export type AnswerCallback<Result, Arguments extends any[] = []> = (result: Result, ...args: Arguments) => Result;

export interface IQuestionAsker<Result = any, Arguments extends any[] = []> {
  ask(result: Result, ...args: Arguments): Result;
}

export interface IQuestion<Result = any, Arguments extends any[] = []> extends IQuestionAsker<Result, Arguments> {
  addAnswer(callback: AnswerCallback<Result, Arguments>): void;
  removeAnswer(callback: AnswerCallback<Result, Arguments>): void;
  addOneTimeAnswer(callback: AnswerCallback<Result, Arguments>): void;
}

export class Question<Result = any, Arguments extends any[] = []> implements IQuestion<Result, Arguments> {
  protected _callbacks: AnswerCallback<Result, Arguments>[] = [];
  protected _callbacksSet: Set<AnswerCallback<Result, Arguments>> = new Set();

  addAnswer(callback: AnswerCallback<Result, Arguments>) {
    if (this._callbacksSet.has(callback)) {
      return;
    }
    this._callbacksSet.add(callback);
    this._callbacks.push(callback);
  }

  removeAnswer(callback: AnswerCallback<Result, Arguments>) {
    if (!this._callbacksSet.has(callback)) {
      return;
    }
    this._callbacksSet.delete(callback);
    this._callbacks = [...this._callbacksSet];
  }

  addOneTimeAnswer(callback: AnswerCallback<Result, Arguments>) {
    const onceCallback: AnswerCallback<Result, Arguments> = (...args) => {
      this.removeAnswer(onceCallback);
      return callback(...args);
    };
    this.addAnswer(onceCallback);
  }

  ask(result: Result, ...args: Arguments): Result {
    for (const callback of this._callbacks) {
      result = callback(result, ...args);
    }
    return result;
  }
}