// Service Worker for Great Lakes Ice Report PWA
const CACHE_NAME = 'ice-report-v4';
const OFFLINE_URL = '/offline.html';

// Files to cache for offline functionality
const CACHE_FILES = [
  '/',
  '/index.html',
  '/admin.html',
  '/privacy.html',
  '/style.css',
  '/app.js',
  '/admin.js',
  '/utils.js',
  '/version-footer.js',
  '/manifest.json',
  OFFLINE_URL
];

// Install event - cache essential files
self.addEventListener('install', (event) => {
  console.log('Service Worker: Installing...');
  
  event.waitUntil(
    caches.open(CACHE_NAME)
      .then((cache) => {
        console.log('Service Worker: Caching files');
        return cache.addAll(CACHE_FILES);
      })
      .then(() => {
        console.log('Service Worker: Files cached successfully');
        return self.skipWaiting();
      })
      .catch((error) => {
        console.error('Service Worker: Cache failed:', error);
      })
  );
});

// Activate event - clean up old caches
self.addEventListener('activate', (event) => {
  console.log('Service Worker: Activating...');
  
  event.waitUntil(
    caches.keys()
      .then((cacheNames) => {
        return Promise.all(
          cacheNames
            .filter((cacheName) => cacheName !== CACHE_NAME)
            .map((cacheName) => {
              console.log('Service Worker: Deleting old cache:', cacheName);
              return caches.delete(cacheName);
            })
        );
      })
      .then(() => {
        console.log('Service Worker: Activated');
        return self.clients.claim();
      })
  );
});

// Fetch event - serve cached content when offline
self.addEventListener('fetch', (event) => {
  // Only handle GET requests
  if (event.request.method !== 'GET') {
    return;
  }

  // Skip cross-origin requests
  if (!event.request.url.startsWith(self.location.origin)) {
    return;
  }

  event.respondWith(
    caches.match(event.request)
      .then((response) => {
        // Return cached version if available
        if (response) {
          return response;
        }

        // Try to fetch from network
        return fetch(event.request)
          .then((response) => {
            // Don't cache non-successful responses
            if (!response || response.status !== 200 || response.type !== 'basic') {
              return response;
            }

            // Clone the response for caching
            const responseToCache = response.clone();

            // Cache successful responses for static assets
            if (event.request.url.match(/\.(js|css|html|png|jpg|jpeg|gif|svg|ico|woff|woff2)$/)) {
              caches.open(CACHE_NAME)
                .then((cache) => {
                  cache.put(event.request, responseToCache);
                });
            }

            return response;
          })
          .catch(() => {
            // If network fails and we're requesting an HTML page, show offline page
            if (event.request.headers.get('accept').includes('text/html')) {
              return caches.match(OFFLINE_URL);
            }
            
            // For other requests, just fail
            throw new Error('Network failed and no cache available');
          });
      })
  );
});

// Background sync for when connection is restored
self.addEventListener('sync', (event) => {
  if (event.tag === 'background-sync') {
    console.log('Service Worker: Background sync triggered');
    // Could implement queued location submissions here
  }
});

// Push notifications (for future use)
self.addEventListener('push', (event) => {
  if (event.data) {
    const data = event.data.json();
    console.log('Service Worker: Push message received:', data);
    
    // Could show notifications about severe weather warnings
    const options = {
      body: data.body,
      icon: '/icons/icon-192.png',
      badge: '/icons/icon-72.png',
      tag: 'ice-report',
      renotify: true
    };
    
    event.waitUntil(
      self.registration.showNotification(data.title, options)
    );
  }
});