const CACHE_NAME = 'mykindlebox-shell-v1'
const SHELL_URLS = ['/', '/favicon.svg', '/icon-192.png', '/manifest.json']

// Vendored Tesseract OCR runtime: the worker, the three feature-detect WASM core
// variants (relaxedSIMD / SIMD / plain LSTM — only one is loaded per browser, but
// we can't know which ahead of time, so all are cached), and the English language
// data. These are large (~16 MB total) but static and versioned with the app, so
// they're precached on install and served cache-first (see the fetch handler):
// once stored they never need re-fetching, and the pedigree scanner must work
// fully offline. See FEATURE_OCR_Pedigree_Scan.md Q7.
//
// UPGRADE CONTRACT: cache-first means installed clients serve these from cache
// forever. If tesseract.js is ever upgraded (package.json pins the exact version
// for this reason) the files under public/tesseract/ must be re-vendored AND
// CACHE_NAME must be bumped, or existing clients keep the old worker/WASM while
// the app bundle uses the new library.
const TESSERACT_URLS = [
  '/tesseract/worker.min.js',
  '/tesseract/tesseract-core-lstm.wasm.js',
  '/tesseract/tesseract-core-simd-lstm.wasm.js',
  '/tesseract/tesseract-core-relaxedsimd-lstm.wasm.js',
  '/tesseract/eng.traineddata',
]

self.addEventListener('install', (event) => {
  event.waitUntil(
    caches.open(CACHE_NAME).then((cache) =>
      Promise.all([
        cache.addAll(SHELL_URLS),
        // The ~16 MB Tesseract batch is best-effort: if it fails (flaky first
        // load, missing file in a bad deploy), the shell must still install —
        // the cache-first fetch branch below backfills these lazily the next
        // time the scanner runs online.
        cache.addAll(TESSERACT_URLS).catch(() => {}),
      ]),
    ),
  )
})

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

// Network-first with a cache fallback for the app shell (HTML/JS/CSS/static
// assets), so a previously-visited bundle still loads offline. API requests
// are left alone — they should fail fast so the UI can show its own inline
// "offline" state instead of serving stale data silently.
self.addEventListener('fetch', (event) => {
  const { request } = event
  if (request.method !== 'GET') return

  const url = new URL(request.url)
  if (url.pathname.startsWith('/api/') || url.pathname.startsWith('/uploads/')) return

  // Tesseract assets are static and large — cache-first. Serve the stored copy
  // outright when present (no network round-trip, works offline), and only hit
  // the network on a cache miss, storing the result for next time.
  if (url.pathname.startsWith('/tesseract/')) {
    event.respondWith(
      caches.match(request).then(
        (cached) =>
          cached ??
          fetch(request).then((response) => {
            if (response.ok) {
              const copy = response.clone()
              caches.open(CACHE_NAME).then((cache) => cache.put(request, copy))
            }
            return response
          }),
      ),
    )
    return
  }

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