/*
 * UdyamLinc service worker — app-shell precache + stale-while-revalidate.
 *
 * Scope of the offline promise (deck feature 7): the enterprise PWA must open,
 * render and accept ledger entries with zero connectivity. Ledger writes are
 * queued in localStorage by the app itself (see lib/ledgerStore.ts); this worker
 * only guarantees the shell and its assets are reachable.
 */
const CACHE = 'udyamlinc-v1'
const SHELL = ['/', '/app', '/index.html', '/manifest.webmanifest', '/udyamlinc-tile.svg']

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

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

self.addEventListener('fetch', (event) => {
  const req = event.request
  if (req.method !== 'GET') return

  const url = new URL(req.url)
  // API calls are never served stale — the app falls back to its local store instead.
  if (url.pathname.includes('/api/')) return

  // Navigations: network first, fall back to the cached shell when offline.
  if (req.mode === 'navigate') {
    event.respondWith(fetch(req).catch(() => caches.match('/index.html')))
    return
  }

  // Assets: cache first, refresh in the background.
  event.respondWith(
    caches.match(req).then((hit) => {
      const network = fetch(req)
        .then((res) => {
          if (res.ok) {
            const copy = res.clone()
            caches.open(CACHE).then((c) => c.put(req, copy))
          }
          return res
        })
        .catch(() => hit)
      return hit || network
    }),
  )
})