Desktop/ts/util/asyncIterables.std.ts

// Copyright 2021 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only

export type MaybeAsyncIterable<T> = Iterable<T> | AsyncIterable<T>;

export function concat<T>(
  iterables: Iterable<MaybeAsyncIterable<T>>
): AsyncIterable<T> {
  return new ConcatAsyncIterable(iterables);
}

class ConcatAsyncIterable<T> implements AsyncIterable<T> {
  readonly #iterables: Iterable<MaybeAsyncIterable<T>>;

  constructor(iterables: Iterable<MaybeAsyncIterable<T>>) {
    this.#iterables = iterables;
  }

  async *[Symbol.asyncIterator](): AsyncIterator<T> {
    for (const iterable of this.#iterables) {
      // oxlint-disable-next-line no-await-in-loop
      for await (const value of iterable) {
        yield value;
      }
    }
  }
}

export function wrapPromise<T>(
  promise: Promise<MaybeAsyncIterable<T>>
): AsyncIterable<T> {
  return new WrapPromiseAsyncIterable(promise);
}

// oxlint-disable-next-line max-classes-per-file
class WrapPromiseAsyncIterable<T> implements AsyncIterable<T> {
  readonly #promise: Promise<MaybeAsyncIterable<T>>;

  constructor(promise: Promise<MaybeAsyncIterable<T>>) {
    this.#promise = promise;
  }

  async *[Symbol.asyncIterator](): AsyncIterator<T> {
    for await (const value of await this.#promise) {
      yield value;
    }
  }
}