vue-tui/packages/runtime-tests/integration/lifecycle/throttle.test.tsx

import { defineComponent, nextTick, shallowRef } from "vue";
import { expect, test, vi } from "vite-plus/test";
import { createApp, Text } from "@vue-tui/runtime";
import stripAnsi from "strip-ansi";
import {
  makeFakeStdin,
  makeFakeWritable,
  captureWrites,
  getContentWrites,
} from "./test-streams.ts";

// Fake timer options: only fake setTimeout/clearTimeout/Date so that
// Vue's internal scheduler (nextTick, queueMicrotask, setImmediate) still
// runs on real clocks. This matches the pattern in use-animation.test.tsx.
const FAKE_TIMER_OPTS = {
  shouldAdvanceTime: false,
  toFake: ["setTimeout", "clearTimeout", "Date"] as ("setTimeout" | "clearTimeout" | "Date")[],
};

test("throttle renders to maxFps", async () => {
  // Port of Ink's "throttle renders to maxFps" — verifies leading+trailing
  // throttle pattern with maxFps=1 (1000ms window).
  vi.useFakeTimers(FAKE_TIMER_OPTS);
  try {
    const msg = shallowRef("Hello");

    const App = defineComponent(() => {
      return () => <Text>{msg.value}</Text>;
    });

    const app = createApp(App);
    const stdout = makeFakeWritable({ columns: 80 });
    const stderr = makeFakeWritable({ columns: 80 });
    const { stream: stdin } = makeFakeStdin();
    const writes = captureWrites(stdout);

    app.mount({
      stdout,
      stdin,
      stderr,
      exitOnCtrlC: false,
      maxFps: 1, // 1 Hz => ~1000ms throttle window
    });

    // Flush Vue scheduler so the initial commit fires (leading edge)
    await nextTick();
    await nextTick();

    const initialWriteCount = writes.length;
    expect(initialWriteCount).toBeGreaterThanOrEqual(1);
    expect(writes.some((w) => w.includes("Hello"))).toBe(true);

    // Trigger a rerender inside the throttle window
    msg.value = "World";
    await nextTick();
    await nextTick();

    // Throttling should have held — no new writes yet
    const midWriteCount = writes.length;
    expect(midWriteCount).toBe(initialWriteCount);

    // Advance 999ms: still within window, no trailing call yet
    vi.advanceTimersByTime(999);
    expect(writes.length).toBe(midWriteCount);

    // Cross the 1000ms boundary: trailing render fires
    vi.advanceTimersByTime(1);
    expect(writes.some((w) => w.includes("World"))).toBe(true);

    app.unmount();
  } finally {
    vi.useRealTimers();
  }
});

test("immediate scheduler in debug mode commits every mutation", async () => {
  // Counterpart to the throttle test: in debug mode (used by the testing
  // helper), the scheduler bypasses throttling and commits synchronously.
  // This verifies the immediate path in createCommitScheduler.
  const msg = shallowRef("A");

  const App = defineComponent(() => {
    return () => <Text>{msg.value}</Text>;
  });

  const app = createApp(App);
  const stdout = makeFakeWritable({ columns: 80 });
  const stderr = makeFakeWritable({ columns: 80 });
  const { stream: stdin } = makeFakeStdin();
  const writes = captureWrites(stdout);

  app.mount({
    stdout,
    stdin,
    stderr,
    debug: true,
    exitOnCtrlC: false,
  });

  await nextTick();
  await nextTick();
  expect(writes.some((w) => w.includes("A"))).toBe(true);

  msg.value = "B";
  await nextTick();
  await nextTick();
  expect(writes.some((w) => w.includes("B"))).toBe(true);

  msg.value = "C";
  await nextTick();
  await nextTick();
  expect(writes.some((w) => w.includes("C"))).toBe(true);

  app.unmount();
});

test("screen reader mode bypasses throttle (immediate commits)", async () => {
  // Port of Ink's screen reader behavior: isScreenReaderEnabled causes
  // the scheduler to use immediate mode, ensuring every frame is flushed
  // without delay for assistive technology.
  const msg = shallowRef("Hello");

  const App = defineComponent(() => {
    return () => <Text>{msg.value}</Text>;
  });

  const app = createApp(App);
  const stdout = makeFakeWritable({ columns: 80 });
  const stderr = makeFakeWritable({ columns: 80 });
  const { stream: stdin } = makeFakeStdin();
  const writes = captureWrites(stdout);

  app.mount({
    stdout,
    stdin,
    stderr,
    exitOnCtrlC: false,
    isScreenReaderEnabled: true,
  });

  await nextTick();
  await nextTick();
  expect(writes.some((w) => w.includes("Hello"))).toBe(true);

  // Even rapid mutations should commit immediately (no throttle)
  msg.value = "World";
  await nextTick();
  await nextTick();
  expect(writes.some((w) => w.includes("World"))).toBe(true);

  app.unmount();
});

test("no throttled renders after unmount", async () => {
  vi.useFakeTimers(FAKE_TIMER_OPTS);
  try {
    const msg = shallowRef("Foo");
    const App = defineComponent(() => () => <Text>{msg.value}</Text>);
    const app = createApp(App);
    const stdout = makeFakeWritable({ columns: 80 });
    const stderr = makeFakeWritable({ columns: 80 });
    const { stream: stdin } = makeFakeStdin();
    const writes = captureWrites(stdout);

    app.mount({ stdout, stdin, stderr, exitOnCtrlC: false });
    await nextTick();
    await nextTick();

    const initialCount = getContentWrites(writes).length;
    expect(initialCount).toBeGreaterThanOrEqual(1);

    msg.value = "Bar";
    await nextTick();
    msg.value = "Baz";
    await nextTick();
    app.unmount();

    const countAfterUnmount = getContentWrites(writes).length;
    vi.advanceTimersByTime(1000);
    expect(getContentWrites(writes).length).toBe(countAfterUnmount);
  } finally {
    vi.useRealTimers();
  }
});

test("unmount forces pending throttled render", async () => {
  vi.useFakeTimers(FAKE_TIMER_OPTS);
  try {
    const msg = shallowRef("Hello");
    const App = defineComponent(() => () => <Text>{msg.value}</Text>);
    const app = createApp(App);
    const stdout = makeFakeWritable({ columns: 80 });
    const stderr = makeFakeWritable({ columns: 80 });
    const { stream: stdin } = makeFakeStdin();
    const writes = captureWrites(stdout);

    app.mount({ stdout, stdin, stderr, exitOnCtrlC: false, maxFps: 1 });
    await nextTick();
    await nextTick();

    expect(getContentWrites(writes).length).toBe(1);
    expect(stripAnsi(getContentWrites(writes)[0]!)).toContain("Hello");

    msg.value = "Final";
    await nextTick();
    await nextTick();
    expect(getContentWrites(writes).length).toBe(1);

    app.unmount();
    const allContent = getContentWrites(writes).map((w) => stripAnsi(w));
    expect(allContent.some((c) => c.includes("Final"))).toBe(true);
  } finally {
    vi.useRealTimers();
  }
});

test("unmount cancels pending throttled log writes when stdout is ended", async () => {
  vi.useFakeTimers(FAKE_TIMER_OPTS);
  try {
    const { PassThrough } = await import("node:stream");
    const stdout = new PassThrough() as unknown as NodeJS.WriteStream;
    stdout.columns = 100;

    const writeErrors: Error[] = [];
    stdout.on("error", (error: Error) => writeErrors.push(error));

    const msg = shallowRef("Hello");
    const App = defineComponent(() => () => <Text>{msg.value}</Text>);
    const app = createApp(App);
    const stderr = makeFakeWritable({ columns: 80 });
    const { stream: stdin } = makeFakeStdin();

    app.mount({ stdout, stdin, stderr, exitOnCtrlC: false, maxFps: 1 });
    await nextTick();
    await nextTick();

    msg.value = "World";
    await nextTick();
    stdout.end();
    app.unmount();
    vi.advanceTimersByTime(1000);

    const hasWriteAfterEndError = writeErrors.some(
      (e) => (e as NodeJS.ErrnoException).code === "ERR_STREAM_WRITE_AFTER_END",
    );
    expect(hasWriteAfterEndError).toBe(false);
  } finally {
    vi.useRealTimers();
  }
});

test("unmount cancels pending throttled render when stdout is ended", async () => {
  vi.useFakeTimers(FAKE_TIMER_OPTS);
  try {
    const { PassThrough } = await import("node:stream");

    // Baseline: mount + end + unmount without pending rerender
    const baseStdout = new PassThrough() as unknown as NodeJS.WriteStream;
    baseStdout.columns = 100;
    const BaseApp = defineComponent(() => () => <Text>Hello</Text>);
    const baseApp = createApp(BaseApp);
    const baseStderr = makeFakeWritable({ columns: 80 });
    const { stream: baseStdin } = makeFakeStdin();
    baseApp.mount({
      stdout: baseStdout,
      stdin: baseStdin,
      stderr: baseStderr,
      exitOnCtrlC: false,
      maxFps: 1,
    });
    await nextTick();
    await nextTick();
    baseStdout.end();
    baseApp.unmount();
    const baselineTimers = vi.getTimerCount();
    vi.runAllTimers();

    // Test: mount + rerender + end + unmount
    const stdout = new PassThrough() as unknown as NodeJS.WriteStream;
    stdout.columns = 100;
    const msg = shallowRef("Hello");
    const App = defineComponent(() => () => <Text>{msg.value}</Text>);
    const app = createApp(App);
    const stderr = makeFakeWritable({ columns: 80 });
    const { stream: stdin } = makeFakeStdin();
    app.mount({ stdout, stdin, stderr, exitOnCtrlC: false, maxFps: 1 });
    await nextTick();
    await nextTick();

    msg.value = "World";
    await nextTick();
    stdout.end();
    app.unmount();

    expect(vi.getTimerCount()).toBe(baselineTimers);
  } finally {
    vi.useRealTimers();
  }
});