feat: implement ironclad offline strategy with pre-caching and root fallback

public/sw.js

@@ -1,5 +1,13 @@
-const CACHE_NAME = 'whisky-vault-v3'; // Increment version to apply new strategy
-const ASSETS_TO_CACHE = [
+const CACHE_NAME = 'whisky-vault-v4'; // Increment version for "Ironclad" strategy
+
+// CONFIG: Core pages and assets to pre-cache immediately on install
+const CORE_PAGES = [
+    '/',              // Dashboard / Home
+    '/tasting/new',   // Critical: Add Tasting Screen
+    '/scan',          // Critical: Scan Screen
+];
+
+const STATIC_ASSETS = [
     '/manifest.json',
     '/icon-192.png',
     '/icon-512.png',
@@ -9,9 +17,12 @@ const ASSETS_TO_CACHE = [
 self.addEventListener('install', (event) => {
     event.waitUntil(
         caches.open(CACHE_NAME).then((cache) => {
-            return cache.addAll(ASSETS_TO_CACHE);
+            console.log('⚡ PWA: Pre-caching core pages and assets...');
+            // Combine items to cache
+            return cache.addAll([...CORE_PAGES, ...STATIC_ASSETS]);
         })
     );
+    self.skipWaiting();
 });
 
 self.addEventListener('activate', (event) => {
@@ -63,7 +74,24 @@ self.addEventListener('fetch', (event) => {
         return;
     }
 
-    // 1. ASSETS & APP SHELL: Stale-While-Revalidate
+    // 1. NEXT.JS DATA (RSC): Stale-While-Revalidate with empty JSON fallback
+    if (url.pathname.startsWith('/_next/data/')) {
+        event.respondWith(
+            fetchWithTimeout(event.request, 2000)
+                .catch(async () => {
+                    const cachedResponse = await caches.match(event.request);
+                    if (cachedResponse) return cachedResponse;
+
+                    // Fallback to empty JSON to prevent "Application Error" screens
+                    return new Response(JSON.stringify({}), {
+                        headers: { 'Content-Type': 'application/json' }
+                    });
+                })
+        );
+        return;
+    }
+
+    // 2. ASSETS & APP SHELL: Stale-While-Revalidate
     const isAsset = event.request.destination === 'style' ||
         event.request.destination === 'script' ||
         event.request.destination === 'worker' ||
@@ -89,18 +117,21 @@ self.addEventListener('fetch', (event) => {
         return;
     }
 
-    // 2. NAVIGATION: Network-First with 3s Timeout
+    // 3. NAVIGATION: Ironclad Navigation Fallback
     if (event.request.mode === 'navigate') {
         event.respondWith(
             fetchWithTimeout(event.request, 3000)
-                .catch(() => {
-                    console.log('[SW] Navigation network failure or timeout, falling back to cache');
-                    return caches.match(event.request);
+                .catch(async () => {
+                    console.log('[SW] Navigation network failure, attempting cache fallback');
+                    const cachedResponse = await caches.match(event.request);
+                    if (cachedResponse) return cachedResponse;
+
+                    // CRITICAL FALLBACK: Load the Root App Shell ('/')
+                    // This allows Next.js to bootstrap and handle the routing client-side
+                    console.warn('⚠️ PWA: Route not in cache, fallback to Root App Shell');
+                    return caches.match('/');
                 })
         );
         return;
     }
-
-    // Default: Network-Only or default fetch
-    return;
 });