feat: enhance routing logic and improve login screen validation; add guarded API call for error handling

flutter/lib/core/api/guarded_api_call.dart

@@ -0,0 +1,18 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import 'api_exception.dart';
+import '../../features/auth/data/auth_providers.dart';
+
+/// Executes [call] and automatically logs out the user if the server
+/// returns 401 Unauthorized. Re-throws the exception so the calling
+/// widget/provider can still display an error if needed.
+Future<T> guardedApiCall<T>(Ref ref, Future<T> Function() call) async {
+  try {
+    return await call();
+  } on ApiException catch (e) {
+    if (e.type == ApiErrorType.unauthorized) {
+      await ref.read(authStateProvider.notifier).logout();
+    }
+    rethrow;
+  }
+}

flutter/lib/core/router/app_router.dart

@@ -1,12 +1,13 @@
-import 'package:flutter/widgets.dart';
+import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
-import '../../core/ui/app_shell.dart';
+import '../ui/app_shell.dart';
+import '../ui/async_state_views.dart';
 import '../../features/auth/data/auth_providers.dart';
-import '../../features/recipes/presentation/recipes_screen.dart';
 import '../../features/auth/presentation/login_screen.dart';
 import '../../features/profile/presentation/profile_screen.dart';
+import '../../features/recipes/presentation/recipes_screen.dart';
 
 final appRouterProvider = Provider<GoRouter>((ref) {
   final authState = ref.watch(authStateProvider);
@@ -17,29 +18,39 @@ final appRouterProvider = Provider<GoRouter>((ref) {
       final isLoading = authState.isLoading;
       final token = authState.valueOrNull;
       final isLoggedIn = token != null && token.isNotEmpty;
-      final isLoginRoute = state.matchedLocation == '/login';
-      final isRootRoute = state.matchedLocation == '/';
+      final location = state.matchedLocation;
+      final isSplash = location == '/';
+      final isLogin = location == '/login';
 
+      // Keep user on splash while auth state is being resolved from storage.
       if (isLoading) {
-        return null;
+        return isSplash ? null : '/';
       }
 
-      if (isRootRoute) {
+      // Redirect away from splash once auth is known.
+      if (isSplash) {
         return isLoggedIn ? '/recipes' : '/login';
       }
 
-      if (!isLoggedIn && !isLoginRoute) {
+      // Unauthenticated user trying to reach a protected route.
+      if (!isLoggedIn && !isLogin) {
         return '/login';
       }
 
-      if (isLoggedIn && isLoginRoute) {
+      // Authenticated user landing on login.
+      if (isLoggedIn && isLogin) {
         return '/recipes';
       }
 
       return null;
     },
     routes: [
-      GoRoute(path: '/', builder: (context, state) => const SizedBox.shrink()),
+      GoRoute(
+        path: '/',
+        builder: (context, state) => const Scaffold(
+          body: LoadingStateView(label: 'Startar...'),
+        ),
+      ),
       GoRoute(
         path: '/login',
         builder: (context, state) => const LoginScreen(),

flutter/lib/features/auth/presentation/login_screen.dart

@@ -13,73 +13,102 @@ class LoginScreen extends ConsumerStatefulWidget {
 }
 
 class _LoginScreenState extends ConsumerState<LoginScreen> {
+  final _formKey = GlobalKey<FormState>();
   final _usernameCtrl = TextEditingController();
   final _passwordCtrl = TextEditingController();
+  final _passwordFocus = FocusNode();
 
   @override
   void dispose() {
     _usernameCtrl.dispose();
     _passwordCtrl.dispose();
+    _passwordFocus.dispose();
     super.dispose();
   }
 
   Future<void> _submit() async {
-    if (_usernameCtrl.text.trim().isEmpty || _passwordCtrl.text.isEmpty) {
+    if (!(_formKey.currentState?.validate() ?? false)) {
       return;
     }
     await ref.read(authStateProvider.notifier).login(
           _usernameCtrl.text.trim(),
           _passwordCtrl.text,
         );
-    if (mounted) {
-      final state = ref.read(authStateProvider);
-      if (state is AsyncData && state.value != null) {
-        if (context.mounted) context.go('/recipes');
-      }
-    }
+    // Router redirect handles navigation when authStateProvider updates.
   }
 
   @override
   Widget build(BuildContext context) {
     final authState = ref.watch(authStateProvider);
+    final isLoading = authState is AsyncLoading;
+
     return Scaffold(
       appBar: AppBar(title: const Text('Logga in')),
-      body: Padding(
-        padding: const EdgeInsets.all(24),
-        child: Column(
-          mainAxisAlignment: MainAxisAlignment.center,
-          children: [
-            TextField(
-              controller: _usernameCtrl,
-              decoration: const InputDecoration(labelText: 'Anvandarnamn'),
-              textInputAction: TextInputAction.next,
-            ),
-            const SizedBox(height: 12),
-            TextField(
-              controller: _passwordCtrl,
-              decoration: const InputDecoration(labelText: 'Lösenord'),
-              obscureText: true,
-              textInputAction: TextInputAction.done,
-              onSubmitted: (_) => _submit(),
-            ),
-            const SizedBox(height: 24),
-            if (authState is AsyncLoading)
-              const CircularProgressIndicator()
-            else
-              ElevatedButton(
-                onPressed: _submit,
-                child: const Text('Logga in'),
+      body: Center(
+        child: SingleChildScrollView(
+          padding: const EdgeInsets.all(24),
+          child: ConstrainedBox(
+            constraints: const BoxConstraints(maxWidth: 400),
+            child: Form(
+              key: _formKey,
+              child: Column(
+                mainAxisSize: MainAxisSize.min,
+                crossAxisAlignment: CrossAxisAlignment.stretch,
+                children: [
+                  TextFormField(
+                    controller: _usernameCtrl,
+                    decoration:
+                        const InputDecoration(labelText: 'Användarnamn'),
+                    textInputAction: TextInputAction.next,
+                    autofocus: true,
+                    enabled: !isLoading,
+                    onFieldSubmitted: (_) =>
+                        FocusScope.of(context).requestFocus(_passwordFocus),
+                    validator: (value) {
+                      if (value == null || value.trim().isEmpty) {
+                        return 'Ange ditt användarnamn.';
+                      }
+                      return null;
+                    },
+                  ),
+                  const SizedBox(height: 16),
+                  TextFormField(
+                    controller: _passwordCtrl,
+                    focusNode: _passwordFocus,
+                    decoration: const InputDecoration(labelText: 'Lösenord'),
+                    obscureText: true,
+                    textInputAction: TextInputAction.done,
+                    enabled: !isLoading,
+                    onFieldSubmitted: (_) => _submit(),
+                    validator: (value) {
+                      if (value == null || value.isEmpty) {
+                        return 'Ange ditt lösenord.';
+                      }
+                      return null;
+                    },
+                  ),
+                  const SizedBox(height: 28),
+                  if (isLoading)
+                    const Center(child: CircularProgressIndicator())
+                  else
+                    FilledButton(
+                      onPressed: _submit,
+                      child: const Text('Logga in'),
+                    ),
+                  if (authState is AsyncError)
+                    Padding(
+                      padding: const EdgeInsets.only(top: 16),
+                      child: Text(
+                        mapErrorToUserMessage(authState.error!),
+                        textAlign: TextAlign.center,
+                        style: TextStyle(
+                            color: Theme.of(context).colorScheme.error),
+                      ),
+                    ),
+                ],
               ),
-            if (authState is AsyncError)
-              Padding(
-                padding: const EdgeInsets.only(top: 12),
-                child: Text(
-                  mapErrorToUserMessage(authState.error!),
-                  textAlign: TextAlign.center,
-                  style: TextStyle(color: Theme.of(context).colorScheme.error),
-                ),
-              ),
-          ],
+            ),
+          ),
         ),
       ),
     );

flutter/lib/features/recipes/data/recipe_providers.dart

@@ -1,8 +1,10 @@
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+
 import '../../../core/api/api_providers.dart';
+import '../../../core/api/guarded_api_call.dart';
 import '../../../features/auth/data/auth_providers.dart';
-import 'recipe_repository.dart';
 import '../domain/recipe.dart';
+import 'recipe_repository.dart';
 
 final recipeRepositoryProvider = Provider<RecipeRepository>((ref) {
   return RecipeRepository(ref.watch(apiClientProvider));
@@ -10,5 +12,8 @@ final recipeRepositoryProvider = Provider<RecipeRepository>((ref) {
 
 final recipesProvider = FutureProvider<List<Recipe>>((ref) async {
   final token = await ref.watch(authStateProvider.future);
-  return ref.watch(recipeRepositoryProvider).fetchRecipes(token: token);
+  return guardedApiCall(
+    ref,
+    () => ref.read(recipeRepositoryProvider).fetchRecipes(token: token),
+  );
 });