/**
 * This class provides methods to manage events dispatches.
 */
export class EventDispatcher {
  /** Map to store listeners by event names. */
  _listeners: {}

  constructor() {
    this._listeners = {}
  }

  /** Resets the Dispatcher */
  public reset(): void {
    Object.keys(this._listeners).forEach((key) => {
      delete this._listeners[key]
    })
  }

  once(eventName: string | number, listener: Function, ...args: any): void {
    const onEvent = (ev) => {
      this.removeEventListener(eventName, onEvent)
      listener(ev)
    }
    this.addEventListener(eventName, onEvent)
  }

  /**
   * Adds an event listener.
   * @param eventName Name of the event to listen.
   * @param listener Callback to trigger when the event is fired.
   */
  addEventListener(eventName: string | number, listener: Function, ...args: any): void {
    console.log(this)
    const listeners = this._listeners
    if (listeners[eventName] === undefined) {
      listeners[eventName] = []
    }

    if (listeners[eventName].indexOf(listener) === -1) {
      listeners[eventName].push(listener)
    }
  }

  /**
   * Checks if an event listener is already added to the list of listeners.
   * @param eventName Name of the event to check.
   * @param listener Callback for the specified event.
   */
  hasEventListener(eventName: string | number, listener: Function, ...args: any): boolean {
    return this._listeners[eventName] !== undefined && this._listeners[eventName].indexOf(listener) !== -1
  }

  /**
   * Removes an event listener.
   * @param eventName Name of the event to remove.
   * @param listener Callback for the specified event.
   */
  removeEventListener(eventName: string | number, listener: Function, ...args: any): void {
    const listenerArray = this._listeners[eventName]
    if (listenerArray !== undefined) {
      const index = listenerArray.indexOf(listener)
      if (index !== -1) {
        listenerArray.splice(index, 1)
      }
    }
  }

  /**
   * Removes all listeners for an event.
   * @param eventName Name of the event to remove.
   */
  removeAllListenersForEvent(eventName: string, deleteEvent?: boolean, ...args: any) {
    if (deleteEvent) {
      delete this._listeners[eventName]
    } else {
      this._listeners[eventName] = []
    }
  }

  /**
   * Dispatches an event with given Entity and Component and increases fired event's count.
   * @param eventName Name of the event to dispatch.
   */
  /**
   * Fire an event type.
   * @param type The type of event that gets fired.
   */
  dispatchEvent(event: { type: string; [attachment: string]: any }, ...args: any): void {
    const listenerArray = this._listeners[event.type]
    if (listenerArray !== undefined) {
      const array = listenerArray.slice(0)

      for (let i = 0; i < array.length; i++) {
        array[i].call(this, event, ...args)
      }
    }
  }
}