const CACHE_NAME = 'din-v1';
const STATIC_ASSETS = [
  '/',
  '/index.html',
  '/style.css',
  '/app.js',
  '/manifest.json',
  '/icon-72.png',
  '/icon-96.png',
  '/icon-128.png',
  '/icon-144.png',
  '/icon-192.png',
  '/icon-512.png'
];

// 安装时缓存静态资源
self.addEventListener('install', (e) => {
  e.waitUntil(
    caches.open(CACHE_NAME).then((cache) => {
      return cache.addAll(STATIC_ASSETS);
    })
  );
  self.skipWaiting();
});

// 激活时清理旧缓存
self.addEventListener('activate', (e) => {
  e.waitUntil(
    caches.keys().then((cacheNames) => {
      return Promise.all(
        cacheNames
          .filter((name) => name !== CACHE_NAME)
          .map((name) => caches.delete(name))
      );
    })
  );
  self.clients.claim();
});

// 拦截请求
self.addEventListener('fetch', (e) => {
  const { request } = e;
  const url = new URL(request.url);

  // API 请求：网络优先，失败时返回缓存
  if (url.pathname.startsWith('/api/')) {
    e.respondWith(
      fetch(request)
        .then((response) => {
          // 缓存成功的 GET 请求
          if (request.method === 'GET') {
            const clone = response.clone();
            caches.open(CACHE_NAME).then((cache) => {
              cache.put(request, clone);
            });
          }
          return response;
        })
        .catch(() => {
          return caches.match(request).then((cached) => {
            if (cached) return cached;
            // 返回离线数据
            if (url.pathname === '/api/stats') {
              return new Response(
                JSON.stringify({ today: 0, week: 0, month: 0, total: 0 }),
                { headers: { 'Content-Type': 'application/json' } }
              );
            }
            if (url.pathname === '/api/din') {
              return new Response(JSON.stringify([]), {
                headers: { 'Content-Type': 'application/json' }
              });
            }
            return new Response('Offline', { status: 503 });
          });
        })
    );
    return;
  }

  // 静态资源：缓存优先
  e.respondWith(
    caches.match(request).then((cached) => {
      return cached || fetch(request);
    })
  );
});

// 后台同步（用于离线时记录的数据）
self.addEventListener('sync', (e) => {
  if (e.tag === 'sync-din') {
    e.waitUntil(syncPendingDins());
  }
});

async function syncPendingDins() {
  // 从 IndexedDB 获取待同步的记录并发送
  // 这里简化处理，实际项目可以用 idb 库
  console.log('Syncing pending dins...');
}