export declare type EventType = number | string;

export interface IEvent {
  callback: (context?: any) => void;
}

export type ICallback = (context?: any) => void;

export class Event {
  private events: Map<EventType, IEvent[]> = new Map();

  public on(eventType: EventType, callback: ICallback): void {
    const event: IEvent = {
      callback
    };

    if (this.events.get(eventType)) {
      this.events.get(eventType).push(event);
    } else {
      this.events.set(eventType, [event]);
    }
  }

  public off(eventType: EventType, callback: ICallback) {
    if (!this.events.get(eventType)) {
      return false;
    }

    const events = this.events.get(eventType).filter(event => {
      return event.callback !== callback;
    });

    this.events.set(eventType, events);

    return true;
  }

  public emit(eventType: EventType, context?: any) {
    if (!eventType || !this.events.get(eventType)) {
      return false;
    }

    this.events.get(eventType).forEach(event => {
      event.callback(context);
    });
  }
}