# Environment Variable Implementation Summary

This document summarizes the implementation of environment variable support for UnitForge, making the application configurable without code changes.

## Overview

The implementation adds comprehensive environment variable support to UnitForge, allowing configuration of:
- Application metadata (name, version, description)
- External links (GitHub, documentation, bug reports)
- Server settings (host, port, debug mode)
- CORS configuration
- Contact information

## Files Modified

### Core Configuration
- **`backend/app/core/config.py`** - New configuration module with Settings class
- **`.env.example`** - Template for environment variables
- **`docs/ENVIRONMENT.md`** - Comprehensive documentation

### Application Integration
- **`backend/app/main.py`** - Updated to use settings and inject template context
- **`backend/cli/__init__.py`** - Updated to use configurable app name and version
- **`backend/__init__.py`** - Updated to use environment variables for metadata

### Templates
- **`frontend/templates/index.html`** - Updated to use template variables
- **`frontend/templates/templates.html`** - Updated to use template variables  
- **`frontend/templates/editor.html`** - Updated to use template variables

### Build and Development
- **`pyproject.toml`** - Added python-dotenv dependency
- **`docker-compose.yml`** - Added env_file support to all services
- **`Makefile`** - Added .env file creation during setup
- **`check-uv.sh`** - Updated to use environment variable for GitHub URL

## Key Features

### 1. Configuration Management
```python
from app.core.config import settings

# Access configuration
print(settings.app_name)
print(settings.github_url)
```

### 2. Template Integration
HTML templates automatically receive configuration variables:
```html
<title>{{ app_name }} - Page Title</title>
<a href="{{ github_url }}">GitHub</a>
```

### 3. Environment File Support
- Automatic loading of `.env` files using python-dotenv
- Fallback to default values when variables are not set
- Docker Compose integration

### 4. Development Workflow
- `make setup-dev` automatically creates `.env` from template
- Environment variables override defaults
- No code changes needed for different deployments

## Configuration Variables

### Application Settings
```bash
APP_NAME=UnitForge
APP_VERSION=1.0.0
APP_DESCRIPTION=Create, validate, and manage systemd unit files
```

### External Links
```bash
GITHUB_URL=https://github.com/will666/unitforge
DOCUMENTATION_URL=https://unitforge.readthedocs.io/
BUG_REPORTS_URL=https://github.com/will666/unitforge/issues
```

### Server Configuration
```bash
HOST=0.0.0.0
PORT=8000
DEBUG=false
CORS_ORIGINS=*
```

### Contact Information
```bash
CONTACT_EMAIL=contact@unitforge.dev
```

## Benefits

1. **Deployment Flexibility** - Same codebase works across environments
2. **Customization** - Easy branding and configuration changes
3. **Security** - Sensitive values can be set via environment
4. **Container Ready** - Full Docker and Kubernetes support
5. **Developer Friendly** - Automatic setup and clear documentation

## Usage Examples

### Development Override
```bash
# Temporary override for testing
GITHUB_URL="https://github.com/myorg/fork" python -m uvicorn backend.app.main:app
```

### Production Deployment
```bash
# Production .env file
APP_NAME=UnitForge Production
DEBUG=false
HOST=0.0.0.0
PORT=80
GITHUB_URL=https://github.com/mycompany/unitforge
SECRET_KEY=production-secret-key
```

### Docker Deployment
```yaml
# docker-compose.yml automatically loads .env
services:
  unitforge:
    env_file: .env
    environment:
      - DEBUG=false  # Override specific values
```

## Testing

All changes have been validated:
- ✅ Configuration loads correctly with defaults
- ✅ Environment variables override defaults
- ✅ Templates render with injected variables
- ✅ CLI shows configured app name and version
- ✅ Docker Compose loads environment files
- ✅ No linting errors or diagnostics issues

## Migration Path

For existing deployments:
1. Copy `.env.example` to `.env`
2. Customize values as needed
3. No code changes required
4. Templates automatically use new variables

## Future Enhancements

Potential additions:
- Database configuration via environment
- Email service configuration
- Logging configuration
- Feature flags
- API rate limiting settings
- Theme customization variables

## Conclusion

This implementation provides a robust, flexible configuration system that follows modern application development best practices while maintaining backward compatibility and ease of use.