// GuestGuard Scanner — minimal service worker.
//
// Why so light: the scanner is an online tool. Letting the SW cache and
// then serve stale check-in submissions would create double-arrivals
// and lost data. So this SW only:
//
//   1. Claims clients on install so the "Add to home screen" launcher
//      opens the latest version straight away.
//   2. Caches the bare app shell (the page itself + jsQR) so the
//      volunteer can re-open the scanner if the phone briefly drops
//      4G. Auth + check-in calls always go to network.
//
// Anything fancier (background sync queues, IndexedDB cache of pending
// check-ins) belongs in a later iteration once we have a story for
// merging conflicts.

const SHELL_CACHE = 'gg-scanner-shell-v1'
const SHELL_URLS = [
  '/scanner',
  'https://cdn.jsdelivr.net/npm/jsqr@1.4.0/dist/jsQR.js',
]

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

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

self.addEventListener('fetch', (event) => {
  const url = new URL(event.request.url)

  // Never cache API calls — stale check-ins are worse than offline.
  if (url.pathname.startsWith('/events/') || url.pathname.startsWith('/auth/')) {
    return
  }

  // Network-first for the shell URLs so a deployment is reflected on
  // the next reload; fall back to cache only when offline.
  if (event.request.mode === 'navigate' || SHELL_URLS.some((u) => event.request.url.endsWith(u))) {
    event.respondWith(
      fetch(event.request)
        .then((res) => {
          const copy = res.clone()
          caches.open(SHELL_CACHE).then((c) => c.put(event.request, copy)).catch(() => {})
          return res
        })
        .catch(() => caches.match(event.request).then((r) => r || Response.error())),
    )
  }
})