refactor(pwa): use sveltekit's pwa example

1 files changed, 67 insertions, 62 deletions

diff --git a/src/service-worker.ts b/src/service-worker.ts
index 91eada58..e5471acc 100644
--- a/src/service-worker.ts
+++ b/src/service-worker.ts
@@ -5,77 +5,82 @@
 
 import { build, files, version } from '$service-worker';
 
-const worker = self as unknown as ServiceWorkerGlobalScope;
-const FILES = `cache${version}`;
-// `build` is an array of all the files generated by the bundler,
-// `files` is an array of everything in the `static` directory
-const to_cache = build.concat(files);
-const staticAssets = new Set(to_cache);
-
-worker.addEventListener('install', (event) => {
-	event.waitUntil(
-		caches
-			.open(FILES)
-			.then((cache) => cache.addAll(to_cache))
-			.then(() => {
-				worker.skipWaiting();
-			})
-	);
+const sw = /** @type {ServiceWorkerGlobalScope} */ /** @type {unknown} */ self;
+
+// Create a unique cache name for this deployment
+const CACHE = `cache-${version}`;
+
+const ASSETS = [
+	...build, // the app itself
+	...files // everything in `static`
+];
+
+self.addEventListener('install', (event) => {
+	// Create a new cache and add all files to it
+	async function addFilesToCache() {
+		const cache = await caches.open(CACHE);
+		await cache.addAll(ASSETS);
+	}
+
+	event.waitUntil(addFilesToCache());
 });
 
-worker.addEventListener('activate', (event) => {
-	event.waitUntil(
-		caches.keys().then(async (keys) => {
-			// delete old caches
-			for (const key of keys) if (key !== FILES) await caches.delete(key);
+self.addEventListener('activate', (event) => {
+	// Remove previous cached data from disk
+	async function deleteOldCaches() {
+		for (const key of await caches.keys()) {
+			if (key !== CACHE) await caches.delete(key);
+		}
+	}
 
-			worker.clients.claim();
-		})
-	);
+	event.waitUntil(deleteOldCaches());
 });
 
-/**
- * Fetch the asset from the network and store it in the cache.
- * Fall back to the cache if the user is offline.
- */
-const fetchAndCache = async (request: Request) => {
-	const cache = await caches.open(`offline${version}`);
+self.addEventListener('fetch', (event) => {
+	// ignore POST requests etc
+	if (event.request.method !== 'GET') return;
 
-	try {
-		const response = await fetch(request);
+	async function respond() {
+		const url = new URL(event.request.url);
+		const cache = await caches.open(CACHE);
 
-		cache.put(request, response.clone());
+		// `build`/`files` can always be served from the cache
+		if (ASSETS.includes(url.pathname)) {
+			const response = await cache.match(url.pathname);
 
-		return response;
-	} catch (err) {
-		const response = await cache.match(request);
+			if (response) {
+				return response;
+			}
+		}
 
-		if (response) return response;
+		// for everything else, try the network first, but
+		// fall back to the cache if we're offline
+		try {
+			const response = await fetch(event.request);
 
-		throw err;
+			// if we're offline, fetch can return a value that is not a Response
+			// 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;
+		}
 	}
-};
-
-worker.addEventListener('fetch', (event) => {
-	if (event.request.method !== 'GET' || event.request.headers.has('range')) return;
-
-	const url = new URL(event.request.url);
-	// don't try to handle e.g. data: URIs
-	const isHttp = url.protocol.startsWith('http');
-	const isDevServerRequest =
-		url.hostname === self.location.hostname && url.port !== self.location.port;
-	const isStaticAsset = url.host === self.location.host && staticAssets.has(url.pathname);
-	const skipBecauseUncached = event.request.cache === 'only-if-cached' && !isStaticAsset;
-
-	if (isHttp && !isDevServerRequest && !skipBecauseUncached)
-		event.respondWith(
-			(async () => {
-				// always serve static files and bundler-generated assets from cache.
-				// if your application has other URLs with data that will never change,
-				// set this variable to true for them and they will only be fetched once.
-				return (
-					(isStaticAsset && (await caches.match(event.request))) || fetchAndCache(event.request)
-				);
-			})()
-		);
+
+	event.respondWith(respond());
 });