const BUILD = '2c4e8c046409'
// The service worker of the BM student app. The Vite plugin bm-service-worker
// (vite.config.ts) emits this file as /sw.js and replaces the build id above,
// so every build that changes an asset gets a fresh cache and an update prompt.
//
// It is deliberately minimal: hashed /assets/* files are cached, navigations
// go to the network with an offline fallback page, and everything else is
// left to the browser untouched.

const CACHE = 'bm-' + BUILD
const OFFLINE_URL = '/offline.html'

// API, realtime, upload and admin paths are never intercepted. The speaker
// deck (/_presentations) holds notes and text meant only for its owner, and
// no response from these prefixes may ever land in a device cache. The list
// mirrors reservedPrefixes in plugins/jz/bm/static.go plus /ws and the admin.
const SKIP_PREFIXES = ['/_user', '/_bm', '/_quizzes', '/_presentations', '/api', '/ws', '/storage', '/bmadmin']

// swRoute classifies a request: 'skip' leaves it to the browser, 'page' is a
// network-only navigation with an offline fallback, 'asset' is cache-first.
function swRoute(method, href, mode, origin) {
  if (method !== 'GET') return 'skip'
  let url
  try {
    url = new URL(href)
  } catch {
    return 'skip'
  }
  if (url.origin !== origin) return 'skip'
  const path = url.pathname
  // The reserved check runs before the navigation check, so even a top-level
  // navigation to /storage/... or /bmadmin is never touched.
  for (const prefix of SKIP_PREFIXES) {
    if (path === prefix || path.startsWith(prefix + '/')) return 'skip'
  }
  if (mode === 'navigate') return 'page'
  if (path.startsWith('/assets/')) return 'asset'
  return 'skip'
}

self.addEventListener('install', (event) => {
  // No skipWaiting here: a new worker waits until the user asks to refresh.
  event.waitUntil(caches.open(CACHE).then((cache) => cache.add(new Request(OFFLINE_URL, { cache: 'reload' }))))
})

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

self.addEventListener('fetch', (event) => {
  const req = event.request
  const route = swRoute(req.method, req.url, req.mode, self.location.origin)
  if (route === 'skip') return

  if (route === 'page') {
    // Navigations are never stored: an HTML response could carry user state.
    event.respondWith(
      fetch(req).catch(() => caches.match(OFFLINE_URL).then((res) => res || Response.error())),
    )
    return
  }

  event.respondWith(
    caches.open(CACHE).then((cache) =>
      cache.match(req).then((hit) => {
        if (hit) return hit
        return fetch(req).then((res) => {
          if (res.status === 200 && res.type === 'basic') cache.put(req, res.clone())
          return res
        })
      }),
    ),
  )
})

self.addEventListener('message', (event) => {
  if (event.data && event.data.type === 'SKIP_WAITING') self.skipWaiting()
})