/**
 * RED scaffold — pushCoalescer (Plan 05-03 turns this GREEN).
 *
 * Asserts that coalesceListPush:
 *   - Fires the dispatch function exactly ONCE when N calls arrive within the coalesce window
 *   - Passes the correct count (N) to the dispatch function
 *   - Passes the actor's own userId as excludeUserId to suppress self-notifications (D-03)
 *
 * These tests fail now because pushCoalescer.ts does not yet exist.
 * Run: pnpm --filter @familysync/api exec vitest run tests/lib/pushCoalescer.test.ts
 */

import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';

describe('pushCoalescer — list-change burst coalescing (D-01)', () => {
  beforeEach(() => {
    vi.useFakeTimers();
    vi.resetModules();
  });

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

  it('collapses N rapid coalesceListPush calls into a single dispatch with count=N', async () => {
    const dispatch = vi.fn().mockResolvedValue(undefined);
    const { coalesceListPush } = await import('../../src/lib/pushCoalescer.js');

    const listId = 1;
    const actorId = 10;
    const N = 5;

    for (let i = 0; i < N; i++) {
      coalesceListPush(listId, actorId, dispatch);
    }

    // Advance time past the coalesce window
    await vi.runAllTimersAsync();

    expect(dispatch).toHaveBeenCalledTimes(1);
    const [calledListId, calledActorId, calledCount] = dispatch.mock.calls[0];
    expect(calledListId).toBe(listId);
    expect(calledActorId).toBe(actorId);
    expect(calledCount).toBe(N);
  });

  it('passes the actor userId as excludeUserId so the actor does not notify themselves (D-03)', async () => {
    const dispatch = vi.fn().mockResolvedValue(undefined);
    const { coalesceListPush } = await import('../../src/lib/pushCoalescer.js');

    const listId = 2;
    const actorId = 99;

    coalesceListPush(listId, actorId, dispatch);
    await vi.runAllTimersAsync();

    expect(dispatch).toHaveBeenCalledTimes(1);
    const [, calledActorId] = dispatch.mock.calls[0];
    expect(calledActorId).toBe(actorId);
  });

  it('fires separate dispatches for different lists independently', async () => {
    const dispatch = vi.fn().mockResolvedValue(undefined);
    const { coalesceListPush } = await import('../../src/lib/pushCoalescer.js');

    coalesceListPush(1, 10, dispatch);
    coalesceListPush(1, 10, dispatch);
    coalesceListPush(2, 10, dispatch); // different list
    coalesceListPush(2, 10, dispatch);

    await vi.runAllTimersAsync();

    // Two separate dispatches — one per distinct listId
    expect(dispatch).toHaveBeenCalledTimes(2);
  });
});
