web: redirect /l/download to App Store

fixes #666

apps/daimo-web/src/middleware.ts

@@ -0,0 +1,18 @@
+import { NextResponse } from "next/server";
+import type { NextRequest } from "next/server";
+
+import { detectPlatform, downloadMetadata } from "./utils/platform";
+
+export function middleware(request: NextRequest) {
+  if (request.nextUrl.pathname === "/l/download") {
+    return redirectMobileToAppStore(request);
+  }
+  return NextResponse.next();
+}
+
+function redirectMobileToAppStore(request: NextRequest) {
+  const ua = request.headers.get("user-agent") || "";
+  const platform = detectPlatform(ua);
+  const { url } = downloadMetadata[platform];
+  return NextResponse.redirect(url);
+}

apps/daimo-web/src/utils/platform.ts

@@ -4,7 +4,7 @@ export function detectPlatform(ua: string): PlatformType {
   // From https://dev.to/konyu/using-javascript-to-determine-whether-the-client-is-ios-or-android-4i1j
   if (/android/i.test(ua)) {
     return "android";
-  } else if (/iPhone|iPod/.test(ua)) {
+  } else if (/iPhone|iPod|iPad/.test(ua)) {
     return "ios";
   }
   return "other";