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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
interface TaggedYieldedValue<T> {  iterator: AsyncIterator<T>;  value: T;}
/** * Multiplexes multiple async iterators into a single stream. It currently * makes an assumption that the final result (the value returned and not * yielded from the iterator) does not matter; if there is any result, it is * discarded. * * @example * ```ts * import { MuxAsyncIterator } from "https://deno.land/std@$STD_VERSION/async/mux_async_iterator.ts"; * * async function* gen123(): AsyncIterableIterator<number> { *   yield 1; *   yield 2; *   yield 3; * } * * async function* gen456(): AsyncIterableIterator<number> { *   yield 4; *   yield 5; *   yield 6; * } * * const mux = new MuxAsyncIterator<number>(); * mux.add(gen123()); * mux.add(gen456()); * for await (const value of mux) { *   // ... * } * // .. * ``` */export class MuxAsyncIterator<T> implements AsyncIterable<T> {  #iteratorCount = 0;  #yields: Array<TaggedYieldedValue<T>> = [];  // deno-lint-ignore no-explicit-any  #throws: any[] = [];  #signal = Promise.withResolvers<void>();
  /** Add an async iterable to the stream. */  add(iterable: AsyncIterable<T>) {    ++this.#iteratorCount;    this.#callIteratorNext(iterable[Symbol.asyncIterator]());  }
  async #callIteratorNext(    iterator: AsyncIterator<T>,  ) {    try {      const { value, done } = await iterator.next();      if (done) {        --this.#iteratorCount;      } else {        this.#yields.push({ iterator, value });      }    } catch (e) {      this.#throws.push(e);    }    this.#signal.resolve();  }
  /** Returns an async iterator of the stream. */  async *iterate(): AsyncIterableIterator<T> {    while (this.#iteratorCount > 0) {      // Sleep until any of the wrapped iterators yields.      await this.#signal.promise;
      // Note that while we're looping over `yields`, new items may be added.      for (const { iterator, value } of this.#yields) {        yield value;        this.#callIteratorNext(iterator);      }
      if (this.#throws.length) {        for (const e of this.#throws) {          throw e;        }        this.#throws.length = 0;      }      // Clear the `yields` list and reset the `signal` promise.      this.#yields.length = 0;      this.#signal = Promise.withResolvers<void>();    }  }
  /** Implements an async iterator for the stream. */  [Symbol.asyncIterator](): AsyncIterator<T> {    return this.iterate();  }}