refactor(i18n): optimize translation loading and initialization

- Updated ensureTranslationsLoaded function to prevent duplicate requests by caching loaded translations and managing loading promises.
- Simplified translation preloading on app startup to only load essential namespaces for the current language.
- Adjusted useTranslationPreloader hook to avoid multiple requests for translations and ensure efficient loading state management.

worklenz-frontend/src/App.tsx

@@ -2,7 +2,6 @@
 import React, { Suspense, useEffect, memo, useMemo, useCallback } from 'react';
 import { RouterProvider } from 'react-router-dom';
 import i18next from 'i18next';
-import { ensureTranslationsLoaded } from './i18n';
 
 // Components
 import ThemeWrapper from './features/theme/ThemeWrapper';
@@ -66,8 +65,8 @@ const App: React.FC = memo(() => {
         // Initialize CSRF token
         await initializeCsrfToken();
 
-        // Preload essential translations
-        await ensureTranslationsLoaded();
+        // Note: Translation preloading is handled in i18n.ts initialization
+        // No need to call ensureTranslationsLoaded here to avoid duplicate requests
       } catch (error) {
         if (isMounted) {
           logger.error('Failed to initialize app:', error);

worklenz-frontend/src/hooks/useTranslationPreloader.ts

@@ -26,7 +26,7 @@ export const useTranslationPreloader = (
       try {
         setIsLoading(true);
 
-        // Ensure translations are loaded
+        // Only load translations for current language to avoid multiple requests
         await ensureTranslationsLoaded(namespaces);
 
         // Wait for i18next to be ready
@@ -47,12 +47,18 @@ export const useTranslationPreloader = (
       }
     };
 
-    loadTranslations();
+    // Only load if not already loaded
+    if (!isLoaded && !ready) {
+      loadTranslations();
+    } else if (ready && !isLoaded) {
+      setIsLoaded(true);
+      setIsLoading(false);
+    }
 
     return () => {
       isMounted = false;
     };
-  }, [namespaces, ready]);
+  }, [namespaces, ready, isLoaded]);
 
   return {
     t,

worklenz-frontend/src/i18n.ts

@@ -12,6 +12,10 @@ const ESSENTIAL_NAMESPACES = [
   'settings',
 ];
 
+// Cache to track loaded translations and prevent duplicate requests
+const loadedTranslations = new Set<string>();
+const loadingPromises = new Map<string, Promise<any>>();
+
 i18n
   .use(HttpApi)
   .use(initReactI18next)
@@ -37,33 +41,67 @@ i18n
   });
 
 // Utility function to ensure translations are loaded
-export const ensureTranslationsLoaded = async (namespaces: string[] = ESSENTIAL_NAMESPACES) => {
-  const currentLang = i18n.language || 'en';
-
+export const ensureTranslationsLoaded = async (
+  namespaces: string[] = ESSENTIAL_NAMESPACES,
+  languages: string[] = [i18n.language || 'en']
+) => {
   try {
-    // Load all essential namespaces for the current language
-    await Promise.all(
-      namespaces.map(ns =>
-        i18n.loadNamespaces(ns).catch(() => {
-          logger.error(`Failed to load namespace: ${ns}`);
-        })
-      )
-    );
+    const loadPromises: Promise<any>[] = [];
 
-    // Also preload for other languages to prevent delays on language switch
-    const otherLangs = ['en', 'es', 'pt', 'alb', 'de'].filter(lang => lang !== currentLang);
-    await Promise.all(
-      otherLangs.map(lang =>
-        Promise.all(
-          namespaces.map(ns =>
-            i18n.loadNamespaces(ns).catch(() => {
-              logger.error(`Failed to load namespace: ${ns}`);
-            })
-          )
-        )
-      )
-    );
+    for (const lang of languages) {
+      for (const ns of namespaces) {
+        const key = `${lang}:${ns}`;
+        
+        // Skip if already loaded
+        if (loadedTranslations.has(key)) {
+          continue;
+        }
 
+        // Check if already loading
+        if (loadingPromises.has(key)) {
+          loadPromises.push(loadingPromises.get(key)!);
+          continue;
+        }
+
+        // Create loading promise
+        const loadingPromise = new Promise<void>((resolve, reject) => {
+          // Switch to the target language temporarily if needed
+          const currentLang = i18n.language;
+          const shouldSwitchLang = currentLang !== lang;
+          
+          const loadForLanguage = async () => {
+            try {
+              if (shouldSwitchLang) {
+                await i18n.changeLanguage(lang);
+              }
+              
+              await i18n.loadNamespaces(ns);
+              
+              // Switch back to original language if we changed it
+              if (shouldSwitchLang && currentLang) {
+                await i18n.changeLanguage(currentLang);
+              }
+              
+              loadedTranslations.add(key);
+              resolve();
+            } catch (error) {
+              logger.error(`Failed to load namespace: ${ns} for language: ${lang}`, error);
+              reject(error);
+            } finally {
+              loadingPromises.delete(key);
+            }
+          };
+
+          loadForLanguage();
+        });
+
+        loadingPromises.set(key, loadingPromise);
+        loadPromises.push(loadingPromise);
+      }
+    }
+
+    // Wait for all loading promises to complete
+    await Promise.all(loadPromises);
     return true;
   } catch (error) {
     logger.error('Failed to load translations:', error);
@@ -71,7 +109,13 @@ export const ensureTranslationsLoaded = async (namespaces: string[] = ESSENTIAL_
   }
 };
 
-// Initialize translations on app startup
-ensureTranslationsLoaded();
+// Preload essential translations for current language only on startup
+const initializeTranslations = async () => {
+  const currentLang = i18n.language || 'en';
+  await ensureTranslationsLoaded(ESSENTIAL_NAMESPACES, [currentLang]);
+};
+
+// Initialize translations on app startup (only once)
+initializeTranslations();
 
 export default i18n;