// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.

/** Create a `ReadableStream` from any kind of iterable.
 *
 * ```ts
 *      import { readableStreamFromIterable } from "https://deno.land/std@$STD_VERSION/streams/readable_stream_from_iterable.ts";
 *
 *      const r1 = readableStreamFromIterable(["foo, bar, baz"]);
 *      const r2 = readableStreamFromIterable(async function* () {
 *        await new Promise(((r) => setTimeout(r, 1000)));
 *        yield "foo";
 *        await new Promise(((r) => setTimeout(r, 1000)));
 *        yield "bar";
 *        await new Promise(((r) => setTimeout(r, 1000)));
 *        yield "baz";
 *      }());
 * ```
 *
 * If the produced iterator (`iterable[Symbol.asyncIterator]()` or
 * `iterable[Symbol.iterator]()`) is a generator, or more specifically is found
 * to have a `.throw()` method on it, that will be called upon
 * `readableStream.cancel()`. This is the case for the second input type above:
 *
 * ```ts
 * import { readableStreamFromIterable } from "https://deno.land/std@$STD_VERSION/streams/readable_stream_from_iterable.ts";
 *
 * const r3 = readableStreamFromIterable(async function* () {
 *   try {
 *     yield "foo";
 *   } catch (error) {
 *     console.log(error); // Error: Cancelled by consumer.
 *   }
 * }());
 * const reader = r3.getReader();
 * console.log(await reader.read()); // { value: "foo", done: false }
 * await reader.cancel(new Error("Cancelled by consumer."));
 * ```
 */
export function readableStreamFromIterable<T>(
  iterable: Iterable<T> | AsyncIterable<T>,
): ReadableStream<T> {
  const iterator: Iterator<T> | AsyncIterator<T> =
    (iterable as AsyncIterable<T>)[Symbol.asyncIterator]?.() ??
      (iterable as Iterable<T>)[Symbol.iterator]?.();
  return new ReadableStream({
    async pull(controller) {
      const { value, done } = await iterator.next();
      if (done) {
        controller.close();
      } else {
        controller.enqueue(value);
      }
    },
    async cancel(reason) {
      if (typeof iterator.throw == "function") {
        try {
          await iterator.throw(reason);
        } catch { /* `iterator.throw()` always throws on site. We catch it. */ }
      }
    },
  });
}