/**
 * 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;
};