⚙️ BaatCheet - Backend Server

The robust Node.js and Express backend for the BaatCheet real-time chat application. It handles RESTful API requests, persistent WebSocket connections, secure authentication, and database management.

🌟 Key Features

• ⚡ Real-Time Engine: Powered by Socket.io for instant message delivery, live online/offline status, and typing indicators.
• 🔐 Secure Authentication: * Stateless sessions using JSON Web Tokens (JWT) stored in HTTP-only cookies.
  • Password hashing via bcryptjs.
  • Email Verification (OTP): Integrated with Nodemailer and Redis for temporary OTP storage and TTL expiration.
• 🛡️ Hardened File Uploads: Custom Binary Signature Validation (Magic Numbers) to rigorously verify uploaded media types, preventing file extension spoofing and malicious uploads.
• 🔗 Rich Media Processing: Server-side Open Graph (OG) scraping to generate rich link previews for URLs shared in the chat.
• 🤝 Connect Code System: Generates unique, friendly 6-digit connection codes for users to easily add friends without exposing email addresses.

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🛠️ Tech Stack

• Runtime: Node.js
• Framework: Express.js
• Database: MongoDB (via Mongoose ODM)
• Caching & OTPs: Redis
• WebSockets: Socket.io
• Authentication: JWT, bcryptjs
• Email Service: Nodemailer

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📂 Project Structure

backend/
├── controllers/    # Request handling logic (authController, messageController)
├── middleware/     # Route protection (protectRoute) and upload handlers (Multer)
├── models/         # Mongoose database schemas (User, Conversation, Message)
├── routes/         # Express API endpoint definitions
├── services/       # External service integrations (RedisService, EmailService)
├── utils/          # Helpers (OTP generator, Magic Number validator, ConnectCode)
└── server.js       # Application entry point & Socket.io initialization

🚀 Getting Started

1. Prerequisites

Ensure you have the following installed and running:

• Node.js (v18+ recommended)
• MongoDB (Local instance or MongoDB Atlas URI)
• Redis (Local instance or Cloud Redis URL)

2. Installation

Clone the repository, navigate to the backend directory, and install dependencies:

npm install

3. Environment Variables

Create a .env file in the root of your backend directory and configure the following variables:

# Server Config
PORT=5000
NODE_ENV=development

# Database & Caching
MONGO_URI=mongodb+srv://<username>:<password>@cluster.mongodb.net/baatcheet
REDIS_URL=redis://localhost:6379  # Or your Upstash/Redis Cloud URL

# Security
JWT_SECRET=your_super_secret_jwt_signature_key

# Email Service (Nodemailer via Gmail App Passwords)
EMAIL_USER=your.email@gmail.com
EMAIL_APP_PASSWORD=your_16_digit_app_password

4. Run the Development Server

Start the server using Nodemon for hot-reloading:

npm run dev

You should see confirmation in your terminal that the Server, MongoDB, and Redis are successfully connected.

📡 API Overview

• POST /api/auth/register - Create a new account (requires OTP verification).
• POST /api/auth/send-otp - Dispatch verification email.
• POST /api/auth/verify-otp - Validate code against Redis store.
• POST /api/auth/login - Authenticate user and assign JWT cookie.
• GET /api/messages/:id - Fetch message history between current user and a friend.
• POST /api/messages/send/:id - Send a text or file message.
• GET /api/users - Fetch user's friends/conversations list.

Built with ❤️ by Biswajit Shaw.