From 66683481973978b766af5190cf5416c7d1a6b98a Mon Sep 17 00:00:00 2001
From: Evan Hahn <69474926+EvanHahn-Signal@users.noreply.github.com>
Date: Tue, 31 May 2022 16:22:31 +0000
Subject: [PATCH] Rewrite `WallClockListener` as `onTimeTravel`

---
 js/wall_clock_listener.js                     | 28 ---------
 ts/background.ts                              |  6 +-
 .../util/startTimeTravelDetector_test.ts      | 59 +++++++++++++++++++
 ts/util/startTimeTravelDetector.ts            | 18 ++++++
 ts/window.d.ts                                |  1 -
 5 files changed, 82 insertions(+), 30 deletions(-)
 delete mode 100644 js/wall_clock_listener.js
 create mode 100644 ts/test-both/util/startTimeTravelDetector_test.ts
 create mode 100644 ts/util/startTimeTravelDetector.ts

diff --git a/js/wall_clock_listener.js b/js/wall_clock_listener.js
deleted file mode 100644
index 4b4bf63b7..000000000
--- a/js/wall_clock_listener.js
+++ /dev/null
@@ -1,28 +0,0 @@
-// Copyright 2017-2020 Signal Messenger, LLC
-// SPDX-License-Identifier: AGPL-3.0-only
-
-/* global Whisper */
-
-// eslint-disable-next-line func-names
-(function () {
-  window.Whisper = window.Whisper || {};
-
-  let lastTime;
-  const interval = 1000;
-  let events;
-  function checkTime() {
-    const currentTime = Date.now();
-    if (currentTime > lastTime + interval * 2) {
-      events.trigger('timetravel');
-    }
-    lastTime = currentTime;
-  }
-
-  Whisper.WallClockListener = {
-    init(_events) {
-      events = _events;
-      lastTime = Date.now();
-      setInterval(checkTime, interval);
-    },
-  };
-})();
diff --git a/ts/background.ts b/ts/background.ts
index f5fadea70..28eaa4942 100644
--- a/ts/background.ts
+++ b/ts/background.ts
@@ -55,6 +55,7 @@ import { removeStorageKeyJobQueue } from './jobs/removeStorageKeyJobQueue';
 import { ourProfileKeyService } from './services/ourProfileKey';
 import { notificationService } from './services/notifications';
 import { areWeASubscriberService } from './services/areWeASubscriber';
+import { startTimeTravelDetector } from './util/startTimeTravelDetector';
 import { shouldRespondWithProfileKey } from './util/shouldRespondWithProfileKey';
 import { LatestQueue } from './util/LatestQueue';
 import { parseIntOrThrow } from './util/parseIntOrThrow';
@@ -1726,7 +1727,10 @@ export async function startApp(): Promise<void> {
     window.setAutoHideMenuBar(hideMenuBar);
     window.setMenuBarVisibility(!hideMenuBar);
 
-    window.Whisper.WallClockListener.init(window.Whisper.events);
+    startTimeTravelDetector(() => {
+      window.Whisper.events.trigger('timetravel');
+    });
+
     window.Whisper.ExpiringMessagesListener.init(window.Whisper.events);
     window.Whisper.TapToViewMessagesListener.init(window.Whisper.events);
 
diff --git a/ts/test-both/util/startTimeTravelDetector_test.ts b/ts/test-both/util/startTimeTravelDetector_test.ts
new file mode 100644
index 000000000..6b720a0cb
--- /dev/null
+++ b/ts/test-both/util/startTimeTravelDetector_test.ts
@@ -0,0 +1,59 @@
+// Copyright 2022 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as sinon from 'sinon';
+
+import { startTimeTravelDetector } from '../../util/startTimeTravelDetector';
+
+describe('startTimeTravelDetector', () => {
+  let sandbox: sinon.SinonSandbox;
+
+  beforeEach(() => {
+    sandbox = sinon.createSandbox({ useFakeTimers: true });
+  });
+
+  afterEach(() => {
+    sandbox.restore();
+  });
+
+  it('calls the callback when the time between checks is more than 2 seconds', async function test() {
+    const callback = sandbox.fake();
+
+    startTimeTravelDetector(callback);
+
+    // Normal clock behavior
+    await sandbox.clock.tickAsync(1234);
+    await sandbox.clock.tickAsync(5678);
+    sinon.assert.notCalled(callback);
+
+    // Time travel ≤2s
+    sandbox.clock.setSystemTime(Date.now() + 1000);
+    await sandbox.clock.tickAsync(1000);
+    sinon.assert.notCalled(callback);
+    sandbox.clock.setSystemTime(Date.now() + 1999);
+    await sandbox.clock.tickAsync(1);
+    sinon.assert.notCalled(callback);
+
+    // Time travel >2s
+    sandbox.clock.setSystemTime(Date.now() + 2001);
+    await sandbox.clock.nextAsync();
+    sinon.assert.calledOnce(callback);
+    sandbox.clock.setSystemTime(Date.now() + 9999);
+    await sandbox.clock.nextAsync();
+    sinon.assert.calledTwice(callback);
+
+    // Normal clock behavior
+    await sandbox.clock.tickAsync(9876);
+    sinon.assert.calledTwice(callback);
+  });
+
+  it('can detect time travel right after initialization', async () => {
+    const callback = sandbox.fake();
+
+    startTimeTravelDetector(callback);
+
+    sandbox.clock.setSystemTime(Date.now() + 2001);
+    await sandbox.clock.nextAsync();
+    sinon.assert.calledOnce(callback);
+  });
+});
diff --git a/ts/util/startTimeTravelDetector.ts b/ts/util/startTimeTravelDetector.ts
new file mode 100644
index 000000000..64107ae80
--- /dev/null
+++ b/ts/util/startTimeTravelDetector.ts
@@ -0,0 +1,18 @@
+// Copyright 2017-2022 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+const INTERVAL = 1000;
+
+export function startTimeTravelDetector(callback: () => unknown): void {
+  let lastTime = Date.now();
+  setInterval(() => {
+    const currentTime = Date.now();
+
+    const sinceLastTime = currentTime - lastTime;
+    if (sinceLastTime > INTERVAL * 2) {
+      callback();
+    }
+
+    lastTime = currentTime;
+  }, INTERVAL);
+}
diff --git a/ts/window.d.ts b/ts/window.d.ts
index e160745c5..17b57ec1c 100644
--- a/ts/window.d.ts
+++ b/ts/window.d.ts
@@ -550,7 +550,6 @@ export type WhisperType = {
   MessageCollection: typeof MessageModelCollectionType;
 
   GroupMemberConversation: WhatIsThis;
-  WallClockListener: WhatIsThis;
 
   deliveryReceiptQueue: PQueue;
   deliveryReceiptBatcher: BatcherType<Receipt>;