/* Respond.js: min/max-width media query polyfill. (c) 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);