/* 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);