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// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { Deferred, deferred } from "./deferred.ts";
interface TaggedYieldedValue<T> {  iterator: AsyncIterator<T>;  value: T;}
/** * The MuxAsyncIterator class 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 * ```typescript * import { MuxAsyncIterator } from "https://deno.land/std@$STD_VERSION/async/mod.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: Deferred<void> = deferred();
  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();  }
  async *iterate(): AsyncIterableIterator<T> {    while (this.#iteratorCount > 0) {      // Sleep until any of the wrapped iterators yields.      await this.#signal;
      // Note that while we're looping over `yields`, new items may be added.      for (let i = 0; i < this.#yields.length; i++) {        const { iterator, value } = this.#yields[i];        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 = deferred();    }  }
  [Symbol.asyncIterator](): AsyncIterator<T> {    return this.iterate();  }}