Matrix-Net Backend

*** Still under development ***

Overview

Social media application backend built with FastAPI. It implements an event-driven architecture with a service layer that follows command/handler/message bus patterns. The application uses SQLAlchemy for database operations with support for both SQLite (development) and PostgreSQL (production) databases.

Technologies

• Framework: FastAPI
• Database: SQLAlchemy with support for SQLite and PostgreSQL
• Authentication: JWT tokens with access/refresh token system
• Architecture: Event-driven service layer with commands, handlers, and message bus
• File Storage: Backblaze B2 integration Not integrated yet
• Monitoring: Sentry for error tracking totally optional and personally I do not like it

Architecture Pattern

• Domain Layer: Contains business entities, commands, and events
• Service Layer: Implements command handlers and business logic
• Adapters: Handles persistence
• Entrypoints: API endpoints and request/response schemas
• Bootstrap: Initializes the message bus and dependency injection

Structure

src/
├── adapters/          # Persistence, notifications, and storage adapters
├── domain/            # Business entities, commands, and events
├── entrypoints/       # API routers and request/response schemas
├── service_layer/     # Command handlers and business logic
├── views/             # Database query helpers
├── bootstrap.py       # Application initialization and message bus setup
├── config.py          # Configuration management
├── db.py              # Database models and connection setup
├── main.py            # FastAPI application and middleware
└── security.py        # Authentication and authorization logic

Building and Running

Prerequisites

• Python 3.8+
• Virtual environment (recommended)

Setup

1. Create and activate a virtual environment:

   python -m venv venv && source venv/bin/activate

2. Install dependencies:

   pip install -r requirements.txt -r dev-requirements.txt

3. Configure environment variables:

   • Copy .env.example to .env
   • Set appropriate values for your environment (ENV, DATABASE_URI, SECRET_KEY, etc.)

Running the Application

• Development: ENV=dev DEV_DATABASE_URI=sqlite:///./local.db DEV_SECRET_KEY=dev-secret uvicorn src.main:app --reload
• Production: Configure appropriate environment variables and run with a production WSGI server

Testing

• Run tests: pytest

Development Conventions

Architecture Patterns

• Commands represent user intentions (actions to be performed)
• Events represent things that have happened (state changes)
• Handlers process commands and emit events
• Aggregates maintain business invariants
• Repositories provide persistence abstraction

Error Handling

• Custom domain exceptions for business logic errors
• HTTP exceptions for API endpoints
• Logging for debugging and monitoring

Security

• Passwords are hashed using bcrypt
• JWT tokens for authentication with configurable expiration
• Input validation using Pydantic schemas
• SQL injection protection through SQLAlchemy ORM

Environment Configuration

The application supports three environments:

• Development (ENV=dev): Uses DEV_ prefixed environment variables
• Production (ENV=prod): Uses PROD_ prefixed environment variables or standard names
• Test (ENV=test): Uses TEST_ prefixed environment variables with defaults

Key configuration variables:

• DATABASE_URI: Database connection string
• SECRET_KEY: Secret key for JWT token signing
• B2_KEY_ID, B2_APPLICATION_KEY, B2_BUCKET_NAME: Backblaze B2 storage configuration
• SENTRY_DSN: Sentry error tracking configuration

API Endpoints

The API is organized into the following routers:

• /api/register - User registration
• /api/token - Authentication token generation
• /api/token/refresh/ - Token refresh
• /api/user/me/ - Current user profile
• /api/user/ - User settings (password change, account deletion)
• /api/posts/ - Post management (including delete functionality)
• /api/comments/ - Comment management (including delete functionality)
• /api/likes/ - Like functionality
• /api/upload/ - File upload endpoints --pending--

New endpoints added:

• DELETE /api/posts/{post_id} - Delete a post (user must be the owner)
• DELETE /api/comments/{comment_id} - Delete a comment (user must be the owner)

Testing Strategy

The application includes:

• Unit tests for business logic
• Integration tests for API endpoints
• Test fixtures for database management
• Mocking capabilities for external dependencies