Language Hub Backend API

A RESTful API backend for a language learning platform built with Node.js, Express, TypeScript, and MongoDB.

🌟 Features

• User Authentication: Registration, login, token refresh, and JWT-based authentication
• Password Management: Forgot password and password reset functionality with email notifications
• AI-Powered Chat: Integration with OpenRouter API for AI-assisted language learning conversations
• Course Progress Tracking: Save and retrieve user progress across different courses and lessons
• Secure: bcrypt password hashing, JWT tokens, and CORS configuration

🛠️ Tech Stack

• Runtime: Node.js
• Framework: Express.js
• Language: TypeScript
• Database: MongoDB with Mongoose ODM
• Authentication: JWT (jsonwebtoken) + bcryptjs
• Email: Nodemailer
• AI Integration: OpenRouter API via Axios
• Development: ts-node-dev for hot reload

📋 Prerequisites

• Node.js (v14 or higher)
• MongoDB (local or cloud instance)
• npm or yarn package manager

🔴 Check Frontend Repository

Make sure to also check out the frontend repository for this project: Language Hub Frontend

Backend Deployed on: Language Hub Backend API

🚀 Getting Started

Installation

1. Clone the repository:

git clone https://github.com/hasinduudara/RAD_Final_Project_Backend.git
cd backend

2. Install dependencies:

npm install

3. Create a .env file in the root directory with the following variables:

# Server Configuration
PORT=5000

# Database
MONGO_URI=your_mongodb_connection_string

# JWT Secrets
JWT_SECRET=your_jwt_secret_key
JWT_REFRESH_SECRET=your_jwt_refresh_secret_key

# Email Configuration (for password reset)
EMAIL_HOST=smtp.gmail.com
EMAIL_PORT=587
EMAIL_USER=your_email@gmail.com
EMAIL_PASS=your_email_password

# OpenRouter API (for AI chat)
OPENROUTER_API_KEY=your_openrouter_api_key

# Frontend URL (for CORS)
FRONTEND_URL=http://localhost:5173

Development

Run the development server with hot reload:

npm run dev

The server will start on http://localhost:5000 (or the PORT specified in your .env file).

Production

1. Build the TypeScript code:

npm run build

2. Start the production server:

npm start

📁 Project Structure

backend/
├── src/
│   ├── controllers/        # Request handlers
│   │   ├── chatController.ts
│   │   ├── course.controller.ts
│   │   ├── password.controller.ts
│   │   └── user.controller.ts
│   ├── middleware/         # Custom middleware
│   │   └── user.ts        # Authentication middleware
│   ├── models/            # MongoDB schemas
│   │   ├── Chat.model.ts
│   │   ├── CourseProgress.model.ts
│   │   ├── resetToken.model.ts
│   │   └── user.model.ts
│   ├── routes/            # API routes
│   │   ├── chatRoutes.ts
│   │   ├── courseRoutes.ts
│   │   ├── password.routes.ts
│   │   └── user.ts
│   ├── utils/             # Utility functions
│   │   ├── mail.ts
│   │   ├── openrouterClient.ts
│   │   └── tokens.ts
│   └── index.ts           # Application entry point
├── package.json
├── tsconfig.json
└── .env

🔌 API Endpoints

User Routes (/api/v1/user)

• POST /register - Register a new user
• POST /login - User login
• POST /refresh - Refresh access token
• GET /welcome - Protected route example

Password Routes (/api/password)

• POST /forgot - Request password reset email
• POST /reset - Reset password with token

Chat Routes (/api/chat)

• POST / - Create new chat session
• POST /message - Send message to AI
• GET /:chatId - Get chat history
• GET /user/:userId - Get all user chats
• DELETE /:chatId - Delete chat

Course Routes (/api/course, /api/v1/course)

• POST /save-progress - Save user course progress
• GET /progress/:userId/:course - Get user progress for a course

🔒 Authentication

The API uses JWT (JSON Web Tokens) for authentication. Protected routes require a valid JWT token in the Authorization header:

Authorization: Bearer <your_jwt_token>

🌐 CORS Configuration

CORS is configured to accept requests from:

• http://localhost:5173 (default Vite frontend)

Update the CORS origin in src/index.ts to match your frontend URL.

📦 Dependencies

Main Dependencies

• express - Web framework
• mongoose - MongoDB ODM
• jsonwebtoken - JWT authentication
• bcryptjs - Password hashing
• nodemailer - Email sending
• axios - HTTP client for OpenRouter API
• cors - CORS middleware
• dotenv - Environment variables

Dev Dependencies

• typescript - TypeScript compiler
• ts-node-dev - Development server with hot reload
• @types/* - TypeScript type definitions

🐛 Error Handling

The API returns appropriate HTTP status codes:

• 200 - Success
• 201 - Created
• 400 - Bad Request
• 401 - Unauthorized
• 404 - Not Found
• 500 - Internal Server Error

📝 License

ISC

👥 Contributing

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

📧 Support

For support, email hasiduudara@gmail.com or open an issue in the repository.

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Made with ❤️ for language learners worldwide