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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
import { assertEquals, assertRejects } from "../assert/mod.ts";import { toTransformStream } from "./to_transform_stream.ts";
Deno.test({  name: "toTransformStream()",  async fn() {    const readable = ReadableStream.from([0, 1, 2])      .pipeThrough(toTransformStream(async function* (src) {        for await (const i of src) {          yield i * 100;        }      }));
    const res = await Array.fromAsync(readable);    assertEquals(res, [0, 100, 200]);  },});
Deno.test({  name: "toTransformStream() handles iterable instead of asyncIterable",  async fn() {    const readable = ReadableStream.from([0, 1, 2])      .pipeThrough(toTransformStream(function* (_src) {        yield 0;        yield 100;        yield 200;      }));
    const res = await Array.fromAsync(readable);    assertEquals(res, [0, 100, 200]);  },});
Deno.test({  name: "toTransformStream() propagates the error from readable 1",  async fn(t) {    // When data is pipelined in the order of readable1 → generator → readable2,    // Propagate the error that occurred in readable1 to generator and readable2.    const expectedError = new Error("Error from readable1");    await t.step({      name: "to readable 2",      async fn() {        // Propagate the error that occurred in readable1 to readable2.        let actualError = null;
        const readable1 = new ReadableStream({          start(controller) {            controller.error(expectedError); // error from readable1          },        });        const readable2 = readable1.pipeThrough(          toTransformStream(async function* (src) {            for await (const i of src) {              yield i;            }          }),        );
        try {          await readable2.getReader().read();        } catch (error) {          actualError = error; // catch error in readable2        }
        assertEquals(actualError, expectedError);      },    });    await t.step({      name: "to generator",      async fn() {        // Propagate the error that occurred in readable1 to generator.        let actualError = null;
        const readable1 = new ReadableStream({          start(controller) {            controller.error(expectedError); // error from readable1          },        });        const readable2 = readable1.pipeThrough(          toTransformStream(async function* (src) {            try {              await src.getReader().read();            } catch (error) {              actualError = error; // catch error in generator            }            yield 0;          }),        );
        await readable2.getReader().read();        assertEquals(actualError, expectedError);      },    });  },});
Deno.test({  name: "toTransformStream() propagates the error from generator",  async fn(t) {    // When data is pipelined in the order of readable1 → generator → readable2,    // Propagate the error that occurred in generator to readable2 and readable1.    const expectedError = new Error("Error from generator");    let actualError1: unknown = null;    let actualError2: unknown = null;
    const readable1 = new ReadableStream({      cancel(reason) {        actualError1 = reason; // catch error in readable1      },    });    const readable2 = readable1.pipeThrough(      // deno-lint-ignore require-yield      toTransformStream(function* () {        throw expectedError; // error from generator      }),    );
    try {      await readable2.getReader().read();    } catch (error) {      actualError2 = error; // catch error in readable2    }
    await t.step({      name: "to readable 1",      fn() {        assertEquals(actualError1, expectedError);      },    });    await t.step({      name: "to readable 2",      fn() {        assertEquals(actualError2, expectedError);      },    });  },});
Deno.test({  name: "toTransformStream() propagates cancellation from readable 2",  async fn(t) {    // When data is pipelined in the order of readable1 → generator → readable2,    // Propagate the cancellation that occurred in readable2 to readable1 and generator.    const expectedError = new Error("Error from readable2");    await t.step({      name: "to readable 1",      async fn() {        let actualError = null;
        const readable1 = new ReadableStream({          cancel(reason) {            actualError = reason; // catch error in readable1          },        });        const readable2 = readable1.pipeThrough(          toTransformStream(function* () {            yield 0;          }),        );
        await readable2.cancel(expectedError); // cancellation from readable2        assertEquals(actualError, expectedError);      },    });    await t.step({      name: "to readable 2",      async fn() {        let actualError = null;
        const readable1 = new ReadableStream();        const readable2 = readable1.pipeThrough(          toTransformStream(function* () {            try {              yield 0;            } catch (error) {              actualError = error; // catch error in generator            }          }),        );
        const reader = readable2.getReader();        await reader.read();        await reader.cancel(expectedError); // cancellation from readable2        assertEquals(actualError, expectedError);      },    });  },});
Deno.test({  name:    "toTransformStream() handles streams cancel with the correct error message",  async fn() {    const src = ReadableStream.from([0, 1, 2]);    // deno-lint-ignore require-yield    const transform = toTransformStream(function* (src) {      src.getReader(); // lock the source stream to cause error at cancel      throw new Error("foo");    });
    await assertRejects(      async () => await Array.fromAsync(src.pipeThrough(transform)),      Error,      "foo",    );  },});