export type EventCallback<T = undefined> = (e?: T) => void | Promise<void>;
export type EventStackItem<T = any> = {
  isOnce: boolean;
  cb: EventCallback<T>;
};

export type EventStack<T = any> = {
  [key: string]: Array<EventStackItem<T>>;
};

export class EventEmitter<EvStack extends EventStack> {
  eventStack: EvStack;

  protected _emitEvent<K extends keyof EvStack>(
    key: K,
    event?: Parameters<EvStack[K][number]['cb']>[0]
  ) {
    const stack = this.eventStack[key];
    stack.forEach((st) => {
      st.cb(event);
      if (st.isOnce) this.off(key, st.cb);
    });
  }

  on<K extends keyof EvStack>(
    eventName: K,
    callback: EvStack[K][number]['cb']
  ) {
    this.eventStack[eventName].push({ isOnce: false, cb: callback });
  }

  once<K extends keyof EvStack>(
    eventName: K,
    callback: EvStack[K][number]['cb']
  ) {
    this.eventStack[eventName].push({ isOnce: true, cb: callback });
  }

  off<K extends keyof EvStack>(
    eventName: K,
    callback: EvStack[K][number]['cb']
  ) {
    const idx = this.eventStack[eventName].findIndex(
      (st) => st.cb === callback
    );
    if (idx >= 0) this.eventStack[eventName].splice(idx, 1);
  }

  constructor(stack: EvStack) {
    this.eventStack = stack;
  }
}