Add sign in feature

package.json

@@ -25,6 +25,7 @@
     "@nestjs/core": "^8.0.0",
     "@nestjs/platform-express": "^8.0.0",
     "@nestjs/typeorm": "^8.0.2",
+    "bcrypt": "^5.0.1",
     "class-transformer": "^0.4.0",
     "class-validator": "^0.13.1",
     "pg": "^8.7.1",

src/auth/auth.controller.ts

@@ -10,4 +10,9 @@ export class AuthController {
   signUp(@Body() authCredentialsDto: AuthCredentialsDto): Promise<void> {
     return this.authService.signUp(authCredentialsDto);
   }
+
+  @Post('/signin')
+  signIn(@Body() authCredentialsDto: AuthCredentialsDto): Promise<string> {
+    return this.authService.signIn(authCredentialsDto);
+  }
 }

src/auth/auth.service.ts

@@ -1,7 +1,8 @@
-import { Injectable } from '@nestjs/common';
+import { Injectable, UnauthorizedException } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { AuthCredentialsDto } from './dto/auth-credentials.dto';
 import { UsersRepository } from './users.repository';
+import * as bcrypt from 'bcrypt';
 
 @Injectable()
 export class AuthService {
@@ -13,4 +14,15 @@ export class AuthService {
   async signUp(authCredentialsDto: AuthCredentialsDto): Promise<void> {
     return this.usersRepository.createUser(authCredentialsDto);
   }
+
+  async signIn(authCredentialsDto: AuthCredentialsDto): Promise<string> {
+    const { username, password } = authCredentialsDto;
+    const user = await this.usersRepository.findOne({ username });
+
+    if (user && (await bcrypt.compare(password, user.password))) {
+      return 'Success!';
+    } else {
+      throw new UnauthorizedException('Please check your login credentials.');
+    }
+  }
 }

src/auth/dto/auth-credentials.dto.ts

@@ -1,4 +1,16 @@
+import { IsString, Matches, MaxLength, MinLength } from 'class-validator';
+
 export class AuthCredentialsDto {
+  @IsString()
+  @MinLength(4)
+  @MaxLength(20)
   username: string;
+
+  @IsString()
+  @MinLength(8)
+  @MaxLength(32)
+  @Matches(/((?=.*\d)|(?=.*\W+))(?![.\n])(?=.*[A-Z])(?=.*[a-z]).*$/, {
+    message: 'Password is too weak.',
+  })
   password: string;
 }

src/auth/user.entity.ts

@@ -2,10 +2,10 @@ import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';
 
 @Entity()
 export class User {
-  @PrimaryGeneratedColumn()
+  @PrimaryGeneratedColumn('uuid')
   id: string;
 
-  @Column()
+  @Column({ unique: true })
   username: string;
 
   @Column()

src/auth/users.repository.ts

@@ -1,12 +1,29 @@
+import {
+  ConflictException,
+  InternalServerErrorException,
+} from '@nestjs/common';
 import { EntityRepository, Repository } from 'typeorm';
 import { AuthCredentialsDto } from './dto/auth-credentials.dto';
 import { User } from './user.entity';
+import * as bcrypt from 'bcrypt';
 
 @EntityRepository(User)
 export class UsersRepository extends Repository<User> {
   async createUser(authCredentialsDto: AuthCredentialsDto): Promise<void> {
     const { username, password } = authCredentialsDto;
-    const user = this.create({ username, password });
-    await this.save(user);
+
+    const salt = await bcrypt.genSalt();
+    const hashedPassword = await bcrypt.hash(password, salt);
+    const user = this.create({ username, password: hashedPassword });
+
+    try {
+      await this.save(user);
+    } catch (error) {
+      if (error.code === '23505') {
+        throw new ConflictException('Username already exists.');
+      } else {
+        throw new InternalServerErrorException();
+      }
+    }
   }
 }