ProdDash/modules/resi-cues/resi.test.js

'use strict';

/**
 * Unit tests for the Resi playhead estimator.
 *
 *   node modules/resi-cues/resi.test.js
 *   node modules/resi-cues/resi.test.js 7000 1000 4000 2000   # one profile
 *
 * Plain Node, no dependencies; exits non-zero on the first failure.
 *
 * The estimator's whole job is to be right about a feed that is coarse, late and
 * irregular, so the fixture is a simulated Resi rather than a list of values: a
 * decoder playing at 1x, and an API that republishes its position every so often,
 * already stale, over a round trip that varies. Nine profiles span what the real
 * one has been seen to do. Feeding it a kind, punctual API proves nothing —
 * against one, three separate breakages of this code go unnoticed.
 */

const assert = require('assert');
const { createPlayhead, surroundingCues, positionToMs, msToPosition } = require('./resi');

let passed = 0;
function test(name, fn) {
  fn();
  passed++;
  console.log(`  ok  ${name}`);
}

/* ── the simulated world ───────────────────────────────────────────────── */

function makeWorld({ cadence, lag, jitter, net }) {
  let seed = 12345;
  const rnd = () => {
    seed = (seed * 1103515245 + 12345) & 0x7fffffff;
    return seed / 0x7fffffff;
  };
  const w = {
    t: 1700000000000,
    media: 8 * 60000 + 48000,
    playing: true,
    published: 0,
    lastPublish: 0,
    nextCadence: cadence,
  };
  w.published = w.media - lag;
  w.lastPublish = w.t;
  w.advance = (ms) => {
    for (let i = 0; i < ms; i += 100) {
      w.t += 100;
      if (w.playing) w.media += 100;
      if (w.t - w.lastPublish >= w.nextCadence) {
        w.lastPublish = w.t;
        w.published = w.media - lag;
        w.nextCadence = Math.max(500, cadence + Math.round((rnd() - 0.5) * 2 * jitter));
      }
    }
  };
  // A poll reads what Resi had when the request left, and the round trip costs time.
  w.poll = () => {
    const body = w.published;
    if (net) w.advance(100 + Math.round(rnd() * net));
    return body;
  };
  return w;
}

const CUES = [
  { name: 'Welcome', ms: 5 * 60000 },
  { name: 'Campus Host', ms: 12 * 60000 + 30000 },
  { name: 'Message', ms: 41 * 60000 },
  { name: 'Closing', ms: 45 * 60000 },
];

function runProfile(cadence, lag, jitter, net) {
  const w = makeWorld({ cadence, lag, jitter, net });
  const head = createPlayhead({ now: () => w.t });
  const tol = lag + 1200 + jitter + net * 0.35;
  const label = `cadence ${cadence} lag ${lag} jitter ${jitter} net ${net}`;

  const second = () => { w.advance(1000); head.note(w.poll()); return head.read(); };
  const seconds = (n) => { let r; for (let i = 0; i < n; i++) r = second(); return r; };

  test(`${label}: locks on, and beats the raw reading it is built from`, () => {
    seconds(40);
    let worstEst = 0;
    let worstRaw = 0;
    for (let i = 0; i < 30; i++) {
      const { estMs } = second();
      worstEst = Math.max(worstEst, w.media - estMs);
      worstRaw = Math.max(worstRaw, w.media - w.published);
    }
    assert.ok(worstEst <= tol, `estimate drifted ${Math.round(worstEst)}ms (allowed ${Math.round(tol)})`);
    if (cadence >= 2000) {
      assert.ok(worstRaw >= cadence * 0.4,
        `fixture is too kind: the raw value only went ${Math.round(worstRaw)}ms stale`);
    }
    assert.ok(head.read().playing, 'should read as playing');
  });

  test(`${label}: ticks every second and never runs backwards`, () => {
    let prev = head.read().estMs;
    let stalls = 0;
    let backwards = 0;
    for (let i = 0; i < 200; i++) {
      const { estMs } = second();
      if (estMs === prev) stalls++;
      if (estMs < prev) backwards++;
      prev = estMs;
    }
    assert.strictEqual(stalls, 0, 'the playhead stalled');
    assert.strictEqual(backwards, 0, 'the playhead went backwards');
  });

  test(`${label}: follows a fired cue, and rolls over the one it passes`, () => {
    w.media = 40 * 60000 + 50000;             // decoder jumps; Resi says nothing yet
    let reported = false;
    for (let i = 0; i < 60 && !reported; i++) {
      second();
      reported = Math.abs((head.read().estMs || 0) - w.media) < 8000;
    }
    assert.ok(reported, 'the jump was never picked up');
    assert.ok(head.takeSeek(), 'the jump was not flagged as a seek');
    const { estMs } = head.read();
    assert.ok(Math.abs(estMs - w.media) <= tol + cadence / 2,
      `resynced ${Math.round(w.media - estMs)}ms off`);
    assert.ok(w.media - estMs >= -400, 'overshot the new playhead');
    assert.strictEqual(surroundingCues(CUES, estMs).next.name, 'Message');
    const after = seconds(15);
    assert.strictEqual(surroundingCues(CUES, after.estMs).next.name, 'Closing');
    assert.strictEqual(surroundingCues(CUES, after.estMs).prev.name, 'Message');
  });

  test(`${label}: follows a seek backwards`, () => {
    w.media = 6 * 60000;
    for (let i = 0; i < 60 && Math.abs((head.read().estMs || 0) - w.media) > 8000; i++) second();
    const { estMs } = head.read();
    assert.ok(Math.abs(estMs - w.media) <= tol + cadence / 2, 'did not follow the seek back');
    assert.strictEqual(surroundingCues(CUES, estMs).next.name, 'Campus Host');
  });

  test(`${label}: freezes on a real pause and re-locks on resume`, () => {
    w.playing = false;
    const stoppedAt = w.media;
    const wait = Math.ceil((Math.max(15000, Math.min(45000, (cadence + jitter) * 2.5 + 6000))
      + cadence + jitter + 6000) / 1000);
    let r = seconds(wait);
    assert.strictEqual(r.playing, false, 'did not notice the pause');
    const held = r.estMs;
    r = seconds(20);
    assert.strictEqual(r.estMs, held, 'kept counting while paused');

    w.playing = true;
    r = seconds(25);
    assert.strictEqual(r.playing, true, 'did not notice the resume');
    assert.ok(Math.abs(r.estMs - w.media) <= tol + cadence, 're-locked in the wrong place');
    assert.ok(held - stoppedAt <= 45000 + cadence + jitter + 2 * net + 3000,
      'the frozen position crept instead of stopping');
  });

  test(`${label}: survives a pause longer than the offset window`, () => {
    w.playing = false;
    let r = seconds(150);
    assert.strictEqual(r.playing, false, 'should still read as paused');
    assert.ok(r.estMs !== null && r.estMs !== undefined, 'lost the position entirely');
    w.playing = true;
    head.takeSeek();
    r = seconds(30);
    assert.strictEqual(r.playing, true, 'did not recover');
    assert.ok(Math.abs(r.estMs - w.media) <= tol + cadence, 're-locked in the wrong place');
    assert.ok(head.takeSeek(), 'a resume after a long pause must flag as a seek');
  });
}

/* ── the plain bits ────────────────────────────────────────────────────── */

test('positionToMs reads Resi positions, and rejects anything else', () => {
  assert.strictEqual(positionToMs('00:00:00.000'), 0);
  assert.strictEqual(positionToMs('01:02:03.500'), 3723500);
  assert.strictEqual(positionToMs('00:00:01'), 1000);
  assert.strictEqual(positionToMs(''), null);
  assert.strictEqual(positionToMs('garbage'), null);
  assert.strictEqual(positionToMs(null), null);
  assert.strictEqual(positionToMs(undefined), null);
});

test('msToPosition round-trips', () => {
  for (const ms of [0, 1500, 3723500, 36000000]) {
    assert.strictEqual(positionToMs(msToPosition(ms)), ms);
  }
});

test('surroundingCues puts a cue you are exactly on behind you', () => {
  assert.strictEqual(surroundingCues(CUES, 12 * 60000 + 30000).next.name, 'Message');
  assert.strictEqual(surroundingCues(CUES, 12 * 60000 + 30000).prev.name, 'Campus Host');
  assert.strictEqual(surroundingCues(CUES, 0).prev, null);
  assert.strictEqual(surroundingCues(CUES, 60 * 60000).next, null);
  assert.strictEqual(surroundingCues([], 1000).next, null);
});

/* ── the matrix ────────────────────────────────────────────────────────── */

const argv = process.argv.slice(2).map(Number);
const PROFILES = argv.length >= 4 ? [argv.slice(0, 4)] : [
  [5000, 500, 0, 0], [5000, 500, 0, 2500], [2000, 0, 0, 800],
  [10000, 3000, 0, 2500], [7000, 1000, 4000, 2000], [3000, 500, 2000, 1000],
  [12000, 2000, 6000, 3000], [1000, 0, 0, 0], [8000, 1500, 3000, 4000],
];
for (const [cadence, lag, jitter, net] of PROFILES) runProfile(cadence, lag, jitter, net);

console.log(`\n${passed} tests passed`);