/**
 * The library between `Play sound` and the audio device. Everything here is about the gap between
 * asking for a sound and being able to play it: the bytes are fetched and decoded on first use, so
 * a stop can land while a play is still in flight.
 *
 * The device is stubbed – nothing makes a noise in a unit test, and Web Audio does not exist here.
 */
import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
import { SoundLibrary } from '../../src/viewport/SoundLibrary';

const FILE = 'a.wav';
const OTHER = 'b.wav';

interface FakeSource {
  buffer: unknown;
  loop: boolean;
  onended: (() => void) | null;
  started: boolean;
  stopped: boolean;
  connect: (target: unknown) => unknown;
  start: () => void;
  stop: () => void;
}

const sources: FakeSource[] = [];

/** Resolves the pending decodes by hand, so a test decides when the bytes arrive. */
let decodes: (() => void)[] = [];

function fakeContext() {
  return {
    state: 'running',
    destination: {},
    resume: () => Promise.resolve(),
    suspend: () => Promise.resolve(),
    decodeAudioData: () => new Promise((resolve) => decodes.push(() => resolve({ duration: 1.5 }))),
    createBufferSource: () => {
      const source: FakeSource = {
        buffer: null,
        loop: false,
        onended: null,
        started: false,
        stopped: false,
        connect: (target: unknown) => target,
        start: () => {
          source.started = true;
        },
        stop: () => {
          source.stopped = true;
        },
      };
      sources.push(source);
      return source;
    },
    createGain: () => ({ gain: { value: 1 }, connect: (target: unknown) => target }),
  };
}

/** Lets the promise chain inside `play` run to the point where it would start a voice. */
const settle = () => new Promise((resolve) => setTimeout(resolve, 0));

beforeEach(() => {
  sources.length = 0;
  decodes = [];
  vi.stubGlobal(
    'AudioContext',
    class {
      constructor() {
        return fakeContext();
      }
    },
  );
  vi.stubGlobal('fetch', () =>
    Promise.resolve({ ok: true, arrayBuffer: () => Promise.resolve(new ArrayBuffer(8)) }),
  );
});

afterEach(() => {
  vi.unstubAllGlobals();
});

/** Plays `file` and lets its bytes arrive, unless `hold` keeps the decode pending. */
async function play(library: SoundLibrary, file = FILE, { hold = false } = {}): Promise<void> {
  library.play(file, 1, false);
  await settle();
  if (hold) return;
  for (const resolve of decodes.splice(0)) resolve();
  await settle();
}

describe('the sound library', () => {
  it('fetches and decodes a file once, however often it is played', async () => {
    const library = new SoundLibrary();
    await play(library);
    await play(library);
    expect(library.stats()).toMatchObject({ started: 2, decoded: 1, playing: 2 });
    // Two voices of one file, both running: plays overlap rather than replacing each other.
    expect(sources.filter((s) => s.started)).toHaveLength(2);
  });

  it('remembers what it last started, so a muted check can see it at all', async () => {
    const library = new SoundLibrary();
    library.play(FILE, 0.25, true);
    await settle();
    for (const resolve of decodes.splice(0)) resolve();
    await settle();
    expect(library.stats().last).toEqual({ file: FILE, volume: 0.25, loop: true });
  });

  it('a stop while the bytes are in flight keeps the sound from starting afterwards', async () => {
    const library = new SoundLibrary();
    await play(library, FILE, { hold: true });
    library.stop(FILE);
    for (const resolve of decodes.splice(0)) resolve();
    await settle();
    expect(library.stats()).toMatchObject({ started: 0, playing: 0 });
  });

  it('but a stop before a play does not: an earlier silence is not a standing veto', async () => {
    const library = new SoundLibrary();
    // Exactly what ending a run does – and the next run has to be able to play that sound again,
    // even though its bytes are still unread at that point.
    library.stop('');
    library.stop(FILE);
    await play(library);
    expect(library.stats()).toMatchObject({ started: 1, playing: 1 });
  });

  it('stopping everything silences every voice, and only the named file otherwise', async () => {
    const library = new SoundLibrary();
    await play(library, FILE);
    await play(library, OTHER);
    library.stop(FILE);
    expect(library.stats()).toMatchObject({ playing: 1, stopped: 1 });

    library.stopAll();
    expect(library.stats()).toMatchObject({ playing: 0, stopped: 2 });
    expect(sources.every((s) => s.stopped)).toBe(true);
  });

  it('a voice that ends by itself leaves the count, without being stopped', async () => {
    const library = new SoundLibrary();
    await play(library);
    sources[0]?.onended?.();
    expect(library.stats()).toMatchObject({ playing: 0, started: 1, stopped: 0 });
  });

  it('a file that cannot be loaded fails once and is never asked for again', async () => {
    const library = new SoundLibrary();
    vi.stubGlobal('fetch', () => Promise.resolve({ ok: false, status: 404 }));
    vi.spyOn(console, 'error').mockImplementation(() => {});
    expect(await library.load(FILE)).toBeNull();
    expect(await library.load(FILE)).toBeNull();
    expect(library.stats()).toMatchObject({ failed: 1, started: 0 });

    library.play(FILE, 1, false);
    await settle();
    expect(library.stats().started).toBe(0);
  });
});