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

// A live event received when the local clock is `skew` ms ahead of the server:
// origin_server_ts = T (server clock), age = a, localTimestamp = (T + a + skew) - a.
const feed = (m: ClockSkewMonitor, skew: number, age = 500, t = 1_700_000_000_000) =>
  m.sample(t, age, t + skew);

test('needs three samples, then reports the median with direction', () => {
  const m = new ClockSkewMonitor();
  assert.equal(feed(m, 60_000).skewMs, null);
  assert.equal(feed(m, 61_000).skewMs, null);
  const s = feed(m, 59_000);
  assert.equal(s.skewMs, 60_000);
  assert.equal(s.warning, true);
  assert.equal(formatSkew(s.skewMs!), '60 seconds ahead');
});

test('one bad sample cannot trip the warning (median) and hysteresis clears only under 15 s', () => {
  const m = new ClockSkewMonitor();
  feed(m, 1000);
  feed(m, 1500);
  assert.equal(feed(m, 90_000).warning, false); // outlier
  assert.equal(m.getState().skewMs, 1500);

  const w = new ClockSkewMonitor();
  [40_000, 41_000, 39_000, 40_000, 40_000].forEach((s) => feed(w, s));
  assert.equal(w.getState().warning, true);
  // drifting down to 20 s: still >= 15 s → stays on
  [20_000, 20_000, 20_000, 20_000, 20_000].forEach((s) => feed(w, s));
  assert.equal(w.getState().warning, true);
  [10_000, 10_000, 10_000, 10_000, 10_000].forEach((s) => feed(w, s));
  assert.equal(w.getState().warning, false);
});

test('stale or missing age is ignored (cache replay must not read as skew)', () => {
  const m = new ClockSkewMonitor();
  const t = 1_700_000_000_000;
  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));
  feed(m, -120_000);
  feed(m, -120_000);
  feed(m, -120_000);
  feed(m, -120_000);
  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/);
});