /*
                 * combinator
                 *  : PLUS S* | GREATER S* | TILDE S* | S+
                 *  ;
                 */    
                 
                var tokenStream = this._tokenStream,
                    value       = null,
                    token;
                
                if(tokenStream.match([Tokens.PLUS, Tokens.GREATER, Tokens.TILDE])){                
                    token = tokenStream.token();
                    value = new Combinator(token.value, token.startLine, token.startCol);
                    this._readWhitespace();
                }
                
                return value;
            },
            
            _unary_operator: function(){
            
                /*
                 * unary_operator
                 *  : '-' | '+'
                 *  ;
                 */
                 
                var tokenStream = this._tokenStream;
                
                if (tokenStream.match([Tokens.MINUS, Tokens.PLUS])){
                    return tokenStream.token().value;
                } else {
                    return null;
                }         
            },
            
            _property: function(){
            
                /*
                 * property
                 *   : IDENT S*
                 *   ;        
                 */
                 
                var tokenStream = this._tokenStream,
                    value       = null,
                    hack        = null,
                    tokenValue,
                    token,
                    line,
                    col;
                    
                //check for star hack - throws error if not allowed
                if (tokenStream.peek() == Tokens.STAR && this.options.starHack){
                    tokenStream.get();
                    token = tokenStream.token();
                    hack = token.value;
                    line = token.startLine;
                    col = token.startCol;
                }
                
                if(tokenStream.match(Tokens.IDENT)){
                    token = tokenStream.token();
                    tokenValue = token.value;
                    
                    //check for underscore hack - no error if not allowed because it's valid CSS syntax
                    if (tokenValue.charAt(0) == "_" && this.options.underscoreHack){
                        hack = "_";
                        tokenValue = tokenValue.substring(1);
                    }
                    
                    value = new PropertyName(tokenValue, hack, (line||token.startLine), (col||token.startCol));
                    this._readWhitespace();
                }
                
                return value;
            },
        
            //Augmented with CSS3 Selectors
            _ruleset: function(){
                /*
                 * ruleset
                 *   : selectors_group
                 *     '{' S* declaration? [ ';' S* declaration? ]* '}' S*
                 *   ;    
                 */    
                 
                var tokenStream = this._tokenStream,
                    tt,
                    selectors;


                /*
                 * Error Recovery: If even a single selector fails to parse,
                 * then the entire ruleset should be thrown away.
                 */
                try {
                    selectors = this._selectors_group();
                } catch (ex){
                    if (ex instanceof SyntaxError && !this.options.strict){
                    
                        //fire error event
                        this.fire({
                            type:       "error",
                            error:      ex,
                            message:    ex.message,
                            line:       ex.line,
                            col:        ex.col
                        });                          
                        
                        //skip over everything until closing brace
                        tt = tokenStream.advance([Tokens.RBRACE]);
                        if (tt == Tokens.RBRACE){
                            //if there's a right brace, the rule is finished so don't do anything
                        } else {
                            //otherwise, rethrow the error because it wasn't handled properly
                            throw ex;
                        }                        
                        
                    } else {
                        //not a syntax error, rethrow it
                        throw ex;
                    }                
                
                    //trigger parser to continue
                    return true;
                }
                
                //if it got here, all selectors parsed
                if (selectors){ 
                                    
                    this.fire({
                        type:       "startrule",
                        selectors:  selectors,
                        line:       selectors[0].line,
                        col:        selectors[0].col
                    });                
                    
                    this._readDeclarations(true);                
                    
                    this.fire({
                        type:       "endrule",
                        selectors:  selectors,
                        line:       selectors[0].line,
                        col:        selectors[0].col
                    });  
                    
                }
                
                return selectors;
                
            },

            //CSS3 Selectors
            _selectors_group: function(){
            
                /*            
                 * selectors_group
                 *   : selector [ COMMA S* selector ]*
                 *   ;
                 */           
                var tokenStream = this._tokenStream,
                    selectors   = [],
                    selector;
                    
                selector = this._selector();
                if (selector !== null){
                
                    selectors.push(selector);
                    while(tokenStream.match(Tokens.COMMA)){
                        this._readWhitespace();
                        selector = this._selector();
                        if (selector !== null){
                            selectors.push(selector);
                        } else {
                            this._unexpectedToken(tokenStream.LT(1));
                        }
                    }
                }

                return selectors.length ? selectors : null;
            },
                
            //CSS3 Selectors
            _selector: function(){
                /*
                 * selector
                 *   : simple_selector_sequence [ combinator simple_selector_sequence ]*
                 *   ;    
                 */
                 
                var tokenStream = this._tokenStream,
                    selector    = [],
                    nextSelector = null,
                    combinator  = null,
                    ws          = null;
                
                //if there's no simple selector, then there's no selector
                nextSelector = this._simple_selector_sequence();
                if (nextSelector === null){
                    return null;
                }
                
                selector.push(nextSelector);
                
                do {
                    
                    //look for a combinator
                    combinator = this._combinator();
                    
                    if (combinator !== null){
                        selector.push(combinator);
                        nextSelector = this._simple_selector_sequence();
                        
                        //there must be a next selector
                        if (nextSelector === null){
                            this._unexpectedToken(this.LT(1));
                        } else {
                        
                            //nextSelector is an instance of SelectorPart
                            selector.push(nextSelector);
                        }
                    } else {
                        
                        //if there's not whitespace, we're done
                        if (this._readWhitespace()){           
        
                            //add whitespace separator
                            ws = new Combinator(tokenStream.token().value, tokenStream.token().startLine, tokenStream.token().startCol);
                            
                            //combinator is not required
                            combinator = this._combinator();
                            
                            //selector is required if there's a combinator
                            nextSelector = this._simple_selector_sequence();
                            if (nextSelector === null){                        
                                if (combinator !== null){
                                    this._unexpectedToken(tokenStream.LT(1));
                                }
                            } else {
                                
                                if (combinator !== null){
                                    selector.push(combinator);
                                } else {
                                    selector.push(ws);
                                }
                                
                                selector.push(nextSelector);
                            }     
                        } else {
                            break;
                        }               
                    
                    }
                } while(true);
                
                return new Selector(selector, selector[0].line, selector[0].col);
            },
            
            //CSS3 Selectors
            _simple_selector_sequence: function(){
                /*
                 * simple_selector_sequence
                 *   : [ type_selector | universal ]
                 *     [ HASH | class | attrib | pseudo | negation ]*
                 *   | [ HASH | class | attrib | pseudo | negation ]+
                 *   ;
                 */
                 
                var tokenStream = this._tokenStream,
                
                    //parts of a simple selector
                    elementName = null,
                    modifiers   = [],
                    
                    //complete selector text
                    selectorText= "",

                    //the different parts after the element name to search for
                    components  = [
                        //HASH
                        function(){
                            return tokenStream.match(Tokens.HASH) ?
                                    new SelectorSubPart(tokenStream.token().value, "id", tokenStream.token().startLine, tokenStream.token().startCol) :
                                    null;
                        },
                        this._class,
                        this._attrib,
                        this._pseudo,
                        this._negation
                    ],
                    i           = 0,
                    len         = components.length,
                    component   = null,
                    found       = false,
                    line,
                    col;
                    
                    
                //get starting line and column for the selector
                line = tokenStream.LT(1).startLine;
                col = tokenStream.LT(1).startCol;
                                        
                elementName = this._type_selector();
                if (!elementName){
                    elementName = this._universal();
                }
                
                if (elementName !== null){
                    selectorText += elementName;
                }                
                
                while(true){

                    //whitespace means we're done
                    if (tokenStream.peek() === Tokens.S){
                        break;
                    }
                
                    //check for each component
                    while(i < len && component === null){
                        component = components[i++].call(this);
                    }
        
                    if (component === null){
                    
                        //we don't have a selector
                        if (selectorText === ""){
                            return null;
                        } else {
                            break;
                        }
                    } else {
                        i = 0;
                        modifiers.push(component);
                        selectorText += component.toString(); 
                        component = null;
                    }
                }

                 
                return selectorText !== "" ?
                        new SelectorPart(elementName, modifiers, selectorText, line, col) :
                        null;
            },            
            
            //CSS3 Selectors
            _type_selector: function(){
                /*
                 * type_selector
                 *   : [ namespace_prefix ]? element_name
                 *   ;
                 */
                 
                var tokenStream = this._tokenStream,
                    ns          = this._namespace_prefix(),
                    elementName = this._element_name();
                    
                if (!elementName){                    
                    /*
                     * Need to back out the namespace that was read due to both
                     * type_selector and universal reading namespace_prefix
                     * first. Kind of hacky, but only way I can figure out
                     * right now how to not change the grammar.
                     */
                    if (ns){
                        tokenStream.unget();
                        if (ns.length > 1){
                            tokenStream.unget();
                        }
                    }
                
                    return null;
                } else {     
                    if (ns){
                        elementName.text = ns + elementName.text;
                        elementName.col -= ns.length;
                    }
                    return elementName;
                }
            },
            
            //CSS3 Selectors
            _class: function(){
                /*
                 * class
                 *   : '.' IDENT
                 *   ;
                 */    
                 
                var tokenStream = this._tokenStream,
                    token;
                
                if (tokenStream.match(Tokens.DOT)){
                    tokenStream.mustMatch(Tokens.IDENT);    
                    token = tokenStream.token();
                    return new SelectorSubPart("." + token.value, "class", token.startLine, token.startCol - 1);        
                } else {
                    return null;
                }
        
            },
            
            //CSS3 Selectors
            _element_name: function(){
                /*
                 * element_name
                 *   : IDENT
                 *   ;
                 */    
                
                var tokenStream = this._tokenStream,
                    token;
                
                if (tokenStream.match(Tokens.IDENT)){
                    token = tokenStream.token();
                    return new SelectorSubPart(token.value, "elementName", token.startLine, token.startCol);        
                
                } else {
                    return null;
                }
            },
            
            //CSS3 Selectors
            _namespace_prefix: function(){
                /*            
                 * namespace_prefix
                 *   : [ IDENT | '*' ]? '|'
                 *   ;
                 */
                var tokenStream = this._tokenStream,
                    value       = "";
                    
                //verify that this is a namespace prefix
                if (tokenStream.LA(1) === Tokens.PIPE || tokenStream.LA(2) === Tokens.PIPE){
                        
                    if(tokenStream.match([Tokens.IDENT, Tokens.STAR])){
                        value += tokenStream.token().value;
                    }
                    
                    tokenStream.mustMatch(Tokens.PIPE);
                    value += "|";
                    
                }
                
                return value.length ? value : null;                
            },
            
            //CSS3 Selectors
            _universal: function(){
                /*
                 * universal
                 *   : [ namespace_prefix ]? '*'
                 *   ;            
                 */
                var tokenStream = this._tokenStream,
                    value       = "",
                    ns;
                    
                ns = this._namespace_prefix();
                if(ns){
                    value += ns;
                }
                
                if(tokenStream.match(Tokens.STAR)){
                    value += "*";
                }
                
                return value.length ? value : null;
                
           },
            
            //CSS3 Selectors
            _attrib: function(){
                /*
                 * attrib
                 *   : '[' S* [ namespace_prefix ]? IDENT S*
                 *         [ [ PREFIXMATCH |
                 *             SUFFIXMATCH |
                 *             SUBSTRINGMATCH |
                 *             '=' |
                 *             INCLUDES |
                 *             DASHMATCH ] S* [ IDENT | STRING ] S*
                 *         ]? ']'
                 *   ;    
                 */
                 
                var tokenStream = this._tokenStream,
                    value       = null,
                    ns,
                    token;
                
                if (tokenStream.match(Tokens.LBRACKET)){
                    token = tokenStream.token();
                    value = token.value;
                    value += this._readWhitespace();
                    
                    ns = this._namespace_prefix();
                    
                    if (ns){
                        value += ns;
                    }
                                        
                    tokenStream.mustMatch(Tokens.IDENT);
                    value += tokenStream.token().value;                    
                    value += this._readWhitespace();
                    
                    if(tokenStream.match([Tokens.PREFIXMATCH, Tokens.SUFFIXMATCH, Tokens.SUBSTRINGMATCH,
                            Tokens.EQUALS, Tokens.INCLUDES, Tokens.DASHMATCH])){
                    
                        value += tokenStream.token().value;                    
                        value += this._readWhitespace();
                        
                        tokenStream.mustMatch([Tokens.IDENT, Tokens.STRING]);
                        value += tokenStream.token().value;                    
                        value += this._readWhitespace();
                    }
                    
                    tokenStream.mustMatch(Tokens.RBRACKET);
                                        
                    return new SelectorSubPart(value + "]", "attribute", token.startLine, token.startCol);
                } else {
                    return null;
                }
            },
            
            //CSS3 Selectors
            _pseudo: function(){
            
                /*
                 * pseudo
                 *   : ':' ':'? [ IDENT | functional_pseudo ]
                 *   ;    
                 */   
            
                var tokenStream = this._tokenStream,
                    pseudo      = null,
                    colons      = ":",
                    line,
                    col;
                
                if (tokenStream.match(Tokens.COLON)){
                
                    if (tokenStream.match(Tokens.COLON)){
                        colons += ":";
                    }
                
                    if (tokenStream.match(Tokens.IDENT)){
                        pseudo = tokenStream.token().value;
                        line = tokenStream.token().startLine;
                        col = tokenStream.token().startCol - colons.length;
                    } else if (tokenStream.peek() == Tokens.FUNCTION){
                        line = tokenStream.LT(1).startLine;
                        col = tokenStream.LT(1).startCol - colons.length;
                        pseudo = this._functional_pseudo();
                    }
                    
                    if (pseudo){
                        pseudo = new SelectorSubPart(colons + pseudo, "pseudo", line, col);
                    }
                }
        
                return pseudo;
            },
            
            //CSS3 Selectors
            _functional_pseudo: function(){
                /*
                 * functional_pseudo
                 *   : FUNCTION S* expression ')'
                 *   ;
                */            
                
                var tokenStream = this._tokenStream,
                    value = null;
                
                if(tokenStream.match(Tokens.FUNCTION)){
                    value = tokenStream.token().value;
                    value += this._readWhitespace();
                    value += this._expression();
                    tokenStream.mustMatch(Tokens.RPAREN);
                    value += ")";
                }
                
                return value;
            },
            
            //CSS3 Selectors
            _expression: function(){
                /*
                 * expression
                 *   : [ [ PLUS | '-' | DIMENSION | NUMBER | STRING | IDENT ] S* ]+
                 *   ;
                 */
                 
                var tokenStream = this._tokenStream,
                    value       = "";
                    
                while(tokenStream.match([Tokens.PLUS, Tokens.MINUS, Tokens.DIMENSION,
                        Tokens.NUMBER, Tokens.STRING, Tokens.IDENT, Tokens.LENGTH,
                        Tokens.FREQ, Tokens.ANGLE, Tokens.TIME,
                        Tokens.RESOLUTION])){
                    
                    value += tokenStream.token().value;
                    value += this._readWhitespace();                        
                }
                
                return value.length ? value : null;
                
            },

            //CSS3 Selectors
            _negation: function(){
                /*            
                 * negation
                 *   : NOT S* negation_arg S* ')'
                 *   ;
                 */

                var tokenStream = this._tokenStream,
                    line,
                    col,
                    value       = "",
                    arg,
                    subpart     = null;
                    
                if (tokenStream.match(Tokens.NOT)){
                    value = tokenStream.token().value;
                    line = tokenStream.token().startLine;
                    col = tokenStream.token().startCol;
                    value += this._readWhitespace();
                    arg = this._negation_arg();
                    value += arg;
                    value += this._readWhitespace();
                    tokenStream.match(Tokens.RPAREN);
                    value += tokenStream.token().value;
                    
                    subpart = new SelectorSubPart(value, "not", line, col);
                    subpart.args.push(arg);
                }
                
                return subpart;
            },