Chat Application Backend

A real-time chat application backend built with FastAPI and SQLite, featuring WebSocket support for instant messaging.

Features

• User authentication with JWT
• User profile management
• Real-time messaging with WebSockets
• Support for direct messages and group chats
• Message read status tracking
• Typing indicators
• RESTful API for chat functionality
• Database migrations with Alembic
• Health check endpoint

Tech Stack

• Framework: FastAPI
• Database: SQLite
• ORM: SQLAlchemy
• Authentication: JWT (JSON Web Tokens)
• Real-time Communication: WebSockets
• Migration: Alembic

Project Structure

.
├── alembic/                 # Database migration files
│   ├── versions/            # Migration version scripts
│   ├── env.py               # Alembic environment configuration
│   └── script.py.mako       # Migration script template
├── app/                     # Application package
│   ├── api/                 # API endpoints
│   │   ├── dependencies/    # Endpoint dependencies (auth, etc.)
│   │   └── endpoints/       # API route definitions
│   ├── core/                # Core application components
│   │   ├── config.py        # Application configuration
│   │   └── security.py      # Security utilities
│   ├── db/                  # Database components
│   │   ├── repositories/    # Database CRUD operations
│   │   └── session.py       # Database session management
│   ├── models/              # SQLAlchemy ORM models
│   ├── schemas/             # Pydantic schemas for validation
│   ├── services/            # Business logic services
│   └── utils/               # Utility functions
├── main.py                  # Application entry point
├── alembic.ini              # Alembic configuration
└── requirements.txt         # Project dependencies

API Endpoints

Authentication

• POST /api/v1/auth/signup - Register a new user
• POST /api/v1/auth/login - Login and get access token
• GET /api/v1/auth/me - Get current user information

User Management

• GET /api/v1/users - List all users
• GET /api/v1/users/{user_id} - Get user details
• PUT /api/v1/users/me - Update current user profile

Conversations

• POST /api/v1/conversations - Create a new conversation
• GET /api/v1/conversations - List user's conversations
• GET /api/v1/conversations/{conversation_id} - Get conversation details
• PUT /api/v1/conversations/{conversation_id} - Update conversation details

Messages

• POST /api/v1/conversations/{conversation_id}/messages - Send a message
• GET /api/v1/conversations/{conversation_id}/messages - Get conversation messages
• PUT /api/v1/messages/{message_id}/read - Mark a message as read
• GET /api/v1/messages/unread/count - Get unread message count

WebSocket

• WebSocket /api/v1/ws - Real-time messaging WebSocket endpoint

Health Check

• GET /health - Application health check endpoint

Getting Started

Prerequisites

• Python 3.8+
• SQLite

Installation

1. Clone the repository
2. Install dependencies:

pip install -r requirements.txt

3. Run database migrations:

alembic upgrade head

4. Start the server:

uvicorn main:app --reload

The API will be available at http://localhost:8000 with documentation at http://localhost:8000/docs.

WebSocket Communication Protocol

The WebSocket endpoint supports the following message types:

Authentication

Client sends:

{
  "token": "your_jwt_token"
}

Send Message

Client sends:

{
  "type": "message",
  "conversation_id": "conversation_uuid",
  "content": "Hello, world!",
  "recipient_id": "recipient_uuid" // Optional, for direct messages
}

Mark Message as Read

Client sends:

{
  "type": "mark_read",
  "message_id": "message_uuid"
}

Typing Indicator

Client sends:

{
  "type": "typing",
  "conversation_id": "conversation_uuid"
}

Server Push Notifications

Server sends:

1. New message:

{
  "type": "new_message",
  "message": {
    "id": "message_uuid",
    "content": "Hello, world!",
    "sender_id": "sender_uuid",
    "recipient_id": "recipient_uuid",
    "conversation_id": "conversation_uuid",
    "is_read": false,
    "created_at": "2023-05-12T10:30:00Z",
    "updated_at": "2023-05-12T10:30:00Z"
  },
  "timestamp": "2023-05-12T10:30:00Z"
}

2. Message read confirmation:

{
  "type": "message_read",
  "message_id": "message_uuid",
  "timestamp": "2023-05-12T10:31:00Z"
}

3. User typing notification:

{
  "type": "user_typing",
  "user_id": "user_uuid",
  "conversation_id": "conversation_uuid",
  "timestamp": "2023-05-12T10:32:00Z"
}

License

This project is licensed under the MIT License.