From 5e3804edbcfeea1a8cfcf4559e768d19f420fb3a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Roman=20Kr=C4=8Dek?= <roman.krcek@tietoevry.com>
Date: Sun, 29 Jun 2025 14:40:04 +0200
Subject: [PATCH] Add service worker

---
 src/service-worker.ts | 84 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 src/service-worker.ts

diff --git a/src/service-worker.ts b/src/service-worker.ts
new file mode 100644
index 0000000..2f88ac4
--- /dev/null
+++ b/src/service-worker.ts
@@ -0,0 +1,84 @@
+/// <reference types="@sveltejs/kit" />
+import { build, files, version } from '$service-worker';
+
+// Create a unique cache name for this deployment
+const CACHE = `cache-${version}`;
+
+console.log("Service worker is live!")
+
+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());
+
+	console.log("Service worker is live!")
+});
+
+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);
+		}
+	}
+
+	event.waitUntil(deleteOldCaches());
+});
+
+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 {
+			const response = await fetch(event.request);
+
+			// 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;
+		}
+	}
+
+	event.respondWith(respond());
+});
\ No newline at end of file