feat: add extension update check

src/background/index.ts

@@ -49,6 +49,12 @@ type BatchSubmitMessage = {
   type: "batch:submit";
 };
 
+type DownloadUpdateMessage = {
+  filename: string;
+  type: "update:download";
+  url: string;
+};
+
 export function registerBackgroundMessageHandler(
   chromeLike: ChromeLike = readChromeLike(),
   dependencies: {
@@ -77,6 +83,22 @@ export function registerBackgroundMessageHandler(
       return true;
     }
 
+    if (isDownloadUpdateMessage(message)) {
+      void triggerUpdateDownload(chromeLike, message)
+        .then(() => {
+          sendResponse({ ok: true, type: "update:download-ack" });
+        })
+        .catch((error) => {
+          sendResponse({
+            error: error instanceof Error ? error.message : String(error),
+            ok: false,
+            type: "update:download-error"
+          });
+        });
+
+      return true;
+    }
+
     if (isBatchSubmitMessage(message)) {
       authController ??= createAuthController({
         authClient: createLogtoAuthClient()
@@ -161,6 +183,23 @@ export function registerBackgroundMessageHandler(
   });
 }
 
+async function triggerUpdateDownload(
+  chromeLike: ChromeLike,
+  message: DownloadUpdateMessage
+): Promise<void> {
+  if (!chromeLike.downloads?.download) {
+    throw new Error("chrome.downloads.download is unavailable");
+  }
+
+  await Promise.resolve(
+    chromeLike.downloads.download({
+      filename: message.filename,
+      saveAs: true,
+      url: message.url
+    })
+  );
+}
+
 async function handleAuthMessage(
   authController: AuthController,
   message: Parameters<typeof isAuthRequestMessage>[0] & { type: string }
@@ -239,6 +278,22 @@ function isDownloadMarketCsvMessage(
   );
 }
 
+function isDownloadUpdateMessage(
+  message: unknown
+): message is DownloadUpdateMessage {
+  if (!message || typeof message !== "object") {
+    return false;
+  }
+
+  const candidate = message as Partial<DownloadUpdateMessage>;
+  return (
+    candidate.type === "update:download" &&
+    typeof candidate.filename === "string" &&
+    typeof candidate.url === "string" &&
+    candidate.url.startsWith("https://")
+  );
+}
+
 function isBatchSubmitMessage(message: unknown): message is BatchSubmitMessage {
   if (!message || typeof message !== "object") {
     return false;