const CACHE_NAME = 'erp-shell-v1';
const OFFLINE_URL = '/offline.html';
const PRECACHE_URLS = ['/', '/index.html', '/manifest.webmanifest', '/pwa-icon.svg', OFFLINE_URL];

self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(CACHE_NAME).then((cache) => cache.addAll(PRECACHE_URLS))
  );
  self.skipWaiting();
});

self.addEventListener('activate', (event) => {
  event.waitUntil(
    caches.keys().then((cacheNames) =>
      Promise.all(
        cacheNames
          .filter((name) => name !== CACHE_NAME)
          .map((name) => caches.delete(name))
      )
    )
  );
  self.clients.claim();
});

self.addEventListener('fetch', (event) => {
  const { request } = event;
  if (request.method !== 'GET') return;

  const url = new URL(request.url);
  if (url.origin !== self.location.origin) return;

  if (request.mode === 'navigate') {
    event.respondWith(
      fetch(request)
        .then((response) => {
          const copy = response.clone();
          caches.open(CACHE_NAME).then((cache) => cache.put(request, copy));
          return response;
        })
        .catch(async () => {
          const cached = await caches.match(request);
          return cached || caches.match(OFFLINE_URL);
        })
    );
    return;
  }

  if (['style', 'script', 'worker', 'font', 'image'].includes(request.destination)) {
    event.respondWith(
      caches.match(request).then((cached) => {
        const networkFetch = fetch(request)
          .then((response) => {
            const copy = response.clone();
            caches.open(CACHE_NAME).then((cache) => cache.put(request, copy));
            return response;
          })
          .catch(() => cached);
        return cached || networkFetch;
      })
    );
  }
});