💬 Chat Application - Backend

A robust, real-time chat application backend built with Node.js, Express, and WebSockets. This server provides RESTful APIs for user management, conversation handling, and message storage, along with real-time communication capabilities.

🚀 Features

• User Authentication: Secure JWT-based authentication system
• Real-time Messaging: WebSocket integration for instant message delivery
• Conversation Management: Create and manage multiple chat conversations
• Media Upload: Profile picture uploads with Cloudinary integration
• Type Safety: Built entirely with TypeScript
• Password Security: Bcrypt-based password hashing
• RESTful API: Clean, versioned API architecture

🛠️ Tech Stack

• Runtime: Node.js
• Framework: Express.js
• Language: TypeScript
• Database: MongoDB (with Mongoose ODM)
• Authentication: JSON Web Tokens (JWT)
• Real-time: WebSockets (Socket.io)
• File Upload: Multer
• Cloud Storage: Cloudinary
• Password Hashing: Bcrypt

📁 Project Structure

backend/
├── src/
│   ├── controllers/          # Route controllers
│   │   ├── user.controller.ts
│   │   ├── conversation.controller.ts
│   │   └── message.controller.ts
│   ├── models/               # Database models
│   │   ├── user.model.ts
│   │   ├── conversation.model.ts
│   │   └── message.model.ts
│   ├── routes/               # API routes
│   │   └── v1/
│   ├── middleware/           # Custom middleware
│   │   ├── auth.ts
│   │   └── multer.middleware.ts
│   ├── config/               # Configuration files
│   │   ├── db/
│   │   │   └── connection.ts
│   │   └── jwt.ts
│   └── server.ts             # Entry point
└── package.json

📦 Installation

1. Clone the repository

   git clone <your-repo-url>
   cd backend

2. Install dependencies

   npm install
   # or
   bun install

3. Set up environment variables

   Create a .env file in the root directory:

   PORT=5000
   MONGODB_URI=your_mongodb_connection_string
   JWT_SECRET=your_jwt_secret_key
   JWT_EXPIRES_IN=7d
   
   # Cloudinary Configuration
   CLOUDINARY_CLOUD_NAME=your_cloud_name
   CLOUDINARY_API_KEY=your_api_key
   CLOUDINARY_API_SECRET=your_api_secret
   
   # CORS
   CLIENT_URL=http://localhost:5173

4. Start the development server

   npm run dev
   # or
   bun dev

🔌 API Endpoints

Authentication

Method	Endpoint	Description	Auth Required
POST	/api/v1/users/register	Register a new user	❌
POST	/api/v1/users/login	Login user and get JWT	❌

User Profile

Method	Endpoint	Description	Auth Required
GET	/api/v1/users/profile	Get current user profile	✅
PUT	/api/v1/users/profile	Update user profile	✅

Conversations

Method	Endpoint	Description	Auth Required
GET	/api/v1/conversations	Get all user conversations	✅
POST	/api/v1/conversations	Create new conversation	✅

Messages

Method	Endpoint	Description	Auth Required
GET	/api/v1/messages/:conversationId	Get messages for a conversation	✅
POST	/api/v1/messages	Send a new message	✅

🔄 WebSocket Events

Client → Server

Event	Payload	Description
join_chat	{ conversationId }	Join a conversation room
send_message	{ conversationId, message }	Send a message
typing	{ conversationId }	User started typing
stop_typing	{ conversationId }	User stopped typing

Server → Client

Event	Payload	Description
connect	-	Connection established
disconnect	-	Connection closed
receive_message	{ message }	New message received
typing_broadcast	{ userId }	User is typing
user_online	{ userId }	User came online
user_offline	{ userId }	User went offline

🗄️ Database Models

User Model

{
  username: string,
  email: string,
  password: string (hashed),
  profilePicture?: string,
  createdAt: Date,
  updatedAt: Date
}

Conversation Model

{
  participants: [userId],
  lastMessage?: messageId,
  createdAt: Date,
  updatedAt: Date
}

Message Model

{
  conversationId: ObjectId,
  sender: userId,
  content: string,
  createdAt: Date,
  updatedAt: Date
}

🔐 Authentication Flow

1. User registers with email and password
2. Password is hashed using bcrypt
3. User logs in with credentials
4. Server validates and returns JWT token
5. Client includes JWT in Authorization header for protected routes
6. Middleware validates JWT for each protected request

🚦 Scripts

npm run dev          # Start development server
npm run build        # Compile TypeScript
npm start            # Start production server
npm run lint         # Run linter

🤝 Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

📄 License

This project is licensed under the MIT License.

👨‍💻 Author

Your Name - [Your GitHub Profile]

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Built with ❤️ using Node.js and TypeScript