implement auth - almost works

mobile/lib/controllers/cart.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:mobile/models/product.dart';
+import 'package:mobile/results.dart';
 
 class ProductIdException implements Exception {}
 
@@ -82,6 +83,10 @@ class CartController extends ChangeNotifier {
     cart.clear();
     notifyListeners();
   }
+
+  Result<Null, String> pay() {
+    return const Err("Not implemented");
+  }
 }
 
 class CartItem {

mobile/lib/controllers/product.dart

@@ -1,15 +1,14 @@
 import 'package:flutter/material.dart';
 import 'package:mobile/models/product.dart';
 import 'package:mobile/results.dart';
-import 'package:mobile/server/mock_server.dart';
 import 'package:mobile/server/server.dart';
 
 class ProductController extends ChangeNotifier {
-  final server = MockServer();
+  final Server server;
 
   List<Product> products = [];
   String query = "";
-  ProductController() {
+  ProductController({required this.server}) {
     fetchProductsFromServer();
   }
 

mobile/lib/controllers/session.dart

@@ -0,0 +1,59 @@
+import 'package:flutter/material.dart';
+import 'package:mobile/models/user.dart';
+import 'package:mobile/results.dart';
+import 'package:mobile/server/server.dart';
+
+class SessionController extends ChangeNotifier {
+  final Server server;
+  String? _sessionToken;
+
+  SessionController({required this.server});
+
+  Future<Result<Null, String>> login(String email, String password) async {
+    switch (await server.login(email, password)) {
+      case Success<String>(data: final token):
+        _sessionToken = token;
+        notifyListeners();
+        return const Ok(null);
+      case Error<String>(message: final message):
+        notifyListeners();
+        return Err(message);
+    }
+  }
+
+  Future<Result<User, Null>> user() async {
+    final token = _sessionToken;
+    if (token == null) {
+      notifyListeners();
+      return const Err(null);
+    }
+    final res = await server.sessionUser(token);
+    switch (res) {
+      case Success<User>(data: final user):
+        return Ok(user);
+      case Error<User>():
+        _sessionToken = null;
+        notifyListeners();
+        return const Err(null);
+    }
+  }
+
+  get sessionToken {
+    return _sessionToken;
+  }
+
+  Future<void> logout() async {
+    final token = _sessionToken;
+    if (token != null) {
+      server.logout(token);
+      _sessionToken = null;
+    }
+    print(_sessionToken);
+    print("notifying listeners");
+    notifyListeners();
+  }
+
+  Result<int, String> pay(int userId, int amount) {
+    return const Err("not implemented");
+  }
+}

mobile/lib/controllers/user.dart

@@ -1,136 +1,20 @@
 import 'package:flutter/material.dart';
 import 'package:mobile/results.dart';
+import 'package:mobile/server/server.dart';
 
-class UsersControllerOld extends ChangeNotifier {
+class UsersController extends ChangeNotifier {
-  int nextId = 0;
+  Server server;
-  final List<User> users = [];
 
-  User? _loggedInUser;
+  UsersController({required this.server});
 
-  UsersControllerOld() {
+  Future<Result<Null, String>> register(
-    addTestUsers();
+      String name, String email, String password) async {
-  }
+    final res = await server.register(name, email, password);
-
+    switch (res) {
-  Result<User, String> getUserById(int id) {
+      case Success<Null>():
-    for (var i = 0; i < users.length; i++) {
+        return const Ok(null);
-      if (users[i].id == id) {
+      case Error<Null>(message: final message):
-        return Ok(users[i]);
+        return Err(message);
-      }
     }
-    return Err("User with id $id doesn't exist");
-  }
-
-  Result<User, String> getUserByMail(String mail) {
-    for (var i = 0; i < users.length; i++) {
-      if (users[i].mail == mail) {
-        return Ok(users[i]);
-      }
-    }
-    return Err("User with mail $mail doesn't exist");
-  }
-
-  Result<User, String> addUser(String name, String mail, String password) {
-    if (getUserByMail(mail) is Ok) {
-      return Err("User with mail $mail already exists");
-    }
-
-    final user = User(
-        id: nextId++,
-        name: name,
-        mail: mail,
-        password: password,
-        balanceInDkkCents: 0);
-    users.add(user);
-
-    return Ok(user);
-  }
-
-  Result<User, String> login(String mail, String password) {
-    User? user;
-    for (var i = 0; i < users.length; i++) {
-      if (users[i].mail == mail) {
-        user = users[i];
-      }
-    }
-    if (user == null) {
-      return Err("User with mail $mail doesn't exist");
-    }
-    if (user.password != password) {
-      return Err("Wrong password for user with mail $mail");
-    }
-    _loggedInUser = user;
-    notifyListeners();
-    return Ok(user);
-  }
-
-  void logout() {
-    _loggedInUser = null;
-    notifyListeners();
-  }
-
-  User? loggedInUser() {
-    return _loggedInUser;
-  }
-
-  Result<int, String> pay(int userId, int amount) {
-    final user = getUserById(userId);
-    if (user is Ok) {
-      return (user as User).pay(amount);
-    }
-    return Err("User with id $userId doesn't exist");
-  }
-
-  void addTestUsers() {
-    users
-      ..add(User(
-          id: nextId++,
-          mail: "test@test.com",
-          name: "test",
-          password: "test",
-          balanceInDkkCents: 10000))
-      ..add(User(
-          id: nextId++,
-          mail: "",
-          name: "",
-          password: "",
-          balanceInDkkCents: 100000));
-  }
-
-  void veryBadNotifyAll() {
-    // ⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️
-    // TODO: THIS SHOULD BE FIXED
-    // FIXME: DO SOMETHING ELSE PLEASE!!!!!
-    // ⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️⚠️
-    notifyListeners();
-  }
-}
-
-class User {
-  final int id;
-  final String mail;
-  final String name;
-  final String password;
-
-  // balance is in øre
-  int balanceInDkkCents;
-
-  User({
-    required this.id,
-    required this.mail,
-    required this.name,
-    required this.password,
-    required this.balanceInDkkCents,
-  });
-
-  void addBalanceFounds(int amount) {
-    balanceInDkkCents += amount;
-  }
-
-  Result<int, String> pay(int amount) {
-    if (balanceInDkkCents < amount) {
-      return Err("User can not afford paying amount $amount");
-    }
-    balanceInDkkCents -= amount;
-    return Ok(balanceInDkkCents);
   }
 }

mobile/lib/main.dart

@@ -1,5 +1,8 @@
 import 'package:flutter/material.dart';
 import 'package:google_fonts/google_fonts.dart';
+import 'package:mobile/controllers/session.dart';
+import 'package:mobile/models/user.dart';
+import 'package:mobile/pages/dashboard.dart';
 import 'package:mobile/pages/log_in_page.dart';
 import 'package:mobile/controllers/add_to_cart_state.dart';
 import 'package:mobile/controllers/cart.dart';
@@ -8,6 +11,7 @@ import 'package:mobile/controllers/paying_state.dart';
 import 'package:mobile/controllers/product.dart';
 import 'package:mobile/controllers/receipt.dart';
 import 'package:mobile/controllers/user.dart';
+import 'package:mobile/server/mock_server.dart';
 import 'package:provider/provider.dart';
 import 'package:mobile/controllers/routing.dart';
 
@@ -20,29 +24,37 @@ class MyApp extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final server = MockServer();
     return MultiProvider(
       providers: [
         ChangeNotifierProvider(create: (_) => RoutingController()),
-        ChangeNotifierProvider(create: (_) => ProductController()),
+        ChangeNotifierProvider(
+            create: (_) => ProductController(server: server)),
         ChangeNotifierProvider(create: (_) => CartController()),
         ChangeNotifierProvider(create: (_) => ReceiptController()),
         ChangeNotifierProvider(create: (_) => PayingStateController()),
         ChangeNotifierProvider(create: (_) => AddToCartStateController()),
         ChangeNotifierProvider(create: (_) => LocationImageController()),
-        ChangeNotifierProvider(create: (_) => UsersControllerOld()),
+        ChangeNotifierProvider(create: (_) => UsersController(server: server)),
+        ChangeNotifierProvider(
+            create: (_) => SessionController(server: server)),
       ],
       child: MaterialApp(
-        title: 'Fresh Plaza',
+          title: 'Fresh Plaza',
-        theme: ThemeData(
+          theme: ThemeData(
-          colorScheme: ColorScheme.fromSeed(
+            colorScheme: ColorScheme.fromSeed(
-              seedColor: const Color.fromARGB(255, 149, 92, 255)),
+                seedColor: const Color.fromARGB(255, 149, 92, 255)),
-          scaffoldBackgroundColor: const Color(0xFFFAFAFF),
+            scaffoldBackgroundColor: const Color(0xFFFAFAFF),
-          textTheme:
+            textTheme:
-              GoogleFonts.merriweatherTextTheme(Theme.of(context).textTheme),
+                GoogleFonts.merriweatherTextTheme(Theme.of(context).textTheme),
-          useMaterial3: true,
+            useMaterial3: true,
-        ),
+          ),
-        home: const LogInPage(),
+          home: Consumer<SessionController>(
-      ),
+            builder: (_, sessionController, __) {
+              if (sessionController.sessionToken is String) return Dashboard();
+              return const LogInPage();
+            },
+          )),
     );
   }
 }

mobile/lib/models/user.dart

@@ -0,0 +1,35 @@
+import 'package:mobile/results.dart';
+
+class User {
+  final int id;
+  final String email;
+  final String name;
+
+  // balance is in øre
+  int balanceInDkkCents;
+
+  User({
+    required this.id,
+    required this.email,
+    required this.name,
+    required this.balanceInDkkCents,
+  });
+
+  User.fromJson(Map<String, dynamic> json)
+      : id = json["id"],
+        email = json["email"],
+        name = json["name"],
+        balanceInDkkCents = json["balanceInDkkCents"];
+
+  void addBalanceFounds(int amount) {
+    balanceInDkkCents += amount;
+  }
+
+  Result<int, String> pay(int amount) {
+    if (balanceInDkkCents < amount) {
+      return Err("User can not afford paying amount $amount");
+    }
+    balanceInDkkCents -= amount;
+    return Ok(balanceInDkkCents);
+  }
+}

mobile/lib/pages/cart_page.dart

@@ -6,7 +6,6 @@ import 'package:mobile/models/product.dart';
 import 'package:mobile/pages/finish_shopping_page.dart';
 import 'package:mobile/controllers/cart.dart';
 import 'package:mobile/controllers/product.dart';
-import 'package:mobile/controllers/user.dart';
 import 'package:mobile/results.dart';
 import 'package:mobile/utils/price.dart';
 import 'package:mobile/widgets/primary_button.dart';
@@ -144,8 +143,7 @@ class CartItemView extends StatelessWidget {
 }
 
 class CartPage extends StatelessWidget {
-  final User user;
+  const CartPage({super.key});
-  const CartPage({super.key, required this.user});
 
   @override
   Widget build(BuildContext context) {
@@ -316,7 +314,7 @@ class CartPage extends StatelessWidget {
                                 context,
                                 MaterialPageRoute(
                                     builder: (context) =>
-                                        FinishShoppingPage(user: user)));
+                                        const FinishShoppingPage()));
                           },
                           child: const Text("Afslut indkøb")),
                     ),

mobile/lib/pages/dashboard.dart

@@ -5,21 +5,16 @@ import 'package:mobile/pages/all_receipts_page.dart';
 import 'package:mobile/pages/home_page.dart';
 import 'package:mobile/controllers/routing.dart';
 import 'package:mobile/controllers/cart.dart';
-import 'package:mobile/controllers/user.dart';
 import 'package:provider/provider.dart';
 
 class Dashboard extends StatelessWidget {
-  final User user;
-
   final List<StatelessWidget> pages = [];
 
-  Dashboard({super.key, required this.user}) {
+  Dashboard({super.key}) {
     pages.addAll([
-      HomePage(
+      const HomePage(),
-        user: user,
-      ),
       const AllProductsPage(),
-      CartPage(user: user),
+      const CartPage(),
       const AllReceiptsPage(),
     ]);
   }

mobile/lib/pages/finish_shopping_page.dart

@@ -3,7 +3,6 @@ import 'package:mobile/controllers/routing.dart';
 import 'package:mobile/controllers/cart.dart';
 import 'package:mobile/controllers/paying_state.dart';
 import 'package:mobile/controllers/receipt.dart';
-import 'package:mobile/controllers/user.dart';
 import 'package:mobile/results.dart';
 import 'package:mobile/utils/price.dart';
 import 'package:mobile/widgets/primary_button.dart';
@@ -11,17 +10,15 @@ import 'package:mobile/widgets/receipt_item.dart';
 import 'package:provider/provider.dart';
 
 class FinishShoppingPage extends StatelessWidget {
-  final User user;
+  const FinishShoppingPage({super.key});
-
-  const FinishShoppingPage({super.key, required this.user});
 
   @override
   Widget build(BuildContext context) {
-    final CartController cartRepo = context.read<CartController>();
+    final CartController cartController = context.read<CartController>();
     final ReceiptController receiptRepo = context.read<ReceiptController>();
     final PayingStateController payingStateRepo =
         context.watch<PayingStateController>();
-    final cart = cartRepo.allCartItems();
+    final cart = cartController.allCartItems();
 
     return Scaffold(
       body: SafeArea(
@@ -50,7 +47,7 @@ class FinishShoppingPage extends StatelessWidget {
                         "Total:",
                         style: TextStyle(fontWeight: FontWeight.bold),
                       ),
-                      Text(formatDkkCents(cartRepo.totalPrice())),
+                      Text(formatDkkCents(cartController.totalPrice())),
                     ],
                   ),
                 ),
@@ -60,7 +57,8 @@ class FinishShoppingPage extends StatelessWidget {
                           onPressed: () async {
                             payingStateRepo.next();
                             await Future.delayed(const Duration(seconds: 1));
-                            if (user.pay(cartRepo.totalPrice()) is Err) {
+                            // TODO: implement paying for user
+                            if (cartController.pay() is Err) {
                               if (context.mounted) {
                                 showDialog<String>(
                                   context: context,
@@ -84,7 +82,7 @@ class FinishShoppingPage extends StatelessWidget {
                             receiptRepo.createReceipt(cart);
                             payingStateRepo.next();
                             await Future.delayed(const Duration(seconds: 1));
-                            cartRepo.clearCart();
+                            cartController.clearCart();
                             payingStateRepo.reset();
                             if (context.mounted) {
                               Navigator.pop(context);

mobile/lib/pages/home_page.dart

@@ -1,15 +1,16 @@
 import 'package:flutter/material.dart';
+import 'package:mobile/controllers/session.dart';
 import 'package:mobile/pages/settings_page.dart';
-import 'package:mobile/controllers/user.dart';
+import 'package:mobile/utils/build_if_session_exists.dart';
 import 'package:mobile/utils/price.dart';
 import 'package:provider/provider.dart';
 
 class HomePage extends StatelessWidget {
-  final User user;
+  const HomePage({super.key});
-  const HomePage({super.key, required this.user});
 
   @override
   Widget build(BuildContext context) {
+    final sessionController = context.read<SessionController>();
     return Column(
       children: [
         Row(
@@ -28,25 +29,29 @@ class HomePage extends StatelessWidget {
         ),
         Card(
           child: Container(
-            decoration: const BoxDecoration(
+              decoration: const BoxDecoration(
-              borderRadius: BorderRadius.all(Radius.circular(10)),
+                borderRadius: BorderRadius.all(Radius.circular(10)),
-              color: Color(0xFFFFFFFF),
+                color: Color(0xFFFFFFFF),
-            ),
+              ),
-            padding: const EdgeInsets.all(10),
+              padding: const EdgeInsets.all(10),
-            child: Consumer<UsersControllerOld>(
+              child: BuildIfSessionExists(
-                builder: (context, usersRepo, _) => Text(
+                  sessionController: sessionController,
-                    "Saldo: ${formatDkkCents(user.balanceInDkkCents)}",
+                  placeholder: const CircularProgressIndicator(),
-                    style: Theme.of(context).textTheme.headlineSmall)),
+                  builder: (context, user) => Text(
-          ),
+                      "Saldo: ${formatDkkCents(user.balanceInDkkCents)}",
+                      style: Theme.of(context).textTheme.headlineSmall))),
         ),
         Expanded(
           child: Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: [
-              Text(
+              BuildIfSessionExists(
-                "Velkommen ${user.name}",
+                  sessionController: sessionController,
-                style: Theme.of(context).textTheme.headlineMedium,
+                  placeholder: const CircularProgressIndicator(),
-              ),
+                  builder: (context, user) => Text(
+                        "Velkommen ${user.name}",
+                        style: Theme.of(context).textTheme.headlineMedium,
+                      ))
             ],
           ),
         ),

mobile/lib/pages/log_in_page.dart

@@ -1,12 +1,11 @@
 import 'package:flutter/material.dart';
+import 'package:mobile/controllers/session.dart';
 import 'package:mobile/pages/register_page.dart';
-import 'package:mobile/controllers/user.dart';
 import 'package:mobile/results.dart';
 import 'package:mobile/widgets/error_box.dart';
 import 'package:mobile/widgets/primary_button.dart';
 import 'package:mobile/widgets/primary_input.dart';
 import 'package:provider/provider.dart';
-import 'dashboard.dart';
 
 class LogInPage extends StatelessWidget {
   const LogInPage({super.key});
@@ -61,19 +60,15 @@ class LogInFormState extends State<LogInForm> {
           controller: passwordController,
         ),
         PrimaryButton(
-            onPressed: () {
+            onPressed: () async {
-              final usersRepo = context.read<UsersControllerOld>();
+              final sessionController = context.read<SessionController>();
-              final loginResult =
+              final loginResult = await sessionController.login(
-                  usersRepo.login(mailController.text, passwordController.text);
+                  mailController.text, passwordController.text);
-
+              switch (loginResult) {
-              if (loginResult is Ok) {
+                case Ok<Null, String>():
-                setState(() => loginError = false);
+                  setState(() => loginError = false);
-                Navigator.of(context).popUntil((_) => false);
+                case Err<Null, String>():
-                Navigator.of(context).push(MaterialPageRoute(
+                  setState(() => loginError = true);
-                    builder: (context) =>
-                        Dashboard(user: (loginResult as Ok).value)));
-              } else {
-                setState(() => loginError = true);
               }
             },
             child: const Text("Log ind")),

mobile/lib/pages/register_page.dart

@@ -71,9 +71,9 @@ class RegisterFormState extends State<RegisterForm> {
             obscure: true),
         PrimaryButton(
             onPressed: () {
-              final usersRepo = context.read<UsersControllerOld>();
+              final sessionsRepo = context.read<UsersController>();
-              if (usersRepo.addUser(nameController.text, mailController.text,
+              if (sessionsRepo.register(nameController.text,
-                  passwordController.text) is Ok) {
+                  mailController.text, passwordController.text) is Ok) {
                 setState(() => registerError = false);
                 Navigator.of(context).pop();
               } else {

mobile/lib/pages/settings_page.dart

@@ -1,7 +1,6 @@
 import 'package:flutter/material.dart';
-import 'package:mobile/pages/log_in_page.dart';
+import 'package:mobile/controllers/session.dart';
 import 'package:mobile/pages/settings_pages/saldo.dart';
-import 'package:mobile/controllers/user.dart';
 import 'package:provider/provider.dart';
 
 class _Page {
@@ -31,11 +30,9 @@ class SettingsPage extends StatelessWidget {
         icon: Icons.door_back_door,
         title: "Log ud",
         action: (context) {
-          final users = context.read<UsersControllerOld>();
+          final sessionsController = context.read<SessionController>();
-          users.logout();
           Navigator.popUntil(context, (_) => false);
-          Navigator.of(context)
+          sessionsController.logout();
-              .push(MaterialPageRoute(builder: (context) => const LogInPage()));
         }),
   ];
 

mobile/lib/pages/settings_pages/saldo.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
-import 'package:mobile/controllers/user.dart';
+import 'package:mobile/controllers/session.dart';
+import 'package:mobile/utils/build_if_session_exists.dart';
 import 'package:mobile/utils/price.dart';
 import 'package:provider/provider.dart';
 
@@ -8,8 +9,7 @@ class SaldoSettingsPage extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final usersRepo = context.watch<UsersControllerOld>();
+    final sessionController = context.watch<SessionController>();
-    final user = usersRepo.loggedInUser()!;
     return Scaffold(
       backgroundColor: Colors.white,
       body: SafeArea(
@@ -25,12 +25,17 @@ class SaldoSettingsPage extends StatelessWidget {
                 ),
               ],
             ),
-            Text("Nuværende saldo: ${formatDkkCents(user.balanceInDkkCents)}",
+            BuildIfSessionExists(
-                style: Theme.of(context).textTheme.bodyLarge),
+              sessionController: sessionController,
+              placeholder: const CircularProgressIndicator(),
+              builder: (context, user) => Text(
+                  "Nuværende saldo: ${formatDkkCents(user.balanceInDkkCents)}",
+                  style: Theme.of(context).textTheme.bodyLarge),
+            ),
             ElevatedButton.icon(
               onPressed: () {
-                user.addBalanceFounds(10000);
+                // TODO: implement add balance
-                usersRepo.veryBadNotifyAll();
+                throw Exception("not implemented: Adding funds");
               },
               icon: const Icon(Icons.add),
               label: const Text("Tilføj 100,00 kr"),

mobile/lib/server/backend_server.dart

@@ -2,6 +2,7 @@ import 'dart:convert';
 
 import 'package:http/http.dart' as http;
 import 'package:mobile/models/product.dart';
+import 'package:mobile/models/user.dart';
 import 'package:mobile/server/server.dart';
 
 class BackendServer implements Server {
@@ -51,16 +52,61 @@ class BackendServer implements Server {
   }
 
   @override
-  Future<Response<Null>> login(
+  Future<Response<String>> login(
-    String name,
     String email,
     String password,
   ) async {
     final res = await _post(
-      endpoint: "auth/login",
+      endpoint: "sessions/login",
       body: {"email": email, "password": password},
     ).then((res) => json.decode(res.body));
 
+    if (res["ok"]) {
+      return Success(data: res["token"]);
+    } else {
+      return Error(message: res["message"]);
+    }
+  }
+
+  @override
+  Future<Response<Null>> logout(String token) async {
+    final res = await _post(
+      endpoint: "sessions/logout",
+      body: {
+        "token": token,
+      },
+    ).then((res) => json.decode(res.body));
+
+    if (res["ok"]) {
+      return Success(data: null);
+    } else {
+      return Error(message: res["message"]);
+    }
+  }
+
+  @override
+  Future<Response<User>> sessionUser(String token) async {
+    final res = await http
+        .get(
+          Uri.parse("$_apiUrl/sessions/user/$token"),
+        )
+        .then((res) => json.decode(res.body));
+    if (res["ok"]) {
+      return Error(message: res["message"]);
+    } else {
+      return Success(data: User.fromJson(res));
+    }
+  }
+
+  @override
+  Future<Response<Null>> payForCart(String token) async {
+    final res = await _post(
+      endpoint: "cart/pay",
+      body: {
+        "token": token,
+      },
+    ).then((res) => json.decode(res.body));
+
     if (res["ok"]) {
       return Success(data: null);
     } else {

mobile/lib/server/mock_server.dart

@@ -1,5 +1,6 @@
 import 'package:mobile/models/coordinate.dart';
 import 'package:mobile/models/product.dart';
+import 'package:mobile/models/user.dart';
 import 'package:mobile/server/server.dart';
 
 class MockServer implements Server {
@@ -108,11 +109,30 @@ class MockServer implements Server {
   }
 
   @override
-  Future<Response<Null>> login(
+  Future<Response<String>> login(
-    String name,
     String email,
     String password,
   ) async {
+    return Success(data: "asdsadasdsad");
+  }
+
+  @override
+  Future<Response<Null>> logout(String token) async {
+    return Success(data: null);
+  }
+
+  @override
+  Future<Response<User>> sessionUser(String token) async {
+    return Success(
+        data: User(
+            id: 0,
+            email: "test@test.com",
+            name: "testuser",
+            balanceInDkkCents: 10000));
+  }
+
+  @override
+  Future<Response<Null>> payForCart(String token) async {
     return Success(data: null);
   }
 }

mobile/lib/server/server.dart

@@ -1,4 +1,5 @@
 import 'package:mobile/models/product.dart';
+import 'package:mobile/models/user.dart';
 
 abstract class Server {
   Future<Response<List<Product>>> allProducts();
@@ -9,11 +10,15 @@ abstract class Server {
     String password,
   );
 
-  Future<Response<Null>> login(
+  Future<Response<String>> login(
-    String name,
     String email,
     String password,
   );
+  Future<Response<Null>> logout(String token);
+
+  Future<Response<User>> sessionUser(String token);
+
+  Future<Response<Null>> payForCart(String token);
 }
 
 sealed class Response<Data> {}

mobile/lib/utils/build_if_session_exists.dart

@@ -0,0 +1,33 @@
+import 'package:flutter/material.dart';
+import 'package:mobile/controllers/session.dart';
+import 'package:mobile/models/user.dart';
+import 'package:mobile/results.dart';
+
+class BuildIfSessionExists extends StatelessWidget {
+  final SessionController sessionController;
+  final Widget placeholder;
+  final Widget Function(BuildContext, User) builder;
+
+  const BuildIfSessionExists(
+      {super.key,
+      required this.sessionController,
+      required this.placeholder,
+      required this.builder});
+
+  @override
+  Widget build(BuildContext context) {
+    return FutureBuilder(
+        future: sessionController.user(),
+        builder: (context, snapshot) {
+          final data = snapshot.data;
+          if (data == null) {
+            return placeholder;
+          }
+          if (data is Ok<User, Null>) {
+            final user = data.value;
+            return builder(context, user);
+          }
+          return Container();
+        });
+  }
+}

mobile/test/widget_test.dart

@@ -13,7 +13,7 @@ import 'package:mobile/main.dart';
 void main() {
   testWidgets('Counter increments smoke test', (WidgetTester tester) async {
     // Build our app and trigger a frame.
-    await tester.pumpWidget(MyApp());
+    await tester.pumpWidget(const MyApp());
 
     // Verify that our counter starts at 0.
     expect(find.text('0'), findsOneWidget);