/* ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is CssHackz.
 *
 * The Initial Developer of the Original Code is
 * Disruptive Innovations SARL.
 * Portions created by the Initial Developer are Copyright (C) 2009
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Daniel Glazman <daniel.glazman@disruptive-innovations.com>, Original author
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */
 
 var CssHackz = {

  mStylesheetLinks: [],

  init: function()
  {
    var links = document.getElementsByTagName("link");
    for (var i = 0; i < links.length; i++)
    {
      var l = links[i];
      if (l.getAttribute("rel")  == "stylesheet" &&
          l.getAttribute("type") == "text/css")
      {
        this.mStylesheetLinks.push( { url:   l.href,
                                      media: l.getAttribute("media"),
                                      elt:   l } );
      }
    }
    var ajaxRequest;

    var requestCallback = function(aRequest, aLink) {

      var ENDIF_IMPL_STR = "@endif-implemented;"; // IE does not know const...

      if (ajaxRequest.readyState == 4)
      {
        if (ajaxRequest.status == 200)
        {
          var cssText = ajaxRequest.responseText;
          var newCssText = "";
          var index = 0;
          while (true)
          {
            var newIndex = cssText.indexOf("@if-implemented", index);
            if (newIndex == -1)
            {
              if (index < cssText.length)
                newCssText += cssText.substr(index);
              break;
            }
            newCssText += cssText.substring(index, newIndex);
            index = newIndex;

            var parametersRegexp = /@if-implemented\s*{([^}]*)}([^@]*)@/ ;
            parametersRegexp.lastIndex = index;
            var match = parametersRegexp.exec(cssText);
            if (!match)
            {
              alert("CssHackz error, cannot parse");
              return;
            }

            var declarations = match[1];
            var ifCases = match[2];
            var elseCases = "";

            index += match[0].length - 1;

            var elseIndex  = cssText.indexOf("@else-implemented;", index);
            var endifIndex = cssText.indexOf(ENDIF_IMPL_STR, index);
            if (endifIndex == -1 ||
                (elseIndex != index && endifIndex != index))
            {
              alert("CssHackz error, cannot parse");
              return;
            }
            if (endifIndex != index)
            {
              var elsecaseRegexp = /@else-implemented\s*;\s*([^@]*)@/ ;
              elsecaseRegexp.lastIndex = index;
              match = elsecaseRegexp.exec(cssText);
              if (!match)
              {
                alert("CssHackz error, cannot parse");
                return;
              }
              elseCases = match[1];
              index += match[0].length - 1;
            }

            if (cssText.substr(index, ENDIF_IMPL_STR.length) != ENDIF_IMPL_STR)
            {
              alert("CssHackz error, cannot parse");
              return;
            }
            index += ENDIF_IMPL_STR.length;

            newCssText += CssHackz.applicableDeclarations(declarations) ?
                            ifCases : elseCases;
          }

          var style = document.createElement("style");
          style.setAttribute("type", "text/css");


          if (aLink.media)
            style.setAttribute("media", aLink.media);
          if (style.styleSheet)
          {   // IE, big piece of crap, cannot insert a text node as child
              // of a style element !!! Unbelievable... Even IE8...
              style.styleSheet.cssText = newCssText;
          }
          else
          {
            var cdata = document.createTextNode(newCssText);
            style.appendChild(cdata);
          }
          aLink.elt.parentNode.insertBefore(style, aLink.elt);
          aLink.elt.parentNode.removeChild(aLink.elt);
        }
        else
        {
          alert("I can't retrieve the source of the stylesheet, sorry");
        }
      }
    };

    for (var i = 0; i < this.mStylesheetLinks.length; i++)
    {
      l = this.mStylesheetLinks[i];
      var url = l.url;

      if (window.XMLHttpRequest)
      {
        ajaxRequest = new XMLHttpRequest();
        ajaxRequest.onreadystatechange = function() { requestCallback(ajaxRequest, l); }

        ajaxRequest.open("GET", url, true);
        ajaxRequest.setRequestHeader("Content-type", "type/plain");
        ajaxRequest.send(null);
      }
      else if (window.ActiveXObject)
      {
        // ie
        ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");
        if (ajaxRequest) {
          ajaxRequest.onreadystatechange = function() { requestCallback(ajaxRequest, l); };
          ajaxRequest.open("GET", url, true);
          ajaxRequest.send();
        }
      }
    }
  },

  applicableDeclarations: function(aDeclarations)
  {
    var declArray = aDeclarations.split(";");
    var span = document.createElement("span");
    for (var i = 0 ; i < declArray.length; i++)
    {
      span.removeAttribute("style");
      span.setAttribute("style", declArray[i]);
      var a = declArray[i].split(":")[0].replace( /^\s*/g , "" ).replace( /\s*$/g , "" );

      if (span.style.getPropertyValue)
      {
        if (!span.style.getPropertyValue(a))
          return false;
      }
      else
      { // IE, again big piece of...
        if (!span.style.cssText)
          return false;
      }
    }
    return true;
  }
};