perf: cache middleware onboarding and language checks (#3197)

Author: Meierschlumpf

apps/nextjs/src/middleware.ts

@@ -5,25 +5,36 @@ import SuperJSON from "superjson";
 
 import type { AppRouter } from "@homarr/api";
 import { createHeadersCallbackForSource, getTrpcUrl } from "@homarr/api/shared";
+import { localeCookieKey } from "@homarr/definitions";
+import type { SupportedLanguage } from "@homarr/translation";
+import { supportedLanguages } from "@homarr/translation";
 import { createI18nMiddleware } from "@homarr/translation/middleware";
 
-export async function middleware(request: NextRequest) {
-  // fetch api does not work because window is not defined and we need to construct the url from the headers
-  // In next 15 we will be able to use node apis and such the db directly
-  const culture = await serverFetchApi.serverSettings.getCulture.query();
+let isOnboardingFinished = false;
 
+export async function middleware(request: NextRequest) {
   // Redirect to onboarding if it's not finished yet
   const pathname = request.nextUrl.pathname;
-  if (!pathname.endsWith("/init")) {
+
+  if (!isOnboardingFinished && !pathname.endsWith("/init")) {
     const currentOnboardingStep = await serverFetchApi.onboard.currentStep.query();
     if (currentOnboardingStep.current !== "finish") {
       return NextResponse.redirect(new URL("/init", request.url));
     }
+
+    isOnboardingFinished = true;
+  }
+
+  // Only run this if the user has not already configured their language
+  const currentLocale = request.cookies.get(localeCookieKey)?.value;
+  let defaultLocale: SupportedLanguage = "en";
+  if (!currentLocale || !supportedLanguages.includes(currentLocale as SupportedLanguage)) {
+    defaultLocale = await serverFetchApi.serverSettings.getCulture.query().then((culture) => culture.defaultLocale);
   }
 
   // We don't want to fallback to accept-language header so we clear it
   request.headers.set("accept-language", "");
-  const next = createI18nMiddleware(culture.defaultLocale);
+  const next = createI18nMiddleware(defaultLocale);
   return next(request);
 }