Merge pull request #7 from SandroMaglione/6-functional-programming

Functional programming (`fpdart`) [6]

README.md

@@ -60,6 +60,7 @@ The project is organized in [releases](https://github.com/SandroMaglione/flutter
 3. [Dependency injection (`injectable`)](https://github.com/SandroMaglione/flutter-supabase-template/tree/v3-dep-injection) 
 4. [Supabase authentication](https://github.com/SandroMaglione/flutter-supabase-template/tree/v4-supabase-auth) 
 5. [Supabase database](https://github.com/SandroMaglione/flutter-supabase-template/tree/v5-supabase-database) 
+6. [Functional programming (`fpdart`)](https://github.com/SandroMaglione/flutter-supabase-template/tree/v6-functional-programming) 
 
 You can review each set of changes individually by [**looking at each release**](https://github.com/SandroMaglione/flutter-supabase-template/tags).
 
@@ -69,6 +70,7 @@ You can review each set of changes individually by [**looking at each release**]
 - [supabase_flutter](https://pub.dev/packages/supabase_flutter): Supabase SDK for Flutter's applications
 - [auto_route](https://pub.dev/packages/auto_route): Routing and navigation using auto-generation
 - [injectable](https://pub.dev/packages/injectable) ([get_it](https://pub.dev/packages/get_it)): Dependency injection using auto-generation
+- [fpdart](https://pub.dev/packages/fpdart): Functional programming in dart and flutter
 
 > **Note**: This setup is opinionated. There are many other possible solutions and packages to achieve the same (or better) result. It would be interesting to start a discussion about each solution (by [opening new PRs](https://github.com/SandroMaglione/flutter-supabase-template/pulls) implementing other options)
 
@@ -79,13 +81,12 @@ Each feature in the app has a [**blog post**](https://www.sandromaglione.com/) a
 3. [Dependency injection (`injectable`)](https://www.sandromaglione.com/techblog/how_to_implement_dependecy_injection_in_flutter)
 4. [Supabase authentication](https://www.sandromaglione.com/techblog/flutter-supabase-authentication-complete-tutorial)
 5. [Supabase database](https://www.sandromaglione.com/techblog/flutter-supabase-database-complete-tutorial)
+6. [Functional programming (`fpdart`)](https://www.sandromaglione.com/techblog/flutter-dart-functional-programming-fpdart-supabase-app)
 
 ## 🛣 Roadmap
 - [x] Adding support for [Supabase database](https://supabase.com/docs/guides/database)
+- [x] Improving the code using [**fpdart**](https://pub.dev/packages/fpdart) (Functional Programming)
 - [ ] Adding support for [Supabase storage](https://supabase.com/docs/guides/storage)
-- [ ] Improving the code using [**fpdart**](https://pub.dev/packages/fpdart) (Functional Programming)
-  - [ ] Using `TaskEither` in [`repository`](lib/app/repository) as return type
-  - [ ] Convert less-specific types to more specific ones using guards (e.g. instead of `String` for `userId`, create a `UserId` type and check the validity using `Either`)
 
 ## 🙏🏼 Contribution
 Every feedback, feature request, and contribution is gladly accepted:

lib/app/failures/get_user_information_failure.dart

@@ -0,0 +1,32 @@
+abstract class GetUserInformationFailure {
+  const GetUserInformationFailure();
+
+  String get mapToErrorMessage {
+    if (this is RequestGetUserInformationFailure) {
+      return 'Error when getting user information';
+    } else if (this is ResponseFormatErrorGetUserInformationFailure) {
+      return 'Invalid response';
+    } else if (this is JsonDecodeGetUserInformationFailure) {
+      return 'Missing valid user information';
+    }
+
+    return 'Unexpected error, please try again';
+  }
+}
+
+class RequestGetUserInformationFailure extends GetUserInformationFailure {
+  final Object error;
+  final StackTrace stackTrace;
+  const RequestGetUserInformationFailure(this.error, this.stackTrace);
+}
+
+class ResponseFormatErrorGetUserInformationFailure
+    extends GetUserInformationFailure {
+  final dynamic response;
+  const ResponseFormatErrorGetUserInformationFailure(this.response);
+}
+
+class JsonDecodeGetUserInformationFailure extends GetUserInformationFailure {
+  final Map<String, dynamic> data;
+  const JsonDecodeGetUserInformationFailure(this.data);
+}

lib/app/failures/login_failure.dart

@@ -0,0 +1,32 @@
+abstract class LoginFailure {
+  const LoginFailure();
+
+  String get mapToErrorMessage {
+    final failure = this;
+    if (failure is AuthErrorLoginFailure) {
+      return failure.message;
+    } else if (failure is ExecutionErrorLoginFailure) {
+      return 'Error when making login request';
+    } else if (failure is MissingUserIdLoginFailure) {
+      return 'Missing user information';
+    }
+
+    return 'Unexpected error, please try again';
+  }
+}
+
+class AuthErrorLoginFailure extends LoginFailure {
+  final String message;
+  final String? statusCode;
+  const AuthErrorLoginFailure(this.message, this.statusCode);
+}
+
+class ExecutionErrorLoginFailure extends LoginFailure {
+  final Object error;
+  final StackTrace stackTrace;
+  const ExecutionErrorLoginFailure(this.error, this.stackTrace);
+}
+
+class MissingUserIdLoginFailure extends LoginFailure {
+  const MissingUserIdLoginFailure();
+}

lib/app/failures/sign_out_failure.dart

@@ -0,0 +1,17 @@
+abstract class SignOutFailure {
+  const SignOutFailure();
+
+  String get mapToErrorMessage {
+    if (this is ExecutionErrorSignOutFailure) {
+      return 'Error when making sign out request';
+    }
+
+    return 'Unexpected error, please try again';
+  }
+}
+
+class ExecutionErrorSignOutFailure extends SignOutFailure {
+  final Object error;
+  final StackTrace stackTrace;
+  const ExecutionErrorSignOutFailure(this.error, this.stackTrace);
+}

lib/app/failures/update_user_information_failure.dart

@@ -0,0 +1,17 @@
+abstract class UpdateUserInformationFailure {
+  const UpdateUserInformationFailure();
+
+  String get mapToErrorMessage {
+    if (this is RequestUpdateUserInformationFailure) {
+      return 'Error when updating user information';
+    }
+
+    return 'Unexpected error, please try again';
+  }
+}
+
+class RequestUpdateUserInformationFailure extends UpdateUserInformationFailure {
+  final Object error;
+  final StackTrace stackTrace;
+  const RequestUpdateUserInformationFailure(this.error, this.stackTrace);
+}

lib/app/pages/home_page.dart

@@ -19,7 +19,7 @@ class HomePage extends StatelessWidget {
         body: Column(
           children: [
             ElevatedButton(
-              onPressed: _onClickSignOut,
+              onPressed: () => _onClickSignOut(context),
               child: const Text("Sign out"),
             ),
             UserInformationText(userId: user.id),
@@ -30,13 +30,18 @@ class HomePage extends StatelessWidget {
     );
   }
 
-  Future<void> _onClickSignOut() async {
-    try {
-      await getIt<AuthRepository>().signOut();
-    } catch (e) {
-      // TODO: Show proper error to users
-      print("Error on sign out");
-      print(e);
-    }
-  }
+  Future<void> _onClickSignOut(BuildContext context) async =>
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text(
+            await getIt<AuthRepository>()
+                .signOut()
+                .match(
+                  (signOutFailure) => signOutFailure.mapToErrorMessage,
+                  (_) => "Sign out successful",
+                )
+                .run(),
+          ),
+        ),
+      );
 }

lib/app/pages/sign_in_page.dart

@@ -53,15 +53,20 @@ class _SignInPageState extends State<SignInPage> {
     );
   }
 
-  Future<void> _onClickSignIn(BuildContext context) async {
-    try {
-      await getIt<AuthRepository>().signInEmailAndPassword(email, password);
-    } catch (e) {
-      // TODO: Show proper error to users
-      print("Sign in error");
-      print(e);
-    }
-  }
+  Future<void> _onClickSignIn(BuildContext context) async =>
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text(
+            await getIt<AuthRepository>()
+                .signInEmailAndPassword(email, password)
+                .match(
+                  (loginFailure) => loginFailure.mapToErrorMessage,
+                  (_) => "Sign in successful",
+                )
+                .run(),
+          ),
+        ),
+      );
 
   void _onClickGoToSignUp(BuildContext context) {
     context.router.push(const SignUpRoute());

lib/app/pages/sign_up_page.dart

@@ -52,15 +52,20 @@ class _SignUpPageState extends State<SignUpPage> {
     );
   }
 
-  Future<void> _onClickSignUp(BuildContext context) async {
-    try {
-      await getIt<AuthRepository>().signUpEmailAndPassword(email, password);
-    } catch (e) {
-      // TODO: Show proper error to users
-      print("Sign up error");
-      print(e);
-    }
-  }
+  Future<void> _onClickSignUp(BuildContext context) async =>
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(
+          content: Text(
+            await getIt<AuthRepository>()
+                .signUpEmailAndPassword(email, password)
+                .match(
+                  (loginFailure) => loginFailure.mapToErrorMessage,
+                  (_) => "Sign up successful",
+                )
+                .run(),
+          ),
+        ),
+      );
 
   void _onClickGoToSignIn(BuildContext context) {
     context.router.pop();

lib/app/repository/auth_repository.dart

@@ -1,6 +1,17 @@
+import 'package:flutter_supabase_complete/app/failures/login_failure.dart';
+import 'package:flutter_supabase_complete/app/failures/sign_out_failure.dart';
+import 'package:fpdart/fpdart.dart';
+
 abstract class AuthRepository {
-  Future<String> signInEmailAndPassword(String email, String password);
-  Future<String> signUpEmailAndPassword(String email, String password);
+  TaskEither<LoginFailure, String> signInEmailAndPassword(
+    String email,
+    String password,
+  );
+
+  TaskEither<LoginFailure, String> signUpEmailAndPassword(
+    String email,
+    String password,
+  );
 
-  Future<void> signOut();
+  TaskEither<SignOutFailure, Unit> signOut();
 }

lib/app/repository/user_database_repository.dart

@@ -1,6 +1,14 @@
+import 'package:flutter_supabase_complete/app/failures/get_user_information_failure.dart';
+import 'package:flutter_supabase_complete/app/failures/update_user_information_failure.dart';
 import 'package:flutter_supabase_complete/app/models/user_model.dart';
+import 'package:fpdart/fpdart.dart';
 
 abstract class UserDatabaseRepository {
-  Future<UserModel> getUserInformation(String userId);
-  Future<UserModel> updateUserInformation(UserModel userModel);
+  TaskEither<GetUserInformationFailure, UserModel> getUserInformation(
+    String userId,
+  );
+
+  TaskEither<UpdateUserInformationFailure, UserModel> updateUserInformation(
+    UserModel userModel,
+  );
 }

lib/app/services/supabase_auth_repository.dart

@@ -1,4 +1,7 @@
+import 'package:flutter_supabase_complete/app/failures/login_failure.dart';
+import 'package:flutter_supabase_complete/app/failures/sign_out_failure.dart';
 import 'package:flutter_supabase_complete/app/repository/auth_repository.dart';
+import 'package:fpdart/fpdart.dart';
 import 'package:injectable/injectable.dart';
 import 'package:supabase_flutter/supabase_flutter.dart';
 
@@ -8,38 +11,47 @@ class SupabaseAuthRepository implements AuthRepository {
   const SupabaseAuthRepository(this._supabase);
 
   @override
-  Future<String> signInEmailAndPassword(String email, String password) async {
-    final response = await _supabase.client.auth.signInWithPassword(
-      email: email,
-      password: password,
-    );
-
-    final userId = response.user?.id;
-    if (userId == null) {
-      throw UnimplementedError();
-    }
-
-    return userId;
-  }
+  TaskEither<LoginFailure, String> signInEmailAndPassword(
+    String email,
+    String password,
+  ) =>
+      _loginRequest(
+        () => _supabase.client.auth
+            .signInWithPassword(email: email, password: password),
+      );
 
   @override
-  Future<String> signUpEmailAndPassword(String email, String password) async {
-    final response = await _supabase.client.auth.signUp(
-      email: email,
-      password: password,
-    );
-
-    final userId = response.user?.id;
-    if (userId == null) {
-      throw UnimplementedError();
-    }
-
-    return userId;
-  }
+  TaskEither<LoginFailure, String> signUpEmailAndPassword(
+    String email,
+    String password,
+  ) =>
+      _loginRequest(
+        () => _supabase.client.auth.signUp(email: email, password: password),
+      );
 
   @override
-  Future<void> signOut() async {
-    await _supabase.client.auth.signOut();
-    return;
-  }
+  TaskEither<SignOutFailure, Unit> signOut() => TaskEither.tryCatch(() async {
+        await _supabase.client.auth.signOut();
+        return unit;
+      }, ExecutionErrorSignOutFailure.new);
+
+  /// Shared logic for login requests (sign in and sign up).
+  TaskEither<LoginFailure, String> _loginRequest(
+    Future<AuthResponse> Function() request,
+  ) =>
+      TaskEither<LoginFailure, AuthResponse>.tryCatch(
+        request,
+        (error, stackTrace) {
+          if (error is AuthException) {
+            return AuthErrorLoginFailure(error.message, error.statusCode);
+          }
+
+          return ExecutionErrorLoginFailure(error, stackTrace);
+        },
+      ).map((response) => response.user?.id).flatMap(
+            (id) => Either.fromNullable(
+              id,
+              (_) => const MissingUserIdLoginFailure(),
+            ).toTaskEither(),
+          );
 }