/**
 * Service Worker - PWA 离线缓存
 * 
 * 功能描述：
 * 提供 PWA 离线访问能力，缓存关键资源。
 * 
 * 缓存策略：
 * - 静态资源：Cache First
 * - API 请求：Network First
 * - 图片资源：Stale While Revalidate
 * 
 * @author Timeline Team
 * @date 2024
 */

const CACHE_NAME = 'timeline-v1';
const STATIC_CACHE = 'timeline-static-v1';
const API_CACHE = 'timeline-api-v1';
const IMAGE_CACHE = 'timeline-image-v1';

// 需要缓存的静态资源
const STATIC_ASSETS = [
  '/',
  '/index.html',
  '/manifest.json',
  '/icons/icon-192x192.png',
  '/icons/icon-512x512.png',
];

// 安装事件
self.addEventListener('install', (event) => {
  console.log('[ServiceWorker] 安装');
  
  event.waitUntil(
    caches.open(STATIC_CACHE).then((cache) => {
      console.log('[ServiceWorker] 缓存静态资源');
      return cache.addAll(STATIC_ASSETS);
    })
  );
  
  // 立即激活
  self.skipWaiting();
});

// 激活事件
self.addEventListener('activate', (event) => {
  console.log('[ServiceWorker] 激活');
  
  event.waitUntil(
    caches.keys().then((cacheNames) => {
      return Promise.all(
        cacheNames.map((cacheName) => {
          // 删除旧版本缓存
          if (cacheName !== STATIC_CACHE && 
              cacheName !== API_CACHE && 
              cacheName !== IMAGE_CACHE) {
            console.log('[ServiceWorker] 删除旧缓存:', cacheName);
            return caches.delete(cacheName);
          }
        })
      );
    })
  );
  
  // 立即控制所有页面
  self.clients.claim();
});

// 请求拦截
self.addEventListener('fetch', (event) => {
  const { request } = event;
  const url = new URL(request.url);
  
  // 只处理同源请求
  if (url.origin !== location.origin) {
    return;
  }
  
  // 根据请求类型选择缓存策略
  if (isApiRequest(url)) {
    // API 请求：Network First
    event.respondWith(networkFirst(request, API_CACHE));
  } else if (isImageRequest(request)) {
    // 图片请求：Stale While Revalidate
    event.respondWith(staleWhileRevalidate(request, IMAGE_CACHE));
  } else {
    // 静态资源：Cache First
    event.respondWith(cacheFirst(request, STATIC_CACHE));
  }
});

/**
 * 判断是否为 API 请求
 */
function isApiRequest(url) {
  return url.pathname.startsWith('/api/') || 
         url.pathname.startsWith('/api/story/') ||
         url.pathname.startsWith('/file/') ||
         url.pathname.startsWith('/user/');
}

/**
 * 判断是否为图片请求
 */
function isImageRequest(request) {
  return request.destination === 'image' ||
         request.url.match(/\.(jpg|jpeg|png|gif|webp|svg)$/i);
}

/**
 * Cache First 策略
 * 优先使用缓存，缓存不存在时请求网络
 */
async function cacheFirst(request, cacheName) {
  const cache = await caches.open(cacheName);
  const cached = await cache.match(request);
  
  if (cached) {
    return cached;
  }
  
  try {
    const response = await fetch(request);
    if (response.ok) {
      cache.put(request, response.clone());
    }
    return response;
  } catch (error) {
    // 网络请求失败，返回离线页面
    if (request.mode === 'navigate') {
      return caches.match('/index.html');
    }
    throw error;
  }
}

/**
 * Network First 策略
 * 优先请求网络，失败时使用缓存
 */
async function networkFirst(request, cacheName) {
  const cache = await caches.open(cacheName);
  
  try {
    const response = await fetch(request);
    if (response.ok) {
      cache.put(request, response.clone());
    }
    return response;
  } catch (error) {
    const cached = await cache.match(request);
    if (cached) {
      return cached;
    }
    throw error;
  }
}

/**
 * Stale While Revalidate 策略
 * 立即返回缓存，同时后台更新
 */
async function staleWhileRevalidate(request, cacheName) {
  const cache = await caches.open(cacheName);
  const cached = await cache.match(request);
  
  // 后台更新缓存
  const fetchPromise = fetch(request).then((response) => {
    if (response.ok) {
      cache.put(request, response.clone());
    }
    return response;
  });
  
  // 返回缓存或等待网络响应
  return cached || fetchPromise;
}

// 推送通知
self.addEventListener('push', (event) => {
  console.log('[ServiceWorker] 收到推送');
  
  const data = event.data ? event.data.json() : {};
  
  const options = {
    body: data.body || '您有新的消息',
    icon: '/icons/icon-192x192.png',
    badge: '/icons/badge-72x72.png',
    vibrate: [100, 50, 100],
    data: {
      url: data.url || '/'
    },
    actions: [
      { action: 'open', title: '查看' },
      { action: 'close', title: '关闭' }
    ]
  };
  
  event.waitUntil(
    self.registration.showNotification(data.title || 'Timeline', options)
  );
});

// 通知点击
self.addEventListener('notificationclick', (event) => {
  console.log('[ServiceWorker] 通知点击');
  
  event.notification.close();
  
  if (event.action === 'open' || !event.action) {
    event.waitUntil(
      clients.openWindow(event.notification.data.url)
    );
  }
});

// 后台同步
self.addEventListener('sync', (event) => {
  console.log('[ServiceWorker] 后台同步:', event.tag);
  
  if (event.tag === 'sync-timeline') {
    event.waitUntil(syncTimeline());
  }
});

/**
 * 同步时间线数据
 */
async function syncTimeline() {
  // 获取待同步的数据
  const pendingData = await getPendingData();
  
  for (const item of pendingData) {
    try {
      await fetch('/api/story/item', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(item)
      });
      
      // 同步成功，删除待同步记录
      await removePendingData(item.id);
    } catch (error) {
      console.error('[ServiceWorker] 同步失败:', error);
    }
  }
}