/* Respond.js: min/max-width media query polyfill. © Scott Jehl. MIT Lic. j.mp/respondjs */ (function( w ){

"use strict";

//exposed namespace
var respond = {};
w.respond = respond;

//define update even in native-mq-supporting browsers, to avoid errors
respond.update = function(){};

//define ajax obj
var requestQueue = [],
        xmlHttp = (function() {
                var xmlhttpmethod = false;
                try {
                        xmlhttpmethod = new w.XMLHttpRequest();
                }
                catch( e ){
                        xmlhttpmethod = new w.ActiveXObject( "Microsoft.XMLHTTP" );
                }
                return function(){
                        return xmlhttpmethod;
                };
        })(),

        //tweaked Ajax functions from Quirksmode
        ajax = function( url, callback ) {
                var req = xmlHttp();
                if (!req){
                        return;
                }
                req.open( "GET", url, true );
                req.onreadystatechange = function () {
                        if ( req.readyState !== 4 || req.status !== 200 && req.status !== 304 ){
                                return;
                        }
                        callback( req.responseText );
                };
                if ( req.readyState === 4 ){
                        return;
                }
                req.send( null );
        },
        isUnsupportedMediaQuery = function( query ) {
                return query.replace( respond.regex.minmaxwh, '' ).match( respond.regex.other );
        };

//expose for testing
respond.ajax = ajax;
respond.queue = requestQueue;
respond.unsupportedmq = isUnsupportedMediaQuery;
respond.regex = {
        media: /@media[^\{]+\{([^\{\}]*\{[^\}\{]*\})+/gi,
        keyframes: /@(?:\-(?:o|moz|webkit)\-)?keyframes[^\{]+\{(?:[^\{\}]*\{[^\}\{]*\})+[^\}]*\}/gi,
        comments: /\/\*[^*]*\*+([^/][^*]*\*+)*\//gi,
        urls: /(url\()['"]?([^\/\)'"][^:\)'"]+)['"]?(\))/g,
        findStyles: /@media *([^\{]+)\{([\S\s]+?)$/,
        only: /(only\s+)?([a-zA-Z]+)\s?/,
        minw: /\(\s*min\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
        maxw: /\(\s*max\-width\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/,
        minmaxwh: /\(\s*m(in|ax)\-(height|width)\s*:\s*(\s*[0-9\.]+)(px|em)\s*\)/gi,
        other: /\([^\)]*\)/g
};

//expose media query support flag for external use
respond.mediaQueriesSupported = w.matchMedia && w.matchMedia( "only all" ) !== null && w.matchMedia( "only all" ).matches;

//if media queries are supported, exit here
if( respond.mediaQueriesSupported ){
        return;
}

//define vars
var doc = w.document,
        docElem = doc.documentElement,
        mediastyles = [],
        rules = [],
        appendedEls = [],
        parsedSheets = {},
        resizeThrottle = 30,
        head = doc.getElementsByTagName( "head" )[0] || docElem,
        base = doc.getElementsByTagName( "base" )[0],
        links = head.getElementsByTagName( "link" ),

        lastCall,
        resizeDefer,

        //cached container for 1em value, populated the first time it's needed
        eminpx,

        // returns the value of 1em in pixels
        getEmValue = function() {
                var ret,
                        div = doc.createElement('div'),
                        body = doc.body,
                        originalHTMLFontSize = docElem.style.fontSize,
                        originalBodyFontSize = body && body.style.fontSize,
                        fakeUsed = false;

                div.style.cssText = "position:absolute;font-size:1em;width:1em";

                if( !body ){
                        body = fakeUsed = doc.createElement( "body" );
                        body.style.background = "none";
                }

                // 1em in a media query is the value of the default font size of the browser
                // reset docElem and body to ensure the correct value is returned
                docElem.style.fontSize = "100%";
                body.style.fontSize = "100%";

                body.appendChild( div );

                if( fakeUsed ){
                        docElem.insertBefore( body, docElem.firstChild );
                }

                ret = div.offsetWidth;

                if( fakeUsed ){
                        docElem.removeChild( body );
                }
                else {
                        body.removeChild( div );
                }

                // restore the original values
                docElem.style.fontSize = originalHTMLFontSize;
                if( originalBodyFontSize ) {
                        body.style.fontSize = originalBodyFontSize;
                }

                //also update eminpx before returning
                ret = eminpx = parseFloat(ret);

                return ret;
        },

        //enable/disable styles
        applyMedia = function( fromResize ){
                var name = "clientWidth",
                        docElemProp = docElem[ name ],
                        currWidth = doc.compatMode === "CSS1Compat" && docElemProp || doc.body[ name ] || docElemProp,
                        styleBlocks     = {},
                        lastLink = links[ links.length-1 ],
                        now = (new Date()).getTime();

                //throttle resize calls
                if( fromResize && lastCall && now - lastCall < resizeThrottle ){
                        w.clearTimeout( resizeDefer );
                        resizeDefer = w.setTimeout( applyMedia, resizeThrottle );
                        return;
                }
                else {
                        lastCall = now;
                }

                for( var i in mediastyles ){
                        if( mediastyles.hasOwnProperty( i ) ){
                                var thisstyle = mediastyles[ i ],
                                        min = thisstyle.minw,
                                        max = thisstyle.maxw,
                                        minnull = min === null,
                                        maxnull = max === null,
                                        em = "em";

                                if( !!min ){
                                        min = parseFloat( min ) * ( min.indexOf( em ) > -1 ? ( eminpx || getEmValue() ) : 1 );
                                }
                                if( !!max ){
                                        max = parseFloat( max ) * ( max.indexOf( em ) > -1 ? ( eminpx || getEmValue() ) : 1 );
                                }

                                // if there's no media query at all (the () part), or min or max is not null, and if either is present, they're true
                                if( !thisstyle.hasquery || ( !minnull || !maxnull ) && ( minnull || currWidth >= min ) && ( maxnull || currWidth <= max ) ){
                                        if( !styleBlocks[ thisstyle.media ] ){
                                                styleBlocks[ thisstyle.media ] = [];
                                        }
                                        styleBlocks[ thisstyle.media ].push( rules[ thisstyle.rules ] );
                                }
                        }
                }

                //remove any existing respond style element(s)
                for( var j in appendedEls ){
                        if( appendedEls.hasOwnProperty( j ) ){
                                if( appendedEls[ j ] && appendedEls[ j ].parentNode === head ){
                                        head.removeChild( appendedEls[ j ] );
                                }
                        }
                }
                appendedEls.length = 0;

                //inject active styles, grouped by media type
                for( var k in styleBlocks ){
                        if( styleBlocks.hasOwnProperty( k ) ){
                                var ss = doc.createElement( "style" ),
                                        css = styleBlocks[ k ].join( "\n" );

                                ss.type = "text/css";
                                ss.media = k;

                                //originally, ss was appended to a documentFragment and sheets were appended in bulk.
                                //this caused crashes in IE in a number of circumstances, such as when the HTML element had a bg image set, so appending beforehand seems best. Thanks to @dvelyk for the initial research on this one!
                                head.insertBefore( ss, lastLink.nextSibling );

                                if ( ss.styleSheet ){
                                        ss.styleSheet.cssText = css;
                                }
                                else {
                                        ss.appendChild( doc.createTextNode( css ) );
                                }

                                //push to appendedEls to track for later removal
                                appendedEls.push( ss );
                        }
                }
        },
        //find media blocks in css text, convert to style blocks
        translate = function( styles, href, media ){
                var qs = styles.replace( respond.regex.comments, '' )
                                .replace( respond.regex.keyframes, '' )
                                .match( respond.regex.media ),
                        ql = qs && qs.length || 0;

                //try to get CSS path
                href = href.substring( 0, href.lastIndexOf( "/" ) );

                var repUrls = function( css ){
                                return css.replace( respond.regex.urls, "$1" + href + "$2$3" );
                        },
                        useMedia = !ql && media;

                //if path exists, tack on trailing slash
                if( href.length ){ href += "/"; }

                //if no internal queries exist, but media attr does, use that
                //note: this currently lacks support for situations where a media attr is specified on a link AND
                        //its associated stylesheet has internal CSS media queries.
                        //In those cases, the media attribute will currently be ignored.
                if( useMedia ){
                        ql = 1;
                }

                for( var i = 0; i < ql; i++ ){
                        var fullq, thisq, eachq, eql;

                        //media attr
                        if( useMedia ){
                                fullq = media;
                                rules.push( repUrls( styles ) );
                        }
                        //parse for styles
                        else{
                                fullq = qs[ i ].match( respond.regex.findStyles ) && RegExp.$1;
                                rules.push( RegExp.$2 && repUrls( RegExp.$2 ) );
                        }

                        eachq = fullq.split( "," );
                        eql = eachq.length;

                        for( var j = 0; j < eql; j++ ){
                                thisq = eachq[ j ];

                                if( isUnsupportedMediaQuery( thisq ) ) {
                                        continue;
                                }

                                mediastyles.push( {
                                        media : thisq.split( "(" )[ 0 ].match( respond.regex.only ) && RegExp.$2 || "all",
                                        rules : rules.length - 1,
                                        hasquery : thisq.indexOf("(") > -1,
                                        minw : thisq.match( respond.regex.minw ) && parseFloat( RegExp.$1 ) + ( RegExp.$2 || "" ),
                                        maxw : thisq.match( respond.regex.maxw ) && parseFloat( RegExp.$1 ) + ( RegExp.$2 || "" )
                                } );
                        }
                }

                applyMedia();
        },

        //recurse through request queue, get css text
        makeRequests = function(){
                if( requestQueue.length ){
                        var thisRequest = requestQueue.shift();

                        ajax( thisRequest.href, function( styles ){
                                translate( styles, thisRequest.href, thisRequest.media );
                                parsedSheets[ thisRequest.href ] = true;

                                // by wrapping recursive function call in setTimeout
                                // we prevent "Stack overflow" error in IE7
                                w.setTimeout(function(){ makeRequests(); },0);
                        } );
                }
        },

        //loop stylesheets, send text content to translate
        ripCSS = function(){

                for( var i = 0; i < links.length; i++ ){
                        var sheet = links[ i ],
                        href = sheet.href,
                        media = sheet.media,
                        isCSS = sheet.rel && sheet.rel.toLowerCase() === "stylesheet";

                        //only links plz and prevent re-parsing
                        if( !!href && isCSS && !parsedSheets[ href ] ){
                                // selectivizr exposes css through the rawCssText expando
                                if (sheet.styleSheet && sheet.styleSheet.rawCssText) {
                                        translate( sheet.styleSheet.rawCssText, href, media );
                                        parsedSheets[ href ] = true;
                                } else {
                                        if( (!/^([a-zA-Z:]*\/\/)/.test( href ) && !base) ||
                                                href.replace( RegExp.$1, "" ).split( "/" )[0] === w.location.host ){
                                                // IE7 doesn't handle urls that start with '//' for ajax request
                                                // manually add in the protocol
                                                if ( href.substring(0,2) === "//" ) { href = w.location.protocol + href; }
                                                requestQueue.push( {
                                                        href: href,
                                                        media: media
                                                } );
                                        }
                                }
                        }
                }
                makeRequests();
        };

//translate CSS
ripCSS();

//expose update for re-running respond later on
respond.update = ripCSS;

//expose getEmValue
respond.getEmValue = getEmValue;

//adjust on resize
function callMedia(){
        applyMedia( true );
}

if( w.addEventListener ){
        w.addEventListener( "resize", callMedia, false );
}
else if( w.attachEvent ){
        w.attachEvent( "onresize", callMedia );
}

})(this);