'use strict'

function eventManager () {
  this.registered = {}
  this.anonymous = {}
}

/*
   * Unregister a listener.
   * Note that if obj is a function. the unregistration will be applied to the dummy obj {}.
   *
   * @param {String} eventName  - the event name
   * @param {Object or Func} obj - object that will listen on this event
   * @param {Func} func         - function of the listeners that will be executed
*/
eventManager.prototype.unregister = function (eventName, obj, func) {
  if (!this.registered[eventName]) {
    return
  }
  if (obj instanceof Function) {
    func = obj
    obj = this.anonymous
  }
  for (let reg in this.registered[eventName]) {
    if (this.registered[eventName][reg].obj === obj && this.registered[eventName][reg].func === func) {
      this.registered[eventName].splice(reg, 1)
    }
  }
}

/*
   * Register a new listener.
   * Note that if obj is a function, the function registration will be associated with the dummy object {}
   *
   * @param {String} eventName  - the event name
   * @param {Object or Func} obj - object that will listen on this event
   * @param {Func} func         - function of the listeners that will be executed
*/
eventManager.prototype.register = function (eventName, obj, func) {
  if (!this.registered[eventName]) {
    this.registered[eventName] = []
  }
  if (obj instanceof Function) {
    func = obj
    obj = this.anonymous
  }
  this.registered[eventName].push({
    obj: obj,
    func: func
  })
}

/*
   * trigger event.
   * Every listener have their associated function executed
   *
   * @param {String} eventName  - the event name
   * @param {Array}j - argument that will be passed to the executed function.
*/
eventManager.prototype.trigger = function (eventName, args) {
  if (!this.registered[eventName]) {
    return
  }
  for (let listener in this.registered[eventName]) {
    const l = this.registered[eventName][listener]
    l.func.apply(l.obj === this.anonymous ? {} : l.obj, args)
  }
}

module.exports = eventManager