/**
 * EventEmitter
 */

function EventEmitter() {
  this._events = this._events || {};
}

EventEmitter.prototype.addListener = function(type, listener) {
  this._events[type] = this._events[type] || [];
  this._events[type].push(listener);
};

EventEmitter.prototype.on = EventEmitter.prototype.addListener;

EventEmitter.prototype.removeListener = function(type, listener) {
  if (!this._events[type]) return;

  var obj = this._events[type]
  , i = obj.length;

  while (i--) {
    if (obj[i] === listener || obj[i].listener === listener) {
      obj.splice(i, 1);
      return;
    }
  }
};

EventEmitter.prototype.off = EventEmitter.prototype.removeListener;

EventEmitter.prototype.removeAllListeners = function(type) {
  if (this._events[type]) delete this._events[type];
};

EventEmitter.prototype.once = function(type, listener) {
  var self = this;
  function on() {
    var args = Array.prototype.slice.call(arguments);
    this.removeListener(type, on);
    return listener.apply(this, args);
  }
  on.listener = listener;
  return this.on(type, on);
};

EventEmitter.prototype.emit = function(type) {
  if (!this._events[type]) return;

  var args = Array.prototype.slice.call(arguments, 1)
  , obj = this._events[type]
  , l = obj.length
  , i = 0;

  for (; i < l; i++) {
    obj[i].apply(this, args);
  }
};

EventEmitter.prototype.listeners = function(type) {
  return this._events[type] = this._events[type] || [];
};

export { EventEmitter };