Todo App API

A RESTful API for managing todos built with NestJS. This API provides CRUD operations for todo items with filtering capabilities and Swagger documentation.

🚀 Technology Stack

Core Framework

• NestJS (v11.0.1) - Progressive Node.js framework for building efficient and scalable server-side applications
• TypeScript (v5.7.3) - Typed superset of JavaScript
• Express (via @nestjs/platform-express) - Web framework

Key Libraries

• @nestjs/swagger (v11.2.3) - API documentation with Swagger/OpenAPI
• class-validator (v0.14.3) - Validation decorators for DTOs
• class-transformer (v0.5.1) - Object transformation utilities
• RxJS (v7.8.1) - Reactive programming library

Development Tools

• Biome (v2.3.8) - Fast formatter and linter
• Jest (v30.0.0) - Testing framework
• TypeScript ESLint - TypeScript linting

📋 Features

• ✅ Create, read, update, and delete todos
• 🔍 Filter todos by status (all, active, completed)
• 📝 Input validation using class-validator
• 📚 Swagger/OpenAPI documentation
• 🏗️ Modular architecture with NestJS modules
• 🧪 Test infrastructure with Jest

🛠️ Installation

# Install dependencies
npm install

# Start development server
npm run start:dev

# Build for production
npm run build

# Start production server
npm run start:prod

📖 API Documentation

Once the server is running, access the Swagger documentation at:

• URL: http://localhost:3000/docs

🔌 API Routes

Todos Endpoints

Method	Route	Description	Query Params
GET	/todos	Get all todos	filter (optional): 'all' | 'active' | 'completed'
GET	/todos/:id	Get a todo by ID	-
POST	/todos	Create a new todo	-
PUT	/todos/:id	Update a todo	-
DELETE	/todos/:id	Delete a todo	-

Request/Response Examples

Create Todo

POST /todos
Content-Type: application/json

{
  "title": "Complete the project"
}

Update Todo

PUT /todos/:id
Content-Type: application/json

{
  "title": "Updated title",
  "completed": true
}

Get All Todos (with filter)

GET /todos?filter=active

📊 Application Flow & Architecture

graph TB
    Client[Client Request] --> Validation[Global ValidationPipe]
    Validation --> Router[Express Router]
    
    Router -->|GET /todos| GetAll[GET /todos<br/>Get All Todos]
    Router -->|GET /todos/:id| GetOne[GET /todos/:id<br/>Get Todo by ID]
    Router -->|POST /todos| Create[POST /todos<br/>Create Todo]
    Router -->|PUT /todos/:id| Update[PUT /todos/:id<br/>Update Todo]
    Router -->|DELETE /todos/:id| Delete[DELETE /todos/:id<br/>Delete Todo]
    
    GetAll --> Controller[TodosController]
    GetOne --> Controller
    Create --> Controller
    Update --> Controller
    Delete --> Controller
    
    Controller --> Service[TodosService]
    
    Service -->|findAllTodos| FilterLogic[Filter Logic<br/>all/active/completed]
    Service -->|findTodoById| FindLogic[Find by ID Logic]
    Service -->|newTodo| CreateLogic[Create Logic<br/>Generate UUID & Date]
    Service -->|updateTodo| UpdateLogic[Update Logic<br/>Merge DTO]
    Service -->|deleteTodo| DeleteLogic[Delete Logic<br/>Filter Array]
    
    FilterLogic --> Memory[In-Memory Storage<br/>Todo Array]
    FindLogic --> Memory
    CreateLogic --> Memory
    UpdateLogic --> Memory
    DeleteLogic --> Memory
    
    Memory --> Response[Response]
    Response --> Client
    
    style Client fill:#e1f5ff
    style Controller fill:#fff4e6
    style Service fill:#f0f9ff
    style Memory fill:#ffe6e6
    style Response fill:#e8f5e9

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🏗️ Project Structure

src/
├── app.module.ts          # Root application module
├── main.ts                # Application entry point
├── common/
│   └── interfaces/
│       └── todo.model.ts  # Todo interface and Filter type
└── todos/
    ├── todos.module.ts    # Todos feature module
    ├── todos.controller.ts # Todos HTTP handlers
    ├── todos.service.ts   # Todos business logic
    └── dto/
        ├── create-todo.dto.ts      # Create todo DTO
        ├── update-todo.dto.ts      # Update todo DTO
        └── todos-response.dto.ts   # Response DTO

🔧 Available Scripts

• npm run build - Build the application
• npm run format - Format code with Prettier
• npm run start - Start the application
• npm run start:dev - Start in development mode (watch mode)
• npm run start:debug - Start in debug mode
• npm run start:prod - Start production server
• npm run lint - Run ESLint
• npm run test - Run unit tests
• npm run test:watch - Run tests in watch mode
• npm run test:cov - Run tests with coverage
• npm run test:e2e - Run end-to-end tests

📝 Data Model

Todo Interface

interface Todo {
  id: string          // UUID
  title: string       // Todo title
  completed: boolean  // Completion status
  createdAt: Date     // Creation timestamp
}

Filter Type

type Filter = 'all' | 'active' | 'completed'

🔒 Validation

• CreateTodoDto: Requires title (string, min length 1)
• UpdateTodoDto: Optional title (string, min length 1) and completed (boolean)

All validation is handled automatically by the global ValidationPipe.

🌐 Default Configuration

• Port: 3000 (configurable via PORT environment variable)
• Documentation: /docs

📄 License

UNLICENSED