const CACHE_NAME = 'faultcodes-v1';
const ASSETS = [
  '/',
  '/static/styles.css',
  '/static/app.js',
  '/static/manifest.webmanifest'
];

self.addEventListener('install', (e) => {
  e.waitUntil((async () => {
    const cache = await caches.open(CACHE_NAME);
    await cache.addAll(ASSETS);
  })());
  self.skipWaiting();
});

self.addEventListener('activate', (e) => {
  e.waitUntil((async () => {
    const keys = await caches.keys();
    await Promise.all(keys.filter(k => k !== CACHE_NAME).map(k => caches.delete(k)));
  })());
  self.clients.claim();
});

self.addEventListener('fetch', (e) => {
  const req = e.request;
  if (req.method !== 'GET') return;
  e.respondWith((async () => {
    const cache = await caches.open(CACHE_NAME);
    const cached = await cache.match(req);
    if (cached) return cached;
    try {
      const fresh = await fetch(req);
      if (fresh && fresh.ok) cache.put(req, fresh.clone());
      return fresh;
    } catch {
      return cached || Response.error();
    }
  })());
});