import Singleton from '../Base/Singleton';
import { EventEnum } from '../Enum';

interface IItem {
  func: Function;
  ctx: unknown;
}

export default class EventManager extends Singleton {
  static get Instance() {
    return super.GetInstance<EventManager>();
  }

  private eventMap: Map<EventEnum, Array<IItem>> = new Map();

  on(event: EventEnum, func: Function, ctx?: unknown) {
    if (this.eventMap.has(event)) {
      this.eventMap.get(event).push({ func, ctx });
    } else {
      this.eventMap.set(event, [{ func, ctx }]);
    }
  }

  off(event: EventEnum, func: Function, ctx?: unknown) {
    if (this.eventMap.has(event)) {
      const index = this.eventMap.get(event).findIndex(i => func === i.func && i.ctx === ctx);
      index > -1 && this.eventMap.get(event).splice(index, 1);
    }
  }

  emit(event: EventEnum, ...params: unknown[]) {
    if (this.eventMap.has(event)) {
      this.eventMap.get(event).forEach(({ func, ctx }) => {
        ctx ? func.apply(ctx, params) : func(...params);
      });
    }
  }

  clear() {
    this.eventMap.clear();
  }
}