/**
 * jQuery-Plugin "preloadCssImages"
 * by Scott Jehl, scott@filamentgroup.com
 * http://www.filamentgroup.com
 * reference article: http://www.filamentgroup.com/lab/update_automatically_preload_images_from_css_with_jquery/
 * demo page: http://www.filamentgroup.com/examples/preloadImages/index_v2.php
 *
 * Copyright (c) 2008 Filament Group, Inc
 * Dual licensed under the MIT (filamentgroup.com/examples/mit-license.txt) and GPL (filamentgroup.com/examples/gpl-license.txt) licenses.
 *
 * Version: 5.0, 10.31.2008
 * Changelog:
 *         02.20.2008 initial Version 1.0
 *    06.04.2008 Version 2.0 : removed need for any passed arguments. Images load from any and all directories.
 *    06.21.2008 Version 3.0 : Added options for loading status. Fixed IE abs image path bug (thanks Sam Pohlenz).
 *    07.24.2008 Version 4.0 : Added support for @imported CSS (credit: http://marcarea.com/). Fixed support in Opera as well.
 *    10.31.2008 Version: 5.0 : Many feature and performance enhancements from trixta
 * --------------------------------------------------------------------
 */

;jQuery.preloadCssImages = function(settings){
        settings = jQuery.extend({
                statusTextEl: null,
                statusBarEl: null,
                errorDelay: 999, // handles 404-Errors in IE
                simultaneousCacheLoading: 2
        }, settings);
        var allImgs = [],
                loaded = 0,
                imgUrls = [],
                thisSheetRules,
                errorTimer;

        function onImgComplete(){
                clearTimeout(errorTimer);
                if (imgUrls && imgUrls.length && imgUrls[loaded]) {
                        loaded++;
                        if (settings.statusTextEl) {
                                var nowloading = (imgUrls[loaded]) ?
                                        'Now Loading: <span>' + imgUrls[loaded].split('/')[imgUrls[loaded].split('/').length - 1] :
                                        'Loading complete'; // wrong status-text bug fixed
                                jQuery(settings.statusTextEl).html('<span class="numLoaded">' + loaded + '</span> of <span class="numTotal">' + imgUrls.length + '</span> loaded (<span class="percentLoaded">' + (loaded / imgUrls.length * 100).toFixed(0) + '%</span>) <span class="currentImg">' + nowloading + '</span></span>');
                        }
                        if (settings.statusBarEl) {
                                var barWidth = jQuery(settings.statusBarEl).width();
                                jQuery(settings.statusBarEl).css('background-position', -(barWidth - (barWidth * loaded / imgUrls.length).toFixed(0)) + 'px 50%');
                        }
                        loadImgs();
                }
        }

        function loadImgs(){
                //only load 1 image at the same time / most browsers can only handle 2 http requests, 1 should remain for user-interaction (Ajax, other images, normal page requests...)
                // otherwise set simultaneousCacheLoading to a higher number for simultaneous downloads
                if(imgUrls && imgUrls.length && imgUrls[loaded]){
                        var img = new Image(); //new img obj
                        img.src = imgUrls[loaded];        //set src either absolute or rel to css dir
                        if(!img.complete){
                                jQuery(img).bind('error load onreadystatechange', onImgComplete);
                        } else {
                                onImgComplete();
                        }
                        errorTimer = setTimeout(onImgComplete, settings.errorDelay); // handles 404-Errors in IE
                }
        }

        function parseCSS(sheets, urls) {
                var w3cImport = false,
                        imported = [],
                        importedSrc = [],
                        baseURL;
                var sheetIndex = sheets.length;
                while(sheetIndex--){//loop through each stylesheet

                        var cssPile = '';//create large string of all css rules in sheet

                        if(urls && urls[sheetIndex]){
                                baseURL = urls[sheetIndex];
                        } else {
                                var csshref = (sheets[sheetIndex].href) ? sheets[sheetIndex].href : 'window.location.href';
                                var baseURLarr = csshref.split('/');//split href at / to make array
                                baseURLarr.pop();//remove file path from baseURL array
                                baseURL = baseURLarr.join('/');//create base url for the images in this sheet (css file's dir)
                                if (baseURL) {
                                        baseURL += '/'; //tack on a / if needed
                                }
                        }
                        var allowStylesheetAccess = false;
                                 try {
                                 if (sheets[sheetIndex].cssRules)
                                 allowStylesheetAccess = true;
                                 }
                         catch (e) {
                         var ex = e;
                         }
                        if (!allowStylesheetAccess) continue;
                        if(sheets[sheetIndex].cssRules || sheets[sheetIndex].rules){
                                thisSheetRules = (sheets[sheetIndex].cssRules) ? //->>> http://www.quirksmode.org/dom/w3c_css.html
                                        sheets[sheetIndex].cssRules : //w3
                                        sheets[sheetIndex].rules; //ie
                                var ruleIndex = thisSheetRules.length;
                                while(ruleIndex--){
                                        if(thisSheetRules[ruleIndex].style && thisSheetRules[ruleIndex].style.cssText){
                                                var text = thisSheetRules[ruleIndex].style.cssText;
                                                if(text.toLowerCase().indexOf('url') != -1){ // only add rules to the string if you can assume, to find an image, speed improvement
                                                        cssPile += text; // thisSheetRules[ruleIndex].style.cssText instead of thisSheetRules[ruleIndex].cssText is a huge speed improvement
                                                }
                                        } else if(thisSheetRules[ruleIndex].styleSheet) {
                                                imported.push(thisSheetRules[ruleIndex].styleSheet);
                                                w3cImport = true;
                                        }

                                }
                        }
                        //parse cssPile for image urls
                        var tmpImage = cssPile.match(/[^\("]+\.(gif|jpg|jpeg|png)/g);//reg ex to get a string of between a "(" and a ".filename" / '"' for opera-bugfix
                        if(tmpImage){
                                var i = tmpImage.length;
                                while(i--){ // handle baseUrl here for multiple stylesheets in different folders bug
                                        var imgSrc = (tmpImage[i].charAt(0) == '/' || tmpImage[i].match('://')) ? // protocol-bug fixed
                                                tmpImage[i] :
                                                baseURL + tmpImage[i];

                                        if(jQuery.inArray(imgSrc, imgUrls) == -1){
                                                imgUrls.push(imgSrc);
                                        }
                                }
                        }

                        if(!w3cImport && sheets[sheetIndex].imports && sheets[sheetIndex].imports.length) {
                                for(var iImport = 0, importLen = sheets[sheetIndex].imports.length; iImport < importLen; iImport++){
                                        var iHref = sheets[sheetIndex].imports[iImport].href;
                                        iHref = iHref.split('/');
                                        iHref.pop();
                                        iHref = iHref.join('/');
                                        if (iHref) {
                                                iHref += '/'; //tack on a / if needed
                                        }
                                        var iSrc = (iHref.charAt(0) == '/' || iHref.match('://')) ? // protocol-bug fixed
                                                iHref :
                                                baseURL + iHref;

                                        importedSrc.push(iSrc);
                                        imported.push(sheets[sheetIndex].imports[iImport]);
                                }


                        }
                }//loop
                if(imported.length){
                        parseCSS(imported, importedSrc);
                        return false;
                }
                var downloads = settings.simultaneousCacheLoading;
                while( downloads--){
                        setTimeout(loadImgs, downloads);
                }
        }
        parseCSS(document.styleSheets);
        return imgUrls;
};