chore: improves example codes

src/application/use-cases/user-case.module.ts

@@ -0,0 +1,12 @@
+import { Module } from '@nestjs/common';
+
+import { DatabaseModule } from '@infra/database/database.module';
+
+import { GetUserByEmailUseCase } from './user/get-user-by-email.use-case';
+
+@Module({
+  imports: [DatabaseModule],
+  providers: [GetUserByEmailUseCase],
+  exports: [GetUserByEmailUseCase],
+})
+export class UseCasesModule {}

src/application/use-cases/user/errors/user-by-email-not-found.error.ts

@@ -0,0 +1,8 @@
+import { DomainError } from '@core/domain/errors/DomainError';
+
+export class UserByEmailNotFoundError extends Error implements DomainError {
+  constructor(email: string) {
+    super(`User with email '${email}' was not found.`);
+    this.name = 'UserNotFound';
+  }
+}

src/application/use-cases/user/get-user-by-email.use-case.spec.ts

@@ -0,0 +1,50 @@
+import { EmailBadFormattedError } from '@domain/value-objects/errors/email-bad-formatted-error';
+
+import { UsersRepository } from '@infra/database/repositories/users.repository';
+
+import { makeFakeUser } from '@test/factories/users.factory';
+import { InMemoryUsersRepository } from '@test/repositories/in-memory-users.repository';
+
+import { UserByEmailNotFoundError } from './errors/user-by-email-not-found.error';
+import { GetUserByEmailUseCase } from './get-user-by-email.use-case';
+
+describe('GetUserByEmailUseCase', () => {
+  let usersRepository: UsersRepository;
+
+  let getUserByEmailUseCase: GetUserByEmailUseCase;
+
+  beforeEach(() => {
+    usersRepository = new InMemoryUsersRepository();
+
+    getUserByEmailUseCase = new GetUserByEmailUseCase(usersRepository);
+  });
+
+  it('should be able to get user by email', async () => {
+    const user = makeFakeUser();
+
+    await usersRepository.create(user);
+
+    const output = await getUserByEmailUseCase.handle(user.email);
+
+    expect(output.isRight()).toBeTruthy();
+    expect(output.value).toEqual(user);
+  });
+
+  it('should be able an error is returned in case an invalid email address is provided', async () => {
+    const invalidEmail = 'invalid_email';
+
+    const output = await getUserByEmailUseCase.handle(invalidEmail);
+
+    expect(output.isLeft()).toBeTruthy();
+    expect(output.value).toBeInstanceOf(EmailBadFormattedError);
+  });
+
+  it('should be able to return user not found error', async () => {
+    const email = 'oi@rocketseat.com.br';
+
+    const output = await getUserByEmailUseCase.handle(email);
+
+    expect(output.isLeft()).toBeTruthy();
+    expect(output.value).toBeInstanceOf(UserByEmailNotFoundError);
+  });
+});

src/application/use-cases/user/get-user-by-email.use-case.ts

@@ -0,0 +1,37 @@
+import { Injectable } from '@nestjs/common';
+
+import { Either, left, right } from '@core/logic/Either';
+
+import { User } from '@domain/entities/user.entity';
+import { Email } from '@domain/value-objects/email';
+import { EmailBadFormattedError } from '@domain/value-objects/errors/email-bad-formatted-error';
+
+import { UsersRepository } from '@infra/database/repositories/users.repository';
+
+import { UserByEmailNotFoundError } from './errors/user-by-email-not-found.error';
+
+type GetUserByEmailResponse = Either<
+  EmailBadFormattedError | UserByEmailNotFoundError,
+  User
+>;
+
+@Injectable()
+export class GetUserByEmailUseCase {
+  constructor(private readonly usersRepository: UsersRepository) {}
+
+  async handle(email: string): Promise<GetUserByEmailResponse> {
+    const isInvalidEmail = !Email.validate(email);
+
+    if (isInvalidEmail) {
+      return left(new EmailBadFormattedError(email));
+    }
+
+    const user = await this.usersRepository.findByEmail(email);
+
+    if (!user) {
+      return left(new UserByEmailNotFoundError(email));
+    }
+
+    return right(user);
+  }
+}

src/config/database.ts

@@ -1,7 +1,7 @@
 import 'dotenv/config';
 
-export const USER = process.env.DATABASE_USER ?? 'docker';
-export const PASSWORD = process.env.DATABASE_PASS ?? 'docker';
+export const USER = process.env.DATABASE_USER ?? 'root';
+export const PASSWORD = process.env.DATABASE_PASS ?? 'toor';
 export const HOST = process.env.DATABASE_HOST ?? 'localhost';
 export const PORT = process.env.DATABASE_PORT ?? '3306';
 export const NAME = process.env.DATABASE_NAME ?? 'app';

src/core/logic/Replace.ts

@@ -0,0 +1,14 @@
+/**
+ * Replaces the property definitions from a given type
+ * @example
+ * ```typescript
+ * type Post {
+ *  id: string;
+ *  name: string;
+ * }
+ *
+ * Replace<Post, {id: number}>
+ * ```
+ **/
+
+export type Replace<T, R> = Omit<T, keyof R> & R;

src/domain/entities/user.entity.ts

@@ -0,0 +1,37 @@
+import { Entity } from '@core/domain/Entity';
+import { Replace } from '@core/logic/Replace';
+
+export type UserProps = {
+  email: string;
+  createdAt: Date;
+};
+
+export class User extends Entity<UserProps> {
+  get email() {
+    return this.props.email;
+  }
+
+  get createdAt() {
+    return this.props.createdAt;
+  }
+
+  static create(
+    props: Replace<
+      UserProps,
+      {
+        createdAt?: Date;
+      }
+    >,
+    id?: string,
+  ) {
+    const user = new User(
+      {
+        ...props,
+        createdAt: props.createdAt ?? new Date(),
+      },
+      id,
+    );
+
+    return user;
+  }
+}

src/domain/value-objects/email.ts

@@ -0,0 +1,27 @@
+import { Either, left, right } from '@core/logic/Either';
+
+import { EmailBadFormattedError } from './errors/email-bad-formatted-error';
+
+export class Email {
+  protected constructor(private readonly email: string) {}
+
+  get value(): string {
+    return this.email;
+  }
+
+  static validate(email: string): boolean {
+    const emailRegex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
+
+    return emailRegex.test(email);
+  }
+
+  static create(email: string): Either<EmailBadFormattedError, Email> {
+    const isValidEmail = this.validate(email);
+
+    if (!isValidEmail) {
+      return left(new EmailBadFormattedError(email));
+    }
+
+    return right(new Email(email));
+  }
+}

src/domain/value-objects/errors/email-bad-formatted-error.ts

@@ -0,0 +1,8 @@
+import { DomainError } from '@core/domain/errors/DomainError';
+
+export class EmailBadFormattedError extends Error implements DomainError {
+  constructor(email: string) {
+    super(`The email '${email}' is bad formatted.`);
+    this.name = 'EmailBadFormatted';
+  }
+}

src/infra/database/database.module.ts

@@ -1,9 +1,17 @@
 import { Module } from '@nestjs/common';
 
 import { PrismaService } from './prisma/prisma.service';
+import { PrismaUsersRepository } from './prisma/repositories/prisma-users-repository';
+import { UsersRepository } from './repositories/users.repository';
 
 @Module({
-  providers: [PrismaService],
-  exports: [PrismaService],
+  providers: [
+    PrismaService,
+    {
+      provide: UsersRepository,
+      useClass: PrismaUsersRepository,
+    },
+  ],
+  exports: [PrismaService, UsersRepository],
 })
 export class DatabaseModule {}

src/infra/database/prisma/mappers/user.mapper.ts

@@ -0,0 +1,22 @@
+import { Prisma, User as RawUser } from '@prisma/client';
+
+import { User } from '@domain/entities/user.entity';
+
+export class UserMapper {
+  static toDomain(raw: RawUser): User {
+    const user = User.create({
+      email: raw.email,
+      createdAt: raw.created_at,
+    });
+
+    return user;
+  }
+
+  static toPersistence(user: User): Prisma.UserCreateInput {
+    return {
+      id: user.id,
+      email: user.email,
+      created_at: user.createdAt,
+    };
+  }
+}

src/infra/database/prisma/repositories/prisma-users-repository.ts

@@ -0,0 +1,37 @@
+import { Injectable } from '@nestjs/common';
+
+import { AsyncMaybe } from '@core/logic/Maybe';
+
+import { User } from '@domain/entities/user.entity';
+
+import { UsersRepository } from '@infra/database/repositories/users.repository';
+
+import { UserMapper } from '../mappers/user.mapper';
+import { PrismaService } from '../prisma.service';
+
+@Injectable()
+export class PrismaUsersRepository implements UsersRepository {
+  constructor(private readonly prisma: PrismaService) {}
+
+  async create(user: User): Promise<User> {
+    await this.prisma.user.create({
+      data: UserMapper.toPersistence(user),
+    });
+
+    return user;
+  }
+
+  async findByEmail(email: string): AsyncMaybe<User> {
+    const user = await this.prisma.user.findUnique({
+      where: {
+        email,
+      },
+    });
+
+    if (!user) {
+      return null;
+    }
+
+    return UserMapper.toDomain(user);
+  }
+}

src/infra/database/repositories/users.repository.ts

@@ -0,0 +1,11 @@
+import { Injectable } from '@nestjs/common';
+
+import { AsyncMaybe } from '@core/logic/Maybe';
+
+import { User } from '@domain/entities/user.entity';
+
+@Injectable()
+export abstract class UsersRepository {
+  abstract create(user: User): Promise<User>;
+  abstract findByEmail(email: string): AsyncMaybe<User>;
+}

src/infra/http/graphql/dto/models/user.model.ts

@@ -0,0 +1,19 @@
+import { Injectable } from '@nestjs/common';
+import { Field, ID, ObjectType } from '@nestjs/graphql';
+
+import { Paginated } from '../../common/dto/models/paginated';
+
+@ObjectType()
+export class User {
+  @Field(() => ID)
+  id: string;
+
+  @Field(() => String)
+  email: string;
+
+  @Field(() => Date)
+  createdAt: Date;
+}
+
+@Injectable()
+export class PaginatedUsers extends Paginated(User) {}