/* Copyright (c) 2006 Brandon Aaron (http://brandonaaron.net)
 * Dual licensed under the MIT (http://www.opensource.org/licenses/mit-license.php) 
 * and GPL (http://www.opensource.org/licenses/gpl-license.php) licenses.
 * Thanks to: http://adomas.org/javascript-mouse-wheel/ for some pointers.
 * Thanks to: Mathias Bank(http://www.mathias-bank.de) for a scope bug fix.
 */

jQuery.fn.extend({
   /**
    * Apply the mousewheel event to the elements in the jQuery object.
    * The handler function should be prepared to take the event object
    * and a param called 'delta'. The 'delta' param is a number
    * either > 0 or < 0. > 0 = up and < 0 = down.
    *
    * Firefox and Opera has some issues preventing default and just using
    * event.preventDefault() will not work. Instead if you need
    * to prevent the default action, just pass in 'true' for the preventDefault
    * param.
    *
    * Only one handler function should be used per an element. 
    * Meaning call $().mousewheel only once per an element.
    *
    * @example $("p").mousewheel(function(event, delta){
    *   if (delta > 0)
    *     // do something on mousewheel scroll up
    *   else if (delta < 0)
    *     //do something on mousewheel scroll down
    * });
    *
    * @name mousewheel
    * @type jQuery
    * @param Function handler The function to call when onmousewheel fires. Should take two params: event and delta.
    * @param Boolean preventDefault Should the default action be prevented?
    * @cat Events
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   /**
    * Apply the mousewheel event to the elements in the jQuery object.
    * The up and down handler functions should be prepared to take the 
    * event object and a param called 'delta'. The 'delta' param is a number
    * either > 0 or < 0. > 0 = up and < 0 = down.
    *
    * Firefox and Opera has some issues preventing default and just using
    * event.preventDefault() will not work. Instead if you need
    * to prevent the default action, just pass in 'true' for the preventDefault
    * param.
    *
    * The method takes two functions. The first is fired only on when the
    * mousewheel is moved up. The second is fired only when the mouswheel is 
    * moved down.
    *
    * Only one handler function should be used per an element. 
    * Meaning call $().mousewheel only once per an element.
    *
    * @example $("p").mousewheel(function(event, delta){
    *   // do something on mousewheel scroll up
    * }, function(event, delta) {
    *   // do something on mousewheel scroll down
    * });
    *
    * @name mousewheel
    * @type jQuery
    * @param Function upHandler The function to call when the mousewheel is moved up. Should take two params: event and delta.
    * @param Function downHandler The function to call when the mousewheel is moved down. Should take two params: event and delta.
    * @param Boolean preventDefault Should the default action be prevented?
    * @cat Events
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   mousewheel: function(up, down, preventDefault) {
      return this.hover(
         function() {
            jQuery.event.mousewheel.giveFocus(this, up, down, preventDefault);
         },
         function() {
            jQuery.event.mousewheel.removeFocus(this);
         }
      );
   },
   
   /**
    * Apply the mousewheeldown event to the elements in the jQuery object.
    * The handler function should be prepared to take the event object
    * and a param called 'delta'. The 'delta' param is a number
    * either > 0 or < 0. > 0 = up and < 0 = down.
    *
    * The handler function is only called if the mousewheel is moved down.
    *
    * Firefox and Opera has some issues preventing default and just using
    * event.preventDefault() will not work. Instead if you need
    * to prevent the default action, just pass in 'true' for the preventDefault
    * param.
    *
    * Only one handler function should be used per an element. 
    * Meaning call $().mousewheel only once per an element. This will
    * overwrite any previous mousewheel event, even a mousewheelup event.
    * To get a seperate up and down function just use mousewheel and pass
    * two functions: the first is the up handler and the second is the 
    * down handler.
    *
    * @example $("p").mousewheeldown(function(event, delta){
    *   //do something on mousewheel scroll down
    * });
    *
    * @name mousewheeldown
    * @type jQuery
    * @param Function handler The function to call when the mousewheel is moved down. Should take two params: event and delta.
    * @param Boolean preventDefault Should the default action be prevented?
    * @cat Events
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   mousewheeldown: function(fn, preventDefault) {
      return this.mousewheel(function(){}, fn, preventDefault);
   },
   
   /**
    * Apply the mousewheelup event to the elements in the jQuery object.
    * The handler function should be prepared to take the event object
    * and a param called 'delta'. The 'delta' param is a number
    * either > 0 or < 0. > 0 = up and < 0 = down.
    *
    * The handler function is only called if the mousewheel is moved down.
    *
    * Firefox and Opera has some issues preventing default and just using
    * event.preventDefault() will not work. Instead if you need
    * to prevent the default action, just pass in 'true' for the preventDefault
    * param.
    *
    * Only one handler function should be used per an element. 
    * Meaning call $().mousewheel only once per an element. This will
    * overwrite any previous mousewheel event, even a mousewheeldown event.
    * To get a seperate up and down function just use mousewheel and pass
    * two functions: the first is the up handler and the second is the 
    * down handler.
    *
    * @example $("p").mousewheeldown(function(event, delta){
    *   //do something on mousewheel scroll down
    * });
    *
    * @name mousewheelup
    * @type jQuery
    * @param Function handler The function to call when the mousewheel is moved up. Should take two params: event and delta.
    * @param Boolean preventDefault Should the default action be prevented?
    * @cat Events
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   mousewheelup: function(fn, preventDefault) {
      return this.mousewheel(fn, function(){}, preventDefault);
   },
   
   /**
    * This method removes the applied mousewheel event from the elements
    * in the jQuery object. The $().mousewheel and $().unmousewheel is only
    * capable of handling one handler function per an element. Therefore,
    * there is no need to pass anything to this method.
    *
    * @name unmousewheel
    * @type jQuery
    * @cat Events
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   unmousewheel: function() {
      return this.each(function() {
         jQuery(this).unmouseover().unmouseout();
         jQuery.event.mousewheel.removeFocus(this);
      });
   },

   /**
    * This method removes the applied mousewheel event from the elements
    * in the jQuery object. The $().mousewheel and $().unmousewheel is only
    * capable of handling one handler function per an element. Therefore,
    * there is no need to pass anything to this method.
    *
    * @name unmousewheeldown
    * @type jQuery
    * @cat Events
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   unmousewheeldown: jQuery.fn.unmousewheel,
   
   /**
    * This method removes the applied mousewheel event from the elements
    * in the jQuery object. The $().mousewheel and $().unmousewheel is only
    * capable of handling one handler function per an element. Therefore,
    * there is no need to pass anything to this method.
    *
    * @name unmousewheelup
    * @type jQuery
    * @cat Events
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   unmousewheelup: jQuery.fn.unmousewheel
});


/**
 * The manager for the mousewheel event.
 * Handles the switching of focus for the
 * different elements that have the
 * mousewheel event attached to them.
 *
 * @private
 * @cat Core   
 * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
 */
jQuery.event.mousewheel = {
   /**
    * Give the element passed the mousewheel event focus.
    * If the element already has mousewheel events attached
    * to it, they will be removed before adding them back.
    *
    * @private
    * @name giveFocus
    * @param HTMLElement element The DOM node to apply the mousewheel event too.
    * @param Function handler The function to call when onmousewheel fires.
    * @param Boolean preventDefault Should the default action be prevented?.
    * @see jQuery.fn.mousewheel
    * @cat Core
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   giveFocus: function(el, up, down, preventDefault) {
//      if (el._handleMousewheel) jQuery(el).unmousewheel();
      
      if (preventDefault == window.undefined && down && down.constructor != Function) {
         preventDefault = down;
         down = null;
      }
      
      if (!el._handleMousewheel) {
         el._handleMousewheel = function(event) {
            if (!event) event = window.event;
            if (preventDefault) // cannot call any methods before preventing default (firefox)
               if (event.preventDefault) event.preventDefault();
               else event.returnValue = false;
            var delta = 0;
            if (event.wheelDelta) {
               delta = event.wheelDelta/120;
               if (window.opera) delta = -delta;
            } else if (event.detail) {
               delta = -event.detail/3;
            }
            if (up && (delta > 0 || !down))
               up.apply(el, [event, delta]);
            else if (down && delta < 0)
               down.apply(el, [event, delta]);
         };
      }
      
      if (window.addEventListener)
         window.addEventListener('DOMMouseScroll', el._handleMousewheel, false);
      window.onmousewheel = document.onmousewheel = el._handleMousewheel;
   },
   
   /**
    * Removes the mousewheel event focus from the
    * element passed in.
    *
    * @private
    * @name removeFocus
    * @see jQuery.fn.unmousewheel
    * @cat Core
    * @author Brandon Aaron (brandon.aaron@gmail.com || http://brandonaaron.net)
    */
   removeFocus: function(el) {
      if (!el._handleMousewheel) return;
      
      if (window.removeEventListener)
         window.removeEventListener('DOMMouseScroll', el._handleMousewheel, false);
      window.onmousewheel = document.onmousewheel = null;
      el._handleMousewheel = null;
   }
};