cinny/src/app/utils/clockSkew.test.ts

import { test } from 'node:test';
import assert from 'node:assert/strict';
import {
  ClockSkewMonitor,
  clockFixHint,
  describeSkewVsServer,
  detectClockFixPlatform,
  formatSkew,
} from './clockSkew';

const T = 1_700_000_000_000;

/**
 * A live event received `atSec` seconds into the test, when the local clock is
 * `skew` ms off the server and the response took `delay` ms to arrive:
 * localTimestamp − origin_server_ts = skew + delay.
 */
const feed = (m: ClockSkewMonitor, skew: number, atSec = 0, delay = 0, wallJump = 0) =>
  m.sample(T, 500, T + skew + delay, { wall: T + atSec * 1000 + wallJump, mono: atSec * 1000 });

test('behind: reported as soon as there are three samples', () => {
  const m = new ClockSkewMonitor();
  assert.equal(feed(m, -60_000, 0).skewMs, null);
  assert.equal(feed(m, -61_000, 1).skewMs, null);
  const s = feed(m, -59_000, 2);
  assert.equal(s.skewMs, -61_000);
  assert.equal(s.warning, true);
  assert.equal(formatSkew(s.skewMs!), '61 seconds behind');
});

test('ahead: only once it has held for a minute', () => {
  const m = new ClockSkewMonitor();
  feed(m, 60_000, 0);
  feed(m, 60_000, 10);
  assert.equal(feed(m, 60_000, 20).warning, false);
  assert.equal(m.getState().skewMs, 60_000);
  assert.equal(feed(m, 60_000, 59).warning, false);
  assert.equal(feed(m, 60_000, 61).warning, true);
});

test('server stall (2026-09-29): a burst of late events does not read as a wrong clock', () => {
  const m = new ClockSkewMonitor();
  // Normal traffic, then the homeserver stalls and one /sync arrives 30 s late
  // with a pile of events, then normal traffic again.
  feed(m, 200, 0);
  feed(m, 150, 5);
  feed(m, 300, 10);
  [1, 2, 3, 4, 5, 6].forEach(() => feed(m, 0, 130, 31_000));
  assert.equal(m.getState().warning, false);
  assert.ok(m.getState().skewMs! < 1000);

  // Fresh client whose first samples are all from the late burst.
  const fresh = new ClockSkewMonitor();
  [1, 2, 3, 4, 5, 6].forEach(() => feed(fresh, 0, 0, 31_000));
  assert.equal(fresh.getState().warning, false);
  // …and the next timely event brings the estimate back down.
  feed(fresh, 0, 70, 100);
  assert.equal(fresh.getState().warning, false);
  assert.equal(fresh.getState().skewMs, 100);
});

test('slow deliveries mixed with fast ones: the fastest one wins', () => {
  const m = new ClockSkewMonitor();
  [0, 20, 40, 60, 80].forEach((at, i) => feed(m, 45_000, at, i === 2 ? 0 : 20_000));
  assert.equal(m.getState().skewMs, 45_000);
  assert.equal(m.getState().warning, true);
});

test('hysteresis: once on, clears only under 15 s', () => {
  const w = new ClockSkewMonitor();
  [0, 1, 2].forEach((at) => feed(w, -40_000, at));
  assert.equal(w.getState().warning, true);
  // Samples expire after 5 minutes; drifting to -20 s keeps it on (>= 15 s).
  [400, 401, 402].forEach((at) => feed(w, -20_000, at));
  assert.equal(w.getState().skewMs, -20_000);
  assert.equal(w.getState().warning, true);
  [800, 801, 802].forEach((at) => feed(w, -10_000, at));
  assert.equal(w.getState().warning, false);
});

test('fixing the local clock starts the measurement afresh', () => {
  const m = new ClockSkewMonitor();
  [0, 1, 2].forEach((at) => feed(m, -14 * 60_000, at));
  assert.equal(m.getState().warning, true);
  // The user sets the clock forward 14 minutes: wall jumps vs the monotonic clock.
  const jump = 14 * 60_000;
  feed(m, 0, 10, 0, jump);
  assert.equal(m.getState().warning, false);
  assert.equal(m.getState().skewMs, null);
  feed(m, 0, 11, 0, jump);
  feed(m, 0, 12, 0, jump);
  assert.equal(m.getState().skewMs, 0);
  assert.equal(m.getState().warning, false);
});

test('stale or missing age is ignored (cache replay must not read as skew)', () => {
  const m = new ClockSkewMonitor();
  m.sample(T, undefined, T + 3_600_000);
  m.sample(T, 40 * 24 * 60 * 60 * 1000, T + 3_600_000);
  m.sample(T, -5, T);
  assert.equal(m.getState().skewMs, null);
});

test('subscribe fires on change only; reset clears', () => {
  const m = new ClockSkewMonitor();
  const seen: (number | null)[] = [];
  m.subscribe((s) => seen.push(s.skewMs));
  [0, 1, 2, 3].forEach((at) => feed(m, -120_000, at));
  assert.deepEqual(seen, [-120_000]);
  assert.equal(formatSkew(-120_000), '2 minutes behind');
  m.reset();
  assert.deepEqual(seen, [-120_000, null]);
});

test('formatSkew picks a sensible unit', () => {
  assert.equal(formatSkew(45_000), '45 seconds ahead');
  assert.equal(formatSkew(-14 * 60_000), '14 minutes behind');
  assert.equal(formatSkew(3 * 3_600_000), '3 hours ahead');
  assert.equal(formatSkew(2 * 86_400_000), '2 days ahead');
  assert.equal(describeSkewVsServer(-3 * 3_600_000), '3 hours behind the server');
  assert.equal(describeSkewVsServer(14 * 60_000), '14 minutes ahead of the server');
});

test('platform hint', () => {
  assert.equal(detectClockFixPlatform('Mozilla/5.0 (Windows NT 10.0; Win64; x64)'), 'windows');
  assert.equal(
    detectClockFixPlatform('Mozilla/5.0 (iPhone; CPU iPhone OS 17_0 like Mac OS X)'),
    'ios',
  );
  assert.equal(detectClockFixPlatform('Mozilla/5.0 (Macintosh; Intel Mac OS X 14_0)'), 'mac');
  assert.match(clockFixHint('windows'), /Sync now/);
});