/**
 * 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
                }
            }
            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;
};