# Core Architecture

## Overview

This document explains the architectural decisions, patterns, and system design of our core package. It provides insights into how the framework components interact and how to extend the system.

> **Related Documentation**
> - See [Core Package Specification](core_package_specification.md) for implementation details
> - See [Foundation Integration Guide](foundation_integration_guide.md) for integration patterns
> - See [Container Package Specification](container_package_specification.md) for dependency injection
> - See [Events Package Specification](events_package_specification.md) for event system

## Architectural Patterns

### 1. Service Container Architecture

The framework is built around a central service container that manages dependencies and provides inversion of control:

```
┌─────────────────────────────────────────┐
│              Application                │
│                                         │
│  ┌─────────────────┐  ┌──────────────┐  │
│  │Service Container│  │Event Dispatch│  │
│  └─────────────────┘  └──────────────┘  │
│                                         │
│  ┌─────────────────┐  ┌──────────────┐  │
│  │Service Providers│  │   Pipeline   │  │
│  └─────────────────┘  └──────────────┘  │
│                                         │
└─────────────────────────────────────────┘
```

Key aspects:
- Central service container manages all dependencies
- Service providers bootstrap framework services
- Event system enables loose coupling
- Pipeline pattern for request/response handling

### 2. Request Lifecycle

The request flows through several layers:

```
┌──────────┐    ┌────────────┐    ┌─────────────┐
│  Server  │ -> │HTTP Kernel │ -> │  Pipeline   │
└──────────┘    └────────────┘    └─────────────┘
                                        |
┌──────────┐    ┌────────────┐    ┌─────▼─────┐
│ Response │ <- │ Controller │ <- │  Router   │
└──────────┘    └────────────┘    └───────────┘
```

Stages:
1. Server receives HTTP request
2. HTTP Kernel applies global middleware
3. Pipeline processes middleware stack
4. Router matches route
5. Controller handles request
6. Response flows back through layers

### 3. Service Provider Pattern

Service providers bootstrap framework components:

```
┌─────────────────┐
│   Application   │
└───────┬─────────┘
        |
┌───────▼─────────┐
│Register Providers│
└───────┬─────────┘
        |
┌───────▼─────────┐
│  Boot Providers │
└───────┬─────────┘
        |
┌───────▼─────────┐
│ Ready to Handle │
└─────────────────┘
```

Process:
1. Register core providers
2. Register package providers
3. Register application providers
4. Boot all providers
5. Application ready

### 4. Event-Driven Architecture

Events enable loose coupling between components:

```
┌────────────┐    ┌─────────────┐    ┌──────────┐
│ Dispatcher │ -> │   Events    │ -> │Listeners │
└────────────┘    └─────────────┘    └──────────┘
                                          |
┌────────────┐    ┌─────────────┐    ┌──────────┐
│  Queued    │ <- │   Handler   │ <- │ Process  │
└────────────┘    └─────────────┘    └──────────┘
```

Features:
- Event dispatching
- Synchronous/async listeners
- Event queueing
- Event subscribers
- Event broadcasting

## Extension Points

### 1. Service Providers

Create custom service providers to:
- Register services
- Bootstrap components
- Configure framework
- Add middleware
- Register routes

```dart
class CustomServiceProvider extends ServiceProvider {
  @override
  void register() {
    // Register services
  }
  
  @override
  void boot() {
    // Bootstrap components
  }
}
```

### 2. Middleware

Add middleware to:
- Process requests
- Modify responses
- Handle authentication
- Rate limiting
- Custom processing

```dart
class CustomMiddleware implements Middleware {
  Future<Response> handle(Request request, Next next) async {
    // Process request
    var response = await next(request);
    // Modify response
    return response;
  }
}
```

### 3. Event Listeners

Create event listeners to:
- React to system events
- Handle async tasks
- Integrate external systems
- Add logging/monitoring
- Custom processing

```dart
class CustomListener {
  void handle(CustomEvent event) {
    // Handle event
  }
}
```

### 4. Console Commands

Add console commands to:
- Run maintenance tasks
- Process queues
- Generate files
- Custom CLI tools
- System management

```dart
class CustomCommand extends Command {
  String get name => 'custom:command';
  
  Future<void> handle() async {
    // Command logic
  }
}
```

## Package Integration

### 1. Core Package Dependencies

```
┌─────────────┐
│    Core     │
└─────┬───────┘
      |
┌─────▼───────┐     ┌────────────┐
│  Container  │ --> │  Events    │
└─────────────┘     └────────────┘
      |
┌─────▼───────┐     ┌────────────┐
│  Pipeline   │ --> │   Route    │
└─────────────┘     └────────────┘
```

### 2. Optional Package Integration

```
┌─────────────┐
│    Core     │
└─────┬───────┘
      |
┌─────▼───────┐     ┌────────────┐
│   Queue     │ --> │    Bus     │
└─────────────┘     └────────────┘
      |
┌─────▼───────┐     ┌────────────┐
│    Cache    │ --> │    Mail    │
└─────────────┘     └────────────┘
```

## Performance Considerations

### 1. Service Container
- Optimize bindings
- Use singletons where appropriate
- Lazy load services
- Cache resolved instances

### 2. Request Handling
- Efficient middleware pipeline
- Route caching
- Response caching
- Resource pooling

### 3. Event System
- Async event processing
- Event batching
- Queue throttling
- Listener optimization

### 4. Memory Management
- Clean up resources
- Limit instance caching
- Monitor memory usage
- Handle memory pressure

## Security Considerations

### 1. Request Validation
- Input sanitization
- CSRF protection
- XSS prevention
- SQL injection prevention

### 2. Authentication
- Secure session handling
- Token management
- Password hashing
- Rate limiting

### 3. Authorization
- Role-based access
- Permission checking
- Policy enforcement
- Resource protection

### 4. Data Protection
- Encryption at rest
- Secure communication
- Data sanitization
- Audit logging

## Development Guidelines

### 1. Core Development
- Follow framework patterns
- Maintain backward compatibility
- Document changes
- Write tests
- Consider performance

### 2. Package Development
- Use service providers
- Integrate with events
- Follow naming conventions
- Add package tests
- Document features

### 3. Application Development
- Use dependency injection
- Handle events properly
- Follow middleware patterns
- Write clean code
- Test thoroughly

## Next Steps

1. Review architecture with team
2. Document design decisions
3. Create development guides
4. Set up monitoring
5. Plan optimizations
6. Schedule security review