Added caching to service worker

sw/service-worker.ts

@@ -1,5 +1,73 @@
 // pack:ignore
 
-self.addEventListener("install", evt => {
+var CACHE = "v-alpha"
+
+self.addEventListener("install", (evt: any) => {
 	console.log("The service worker is being installed.")
-})
+
+	evt.waitUntil(installCache())
+})
+
+self.addEventListener("activate", (evt: any) => {
+	evt.waitUntil((self as any).clients.claim())
+})
+
+self.addEventListener("fetch", async (evt: any) => {
+	let request = evt.request
+
+	console.log("Serving:", request.url, request, request.method)
+
+	// Do not use cache in some cases
+	if(request.method !== "GET" || request.url.includes("/auth/") || request.url.includes("chrome-extension")) {
+		return evt.waitUntil(evt.respondWith(fetch(request)))
+	}
+	
+	// Start fetching the request
+	let refresh = fetch(request).then(response => {
+		let clone = response.clone()
+
+		// Save the new version of the resource in the cache
+		caches.open(CACHE).then(cache => {
+			cache.put(request, clone)
+		})
+
+		return response
+	})
+
+	// Try to serve cache first and fall back to network response
+	let networkOrCache = fromCache(request).catch(error => {
+		console.log("Cache MISS:", request.url)
+		return refresh
+	})
+
+	return evt.waitUntil(evt.respondWith(networkOrCache))
+})
+
+function installCache() {
+	return caches.open(CACHE).then(cache => {
+		return cache.addAll([
+			"./",
+			"./scripts",
+			"https://fonts.gstatic.com/s/ubuntu/v10/2Q-AW1e_taO6pHwMXcXW5w.ttf"
+		])
+	})
+}
+
+function fromCache(request) {
+	return caches.open(CACHE).then(cache => {
+		return cache.match(request).then(matching => {
+			if(matching) {
+				console.log("Cache HIT:", request.url)
+				return Promise.resolve(matching)
+			}
+
+			return Promise.reject("no-match")
+		})
+	})
+}
+
+function updateCache(request, response) {
+	return caches.open(CACHE).then(cache => {
+		cache.put(request, response)
+	})
+}