const CACHE_NAME = 'mims-library-v1';
const PRECACHE_URLS = [
  '/',
  '/offline.html',
  '/favicon.svg',
  '/manifest.json'
];

// Install: precache essential resources
self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(CACHE_NAME).then((cache) => cache.addAll(PRECACHE_URLS))
  );
  self.skipWaiting();
});

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

// Fetch: tiered caching strategy
self.addEventListener('fetch', (event) => {
  const { request } = event;
  const url = new URL(request.url);

  // Only handle same-origin
  if (url.origin !== location.origin) return;

  // Static assets: cache-first
  if (/\.(css|js|jpg|jpeg|png|gif|svg|woff|woff2|ico)$/.test(url.pathname)) {
    event.respondWith(
      caches.match(request).then((cached) =>
        cached || fetch(request).then((response) => {
          const clone = response.clone();
          caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
          return response;
        })
      )
    );
    return;
  }

  // PDFs: network-first, cache on success
  if (/\.pdf$/.test(url.pathname)) {
    event.respondWith(
      fetch(request)
        .then((response) => {
          const clone = response.clone();
          caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
          return response;
        })
        .catch(() => caches.match(request))
    );
    return;
  }

  // HTML pages: network-first with offline fallback
  event.respondWith(
    fetch(request)
      .then((response) => {
        const clone = response.clone();
        caches.open(CACHE_NAME).then((cache) => cache.put(request, clone));
        return response;
      })
      .catch(() =>
        caches.match(request).then((cached) => cached || caches.match('/offline.html'))
      )
  );
});