const CACHE_NAME = 'credittracker-v47';
const ASSETS = [
  './index.html',
  './manifest.json',
  './icon.svg',
  './icon-maskable.svg'
];

// Install: pre-cache all app shell files
self.addEventListener('install', event => {
  event.waitUntil(
    caches.open(CACHE_NAME).then(cache => cache.addAll(ASSETS))
  );
  self.skipWaiting();
});

// Activate: clean up 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();
});

// Lets the page ask "what version are you actually running" (Settings screen indicator)
self.addEventListener('message', event => {
  if (event.data && event.data.type === 'GET_VERSION') {
    event.source.postMessage({ type: 'VERSION', version: CACHE_NAME });
  }
});

// Fetch: network-first for the app shell (so edits show up without a version bump),
// cache-first for everything else (icons, manifest, external libs)
self.addEventListener('fetch', event => {
  if (event.request.method !== 'GET') return;

  const reqUrl = new URL(event.request.url);
  const isSameOrigin = reqUrl.origin === self.location.origin;
  const isAppShell = isSameOrigin && (event.request.mode === 'navigate' || reqUrl.pathname.endsWith('/index.html'));

  if (isAppShell) {
    event.respondWith(
      fetch(event.request).then(response => {
        if (response.ok) {
          const clone = response.clone();
          caches.open(CACHE_NAME).then(cache => cache.put(event.request, clone));
        }
        return response;
      }).catch(() => caches.match(event.request).then(cached => cached || caches.match('./index.html')))
    );
    return;
  }

  event.respondWith(
    caches.match(event.request).then(cached => {
      if (cached) return cached;
      return fetch(event.request).then(response => {
        if (response.ok && isSameOrigin) {
          const clone = response.clone();
          caches.open(CACHE_NAME).then(cache => cache.put(event.request, clone));
        }
        return response;
      });
    }).catch(() => {
      // Offline fallback only for external CDN fetches: fail loudly instead of masking with app HTML
      if (isSameOrigin) return caches.match('./index.html');
      return Response.error();
    })
  );
});