/**
* @author Alexander Farkas
* v. 1.21
*/

(function ($) {
   if (!document.defaultView || !document.defaultView.getComputedStyle) { // IE6-IE8
      var oldCurCSS = jQuery.curCSS;
      jQuery.curCSS = function (elem, name, force) {
         if (name === 'background-position') {
            name = 'backgroundPosition';
         }
         if (name !== 'backgroundPosition' || !elem.currentStyle || elem.currentStyle[name]) {
            return oldCurCSS.apply(this, arguments);
         }
         var style = elem.style;
         if (!force && style && style[name]) {
            return style[name];
         }
         return oldCurCSS(elem, 'backgroundPositionX', force) + ' ' + oldCurCSS(elem, 'backgroundPositionY', force);
      };
   }

   var oldAnim = $.fn.animate;
   $.fn.animate = function (prop) {
      if ('background-position' in prop) {
         prop.backgroundPosition = prop['background-position'];
         delete prop['background-position'];
      }
      if ('backgroundPosition' in prop) {
         prop.backgroundPosition = '(' + prop.backgroundPosition;
      }
      return oldAnim.apply(this, arguments);
   };

   function toArray(strg) {
      strg = strg.replace(/left|top/g, '0px');
      strg = strg.replace(/right|bottom/g, '100%');
      strg = strg.replace(/([0-9\.]+)(\s|\)|$)/g, "$1px$2");
      var res = strg.match(/(-?[0-9\.]+)(px|\%|em|pt)\s(-?[0-9\.]+)(px|\%|em|pt)/);
      return [parseFloat(res[1], 10), res[2], parseFloat(res[3], 10), res[4]];
   }

   $.fx.step.backgroundPosition = function (fx) {
      if (!fx.bgPosReady) {
         var start = $.curCSS(fx.elem, 'backgroundPosition');

         if (!start) {//FF2 no inline-style fallback
            start = '0px 0px';
         }

         start = toArray(start);

         fx.start = [start[0], start[2]];

         var end = toArray(fx.options.curAnim.backgroundPosition);
         fx.end = [end[0], end[2]];

         fx.unit = [end[1], end[3]];
         fx.bgPosReady = true;
      }
      //return;
      var nowPosX = [];
      nowPosX[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
      nowPosX[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];
      fx.elem.style.backgroundPosition = nowPosX[0] + ' ' + nowPosX[1];

   };
})(jQuery);