Add service worker for offline compatibility

Makefile

@@ -8,7 +8,7 @@ build:
 
 dist: build
 	mkdir -p $(BUILD)/build
-	cp -r $(SRC)/*.html $(SRC)/term.js src/examples $(BUILD)
+	cp -r $(SRC)/*.html $(SRC)/term.js src/examples $(SRC)/sw.js $(BUILD)
 	cp $(SRC)/build/firmware.js $(SRC)/build/simulator.js $(SRC)/build/firmware.wasm  $(BUILD)/build/
 
 watch: dist

src/simulator.ts

@@ -15,6 +15,26 @@ declare global {
   }
 }
 
+function initServiceWorker() {
+  window.addEventListener("load", () => {
+    if ("serviceWorker" in navigator) {
+      navigator.serviceWorker.register("sw.js").then(
+        (registration) => {
+          console.log("Simulator service worker registration successful");
+        },
+        (error) => {
+          console.error(
+            `Simulator service worker registration failed: ${error}`
+          );
+        }
+      );
+    } else {
+      console.error("Service workers are not supported.");
+    }
+  });
+}
+
+initServiceWorker();
 const fs = new FileSystem();
 const board = createBoard(new Notifications(window.parent), fs);
 window.addEventListener("message", createMessageListener(board));

src/sw.js

@@ -0,0 +1,46 @@
+const version = "v0.0.1";
+const assets = ["simulator.html", "build/simulator.js", "build/firmware.js"];
+const cacheName = `simulator-${version}`;
+
+self.addEventListener("install", (event) => {
+  console.log("Installing simulator service worker...");
+  event.waitUntil(
+    (async () => {
+      const cache = await caches.open(cacheName);
+      await cache.addAll(assets);
+      self.skipWaiting();
+    })()
+  );
+});
+
+self.addEventListener("activate", (event) => {
+  console.log("Activating simulator service worker...");
+  event.waitUntil(
+    (async () => {
+      const names = await caches.keys();
+      await Promise.all(
+        names.map((name) => {
+          if (name !== cacheName) {
+            return caches.delete(name);
+          }
+        })
+      );
+      await clients.claim();
+    })()
+  );
+});
+
+self.addEventListener("fetch", (event) => {
+  event.respondWith(
+    (async () => {
+      const cachedResponse = await caches.match(event.request);
+      if (cachedResponse) {
+        return cachedResponse;
+      }
+      const response = await fetch(event.request);
+      const cache = await caches.open(cacheName);
+      cache.put(event.request, response.clone());
+      return response;
+    })()
+  );
+});