import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
import { act, renderHook } from '@testing-library/react';

let statusListener: ((connected: boolean) => void) | null = null;
let currentConnected = false;
vi.mock('../api', () => ({
  onRealtimeStatus: (cb: (connected: boolean) => void) => {
    statusListener = cb;
    cb(currentConnected);
    return () => (statusListener = null);
  },
}));

import { useServerOnline, SERVER_OFFLINE_GRACE_MS } from '../useServerOnline';

function setDeviceOnline(value: boolean) {
  Object.defineProperty(navigator, 'onLine', { value, configurable: true });
}

describe('useServerOnline', () => {
  beforeEach(() => {
    vi.useFakeTimers();
    currentConnected = false;
    setDeviceOnline(true);
  });
  afterEach(() => vi.useRealTimers());

  it('stays online during the grace period at app start', () => {
    const { result } = renderHook(() => useServerOnline());
    expect(result.current).toBe(true);
    act(() => statusListener?.(true));
    act(() => vi.advanceTimersByTime(SERVER_OFFLINE_GRACE_MS + 100));
    expect(result.current).toBe(true);
  });

  it('turns offline once the server stays unreachable and back online on reconnect', () => {
    currentConnected = true;
    const { result } = renderHook(() => useServerOnline());
    act(() => statusListener?.(false));
    expect(result.current).toBe(true);
    act(() => vi.advanceTimersByTime(SERVER_OFFLINE_GRACE_MS + 100));
    expect(result.current).toBe(false);
    act(() => statusListener?.(true));
    expect(result.current).toBe(true);
  });

  it('repeated failed reconnects do not postpone the offline state', () => {
    currentConnected = true;
    const { result } = renderHook(() => useServerOnline());
    for (let i = 0; i < 4; i++) {
      act(() => statusListener?.(false));
      act(() => vi.advanceTimersByTime(SERVER_OFFLINE_GRACE_MS / 2));
    }
    expect(result.current).toBe(false);
  });

  it('is offline right away without device network', () => {
    currentConnected = true;
    const { result } = renderHook(() => useServerOnline());
    act(() => {
      setDeviceOnline(false);
      statusListener?.(false);
    });
    expect(result.current).toBe(false);
  });
});