Initial proof of concept

sw.js

@@ -0,0 +1,33 @@
+const CACHE_NAME = 'lips-pwa';
+const urlsToCache = ['/',
+		     '/index.html',
+		     '/app.scm',
+		     '/manifest.json',
+		     'https://cdn.jsdelivr.net/npm/lips@beta/dist/lips.min.js',
+		     'https://cdnjs.cloudflare.com/ajax/libs/mithril/2.2.2/mithril.min.js'];
+
+// Install event: cache the assets
+self.addEventListener('install', event => {
+    event.waitUntil(
+	caches.open(CACHE_NAME)
+	    .then(cache => {
+		console.log('Opened cache');
+		return cache.addAll(urlsToCache);
+	    })
+    );
+});
+
+// Fetch event: serve cached assets when offline
+self.addEventListener('fetch', event => {
+    event.respondWith(
+	caches.match(event.request)
+	    .then(response => {
+		// Cache hit - return the response
+		if (response) {
+		    return response;
+		}
+		// Otherwise, fetch from network
+		return fetch(event.request);
+	    })
+    );
+});