import test from 'node:test';
import assert from 'node:assert/strict';
import { readFileSync } from 'node:fs';
import vm from 'node:vm';

const ROOT = new URL('../test-fixtures/reference-exhibits/museum-gallery/', import.meta.url);
const SHARED = new URL('../test-fixtures/reference-exhibits/shared/', import.meta.url);

function source(base, file) {
  return readFileSync(new URL(file, base), 'utf8');
}

/** Strips vm-realm object/array identity so assert.deepEqual compares plain
 * host-realm structures instead of failing on cross-realm prototypes. */
function plain(value) {
  return JSON.parse(JSON.stringify(value));
}

/**
 * A fresh vm context standing in for one browser document. `BroadcastChannel`
 * is Node's real global implementation (same spec surface as the DOM one),
 * shared process-wide by channel name -- so two contexts with the same
 * channel name genuinely talk to each other, the same cross-document shape
 * Contract 5.3 Section 31.7 and the Step 6.1 architecture document describe,
 * minus only the literal separate-window/separate-origin browser plumbing.
 *
 * Every test that opens channels is responsible for closing them (see
 * closeAll below) -- Node's BroadcastChannel is a process-wide bus by name,
 * so a leftover open channel from one test would otherwise go on answering
 * a later test's attach requests.
 */
function makeContext() {
  return vm.createContext({
    window: {},
    BroadcastChannel,
    setTimeout,
    clearTimeout,
    Math,
    Date,
    console
  });
}

function makeOwner(options) {
  const ctx = makeContext();
  vm.runInContext(source(SHARED, 'contract-core.js'), ctx);
  for (const file of ['exhibit.js', 'contract-adapter.js', 'surface-bus.js']) {
    vm.runInContext(source(ROOT, file), ctx);
  }
  const gallery = new ctx.window.MuseumGalleryExhibit.Gallery();
  const core = ctx.window.MuseumGalleryContract.create(gallery);
  const bus = ctx.window.MuseumGallerySurfaceBus.createOwner(core, options);
  return { ctx, gallery, core, bus };
}

/** A non-primary-surface context. Deliberately loads ONLY surface-bus.js --
 * not contract-core.js, not exhibit.js, not contract-adapter.js -- so it is
 * structurally incapable of constructing a second Core. */
function makeSurfaceContext() {
  const ctx = makeContext();
  vm.runInContext(source(ROOT, 'surface-bus.js'), ctx);
  return ctx;
}

function attachSurface(ctx, timeoutMs) {
  const events = [];
  return new Promise((resolve, reject) => {
    const link = ctx.window.MuseumGallerySurfaceBus.attach({
      timeoutMs: timeoutMs || 500,
      onSnapshot: (snapshot, registryRevision) => resolve({ link, events, snapshot: plain(snapshot), registryRevision }),
      onEvent: (event) => events.push(plain(event)),
      onTimeout: () => reject(new Error('attach timed out waiting for an owner'))
    });
  });
}

function expectTimeout(ctx, timeoutMs) {
  return new Promise((resolve, reject) => {
    const link = ctx.window.MuseumGallerySurfaceBus.attach({
      timeoutMs: timeoutMs || 150,
      onSnapshot: () => reject(new Error('unexpectedly attached')),
      onTimeout: () => resolve(link)
    });
  });
}

function waitForEvent(events, predicate, timeoutMs) {
  const deadline = Date.now() + (timeoutMs || 500);
  return new Promise((resolve, reject) => {
    (function poll() {
      const found = events.find(predicate);
      if (found) return resolve(found);
      if (Date.now() > deadline) return reject(new Error('timed out waiting for event'));
      setTimeout(poll, 5);
    })();
  });
}

/** Closes every channel/link handed to it, tolerating already-closed ones. */
function closeAll(...handles) {
  for (const h of handles) {
    try {
      if (!h) continue;
      if (typeof h.close === 'function') h.close();
      else if (h.link && typeof h.link.detach === 'function') h.link.detach();
      else if (h.bus && typeof h.bus.close === 'function') h.bus.close();
    } catch {
      /* best-effort cleanup */
    }
  }
}

/* ------------------------------------------------------------------ *
 * 1-4: Contract 5.3 describe / surface descriptor conformance
 * ------------------------------------------------------------------ */

test('Museum Gallery describe reports Contract 5.3 with a valid, single-primary surfaces array', () => {
  const { core, bus } = makeOwner();
  try {
    const description = plain(core.describe());

    assert.equal(description.contract.major, 5);
    assert.equal(description.contract.minor, 3);
    assert.ok(Array.isArray(description.surfaces), 'surfaces must be an array');
    assert.equal(description.surfaces.length, 3);

    const ids = description.surfaces.map((s) => s.id).sort();
    assert.deepEqual(ids, ['surface.artifact', 'surface.control', 'surface.info-wall']);

    const primaries = description.surfaces.filter((s) => s.primary === true);
    assert.equal(primaries.length, 1, 'exactly one primary surface');
    assert.equal(primaries[0].id, 'surface.control');

    for (const s of description.surfaces) {
      assert.equal(s.kind, 'surface');
      assert.match(s.id, /^[a-z][a-z0-9-]*(\.[a-z][a-z0-9-]*)+$/, 'canonical dotted id grammar (Contract 8.1)');
      assert.equal(typeof s.label, 'string');
      assert.ok(s.label.length > 0);
      assert.equal(typeof s.url, 'string');
      assert.ok(!/^[a-zA-Z][a-zA-Z0-9+.-]*:/.test(s.url), 'url must not carry a scheme');
      assert.ok(s.url.indexOf('//') !== 0, 'url must not be protocol-relative');
    }
  } finally {
    closeAll(bus);
  }
});

test('Non-surface-aware exhibits are unaffected: describe() omits `surfaces` entirely with no options.surfaces', () => {
  const ctx = makeContext();
  vm.runInContext(source(SHARED, 'contract-core.js'), ctx);
  const Core = ctx.window.XZBTContractCore;
  const catalog = new Core.Catalog([
    { id: 'mix.master', kind: 'range', min: 0, max: 1, step: 0.01, readable: true, writable: true, restorable: true, category: 'mix', requires: [] }
  ]);
  const caps = new Core.CapabilityRegistry();
  const core = new Core.ContractCore({
    identity: { product: 'plain', version: '1', build: 'x' },
    catalog, capabilities: caps,
    setters: { 'mix.master': () => ({ changed: false }) },
    readers: { 'mix.master': () => 0.5 }
  });
  const description = plain(core.describe());
  assert.equal('surfaces' in description, false);
  assert.equal(description.contract.major, 5);
  assert.equal(description.contract.minor, 3, 'shared contract-core.js now defaults every exhibit forward to Contract 5.3; surfaces stays opt-in regardless');
});

/* ------------------------------------------------------------------ *
 * SurfaceCatalog validation order (Contract 5.3 Section 31.3, Part A2)
 * ------------------------------------------------------------------ */

test('SurfaceCatalog: an individually-invalid entry is discarded before the primary invariant is evaluated', () => {
  const ctx = makeContext();
  vm.runInContext(source(SHARED, 'contract-core.js'), ctx);
  const SurfaceCatalog = ctx.window.XZBTContractCore.SurfaceCatalog;

  const catalog = new SurfaceCatalog([
    { id: 'not_dotted', label: 'Bad', kind: 'surface', primary: true, url: 'bad.html' },
    { id: 'surface.control', label: 'Control', kind: 'surface', primary: true, url: 'control.html' },
    { id: 'surface.artifact', label: 'Artifact', kind: 'surface', primary: false, url: 'artifact.html' }
  ]);

  assert.equal(catalog.isEmpty(), false);
  assert.equal(catalog.wasRejectedAsMalformed(), false);
  assert.equal(catalog.descriptors().length, 2);
  assert.equal(catalog.primaryId(), 'surface.control');
});

test('SurfaceCatalog: zero primary among valid entries rejects the whole catalog and falls back to absent', () => {
  const ctx = makeContext();
  vm.runInContext(source(SHARED, 'contract-core.js'), ctx);
  const SurfaceCatalog = ctx.window.XZBTContractCore.SurfaceCatalog;

  const catalog = new SurfaceCatalog([
    { id: 'surface.artifact', label: 'Artifact', kind: 'surface', primary: false, url: 'artifact.html' },
    { id: 'surface.info-wall', label: 'Info', kind: 'surface', primary: false, url: 'info-wall.html' }
  ]);

  assert.equal(catalog.isEmpty(), true);
  assert.equal(catalog.wasRejectedAsMalformed(), true);
  assert.equal(catalog.descriptors().length, 0);
  assert.ok(catalog.diagnostics().some((d) => /exactly one/.test(d)));
});

test('SurfaceCatalog: multiple primary among valid entries rejects the whole catalog', () => {
  const ctx = makeContext();
  vm.runInContext(source(SHARED, 'contract-core.js'), ctx);
  const SurfaceCatalog = ctx.window.XZBTContractCore.SurfaceCatalog;

  const catalog = new SurfaceCatalog([
    { id: 'surface.control', label: 'Control', kind: 'surface', primary: true, url: 'control.html' },
    { id: 'surface.artifact', label: 'Artifact', kind: 'surface', primary: true, url: 'artifact.html' }
  ]);

  assert.equal(catalog.isEmpty(), true);
  assert.equal(catalog.wasRejectedAsMalformed(), true);
});

test('SurfaceCatalog: discarding every entry (all individually invalid) behaves as absent, not malformed', () => {
  const ctx = makeContext();
  vm.runInContext(source(SHARED, 'contract-core.js'), ctx);
  const SurfaceCatalog = ctx.window.XZBTContractCore.SurfaceCatalog;

  const catalog = new SurfaceCatalog([
    { id: 'bad id', label: 'x', kind: 'surface', primary: true, url: 'x.html' },
    { id: 'surface.y', label: '', kind: 'surface', primary: true, url: 'y.html' }
  ]);

  assert.equal(catalog.isEmpty(), true);
  assert.equal(catalog.wasRejectedAsMalformed(), false, 'empty valid set is absent-equivalent, not a primary violation');
});

test('SurfaceCatalog: an absolute or scheme-carrying url is rejected as an individually invalid entry', () => {
  const ctx = makeContext();
  vm.runInContext(source(SHARED, 'contract-core.js'), ctx);
  const SurfaceCatalog = ctx.window.XZBTContractCore.SurfaceCatalog;

  const catalog = new SurfaceCatalog([
    { id: 'surface.control', label: 'Control', kind: 'surface', primary: true, url: 'https://evil.example/control.html' },
    { id: 'surface.artifact', label: 'Artifact', kind: 'surface', primary: false, url: '//evil.example/artifact.html' },
    { id: 'surface.info-wall', label: 'Info', kind: 'surface', primary: false, url: 'info-wall.html' }
  ]);

  // Only the third entry is individually valid; the valid set then has zero
  // primary entries and is rejected as a whole, falling back to absent.
  assert.equal(catalog.isEmpty(), true);
});

/* ------------------------------------------------------------------ *
 * 5, 12-13: one authoritative Core; primary works fully standalone
 * ------------------------------------------------------------------ */

test('The primary surface is fully usable standalone: the Core alone supports full read/set/invoke', () => {
  const { core, bus } = makeOwner();
  try {
    assert.equal(core.stateSnapshot().values['artifact.selected'], 'the-orrery');
    const setResult = core.applyMutation('lighting.level', 0.2, 'ui');
    assert.equal(setResult.ok, true);
    assert.equal(setResult.revisionChanged, true);
    assert.equal(core.stateSnapshot().values['lighting.level'], 0.2);

    const invokeResult = core.invokeAction('action.spotlight-flash', {}, 'ui');
    assert.equal(invokeResult.ok, true);
    assert.ok(core.eventLog().some((e) => e.type === 'action.executed' && e.target === 'action.spotlight-flash'));
    // None of this touched any surface or bus -- this is a plain Core call,
    // exactly what a person opening control.html directly, with no NGN and
    // no other surface open, gets.
  } finally {
    closeAll(bus);
  }
});

test('Exactly one Exhibit State Core exists: non-primary surface contexts cannot construct one', () => {
  const ctx = makeSurfaceContext();
  assert.equal(ctx.window.MuseumGalleryContract, undefined, 'contract-adapter.js was never loaded here');
  assert.equal(ctx.window.XZBTContractCore, undefined, 'contract-core.js was never loaded here');
  assert.equal(typeof ctx.window.MuseumGallerySurfaceBus.attach, 'function');
});

/* ------------------------------------------------------------------ *
 * 6, 7, 8, 9, 11: cross-document synchronization via the real attachment bus
 * ------------------------------------------------------------------ */

test('Attach sequence: a surface opened after state already changed receives the CURRENT snapshot', async () => {
  const { core, bus } = makeOwner();
  let surface;
  try {
    core.applyMutation('lighting.level', 0.9, 'ui');
    assert.equal(core.stateRevision, 1);

    const artifactCtx = makeSurfaceContext();
    surface = await attachSurface(artifactCtx);

    assert.equal(surface.snapshot.stateRevision, 1);
    assert.equal(surface.snapshot.values['lighting.level'], 0.9, 'reopen/reattach gets current state, not stale or default state');
    assert.equal(surface.registryRevision, core.registryRevision);
  } finally {
    closeAll(bus, surface);
  }
});

test('State changes from the primary propagate to open non-primary surfaces', async () => {
  const { core, bus } = makeOwner();
  let artifact, info;
  try {
    artifact = await attachSurface(makeSurfaceContext());
    info = await attachSurface(makeSurfaceContext());

    core.applyMutation('rotation.speed', 1.2, 'ui'); // simulates the primary UI's own slider

    const artifactEvent = await waitForEvent(artifact.events, (e) => e.type === 'state.changed' && e.target === 'rotation.speed');
    const infoEvent = await waitForEvent(info.events, (e) => e.type === 'state.changed' && e.target === 'rotation.speed');
    assert.equal(artifactEvent.value, 1.2);
    assert.equal(infoEvent.value, 1.2);
    assert.equal(artifactEvent.stateRevision, core.stateRevision);
    assert.equal(infoEvent.stateRevision, core.stateRevision);
  } finally {
    closeAll(bus, artifact, info);
  }
});

test('A native interaction on a non-primary surface updates the primary AND the other non-primary surface, through the canonical mutation path', async () => {
  const { core, bus } = makeOwner();
  let artifact, info;
  try {
    artifact = await attachSurface(makeSurfaceContext());
    info = await attachSurface(makeSurfaceContext());

    const before = core.stateRevision;
    const ok = artifact.link.mutate('set', 'artifact.selected', 'star-map');
    assert.equal(ok, true);

    const infoEvent = await waitForEvent(info.events, (e) => e.type === 'selection.changed' && e.target === 'artifact.selected');
    assert.equal(infoEvent.value, 'star-map');
    assert.equal(infoEvent.source, 'ui', 'surface interactions use the same source vocabulary as primary UI (Contract 5.3 15)');

    // "The primary" here IS the Core itself (control.html owns it) -- its
    // authoritative state reflects the change made from the artifact surface.
    assert.equal(core.readValue('artifact.selected'), 'star-map');
    assert.equal(core.stateRevision, before + 1, 'stateRevision increments exactly once for the one mutation transaction');
  } finally {
    closeAll(bus, artifact, info);
  }
});

test('Event sequence remains one stream regardless of which surface originated the interaction', async () => {
  const { core, bus } = makeOwner();
  let artifact;
  try {
    artifact = await attachSurface(makeSurfaceContext());

    core.applyMutation('lighting.level', 0.3, 'ui'); // "primary UI" origin
    artifact.link.mutate('set', 'rotation.speed', 0.8); // non-primary surface origin
    await waitForEvent(artifact.events, (e) => e.type === 'state.changed' && e.target === 'rotation.speed');

    const sequences = core.eventLog().map((e) => e.sequence);
    const sorted = sequences.slice().sort((a, b) => a - b);
    assert.deepEqual(sequences, sorted, 'sequence is monotonic across both origins');
    assert.equal(new Set(sequences).size, sequences.length, 'no duplicate sequence numbers -- one stream, not one per surface');
  } finally {
    closeAll(bus, artifact);
  }
});

test('Attachment triggers connection callback without state mutation', async () => {
  const counts = [];
  let detached;
  const detachNotification = new Promise((resolve) => { detached = resolve; });
  const { core, bus } = makeOwner({
    onConnectionChange(count) {
      assert.equal(count, bus.attachedCount(), 'callback reports the current owner count');
      counts.push(count);
      if (count === 0) detached();
    }
  });
  let surface;
  try {
    const before = plain(core.stateSnapshot());
    const eventsBefore = plain(core.eventLog());
    assert.equal(bus.attachedCount(), 0);
    assert.deepEqual(counts, []);

    surface = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 1);
    assert.deepEqual(counts, [1]);
    assert.deepEqual(plain(core.stateSnapshot()), before);
    assert.deepEqual(plain(core.eventLog()), eventsBefore);

    surface.link.detach();
    surface = undefined;
    let timer;
    try {
      await Promise.race([
        detachNotification,
        new Promise((_, reject) => {
          timer = setTimeout(() => reject(new Error('detach callback timed out')), 500);
        })
      ]);
    } finally {
      clearTimeout(timer);
    }
    assert.equal(bus.attachedCount(), 0);
    assert.deepEqual(counts, [1, 0]);

    // Irrelevant messages and an extra detach at zero are not count changes.
    for (const data of [null, { type: 'unrelated' }, { type: 'detach' }]) {
      bus.channel.onmessage({ data });
    }
    assert.equal(bus.attachedCount(), 0);
    assert.deepEqual(counts, [1, 0]);
    assert.deepEqual(plain(core.stateSnapshot()), before);
    assert.deepEqual(plain(core.eventLog()), eventsBefore, 'no fake core events');
  } finally {
    closeAll(bus, surface);
  }
});

test('Detach does not mutate state, and a later reattach still observes it correctly', async () => {
  const { core, bus } = makeOwner();
  let first, second;
  try {
    first = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 1);

    const revisionBeforeDetach = core.stateRevision;
    const eventCountBeforeDetach = core.eventLog().length;
    first.link.detach();
    await new Promise((r) => setTimeout(r, 20));

    assert.equal(core.stateRevision, revisionBeforeDetach, 'closing a surface must not change stateRevision');
    assert.equal(core.eventLog().length, eventCountBeforeDetach, 'closing a surface must not itself emit a contract event');

    core.applyMutation('labels.enabled', false, 'ui');

    second = await attachSurface(makeSurfaceContext());
    assert.equal(second.snapshot.values['labels.enabled'], false, 'reopened surface reflects current state automatically');
  } finally {
    closeAll(bus, first, second);
  }
});

test('No independent per-surface state exists: two surfaces attached at once never disagree', async () => {
  const { core, bus } = makeOwner();
  let surfaceA, surfaceB;
  try {
    surfaceA = await attachSurface(makeSurfaceContext());
    surfaceB = await attachSurface(makeSurfaceContext());

    for (const value of [0.1, 0.5, 0.95]) {
      core.applyMutation('lighting.level', value, 'ui');
    }
    await waitForEvent(surfaceB.events, (e) => e.target === 'lighting.level' && e.value === 0.95, 500);
    await new Promise((r) => setTimeout(r, 20));

    const aValues = surfaceA.events.filter((e) => e.target === 'lighting.level').map((e) => e.value);
    const bValues = surfaceB.events.filter((e) => e.target === 'lighting.level').map((e) => e.value);
    assert.deepEqual(aValues, [0.1, 0.5, 0.95]);
    assert.deepEqual(bValues, [0.1, 0.5, 0.95]);
    assert.equal(core.readValue('lighting.level'), 0.95, 'the Core remains the single source of truth both surfaces converged on');
  } finally {
    closeAll(bus, surfaceA, surfaceB);
  }
});

/* ------------------------------------------------------------------ *
 * Standalone degrade behavior: a non-primary surface opened with no owner
 * ------------------------------------------------------------------ */

test('A non-primary surface opened without the Control Room present times out and does not invent a second Core', async () => {
  // No makeOwner() call in this test at all -- nothing is listening on the
  // channel, matching "artifact.html opened with no control.html open".
  const ctx = makeSurfaceContext();
  const link = await expectTimeout(ctx, 150);
  assert.equal(ctx.window.MuseumGalleryContract, undefined);
  closeAll({ link });
});

/* ------------------------------------------------------------------ *
 * Participant lifecycle bookkeeping (Step 6.5B live defect regression)
 *
 * These simulate, at the surface-bus level, exactly what NGN's
 * local-surfaces.js now does around a frame reload/close/reopen: it calls
 * the frame's `__xzbtSurfaceDispose` hook (== the surface's own
 * `link.detach()`) synchronously before removing the old iframe, and a
 * reload/reopen produces a brand-new attach() call with its own fresh
 * participant identity, exactly as a freshly-loaded document would.
 * ------------------------------------------------------------------ */

/** Simulates NGN reloading/replacing one secondary's iframe: dispose the
 * old attachment (as local-surfaces.js's release() does before removing
 * the frame), then attach a fresh one (as the reloaded document does). */
async function simulateReload(oldSurface) {
  oldSurface.link.detach();
  return attachSurface(makeSurfaceContext());
}

test('Participant lifecycle: two secondaries attach to a count of exactly 2', async () => {
  const { bus } = makeOwner();
  let a, b;
  try {
    assert.equal(bus.attachedCount(), 0);
    a = await attachSurface(makeSurfaceContext());
    b = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 2);
  } finally {
    closeAll(bus, a, b);
  }
});

test('Participant lifecycle: reloading one secondary does not ratchet the count up', async () => {
  const { bus } = makeOwner();
  let a, b;
  try {
    a = await attachSurface(makeSurfaceContext());
    b = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 2);

    a = await simulateReload(a);
    assert.equal(bus.attachedCount(), 2, 'reload retires the old participant and adopts the new one -- net zero');
  } finally {
    closeAll(bus, a, b);
  }
});

test('Participant lifecycle: repeated reloads leave the count stable', async () => {
  const { bus } = makeOwner();
  let a, b;
  try {
    a = await attachSurface(makeSurfaceContext());
    b = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 2);

    for (let i = 0; i < 5; i += 1) {
      a = await simulateReload(a);
      assert.equal(bus.attachedCount(), 2, `count must remain 2 after reload #${i + 1}`);
    }
  } finally {
    closeAll(bus, a, b);
  }
});

test('Participant lifecycle: closing a secondary decrements deterministically without waiting for a Core mutation', async () => {
  const { core, bus } = makeOwner();
  let a, b;
  try {
    a = await attachSurface(makeSurfaceContext());
    b = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 2);

    const revisionBeforeClose = core.stateRevision;
    b.link.detach();
    b = undefined;
    await new Promise((r) => setTimeout(r, 20));

    assert.equal(bus.attachedCount(), 1, 'close must decrement immediately, with no Core mutation involved');
    assert.equal(core.stateRevision, revisionBeforeClose, 'closing a secondary never mutates exhibit state');
  } finally {
    closeAll(bus, a, b);
  }
});

test('Participant lifecycle: reopening a closed secondary increments exactly once', async () => {
  const { bus } = makeOwner();
  let a, b;
  try {
    a = await attachSurface(makeSurfaceContext());
    b = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 2);

    b.link.detach();
    b = undefined;
    await new Promise((r) => setTimeout(r, 20));
    assert.equal(bus.attachedCount(), 1);

    b = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 2, 'reopen brings the count back to 2, not higher');
  } finally {
    closeAll(bus, a, b);
  }
});

test('Participant lifecycle: repeated close/reopen never ratchets in either direction', async () => {
  const { bus } = makeOwner();
  let a, b;
  try {
    a = await attachSurface(makeSurfaceContext());
    b = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 2);

    for (let i = 0; i < 3; i += 1) {
      b.link.detach();
      await new Promise((r) => setTimeout(r, 10));
      assert.equal(bus.attachedCount(), 1, `count must be 1 after close #${i + 1}`);
      b = await attachSurface(makeSurfaceContext());
      assert.equal(bus.attachedCount(), 2, `count must be 2 after reopen #${i + 1}`);
    }
  } finally {
    closeAll(bus, a, b);
  }
});

test('Participant lifecycle: duplicate/late attach and detach messages cannot inflate or underflow the count', async () => {
  const { bus } = makeOwner();
  let a;
  try {
    a = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 1);

    // A replayed/duplicated attach for a participant id that is already
    // live (e.g. a retried message) must not inflate the count -- the
    // owner tracks identities in a Set, so re-adding a live id is a no-op.
    bus.channel.onmessage({ data: { type: 'attach', requestId: 'dup-req', participantId: 'known-participant' } });
    bus.channel.onmessage({ data: { type: 'attach', requestId: 'dup-req', participantId: 'known-participant' } });
    assert.equal(bus.attachedCount(), 2, 'two attach messages for the SAME id count as exactly one participant');

    bus.channel.onmessage({ data: { type: 'detach', participantId: 'known-participant' } });
    assert.equal(bus.attachedCount(), 1, 'detaching that id removes exactly the one participant it represents');

    // A late/duplicate detach for an id that is no longer (or never was)
    // present must not underflow the count.
    bus.channel.onmessage({ data: { type: 'detach', participantId: 'known-participant' } });
    bus.channel.onmessage({ data: { type: 'detach', participantId: 'not-a-real-participant' } });
    assert.equal(bus.attachedCount(), 1, 'stale/unknown detach ids must not drive the count below the real count');

    a.link.detach();
    await new Promise((r) => setTimeout(r, 20));
    assert.equal(bus.attachedCount(), 0);

    bus.channel.onmessage({ data: { type: 'detach', participantId: 'not-a-real-participant' } });
    assert.equal(bus.attachedCount(), 0, 'never goes negative or otherwise corrupts at zero');
  } finally {
    closeAll(bus, a);
  }
});

test('Participant lifecycle: synchronization is unaffected by the lifecycle bookkeeping change', async () => {
  const { core, bus } = makeOwner();
  let a, b;
  try {
    a = await attachSurface(makeSurfaceContext());
    b = await attachSurface(makeSurfaceContext());
    assert.equal(bus.attachedCount(), 2);

    // Control mutation still reaches both mirrors.
    core.applyMutation('lighting.level', 0.42, 'ui');
    await waitForEvent(a.events, (e) => e.target === 'lighting.level' && e.value === 0.42, 500);
    await waitForEvent(b.events, (e) => e.target === 'lighting.level' && e.value === 0.42, 500);

    // A secondary mutation request still reaches the primary and the other
    // mirror through the canonical mutation path.
    a.link.mutate('set', 'labels.enabled', false); // default is true, so false is an actual change
    await waitForEvent(b.events, (e) => e.target === 'labels.enabled' && e.value === false, 500);
    assert.equal(core.readValue('labels.enabled'), false);

    // A reload (dispose + fresh attach) still gets a correct, current
    // snapshot -- late-join/attach.snapshot behavior survives the change.
    a = await simulateReload(a);
    assert.equal(a.snapshot.values['lighting.level'], 0.42);
    assert.equal(a.snapshot.values['labels.enabled'], false);
    assert.equal(bus.attachedCount(), 2);
  } finally {
    closeAll(bus, a, b);
  }
});