// >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
function EvEmitter() {}

var proto = EvEmitter.prototype

proto.on = function(eventName, listener) {
  if (!eventName || !listener) {
    return
  }
  // set events hash
  var events = (this._events = this._events || {})
  // set listeners array
  var listeners = (events[eventName] = events[eventName] || [])
  // only add once
  if (listeners.indexOf(listener) == -1) {
    listeners.push(listener)
  }

  return this
}

proto.once = function(eventName, listener) {
  if (!eventName || !listener) {
    return
  }
  // add event
  this.on(eventName, listener)
  // set once flag
  // set onceEvents hash
  var onceEvents = (this._onceEvents = this._onceEvents || {})
  // set onceListeners object
  var onceListeners = (onceEvents[eventName] = onceEvents[eventName] || {})
  // set flag
  onceListeners[listener] = true

  return this
}

proto.off = function(eventName, listener) {
  var listeners = this._events && this._events[eventName]
  if (!listeners || !listeners.length) {
    return
  }
  var index = listeners.indexOf(listener)
  if (index != -1) {
    listeners.splice(index, 1)
  }

  return this
}

proto.emitEvent = function(eventName, args) {
  var listeners = this._events && this._events[eventName]
  if (!listeners || !listeners.length) {
    return
  }
  // copy over to avoid interference if .off() in listener
  listeners = listeners.slice(0)
  args = args || []
  // once stuff
  var onceListeners = this._onceEvents && this._onceEvents[eventName]

  for (var i = 0; i < listeners.length; i++) {
    var listener = listeners[i]
    var isOnce = onceListeners && onceListeners[listener]
    if (isOnce) {
      // remove listener
      // remove before trigger to prevent recursion
      this.off(eventName, listener)
      // unset once flag
      delete onceListeners[listener]
    }
    // trigger listener
    listener.apply(this, args)
  }

  return this
}

proto.allOff = function() {
  delete this._events
  delete this._onceEvents
}

module.exports = EvEmitter