Method andThen

src/effected.ts:941–960

(handler: (value: R) => unknown)

    handler: (value: R) => Generator<F, S, unknown> | Effected<F, S> | S,
  ): Effected<E | F, S>;
  andThen(handler: (value: R) => unknown): Effected<Effect, unknown> {
    return effected(() => {
      const iterator = this[Symbol.iterator]();
      let originalIteratorDone = false;
      let appendedIterator: Iterator<Effect, unknown, unknown>;
      return {
        next: (...args: [] | [R]) => {
          if (originalIteratorDone) return appendedIterator.next(...args);
          const result = iterator.next(...args);
          if (!result.done) return result;
          originalIteratorDone = true;
          const it = handler(result.value);
          if (!(it instanceof Effected) && !isGenerator(it) && !isEffectedIterator(it))
            return { done: true, value: it };
          appendedIterator = Symbol.iterator in it ? it[Symbol.iterator]() : it;
          return appendedIterator.next();
        },
      };
    });
  }

  /**
   * Tap the return value of the effected program.