# Configuration System Implementation Summary

## Overview

This project now includes a comprehensive TOML-based configuration system with environment variable overrides, designed to handle complex application settings in a structured and maintainable way.

## 🚀 Key Features

### ✅ TOML Configuration Files
- **Structured configuration** using TOML format
- **Environment-specific configs** (dev, staging, prod)
- **Hierarchical settings** organization
- **Comments and documentation** in config files

### ✅ Environment Variable Support
- **Override any setting** via environment variables
- **Environment variable substitution** in TOML files (`${VAR_NAME}`)
- **Automatic environment detection** (dev/prod)
- **Secure credential management**

### ✅ Configuration Validation
- **Comprehensive validation** of all settings
- **TLS certificate validation** when HTTPS is enabled
- **Database URL validation**
- **Production security checks**

### ✅ Developer Tools
- **Configuration CLI tool** for management and validation
- **Setup script** for easy initialization
- **Example configurations** for different environments
- **Migration guide** from environment-only setup

## 📁 File Structure

```
template/
├── config.toml                    # Default configuration
├── config.dev.toml                # Development environment
├── config.prod.toml               # Production environment
├── .env.example                   # Environment variables example
├── CONFIG_README.md               # Detailed documentation
├── CONFIG_SUMMARY.md              # This summary
├── MIGRATION_GUIDE.md             # Migration from old system
├── scripts/
│   └── setup-config.sh           # Setup script
└── server/
    ├── src/
    │   ├── config/
    │   │   └── mod.rs             # Configuration implementation
    │   ├── bin/
    │   │   └── config_tool.rs     # CLI management tool
    │   └── main.rs                # Updated to use new config
    └── examples/
        └── config_example.rs      # Usage examples
```

## 🔧 Configuration Sections

### Server Configuration
- Protocol (HTTP/HTTPS)
- Host and port binding
- Environment detection
- TLS certificate paths
- Logging levels

### Database Configuration
- Connection URL with environment substitution
- Connection pool settings
- Timeout configurations
- Connection lifecycle management

### Security Configuration
- CSRF protection settings
- Rate limiting configuration
- BCrypt cost settings
- Session management
- Cookie security settings

### Feature Flags
- Authentication system
- TLS support
- Content database
- Two-factor authentication
- OAuth providers

### Email Configuration
- Email provider selection (SMTP, SendGrid, Console)
- Internationalized template system
- Language detection and fallback
- Template directory structure
- SMTP server configuration
- SendGrid API integration
- Development email testing

### Additional Sections
- CORS policies
- Static file serving
- Redis configuration
- OAuth provider settings
- Application metadata
- Logging configuration
- Content management

## 🛠️ Usage Examples

### Loading Configuration
```rust
use server::config::Config;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Load configuration from TOML with env overrides
    let config = Config::load()?;
    
    // Use configuration
    let server_addr = config.server_address();
    let db_config = config.database_pool_config();
    
    println!("Server: {}", server_addr);
    println!("Database: {}", config.database.url);
    
    Ok(())
}
```

### Environment Variable Overrides
```bash
# Override server settings
export SERVER_HOST="0.0.0.0"
export SERVER_PORT="8080"
export ENVIRONMENT="production"

# Override database settings
export DATABASE_URL="postgresql://user:pass@db:5432/myapp"

# Override security settings
export SESSION_SECRET="super-secret-production-key"
```

### Configuration Management
```bash
# Validate current configuration
cargo run --bin config_tool -- validate

# Show all configuration values
cargo run --bin config_tool -- show

# Generate environment-specific config
cargo run --bin config_tool -- generate --env prod

# Check environment variables
cargo run --bin config_tool -- check-env
```

## 🎯 Environment-Specific Configurations

### Development (`config.dev.toml`)
- HTTP protocol for easy development
- Debug logging enabled
- Relaxed security settings
- Local database connections
- Development OAuth credentials
- Disabled CSRF for easier testing

### Production (`config.prod.toml`)
- HTTPS with TLS certificates
- Strict security settings
- Production database connections
- Environment variable substitution for secrets
- Optimized for performance
- Comprehensive monitoring

## 🔒 Security Features

### Secret Management
- Environment variable substitution for sensitive data
- No hardcoded secrets in configuration files
- Production validation for insecure defaults
- Secure session management

### TLS Support
- Automatic TLS configuration validation
- Certificate path verification
- Optional TLS feature flag
- Development vs production TLS settings

### CORS & Security Headers
- Configurable CORS policies
- Environment-specific allowed origins
- Security headers configuration
- Rate limiting settings

## 🚀 Migration Path

### From Environment-Only Configuration
1. **Identify** current environment variables
2. **Create** base TOML configuration
3. **Update** code to use `Config::load()`
4. **Move** sensitive data to environment variables
5. **Create** environment-specific configs
6. **Test** configuration loading
7. **Update** deployment scripts

### Migration Tools
- **Migration guide** with step-by-step instructions
- **Configuration tool** for validation
- **Example configurations** for reference
- **Rollback procedures** if needed

## 📊 Configuration Hierarchy

1. **Default values** (in code)
2. **TOML file** (config.toml or environment-specific)
3. **Environment variables** (highest priority)
4. **Environment variable substitution** (resolved last)

## 🔧 CLI Tools

### Configuration Tool (`config_tool`)
```bash
# Available commands
cargo run --bin config_tool -- validate    # Validate configuration
cargo run --bin config_tool -- show        # Display current config
cargo run --bin config_tool -- generate    # Generate config files
cargo run --bin config_tool -- check-env   # Check environment variables
cargo run --bin config_tool -- help        # Show help
```

### Setup Script (`setup-config.sh`)
```bash
# Interactive setup
./scripts/setup-config.sh

# Environment-specific setup
./scripts/setup-config.sh --env dev
./scripts/setup-config.sh --env prod

# Force overwrite existing files
./scripts/setup-config.sh --force
```

## 📈 Benefits

### For Developers
- **Easier configuration management** with structured TOML
- **Environment-specific settings** without code changes
- **Validation and error checking** for configuration issues
- **Documentation** within configuration files

### For DevOps
- **Flexible deployment** with environment overrides
- **Secure credential management** via environment variables
- **Validation tools** for configuration verification
- **Standardized configuration** across environments

### For Security
- **No secrets in code** or configuration files
- **Environment variable substitution** for sensitive data
- **Production validation** for security settings
- **TLS certificate validation**

## 🎨 Customization

### Adding New Configuration Sections
1. **Define struct** with serde attributes
2. **Add to main Config struct**
3. **Update TOML files** with new section
4. **Add validation logic** if needed
5. **Update documentation**

### Environment Variables
- **Follow naming convention**: `SECTION_FIELD`
- **Add to environment override logic**
- **Document in README**
- **Add to validation checks**

## 🧪 Testing

### Available Tests
- **Configuration loading** from TOML files
- **Environment variable overrides**
- **Environment variable substitution**
- **Validation logic**
- **Error handling**

### Test Commands
```bash
# Run configuration example
cargo run --example config_example

# Run unit tests
cargo test config::tests

# Validate configuration
cargo run --bin config_tool -- validate
```

## 📧 Email Configuration System

### Email Provider Support
- **Console Provider** - Development email testing (prints to terminal)
- **SMTP Provider** - Standard SMTP servers (Gmail, Outlook, custom)
- **SendGrid Provider** - Production email delivery service

### Internationalized Templates
- **Language-specific templates** with automatic fallback
- **Template directory structure**: `templates/email/{lang}_/{html|text}/`
- **Supported languages**: English (en), Spanish (es), French (fr), German (de)
- **Language detection** from user profile, Accept-Language header, or default

### Template Features
- **Handlebars templating** with custom helpers
- **HTML and text versions** for all templates
- **Template variables** for dynamic content
- **Date formatting** and text manipulation helpers
- **Automatic language fallback** to English

### Email Configuration Structure
```toml
[email]
enabled = true
provider = "console"              # "smtp", "sendgrid", "console"
from_email = "noreply@app.com"
from_name = "Your App"
template_dir = "templates/email"

# SMTP Configuration
smtp_host = "smtp.gmail.com"
smtp_port = 587
smtp_username = "your-email@gmail.com"
smtp_password = "${SMTP_PASSWORD}"
smtp_use_starttls = true

# SendGrid Configuration
sendgrid_api_key = "${SENDGRID_API_KEY}"
```

### Environment-Specific Email Settings
- **Development**: Console provider for easy testing
- **Staging**: SMTP testing with Mailtrap or similar
- **Production**: SendGrid for reliable delivery

### Email Template Structure
```
templates/email/
├── en_/                    # English templates (default)
│   ├── html/              # HTML email templates
│   │   ├── contact.hbs    # Contact form template
│   │   └── notification.hbs # Notification template
│   └── text/              # Plain text templates
├── es_/                   # Spanish templates
│   ├── html/
│   └── text/
└── README.md              # Template documentation
```

### Email Template Variables
- `{{name}}` - User's name
- `{{email}}` - User's email address
- `{{subject}}` - Message subject
- `{{message}}` - Message content
- `{{submitted_at}}` - Submission timestamp
- `{{form_type}}` - Type of form submission

### Custom Handlebars Helpers
- `{{date_format submitted_at "%B %d, %Y"}}` - Format dates
- `{{capitalize form_type}}` - Capitalize text
- `{{truncate user_agent 100}}` - Truncate text
- `{{default action_text "Click Here"}}` - Default values
- `{{url_encode email}}` - URL encode text

## 📚 Documentation

### Available Documentation
- **CONFIG_README.md** - Comprehensive usage guide
- **MIGRATION_GUIDE.md** - Migration from old system
- **CONFIG_SUMMARY.md** - This summary
- **templates/email/README.md** - Email template documentation
- **Inline documentation** in code
- **Example configurations** for all environments

### Getting Started
1. **Read** CONFIG_README.md for detailed instructions
2. **Run** setup script: `./scripts/setup-config.sh`
3. **Customize** configuration files for your needs
4. **Set** required environment variables
5. **Test** with configuration tool
6. **Deploy** with your preferred method

## 🔄 Maintenance

### Regular Tasks
- **Review** configuration files for outdated settings
- **Update** environment-specific configurations
- **Validate** production configurations
- **Rotate** secrets and credentials
- **Update** documentation

### Monitoring
- **Monitor** configuration loading in production
- **Alert** on configuration validation failures
- **Log** configuration changes
- **Backup** configuration files

## 📞 Support

### Getting Help
- **Check** CONFIG_README.md for detailed documentation
- **Run** config tool help: `cargo run --bin config_tool -- help`
- **Review** examples in `server/examples/`
- **Check** migration guide for common issues
- **Validate** configuration: `cargo run --bin config_tool -- validate`

### Common Issues
- **Configuration file not found** - Check file path and permissions
- **Environment variable not found** - Set required variables
- **TLS configuration errors** - Verify certificate paths
- **Database connection errors** - Check database URL format
- **Validation failures** - Review configuration values
- **Email template not found** - Check template directory structure
- **Email delivery failed** - Verify email provider credentials
- **SMTP authentication failed** - Check username/password or use App Password for Gmail

This configuration system provides a robust, flexible, and secure foundation for managing application settings across different environments while maintaining developer productivity and operational security.