Backend Documentation

Overview

This is the backend for the Chat Application, built with Node.js, Express, and MongoDB. It handles user authentication, real-time messaging via Socket.IO, and data persistence.

Tech Stack & Libraries

• Core: Node.js, Express
• Database: MongoDB, Mongoose
• Real-time: Socket.IO
• Authentication: JSON Web Token (JWT), Bcrypt
• Email: Node Mailjet
• Utilities: Dotenv, Cors
• Dev Tools: TypeScript, Nodemon, Prettier

Architecture

The project follows a standard MVC-like structure:

• Controller/: Handles incoming HTTP requests and responses.
• routes/: Defines API endpoints and maps them to controllers.
• model/: Mongoose schemas for MongoDB interaction.
• sockets/: Contains Socket.IO event handlers and logic.
• middleware/: Custom middleware (e.g., authentication).
• config/: Configuration files (e.g., database connection).
• services/: Business logic and external services (e.g., email).
• utils/: Utility functions.

Setup & Installation

1. Prerequisites: Node.js and MongoDB installed.
2. Clone the Repository:

   git clone https://github.com/Eng1Mahmoud/backend-chat-app.git
   cd backend-chat-app

3. Install Dependencies:

   npm install

4. Environment Variables: Create a .env file in the root directory with the following variables:

   PORT=4000
   MONGO_URI=your_mongodb_connection_string
   JWT_SECRET=your_jwt_secret
   # Email Service Credentials (Mailjet/Nodemailer)
   MAILJET_API_KEY=...
   MAILJET_API_SECRET=...
   # Client URL for CORS
   CLIENT_URL=http://localhost:3000

5. Run Development Server:

   npm run dev

6. Build & Start Production:

   npm run build
   npm start

API Endpoints

Authentication (/api/auth)

Method	Endpoint	Description	Body Parameters
POST	/signup	Register a new user	username, email, password
GET	/verify-email	Verify email address	token (query param)
POST	/login	Authenticate user	email, password
POST	/forgot-password	Request password reset	email
POST	/reset-password	Reset password	token, newPassword

Users (/api/users)

Requires Authentication Header: Authorization: Bearer <token>

Method	Endpoint	Description
GET	/profile	Get current user profile
GET	/	Get all users. Response includes unreadCount for each user.

Messages (/api/messages)

Requires Authentication Header: Authorization: Bearer <token>

Method	Endpoint	Description
GET	/:id	Get conversation with a specific user ID

Socket.IO Events

The backend listens for and emits the following events. Authentication is handled via a handshake token.

Client -> Server

Event	Payload	Description
send_message	{ receiverId, text }	Send a new message.
user_typing	{ receiverId }	Notify that user is typing.
user_stopped_typing	{ receiverId }	Notify that user stopped typing.
mark_as_read	{ senderId }	Mark messages from a sender as read.
disconnect	N/A	Handle user disconnection.

Server -> Client

Event	Payload	Description
user_online	userId	Broadcast when a user comes online.
online_users	[userIds]	Sent to a newly connected user with list of online users.
unread_counts	{ userId: count }	Sent to a newly connected user with initial unread counts.
receive_message	Message object	Received by both sender and receiver.
user_typing	{ userId }	Notification that a user is typing.
user_stopped_typing	{ userId }	Notification that a user stopped typing.
messages_read_update	{ receiverId, status: 'read' }	Notify sender that their messages were read.
unread_count_update	{ userId, count }	Update the unread message count for a specific user.
user_offline	userId	Broadcast when a user goes offline.

Database Schema

User

• username: String, unique
• email: String, unique
• password: String (hashed)
• isVerified: Boolean
• online: Boolean
• verificationToken: String
• verificationTokenExpires: Date
• resetPasswordToken: String
• resetPasswordExpires: Date

Message

• sender: ObjectId (User)
• receiver: ObjectId (User)
• text: String
• status: Enum ('sent', 'delivered', 'read')
• timestamps: CreatedAt, UpdatedAt