stage 1

public/sw.js

@@ -0,0 +1,118 @@
+const CACHE_NAME = 'check-list-poc-v3';
+const DYNAMIC_CACHE_LIMIT = 50;
+const APP_SHELL = [
+  '/',
+  '/user.html',
+  '/admin.html',
+  '/styles.css',
+  '/app.js',
+  '/manifest.webmanifest',
+  '/js/constants.js',
+  '/js/state.js',
+  '/js/i18n.js',
+  '/js/utils.js',
+  '/js/db.js',
+  '/js/api.js',
+  '/js/validation.js',
+  '/js/images.js',
+  '/js/image-worker.js',
+  '/js/forms.js',
+  '/js/renderer.js',
+  '/js/export.js'
+];
+
+/*
+ * P5 — Bounded SW cache with LRU eviction. Static shell assets use cache-first.
+ * API requests use network-first with automatic pruning of old dynamic entries
+ * so the cache stays within DYNAMIC_CACHE_LIMIT.
+ */
+self.addEventListener('install', (event) => {
+  event.waitUntil(caches.open(CACHE_NAME).then((cache) => cache.addAll(APP_SHELL)));
+  self.skipWaiting();
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((keys) =>
+      Promise.all(
+        keys.filter((key) => key !== CACHE_NAME).map((key) => caches.delete(key))
+      )
+    )
+  );
+  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;
+  }
+
+  if (url.pathname.startsWith('/api/')) {
+    event.respondWith(networkFirst(request));
+    return;
+  }
+
+  event.respondWith(cacheFirst(request));
+});
+
+async function cacheFirst(request) {
+  const cache = await caches.open(CACHE_NAME);
+  const cached = await cache.match(request);
+
+  if (cached) {
+    return cached;
+  }
+
+  const response = await fetch(request);
+  cache.put(request, response.clone());
+  return response;
+}
+
+async function networkFirst(request) {
+  const cache = await caches.open(CACHE_NAME);
+
+  try {
+    const response = await fetch(request);
+    cache.put(request, response.clone());
+    await trimCache(cache, DYNAMIC_CACHE_LIMIT);
+    return response;
+  } catch {
+    const cached = await cache.match(request);
+
+    if (cached) {
+      return cached;
+    }
+
+    return new Response(JSON.stringify({ message: 'Offline and no cached response available.' }), {
+      status: 503,
+      headers: { 'Content-Type': 'application/json' }
+    });
+  }
+}
+
+/**
+ * P5 — Remove oldest entries once the cache exceeds the limit. Only dynamic
+ * (non-shell) entries are evicted so the app shell remains always available.
+ */
+async function trimCache(cache, maxEntries) {
+  const keys = await cache.keys();
+
+  if (keys.length <= maxEntries) {
+    return;
+  }
+
+  const shellSet = new Set(APP_SHELL.map((path) => new URL(path, self.location.origin).href));
+  const evictable = keys.filter((request) => !shellSet.has(request.url));
+
+  while (evictable.length + APP_SHELL.length > maxEntries && evictable.length > 0) {
+    await cache.delete(evictable.shift());
+  }
+}