voiceagent/tests/js/pcm-player.test.mjs

import assert from "node:assert/strict";
import { test } from "node:test";

import { PCMPlayer } from
  "../../src/voice_assistant/audio_gateway/web/pcm-player.js";

class FakeAudioSource {
  constructor(context) {
    this.context = context;
    this.buffer = null;
    this.onended = null;
    this.startedAt = null;
    this.stopped = false;
  }

  connect() {}

  disconnect() {}

  start(time) {
    this.startedAt = time;
    this.context.sources.push(this);
  }

  stop() {
    this.stopped = true;
  }

  end() {
    this.onended?.();
  }
}

class FakeAudioContext {
  constructor() {
    this.currentTime = 0;
    this.destination = {};
    this.sources = [];
  }

  async resume() {}

  createAnalyser() {
    return {
      fftSize: 1024,
      smoothingTimeConstant: 0.65,

      connect() {},
      disconnect() {},

      getFloatTimeDomainData(array) {
        array.fill(0);
      },

      getByteFrequencyData(array) {
        array.fill(0);
      },
    };
  }

  createBuffer(channels, length, sampleRate) {
    return {
      duration: length / sampleRate,
      copyToChannel(samples) {
        this.samples = samples;
      },
    };
  }

  createBufferSource() {
    return new FakeAudioSource(this);
  }
}

function pcm(values) {
  const buffer = new ArrayBuffer(values.length * 2);
  const view = new DataView(buffer);

  values.forEach((value, index) => {
    view.setInt16(index * 2, value, true);
  });

  return buffer;
}

test("decodes signed PCM16 correctly", () => {
  const player = new PCMPlayer({
    audioContext: new FakeAudioContext(),
  });

  const samples = player.decodePCM(
    pcm([-32768, 0, 16384, 32767])
  );

  assert.equal(samples[0], -1);
  assert.equal(samples[1], 0);
  assert.equal(samples[2], 0.5);
  assert.ok(samples[3] > 0.99);
});

test("schedules chunks in order", async () => {
  const context = new FakeAudioContext();
  const player = new PCMPlayer({
    audioContext: context,
  });

  await player.enqueue(pcm([100, 200, 300, 400]));
  await player.enqueue(pcm([500, 600, 700, 800]));

  assert.equal(context.sources.length, 2);

  const first = context.sources[0];
  const second = context.sources[1];

  assert.ok(second.startedAt >=
    first.startedAt + first.buffer.duration);
});

test("waits for actual playback completion", async () => {
  const context = new FakeAudioContext();
  const player = new PCMPlayer({
    audioContext: context,
  });

  await player.enqueue(pcm([100, 200]));

  player.finish();

  let completed = false;

  const waiting = player.waitForCompletion().then(() => {
    completed = true;
  });

  await Promise.resolve();

  assert.equal(completed, false);

  context.sources[0].end();

  await waiting;

  assert.equal(completed, true);
});

test("stop interrupts scheduled playback", async () => {
  const context = new FakeAudioContext();
  const player = new PCMPlayer({
    audioContext: context,
  });

  await player.enqueue(pcm([100, 200]));

  player.stop();

  assert.equal(context.sources[0].stopped, true);
  assert.equal(player.sources.size, 0);
  assert.equal(player.playing, false);
});

test("reset allows a new playback turn", async () => {
  const context = new FakeAudioContext();
  const player = new PCMPlayer({
    audioContext: context,
  });

  await player.enqueue(pcm([100, 200]));
  player.finish();
  context.sources[0].end();

  await player.waitForCompletion();

  player.reset();

  await player.enqueue(pcm([300, 400]));

  assert.equal(context.sources.length, 2);
  assert.equal(player.finished, false);
});

test("rejects invalid PCM buffers", () => {
  const player = new PCMPlayer({
    audioContext: new FakeAudioContext(),
  });

  assert.throws(
    () => player.decodePCM(new ArrayBuffer(3)),
    /Invalid PCM byte length/
  );
});

test("exposes playback analyser", () => {
  const context = new FakeAudioContext();

  const player = new PCMPlayer({
    audioContext: context,
  });

  assert.equal(
    player.getAnalyser(),
    player.analyser
  );
});