Chat App Backend

This repository contains the backend service for a real-time chat application. It is built with Node.js, Express, MongoDB, and Socket.IO, providing a robust foundation for handling user authentication, one-on-one messaging, and group chats.

Features

• User Authentication: Secure user registration and login using JWT (JSON Web Tokens).
• Real-time Messaging: Instant one-on-one and group messaging powered by Socket.IO.
• User Presence: Real-time tracking of online/offline user status.
• Message History: Ability to fetch complete chat history for both private and group chats.
• Group Management: Create new groups, join existing groups, and view a list of all available groups.
• Typing Indicators: Shows when a user is typing a message in a one-on-one chat.
• Read Receipts: Track if messages have been read by recipients, implemented for both one-on-one and group chats.
• RESTful API: A well-structured API for managing users, messages, and groups.
• Validation: Robust server-side request validation using Joi.

Tech Stack

• Backend: Node.js, Express.js
• Database: MongoDB with Mongoose
• Real-time Communication: Socket.IO
• Authentication: JSON Web Token (jsonwebtoken), bcryptjs for password hashing
• Validation: Joi
• Environment Variables: dotenv
• CORS: cors

Getting Started

Follow these instructions to get a copy of the project up and running on your local machine for development and testing purposes.

Prerequisites

• Node.js (v14 or newer)
• npm
• MongoDB (local instance or a cloud service like MongoDB Atlas)

Installation

1. Clone the repository:

   git clone https://github.com/Vidhuprakash/chat_app_backend.git
   cd chat_app_backend

2. Install dependencies:

   npm install

3. Set up environment variables: Create a .env file in the root of the project and add the following variables.

   # Server configuration
   PORT=4000
   
   # MongoDB connection string
   MONGO_URI=your_mongodb_connection_string
   
   # URL of the client application for CORS
   CLIENT_URL=http://localhost:3000
   
   # JWT configuration
   JWT_SECRET=your_super_secret_jwt_key
   AUTH_TOKEN_COOKIE=auth_token

Running the Server

• To run the server in development mode with hot-reloading:

  npm run dev

• To run the server in production mode:

  npm start

The server will be running on http://localhost:4000 (or the port you specified in your .env file).

Project Structure

The application is organized into a modular structure to promote separation of concerns and maintainability.

src/
├── config/             # Database, Socket.IO, and response message configurations
├── exceptions/         # Custom error classes
├── modules/            # Core application logic divided by feature
│   ├── auth/           # Authentication logic (login, register)
│   ├── group/          # Group chat management
│   ├── message/        # One-on-one and group messaging logic
│   └── user/           # User management
├── router/             # Main application router
└── utils/              # Helper functions and utilities

API Endpoints

The following are the available REST API endpoints. All routes are prefixed with /api. Authentication is required for all endpoints except login and register.

Method	Endpoint	Description
POST	/auth/register	Registers a new user.
POST	/auth/login	Logs in a user and returns a JWT.
POST	/auth/logout	Clears the authentication cookie.
GET	/users	Gets a list of all registered users.
GET	/messages/:receiver	Gets chat history with a specific user.
GET	/messages/group/:groupId	Gets chat history for a specific group.
PATCH	/messages/:messageId/read	Marks a one-on-one message as read.
GET	/groups	Gets a list of all available groups.

Socket.IO Events

The application uses Socket.IO for real-time bidirectional communication between the client and server.

Client Emits (to Server)

Event	Payload	Description
getGroups	-	Requests the list of all available groups.
createGroup	{ name: string }	Creates a new group with the given name.
joinGroup	{ groupId: string }	Adds the current user to a specific group.
getChatHistory	{ receiver: string }	Requests one-on-one chat history with another user.
getGroupChatHistory	{ groupId: string }	Requests the chat history of a group.
sendUserMessage	{ receiver: string, message: string }	Sends a message to a specific user.
sendGroupMessage	{ groupId: string, message: string }	Sends a message to a group.
markAsRead	{ messageId: string, isGroup: boolean }	Marks a specific message as read.
typing	{ receiverId: string }	Notifies that the user has started typing.
stopTyping	{ receiverId: string }	Notifies that the user has stopped typing.

Server Emits (to Client)

Event	Payload	Description
userStatus	Array<{ _id, username, online }>	Broadcasts the online status of all users to all connected clients.
groupList	Array<{ id, name }>	Sends the list of all available groups.
chatHistory	Array<Message>	Sends the requested one-on-one chat history.
groupChatHistory	Array<GroupMessage>	Sends the requested group chat history.
messageSent	Message or GroupMessage	Confirms to the sender that their message was sent successfully.
receiveMessage	Message	Delivers a new one-on-one message to the recipient.
receiveGroupMessage	GroupMessage	Delivers a new group message to all members of the group.
messageRead	{ messageId, read } or { messageId, readBy }	Notifies that a message has been read.
userTyping	{ sender, username }	Informs a client that another user is typing to them.
userStoppedTyping	{ sender }	Informs a client that another user has stopped typing.
error	{ message: string }	Sends an error message to the client (e.g., failed to send message).