add comments and docs to sw.js,

add service worker ADR

source/sw.js

@@ -28,20 +28,34 @@ const ASSETS = [
 	"assets/scripts/ReviewDetails.js",
 ];
 
+/**
+ * Adds the install listener where the app assets are added to the cache
+ */
 self.addEventListener("install", async () => {
+	// open the cace
 	const cache = await caches.open(CACHE_NAME);
+	// add all elements in ASSETS to the cache, these are all the files requried for the app to run
 	await cache.addAll(ASSETS);
 });
 
+/**
+ * Adds an event listener on fetch events to serve cached resources while offline
+ * Uses a network first structure to prioritize fetching from network in case of app updates.
+ * If there are important updates, we want the user to get those if possible.
+ */
 self.addEventListener("fetch", (event) => {
-	console.log(`fetching: ${event.request.url}`);
+	// add a response to the fetch event
 	event.respondWith(caches.open(CACHE_NAME).then((cache) => {
+		// try to return a network fetch response
 		return fetch(event.request).then((fetchedResponse) => {
+			// if there is a response, add it to the cache
 			cache.put(event.request, fetchedResponse.clone());
-			console.log(typeof(fetchedResponse));
+			// return the network response
 			return fetchedResponse;
 		}).catch(() => {
-			console.log(cache.match(event.request, {ignoreVary: true}));
+			// If there is not a network response, return the cached response
+			// The ignoreVary option is used here to fix an issue where the service worker 
+			// would not serve certain requests unless the page was refreshed at least once
 			return cache.match(event.request, {ignoreVary: true}); 
 		});
 	}));

specs/adrs/120222-serviceworker-netfirst.md

@@ -0,0 +1,19 @@
+# Use a network first cache second for service worker architecture 
+
+- Status: in consideration
+- Deciders: Arthur Lu
+- Date: 12 / 02 / 22
+
+## Decision Drivers
+
+- Need to balance the need for user ease of use and local first priority
+- Users should expect to update their app easily when they have network, but may not be expected to know how to perform a hard refresh
+- Local first priority means we should avoid unnecessary network activity when possible
+
+## Considered Options
+- Network first cache second
+- Cache first network second
+
+## Decision Outcome
+
+Chosen Option: TBD