const CACHE_NAME = 'coastal-timesheet-v1';
const STATIC_ASSETS = [
  '/',
  '/manifest.json',
  '/icons/icon-192.svg',
  '/icons/icon-512.svg',
];

// Install: cache shell
self.addEventListener('install', (e) => {
  e.waitUntil(
    caches.open(CACHE_NAME).then((cache) => cache.addAll(STATIC_ASSETS))
  );
  self.skipWaiting();
});

// Activate: clean old caches
self.addEventListener('activate', (e) => {
  e.waitUntil(
    caches.keys().then((keys) =>
      Promise.all(keys.filter((k) => k !== CACHE_NAME).map((k) => caches.delete(k)))
    )
  );
  self.clients.claim();
});

// Fetch: network-first for API, cache-first for assets
self.addEventListener('fetch', (e) => {
  const { request } = e;
  const url = new URL(request.url);

  // Skip non-GET
  if (request.method !== 'GET') return;

  // API calls: network-first with offline fallback
  if (url.pathname.startsWith('/api/')) {
    e.respondWith(
      fetch(request)
        .then((res) => {
          // Cache successful GET API responses for offline use
          if (res.ok) {
            const clone = res.clone();
            caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
          }
          return res;
        })
        .catch(() => caches.match(request).then((cached) => cached || offlineResponse()))
    );
    return;
  }

  // Static assets: cache-first
  e.respondWith(
    caches.match(request).then((cached) => {
      if (cached) {
        // Background refresh
        fetch(request).then((res) => {
          if (res.ok) caches.open(CACHE_NAME).then((cache) => cache.put(request, res));
        }).catch(() => {});
        return cached;
      }
      return fetch(request).then((res) => {
        if (res.ok) {
          const clone = res.clone();
          caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
        }
        return res;
      }).catch(() => caches.match('/'));
    })
  );
});

function offlineResponse() {
  return new Response(
    JSON.stringify({ error: 'offline', message: 'You are currently offline. Data will sync when connection is restored.' }),
    { status: 503, headers: { 'Content-Type': 'application/json' } }
  );
}