/* ************************************************************************

   qooxdoo - the new era of web development

   http://qooxdoo.org

   Copyright:
     2007-2008 1&1 Internet AG, Germany, http://www.1und1.de

   License:
     LGPL: http://www.gnu.org/licenses/lgpl.html
     EPL: http://www.eclipse.org/org/documents/epl-v10.php
     See the LICENSE file in the project's top-level directory for details.

   Authors:
     * Fabian Jakobs (fjakobs)
     * Sebastian Werner (wpbasti)
     * Alexander Steitz (aback)
     * Christian Hagendorn (chris_schmidt)

   ======================================================================

   This class contains code based on the following work:

   * Juriy Zaytsev
     http://thinkweb2.com/projects/prototype/detecting-event-support-without-browser-sniffing/

     Copyright (c) 2009 Juriy Zaytsev

     Licence:
       BSD: http://github.com/kangax/iseventsupported/blob/master/LICENSE

     ----------------------------------------------------------------------

     http://github.com/kangax/iseventsupported/blob/master/LICENSE

     Copyright (c) 2009 Juriy Zaytsev

     Permission is hereby granted, free of charge, to any person
     obtaining a copy of this software and associated documentation
     files (the "Software"), to deal in the Software without
     restriction, including without limitation the rights to use,
     copy, modify, merge, publish, distribute, sublicense, and/or sell
     copies of the Software, and to permit persons to whom the
     Software is furnished to do so, subject to the following
     conditions:

     The above copyright notice and this permission notice shall be
     included in all copies or substantial portions of the Software.

     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
     OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
     HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
     WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
     OTHER DEALINGS IN THE SOFTWARE.

************************************************************************ */

/**
 * Wrapper around native event management capabilities of the browser.
 * This class should not be used directly normally. It's better
 * to use {@link qx.event.Registration} instead.
 */
qx.Bootstrap.define("qx.bom.Event",
{
  statics :
  {
    /**
     * Use the low level browser functionality to attach event listeners
     * to DOM nodes.
     *
     * Use this with caution. This is only thought for event handlers and
     * qualified developers. These are not mem-leak protected!
     *
     * @param target {Object} Any valid native event target
     * @param type {String} Name of the event
     * @param listener {Function} The pointer to the function to assign
     * @param useCapture {Boolean ? false} A Boolean value that specifies the event phase to add
     *    the event handler for the capturing phase or the bubbling phase.
     */
    addNativeListener : function(target, type, listener, useCapture)
    {
      if (target.addEventListener) {
        target.addEventListener(type, listener, !!useCapture);
      } else if (target.attachEvent) {
        target.attachEvent("on" + type, listener);
      } else if (typeof target["on" + type] != "undefined") {
        target["on" + type] = listener;
      } else {
        if (qx.core.Environment.get("qx.debug")) {
          qx.log.Logger.warn("No method available to add native listener to " + target);
        }
      }
    },


    /**
     * Use the low level browser functionality to remove event listeners
     * from DOM nodes.
     *
     * @param target {Object} Any valid native event target
     * @param type {String} Name of the event
     * @param listener {Function} The pointer to the function to assign
     * @param useCapture {Boolean ? false} A Boolean value that specifies the event phase to remove
     *    the event handler for the capturing phase or the bubbling phase.
     */
    removeNativeListener : function(target, type, listener, useCapture)
    {
      if (target.removeEventListener)
      {
        target.removeEventListener(type, listener, !!useCapture);
      }
      else if (target.detachEvent)
      {
        try {
          target.detachEvent("on" + type, listener);
        }
        catch(e)
        {
          // IE7 sometimes dispatches "unload" events on protected windows
          // Ignore the "permission denied" errors.
          if(e.number !== -2146828218) {
            throw e;
          };
        }
      }
      else if (typeof target["on" + type] != "undefined")
      {
        target["on" + type] = null;
      }
      else
      {
        if (qx.core.Environment.get("qx.debug")) {
          qx.log.Logger.warn("No method available to remove native listener from " + target);
        }
      }
    },


    /**
     * Returns the target of the event.
     *
     * @param e {Event} Native event object
     * @return {Object} Any valid native event target
     */
    getTarget : function(e) {
      return e.target || e.srcElement;
    },


    /**
     * Computes the related target from the native DOM event
     *
     * @param e {Event} Native DOM event object
     * @return {Element} The related target
     */
    getRelatedTarget : function(e)
    {
      if (e.relatedTarget !== undefined)
      {
        // In Firefox the related target of mouse events is sometimes an
        // anonymous div inside of a text area, which raises an exception if
        // the nodeType is read. This is why the try/catch block is needed.
        if ((qx.core.Environment.get("engine.name") == "gecko"))
        {
          try {
            e.relatedTarget && e.relatedTarget.nodeType;
          } catch (ex) {
            return null;
          }
        }

        return e.relatedTarget;
      }
      else if (e.fromElement !== undefined && e.type === "mouseover") {
        return e.fromElement;
      } else if (e.toElement !== undefined) {
        return e.toElement;
      } else {
        return null;
      }
    },


    /**
     * Prevent the native default of the event to be processed.
     *
     * This is useful to stop native keybindings, native selection
     * and other native functionality behind events.
     *
     * @param e {Event} Native event object
     */
    preventDefault : function(e)
    {
      if (e.preventDefault) {
        e.preventDefault();
      }
      else {
        try {
          // this allows us to prevent some key press events in IE.
          // See bug #1049
          e.keyCode = 0;
        } catch(ex) {}

        e.returnValue = false;
      }
    },


    /**
     * Stops the propagation of the given event to the parent element.
     *
     * Only useful for events which bubble e.g. mousedown.
     *
     * @param e {Event} Native event object
     */
    stopPropagation : function(e)
    {
      if (e.stopPropagation) {
        e.stopPropagation();
      } else {
        e.cancelBubble = true;
      }
    },


    /**
     * Fires a synthetic native event on the given element.
     *
     * @param target {Element} DOM element to fire event on
     * @param type {String} Name of the event to fire
     * @return {Boolean} A value that indicates whether any of the event handlers called {@link #preventDefault}.
     *  <code>true</code> The default action is permitted, <code>false</code> the caller should prevent the default action.
     */
    fire : function(target, type)
    {
      // dispatch for standard first
      if (document.createEvent)
      {
        var evt = document.createEvent("HTMLEvents");
        evt.initEvent(type, true, true);

        return !target.dispatchEvent(evt);
      }

      // dispatch for IE
      else
      {
        var evt = document.createEventObject();
        return target.fireEvent("on" + type, evt);
      }
    },


    /**
     * Whether the given target supports the given event type.
     *
     * Useful for testing for support of new features like
     * touch events, gesture events, orientation change, on/offline, etc.
     *
     * @signature function(target, type)
     * @param target {var} Any valid target e.g. window, dom node, etc.
     * @param type {String} Type of the event e.g. click, mousedown
     * @return {Boolean} Whether the given event is supported
     */
    supportsEvent : function(target, type)
    {
      var eventName = "on" + type;

      var supportsEvent = (eventName in target);

      if (!supportsEvent)
      {
        supportsEvent = typeof target[eventName] == "function";

        if (!supportsEvent && target.setAttribute)
        {
          target.setAttribute(eventName, "return;");
          supportsEvent = typeof target[eventName] == "function";

          target.removeAttribute(eventName);
        }
      }

      return supportsEvent;
    }
  }
});
