/* Service Worker: App-Shell cachen (Offline + schneller Start).
   Version bei jeder Template-/Asset-Änderung bumpen (SHELL_VERSION),
   damit alte Caches beim Activate bereinigt werden. */
const SHELL_VERSION = 'v1';
const SHELL_CACHE = 'essen-shell-' + SHELL_VERSION;
const SHELL = [
  '/',
  '/manifest.webmanifest',
  '/js/htmx.min.js',
  '/js/sortable.min.js',
  '/icons/icon-192.png',
  '/icons/icon-512.png',
];

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

self.addEventListener('activate', (event) => {
  event.waitUntil(
    caches
      .keys()
      .then((keys) =>
        Promise.all(
          keys
            .filter((key) => key.startsWith('essen-shell-') && key !== SHELL_CACHE)
            .map((key) => caches.delete(key))
        )
      )
      .then(() => self.clients.claim())
  );
});

self.addEventListener('fetch', (event) => {
  const url = new URL(event.request.url);
  if (event.request.method !== 'GET' || url.origin !== self.location.origin) {
    return;
  }

  // Navigations: erst Netzwerk (frische Deploys!), dann Cache (Offline).
  if (event.request.mode === 'navigate') {
    event.respondWith(
      fetch(event.request)
        .then((response) => {
          const kopie = response.clone();
          caches.open(SHELL_CACHE).then((cache) => cache.put(event.request, kopie));
          return response;
        })
        .catch(() =>
          caches.match(event.request).then((treffer) => treffer || caches.match('/'))
        )
    );
    return;
  }

  // Statische Assets: Cache-first (unveränderlich pro Version).
  if (
    url.pathname.startsWith('/js/') ||
    url.pathname.startsWith('/icons/') ||
    url.pathname === '/manifest.webmanifest'
  ) {
    event.respondWith(
      caches.match(event.request).then(
        (treffer) =>
          treffer ||
          fetch(event.request).then((response) => {
            const kopie = response.clone();
            caches.open(SHELL_CACHE).then((cache) => cache.put(event.request, kopie));
            return response;
          })
      )
    );
  }
});