feat(pwa): migrate service worker to SvelteKit native

Story 3: Migrate Service Worker to SvelteKit Native
- Replace workbox imports with SvelteKit $service-worker module
- Use build, files, version arrays for manual cache management
- Implement manual asset caching and cache cleanup
- Replace NavigationRoute with manual fetch handling
- Preserve all push notification event handlers exactly
- Preserve background sync and message handling functionality
- Service worker builds successfully as service-worker.mjs

SvelteKit native implementation ready - now need to enable registration

Refs: docs/plans/MigrateToNativeSvelteKitPWA.md

src/service-worker.ts

@@ -1,13 +1,20 @@
-/// <reference types="vite/client" />
+/// <reference types="@sveltejs/kit" />
+/// <reference no-default-lib="true"/>
+/// <reference lib="esnext" />
 /// <reference lib="webworker" />
 
-// Standard workbox imports - let the build process handle these
+import { build, files, version } from '$service-worker';
-import { cleanupOutdatedCaches, createHandlerBoundToURL, precacheAndRoute } from 'workbox-precaching';
-import { NavigationRoute, registerRoute } from 'workbox-routing';
 
 declare let self: ServiceWorkerGlobalScope;
 
-// Global error handler for service worker
+// Create a unique cache name for this deployment  
+const CACHE = `cache-${version}`;
+const ASSETS = [
+  ...build, // the app itself
+  ...files  // everything in `static`
+];
+
+// Global error handlers (preserve existing)
 self.addEventListener('error', (event) => {
   console.error('[SW] Global error:', event.error);
   console.error('[SW] Error details:', {
@@ -19,7 +26,6 @@ self.addEventListener('error', (event) => {
   });
 });
 
-// Unhandled promise rejection handler
 self.addEventListener('unhandledrejection', (event) => {
   console.error('[SW] Unhandled promise rejection:', event.reason);
   event.preventDefault(); // Prevent default browser behavior
@@ -27,90 +33,81 @@ self.addEventListener('unhandledrejection', (event) => {
 
 console.log('[SW] Service worker script loading...');
 
-// Get the workbox manifest - this will be injected by the build process
+// Install event - cache all assets
-const workboxManifest = self.__WB_MANIFEST;
+self.addEventListener('install', (event) => {
+  console.log('[SW] Installing service worker...');
+  
+  async function addFilesToCache() {
+    const cache = await caches.open(CACHE);
+    await cache.addAll(ASSETS);
+    console.log(`[SW] Cached ${ASSETS.length} assets`);
+  }
 
-// Wrap workbox initialization in try-catch with granular error handling
+  event.waitUntil(addFilesToCache());
-try {
+});
-  console.log('[SW] Initializing workbox...');
+
+// Activate event - clean up old caches
+self.addEventListener('activate', (event) => {
+  console.log('[SW] Activating service worker...');
   
-  // Check if workbox functions are available
+  async function deleteOldCaches() {
-  if (typeof precacheAndRoute !== 'function' || typeof cleanupOutdatedCaches !== 'function') {
+    for (const key of await caches.keys()) {
-    throw new Error('Workbox functions not available');
+      if (key !== CACHE) {
-  }
+        console.log('[SW] Deleting old cache:', key);
-  
+        await caches.delete(key);
-  // Detect environment - in production, workbox manifest should be injected
+      }
-  const isDevelopment = !workboxManifest || (workboxManifest && workboxManifest.length === 0);
-  console.log(`[SW] Running in ${isDevelopment ? 'development' : 'production'} mode`);
-  
-  // Enhanced manifest validation with detailed logging
-  if (!workboxManifest) {
-    if (isDevelopment) {
-      console.info('[SW] Workbox manifest not injected - running in development mode, precaching disabled');
-    } else {
-      console.warn('[SW] Workbox manifest not found in production build - this may be a build issue');
     }
-  } else if (!Array.isArray(workboxManifest)) {
+  }
-    console.error('[SW] Workbox manifest exists but is invalid format:', typeof workboxManifest);
+
-  } else if (workboxManifest.length === 0) {
+  event.waitUntil(deleteOldCaches());
-    console.warn('[SW] Workbox manifest is empty - no assets to precache');
+});
-  } else {
+
-    console.log(`[SW] Workbox manifest found with ${workboxManifest.length} entries`);
+// Fetch event - serve from cache with network fallback
-    console.debug('[SW] Manifest entries:', workboxManifest.slice(0, 5)); // Log first 5 for debugging
+self.addEventListener('fetch', (event) => {
-    
+  // ignore POST requests etc
+  if (event.request.method !== 'GET') return;
+
+  async function respond() {
+    const url = new URL(event.request.url);
+    const cache = await caches.open(CACHE);
+
+    // `build`/`files` can always be served from the cache
+    if (ASSETS.includes(url.pathname)) {
+      const response = await cache.match(url.pathname);
+      if (response) {
+        return response;
+      }
+    }
+
+    // for everything else, try the network first, but
+    // fall back to the cache if we're offline
     try {
-      precacheAndRoute(workboxManifest);
+      const response = await fetch(event.request);
-      console.log('[SW] Precaching completed successfully');
+      
-    } catch (precacheError) {
+      // if we're offline, fetch can return a value that is not a Response
-      console.error('[SW] Error during precaching:', precacheError);
+      // instead of throwing - and we can't pass this non-Response to respondWith
+      if (!(response instanceof Response)) {
+        throw new Error('invalid response from fetch');
+      }
+
+      if (response.status === 200) {
+        cache.put(event.request, response.clone());
+      }
+      return response;
+    } catch (err) {
+      const response = await cache.match(event.request);
+      if (response) {
+        return response;
+      }
+      
+      // if there's no cache, then just error out
+      // as there is nothing we can do to respond to this request
+      throw err;
     }
   }
-  
+
-  // Always try to cleanup outdated caches
+  event.respondWith(respond());
-  try {
+});
-    cleanupOutdatedCaches();
-    console.log('[SW] Cache cleanup completed');
-  } catch (cleanupError) {
-    console.error('[SW] Error during cache cleanup:', cleanupError);
-  }
-  
-  // Handle navigation requests with additional error handling
-  try {
-    console.log('[SW] Setting up navigation routing...');
-    if (typeof createHandlerBoundToURL === 'function' && typeof NavigationRoute === 'function' && typeof registerRoute === 'function') {
-      const handler = createHandlerBoundToURL('/');
-      const navigationRoute = new NavigationRoute(handler, {
-        denylist: [/^\/api/]
-      });
-      registerRoute(navigationRoute);
-      console.log('[SW] Navigation routing configured successfully');
-    } else {
-      throw new Error('Navigation routing functions not available');
-    }
-  } catch (routingError) {
-    console.error('[SW] Error setting up navigation routing:', routingError);
-    // Continue without navigation routing if it fails
-  }
-  
-  console.log('[SW] Workbox initialization completed');
-} catch (error) {
-  console.error('[SW] Critical error initializing workbox:', error);
-  console.error('[SW] Error details:', {
-    name: error.name,
-    message: error.message,
-    stack: error.stack
-  });
-  
-  // In development mode, this is expected behavior
-  if (!workboxManifest || (Array.isArray(workboxManifest) && workboxManifest.length === 0)) {
-    console.info('[SW] Continuing with limited functionality in development mode');
-  } else {
-    console.error('[SW] Production build should have workbox manifest - check build configuration');
-  }
-  
-  // Continue with service worker registration even if workbox fails
-  // This allows push notifications and other features to still work
-}
 
 // Push notification handling
 self.addEventListener('push', (event) => {