Learn Production Architecture with NestJS

src/
├── main.ts                    # Entry point
├── app.module.ts              # Root module
├── health/
│   ├── health.module.ts       # Health module
│   └── health.controller.ts   # Health controller
└── projects/
    ├── projects.module.ts     # Projects module
    ├── projects.controller.ts # Handles routing
    ├── projects.service.ts    # Business logic
    └── dto/
        ├── create-project.dto.ts
        └── update-project.dto.ts

import { NestFactory } from '@nestjs/core';
import { ValidationPipe } from '@nestjs/common';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);

  // CORS configuration
  app.enableCors({
    origin: ['http://localhost:5173'],
    credentials: true,
  });

  // Global validation pipe
  app.useGlobalPipes(new ValidationPipe({
    whitelist: true,
    transform: true,
  }));

  await app.listen(8000);
  console.log('🚀 NestJS running on http://localhost:8000');
}

bootstrap();

import { Module } from '@nestjs/common';
import { HealthModule } from './health/health.module';
import { ProjectsModule } from './projects/projects.module';

@Module({
  imports: [HealthModule, ProjectsModule],
})
export class AppModule {}

import { IsString, IsOptional, MinLength, MaxLength } from 'class-validator';

export class CreateProjectDto {
  @IsString()
  @MinLength(1)
  @MaxLength(100)
  name: string;

  @IsOptional()
  @IsString()
  @MaxLength(500)
  description?: string;
}

import { Controller, Get, Post, Body, Param, Delete, HttpCode } from '@nestjs/common';
import { ProjectsService } from './projects.service';
import { CreateProjectDto } from './dto/create-project.dto';

@Controller('api/v1/projects')  // Route prefix
export class ProjectsController {
  // Dependency injection
  constructor(private readonly projectsService: ProjectsService) {}

  @Post()
  @HttpCode(201)
  create(@Body() createProjectDto: CreateProjectDto) {
    return this.projectsService.create(createProjectDto);
  }

  @Get()
  findAll() {
    return this.projectsService.findAll();
  }

  @Get(':id')
  findOne(@Param('id') id: string) {
    return this.projectsService.findOne(id);
  }

  @Delete(':id')
  @HttpCode(204)
  remove(@Param('id') id: string) {
    return this.projectsService.remove(id);
  }
}

import { Injectable, NotFoundException } from '@nestjs/common';
import { CreateProjectDto } from './dto/create-project.dto';

@Injectable()  // Register in DI container
export class ProjectsService {
  private projects = new Map();

  create(dto: CreateProjectDto) {
    const project = {
      id: crypto.randomUUID(),
      name: dto.name,
      description: dto.description || null,
      created_at: new Date().toISOString(),
    };
    this.projects.set(project.id, project);
    return project;
  }

  findAll() {
    return {
      items: Array.from(this.projects.values()),
      total: this.projects.size,
    };
  }

  findOne(id: string) {
    const project = this.projects.get(id);
    if (!project) throw new NotFoundException('Project not found');
    return project;
  }

  remove(id: string) {
    if (!this.projects.delete(id)) {
      throw new NotFoundException('Project not found');
    }
  }
}