/* listen.js
 *
 * Author: nanto_vi (TOYAMA Nao)
 * Lisence: Public Domain
 * Usage:
 *   (function (e) {doSomething();}).listen(element, eventType);
 */

(function () {
  var targetIdSeed   = 0;
  var listenerIdSeed = 0;
  var typeResolver   = {};

  this._lsn_listeners = {};

  if (document.addEventListener) {
    var getListenerWrapper = function (listener) {
      var listenerId = listener._lsn_listenerId;
      if (listenerId)
        return _lsn_listeners[listenerId].wrapper;
      listenerId = listener._lsn_listenerId = ++listenerIdSeed;
      _lsn_listeners[listenerId] = {
        listener: listener,
        wrapper:  function (e) {
          _lsn_listeners[listenerId].listener.call(this, e);
        }
      };
      listener = null;
      return _lsn_listeners[listenerId].wrapper;
    };
  } else if (document.attachEvent) {
    var getListenerWrapper = function (listener, target) {
      if (!target) return listener;
      var targetId = target._lsn_targetId;
      var listenerId = listener._lsn_listenerId;
      if (targetId && listenerId)
        return _lsn_listeners[targetId][listenerId].wrapper;
      if (!targetId) {
        targetId = target._lsn_targetId = ++targetIdSeed;
        _lsn_listeners[targetId] = {target: target};
      }
      if (!listenerId) {
        listenerId = listener._lsn_listenerId = ++listenerIdSeed;
      }
      _lsn_listeners[targetId][listenerId] = {
        listener: listener,
        wrapper:  function (e) {
          fixEvent(e, _lsn_listeners[targetId].target);
          _lsn_listeners[targetId][listenerId].listener
                                              .call(e.currentTarget, e);
        }
      };
      listener = target = null;
      return _lsn_listeners[targetId][listenerId].wrapper;
    };
    var htmlIsRoot = ("compatMode" in document &&
                      document.compatMode == "CSS1Compat");
    var fixEvent = function (e, currentTarget) {
      var type = e.type;
      e.target        = e.srcElement;
      e.currentTarget = currentTarget;
      e.relatedTarget = (type == "mouseover") ? e.fromElement :
                        (type == "mouseout")  ? e.toElement   : null;
      e.detail = (type == "click")      ? 1 :
                 (type == "dblclick")   ? 2 :
                 (type == "mousewheel") ? -e.wheelDelta : 0;
      e.which = (type.indexOf("key") != -1) ? e.keyCode : e.button;
      var root = htmlIsRoot ? document.documentElement : document.body;
      e.pageX = e.clientX + root.scrollLeft - root.clientLeft;
      e.pageY = e.clientY + root.scrollTop  - root.clientTop;
      e.stopPropagation = stopPropagation;
      e.preventDefault  = preventDefault;
    };
    var stopPropagation = function () {
      this.cancelBubble = true;
    };
    var preventDefault = function () {
      this.returnValue = false;
    };
    typeResolver.DOMMouseScroll = "mousewheel";
  }

  Function.prototype.listen = function (target, type) {
    if (type in typeResolver) type = typeResolver[type];
    if (target.addEventListener)
      target.addEventListener(type, getListenerWrapper(this), false);
    else if (target.attachEvent)
      target.attachEvent("on" + type, getListenerWrapper(this, target));
    return this;
  };

  Function.prototype.unlisten = function (target, type) {
    if (type in typeResolver) type = typeResolver[type];
    if (target.removeEventListener)
      target.removeEventListener(type, getListenerWrapper(this), false);
    else if (target.detachEvent)
      target.detachEvent("on" + type, getListenerWrapper(this, target));
    return this;
  };
})();