// musicshare service worker.
// Deliberately small: live data must always come from the network, so we only
// cache Next.js's immutable build assets, and show an offline page when a
// navigation fails. (Web push notifications will hook in here later.)
const VERSION = 'v1';
const STATIC_CACHE = `static-${VERSION}`;
const OFFLINE_URL = '/offline.html';

self.addEventListener('install', (event) => {
  event.waitUntil(caches.open(STATIC_CACHE).then((cache) => cache.addAll([OFFLINE_URL, '/icon-192.png'])));
  self.skipWaiting();
});

self.addEventListener('activate', (event) => {
  event.waitUntil(
    caches
      .keys()
      .then((keys) => Promise.all(keys.filter((k) => k !== STATIC_CACHE).map((k) => caches.delete(k))))
      .then(() => 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; // API calls, artwork, etc.: straight to the network

  // Hashed build assets never change: cache first.
  if (url.pathname.startsWith('/_next/static/')) {
    event.respondWith(
      caches.match(request).then(
        (hit) =>
          hit ||
          fetch(request).then((res) => {
            const copy = res.clone();
            caches.open(STATIC_CACHE).then((cache) => cache.put(request, copy));
            return res;
          }),
      ),
    );
    return;
  }

  // Pages: always fresh; offline page if the network is gone.
  if (request.mode === 'navigate') {
    event.respondWith(fetch(request).catch(() => caches.match(OFFLINE_URL)));
  }
});