# Backend Development Guide

The backend is a FastAPI application providing a RESTful API and WebSocket support for the Radionica 3D platform.

## Key Technologies
- **FastAPI**: High-performance Python framework.
- **SQLite**: Local database, chosen for simplicity and zero-latency access on small/medium traffic.
- **Pydantic**: Data validation and serialization.
- **JWT**: Token-based authentication.
- **WebSockets**: Real-time communication for the order chat.

## API Structure (`backend/routers/`)
- `auth.py`: Login, Registration, Password Reset, and Token management.
- `orders.py`: Order creation, tracking, and management.
- `admin.py`: High-privileged endpoints for managing users, reviews, and site settings.
- `files.py`: Handling uploads and serving protected files (STL models, invoice PDFs).
- `warehouse.py`: Inventory management for materials and filaments.

## Business Logic (`backend/services/`)
We avoid putting heavy logic in routers. Use services instead:
- **`AuditService`**: Logs every state change (e.g., when an admin changes an order price).
- **`FiscalService`**: Implements the Montenegrin Electronic Fiscalization (EFI). Generates JIKR/IKOF codes and signed XMLs.
- **`PricingService`**: Calculates the quote based on print time, material usage, and fixed costs.

## Database Management
The project uses raw SQL for schema definitions (`schema.sql`) and migrations.
- **Initialization**: `init_db.py` (archived in `legacy/`) was used initially.
- **Migrations**: New changes are added via SQL files in `backend/migrations/` and executed via `run_migrations.py`.

## Authentication
We use a custom dependency `get_current_user` in `backend/auth_utils.py` to protect routes.
Example usage:
```python
@router.get("/my-orders")
async def get_orders(current_user: User = Depends(get_current_user)):
    return await order_service.get_for_user(current_user.id)
```

## Running the Backend
1. Ensure the virtual environment is activated:
   ```bash
   # Windows
   backend\.venv\Scripts\activate
   ```
2. Install dependencies: `pip install -r backend/requirements.txt`
3. Run with Uvicorn:
   ```bash
   python -m uvicorn main:app --app-dir backend --port 8000 --reload
   ```

## Adding a New Feature
1. **Define Schema**: Add a Pydantic model in `backend/schemas.py`.
2. **Define Logic**: Create a new service or add a method to an existing one in `backend/services/`.
3. **Define Endpoint**: Create a route in the appropriate router file.
4. **Register Router**: Ensure the router is included in `backend/main.py`.