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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
// Utility for representing n-tupletype Tuple<T, N extends number> = N extends N  ? number extends N ? T[] : TupleOf<T, N, []>  : never;type TupleOf<T, N extends number, R extends unknown[]> = R["length"] extends N  ? R  : TupleOf<T, N, [T, ...R]>;
interface QueueNode<T> {  value: T;  next: QueueNode<T> | undefined;}
class Queue<T> {  #source: AsyncIterator<T>;  #queue: QueueNode<T>;  head: QueueNode<T>;
  done: boolean;
  constructor(iterable: AsyncIterable<T>) {    this.#source = iterable[Symbol.asyncIterator]();    this.#queue = {      value: undefined!,      next: undefined,    };    this.head = this.#queue;    this.done = false;  }
  async next() {    const result = await this.#source.next();    if (!result.done) {      const nextNode: QueueNode<T> = {        value: result.value,        next: undefined,      };      this.#queue.next = nextNode;      this.#queue = nextNode;    } else {      this.done = true;    }  }}
/** * Branches the given async iterable into the n branches. * * Example: * * ```ts *     import { tee } from "./tee.ts"; * *     const gen = async function* gen() { *       yield 1; *       yield 2; *       yield 3; *     } * *     const [branch1, branch2] = tee(gen()); * *     for await (const n of branch1) { *       console.log(n); // => 1, 2, 3 *     } * *     for await (const n of branch2) { *       console.log(n); // => 1, 2, 3 *     } * ``` */export function tee<T, N extends number = 2>(  iterable: AsyncIterable<T>,  n: N = 2 as N,): Tuple<AsyncIterable<T>, N> {  const queue = new Queue<T>(iterable);
  async function* generator(): AsyncGenerator<T> {    let buffer = queue.head;    while (true) {      if (buffer.next) {        buffer = buffer.next;        yield buffer.value;      } else if (queue.done) {        return;      } else {        await queue.next();      }    }  }
  const branches = Array.from({ length: n }).map(    () => generator(),  ) as Tuple<    AsyncIterable<T>,    N  >;  return branches;}