/**
 * Service Worker 등록 유틸리티
 * 
 * 클라이언트 측에서 Service Worker를 등록하고
 * 캐시 상태를 확인할 수 있는 헬퍼 함수들
 */

export interface CacheStatus {
  total: number;
  cached: number;
  urls: Array<{ url: string; cached: boolean }>;
}

/**
 * Service Worker 등록
 */
export async function registerServiceWorker(): Promise<ServiceWorkerRegistration | null> {
  if (typeof window === 'undefined' || !('serviceWorker' in navigator)) {
    console.log('Service Worker not supported (supports https or localhost only)');
    return null;
  }

  try {
    const registration = await navigator.serviceWorker.register('/service-worker.js', {
      scope: '/',
    });

    console.log('Service Worker registered:', registration);

    // 업데이트 확인
    registration.addEventListener('updatefound', () => {
      const newWorker = registration.installing;
      console.log('Service Worker update found');

      newWorker?.addEventListener('statechange', () => {
        if (newWorker.state === 'installed' && navigator.serviceWorker.controller) {
          console.log('New Service Worker available. Refresh to update.');
          // 필요시 사용자에게 알림 표시 가능
        }
      });
    });

    return registration;
  } catch (error) {
    console.error('Service Worker registration failed:', error);
    return null;
  }
}

/**
 * Service Worker 캐시 상태 확인
 */
export async function getCacheStatus(): Promise<CacheStatus | null> {
  if (typeof window === 'undefined' || !navigator.serviceWorker.controller) {
    return null;
  }

  return new Promise((resolve) => {
    const messageChannel = new MessageChannel();

    messageChannel.port1.onmessage = (event) => {
      resolve(event.data);
    };

    navigator.serviceWorker.controller.postMessage(
      { type: 'GET_CACHE_STATUS' },
      [messageChannel.port2]
    );

    // 타임아웃 설정 (3초)
    setTimeout(() => resolve(null), 3000);
  });
}

/**
 * Service Worker 캐시 삭제
 */
export async function clearCache(): Promise<boolean> {
  if (typeof window === 'undefined' || !navigator.serviceWorker.controller) {
    return false;
  }

  return new Promise((resolve) => {
    const messageChannel = new MessageChannel();

    messageChannel.port1.onmessage = (event) => {
      resolve(event.data.success);
    };

    navigator.serviceWorker.controller.postMessage(
      { type: 'CLEAR_CACHE' },
      [messageChannel.port2]
    );

    setTimeout(() => resolve(false), 3000);
  });
}

/**
 * Service Worker 등록 해제
 */
export async function unregisterServiceWorker(): Promise<boolean> {
  if (typeof window === 'undefined' || !('serviceWorker' in navigator)) {
    return false;
  }

  try {
    const registrations = await navigator.serviceWorker.getRegistrations();
    for (const registration of registrations) {
      await registration.unregister();
    }
    return true;
  } catch (error) {
    console.error('Service Worker unregistration failed:', error);
    return false;
  }
}