# Architecture Overview

Comprehensive overview of MCP Standards Server architecture and design principles.

## System Architecture

```
┌─────────────────────────────────────────────────────────────────┐
│                        Client Layer                            │
├─────────────────┬─────────────────┬─────────────────────────────┤
│   IDE Plugins   │   CLI Tools     │   CI/CD Integrations       │
│   (VS Code,     │   (mcp-std)     │   (GitHub Actions,         │
│    JetBrains)   │                 │    GitLab CI, Jenkins)     │
└─────────────────┴─────────────────┴─────────────────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────────────┐
│                    MCP Protocol Layer                          │
├─────────────────────────────────────────────────────────────────┤
│  • Tool Registration     • Message Routing                     │
│  • Schema Validation     • Error Handling                      │
│  • Authentication        • Request/Response Management         │
└─────────────────────────────────────────────────────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────────────┐
│                      API Gateway                               │
├─────────────────────────────────────────────────────────────────┤
│  • Rate Limiting         • CORS Handling                       │
│  • Request Validation    • Response Formatting                 │
│  • Metrics Collection    • Health Checks                       │
└─────────────────────────────────────────────────────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────────────┐
│                    Business Logic Layer                        │
├─────────────┬─────────────────┬─────────────────┬─────────────────┤
│   Standards │   Validation    │   Rule Engine   │   Analytics     │
│   Engine    │   Engine        │                 │   Engine        │
│             │                 │                 │                 │
│ • Discovery │ • Multi-lang    │ • Condition     │ • Usage Stats   │
│ • Selection │   Analysis      │   Evaluation    │ • Performance   │
│ • Metadata  │ • Auto-fix      │ • Priority      │ • Reporting     │
│ • Caching   │ • Reporting     │   Resolution    │ • Trends        │
└─────────────┴─────────────────┴─────────────────┴─────────────────┘
                           │
                           ▼
┌─────────────────────────────────────────────────────────────────┐
│                     Storage Layer                              │
├─────────────┬─────────────────┬─────────────────┬─────────────────┤
│  Standards  │   Cache Layer   │   Config Store  │   Analytics DB  │
│  Repository │                 │                 │                 │
│             │ • Redis (L1)    │ • YAML Files    │ • SQLite        │
│ • Git Repo  │ • File (L2)     │ • Env Vars      │ • Metrics       │
│ • Local Dir │ • Memory (Hot)  │ • Validation    │ • Audit Logs    │
│ • Sync Mgmt │ • Compression   │ • Defaults      │ • Performance   │
└─────────────┴─────────────────┴─────────────────┴─────────────────┘
```

## Core Components

### 1. MCP Server Core

The central component implementing the Model Context Protocol specification.

**Key responsibilities:**
- Protocol message handling
- Tool registration and discovery
- Client connection management
- Authentication and authorization
- Error handling and recovery

**Implementation files:**
- `src/mcp_server.py` - Main server implementation
- `src/core/mcp/` - MCP protocol handlers
- `src/core/mcp/tools/` - MCP tool implementations

### 2. Standards Engine

Manages standards repository, discovery, and selection logic.

**Key features:**
- **Standards Discovery**: Automatic detection of applicable standards
- **Metadata Management**: Standards metadata and relationships
- **Rule-based Selection**: Intelligent standard selection using rules
- **Semantic Search**: Content-based standard discovery
- **Caching**: Multi-tier caching for performance

**Implementation files:**
- `src/core/standards/engine.py` - Main engine
- `src/core/standards/rule_engine.py` - Rule evaluation
- `src/core/standards/semantic_search.py` - Semantic search
- `src/core/standards/sync.py` - Repository synchronization

### 3. Validation Engine

Multi-language code analysis and validation system.

**Supported languages:**
- Python (AST analysis, PEP compliance)
- JavaScript/TypeScript (ESLint integration, patterns)
- Go (go vet, golint integration)
- Java (PMD, SpotBugs integration)
- Rust (clippy integration)

**Key features:**
- **Multi-language Analysis**: Language-specific analyzers
- **Auto-fix Capabilities**: Automatic issue resolution
- **Incremental Validation**: Only validate changed code
- **Parallel Processing**: Concurrent file analysis
- **Custom Rules**: User-defined validation rules

**Implementation files:**
- `src/analyzers/` - Language-specific analyzers
- `src/core/validation/` - Validation engine core

### 4. Cache Layer

Multi-tier caching system for optimal performance.

**Cache Architecture:**
```
L0: Memory Cache (Hot Data)
├── Recently accessed standards
├── Parsed rule trees
└── Active validation results

L1: Redis Cache (Warm Data)
├── Standards metadata
├── Search indexes
└── User sessions

L2: File Cache (Cold Data)
├── Full standards content
├── Compiled rules
└── Historical analytics
```

**Features:**
- **Smart Eviction**: LRU with priority weighting
- **Compression**: Gzip compression for large data
- **TTL Management**: Configurable time-to-live
- **Cache Warming**: Pre-populate frequently used data

### 5. Rule Engine

Condition-based standards selection and validation rules.

**Rule Types:**
- **Project Type Rules**: Web app, API, CLI, library
- **Language Rules**: Python, JavaScript, Go, etc.
- **Framework Rules**: React, Django, Express, etc.
- **Requirement Rules**: Security, accessibility, performance
- **Context Rules**: File type, directory structure

**Rule Evaluation:**
```python
# Example rule structure
rule = {
    "id": "react-typescript-web-app",
    "conditions": {
        "project_type": ["web_application"],
        "framework": ["react"],
        "language": ["typescript"]
    },
    "standards": ["react-patterns", "typescript-strict"],
    "priority": 10
}
```

## Data Flow

### 1. Standards Synchronization

```
1. Timer/Manual Trigger
   ↓
2. Git Repository Check
   ↓
3. Download New/Changed Standards
   ↓
4. Parse and Validate
   ↓
5. Update Cache
   ↓
6. Notify Clients
```

### 2. Standard Selection

```
1. Client Request (project context)
   ↓
2. Rule Engine Evaluation
   ↓
3. Semantic Search (if needed)
   ↓
4. Priority Resolution
   ↓
5. Cache Result
   ↓
6. Return Applicable Standards
```

### 3. Code Validation

```
1. Validation Request
   ↓
2. Language Detection
   ↓
3. Standard Selection
   ↓
4. File Analysis (Parallel)
   ↓
5. Rule Application
   ↓
6. Auto-fix (if enabled)
   ↓
7. Result Aggregation
   ↓
8. Report Generation
```

## Design Principles

### 1. Modularity

- **Loose Coupling**: Components communicate through well-defined interfaces
- **Plugin Architecture**: Extensible analyzer and validator system
- **Configuration-Driven**: Behavior controlled through configuration
- **Language Agnostic**: Core engine independent of specific languages

### 2. Performance

- **Lazy Loading**: Load standards and rules on-demand
- **Caching Strategy**: Multi-tier caching with intelligent eviction
- **Parallel Processing**: Concurrent validation and analysis
- **Resource Management**: Memory and CPU usage optimization

### 3. Scalability

- **Horizontal Scaling**: Multiple server instances with shared cache
- **Asynchronous Processing**: Non-blocking I/O operations
- **Resource Pooling**: Connection and worker thread pools
- **Load Balancing**: Distribute requests across instances

### 4. Reliability

- **Graceful Degradation**: Fallback when external services fail
- **Error Recovery**: Automatic retry with exponential backoff
- **Health Monitoring**: Comprehensive health checks and metrics
- **Data Consistency**: Atomic operations and transaction safety

### 5. Extensibility

- **Plugin System**: Add new analyzers and validators
- **Custom Standards**: Support for organization-specific standards
- **API Versioning**: Backward compatibility maintenance
- **Integration Points**: Hooks for external systems

## Security Architecture

### 1. Authentication & Authorization

```
Client Request
   ↓
API Key Validation
   ↓
Role-Based Access Control
   ↓
Resource Permissions Check
   ↓
Request Processing
```

**Security measures:**
- **API Key Management**: Secure key generation and rotation
- **JWT Tokens**: Stateless authentication with expiration
- **Role-Based Access**: Granular permissions system
- **Rate Limiting**: DDoS protection and resource management

### 2. Data Security

- **Encryption**: TLS for transport, AES for storage
- **Sanitization**: Input validation and output encoding
- **Audit Logging**: Comprehensive activity tracking
- **Privacy Protection**: No sensitive code storage

### 3. Network Security

- **CORS Configuration**: Proper cross-origin controls
- **Input Validation**: Strict request validation
- **Output Filtering**: Sensitive data redaction
- **Network Isolation**: Firewall and VPC configuration

## Monitoring & Observability

### 1. Metrics Collection

**Application Metrics:**
- Request count and latency
- Validation success/failure rates
- Cache hit/miss ratios
- Memory and CPU usage

**Business Metrics:**
- Standards usage frequency
- Validation coverage
- Auto-fix success rates
- User adoption trends

### 2. Logging Strategy

**Log Levels:**
- **ERROR**: System errors and failures
- **WARNING**: Performance issues and degradation
- **INFO**: Normal operation events
- **DEBUG**: Detailed troubleshooting information

**Log Formats:**
- Structured JSON for machine processing
- Human-readable for development
- Audit logs for compliance

### 3. Health Checks

**Endpoint: `/health`**
```json
{
  "status": "healthy",
  "timestamp": "2024-01-15T10:30:00Z",
  "components": {
    "database": "healthy",
    "cache": "healthy",
    "standards_repo": "healthy",
    "external_apis": "degraded"
  },
  "metrics": {
    "uptime": "7d 14h 32m",
    "memory_usage": "67%",
    "cache_hit_rate": "94%"
  }
}
```

## Deployment Architecture

### 1. Single Instance Deployment

```
┌─────────────────────────┐
│    Load Balancer        │
└───────────┬─────────────┘
            │
┌───────────▼─────────────┐
│   MCP Standards Server  │
│                         │
│ ┌─────────┐ ┌─────────┐ │
│ │ App     │ │ Cache   │ │
│ │ Server  │ │ (Redis) │ │
│ └─────────┘ └─────────┘ │
└─────────────────────────┘
```

### 2. High Availability Deployment

```
┌─────────────────────────┐
│    Load Balancer        │
└───────┬─────────┬───────┘
        │         │
┌───────▼───┐ ┌───▼───────┐
│ Server 1  │ │ Server 2  │
└───────┬───┘ └───┬───────┘
        │         │
    ┌───▼─────────▼───┐
    │  Shared Cache   │
    │    (Redis)      │
    └─────────────────┘
```

### 3. Microservices Deployment

```
┌─────────────────────────┐
│      API Gateway        │
└───┬─────────┬───────────┘
    │         │
┌───▼───┐ ┌───▼─────────┐
│ Auth  │ │ Standards   │
│Service│ │ Service     │
└───────┘ └─────────────┘
    │         │
┌───▼─────────▼───────────┐
│   Validation Service    │
└─────────────────────────┘
```

## Development Architecture

### 1. Code Organization

```
src/
├── core/                 # Core business logic
│   ├── mcp/              # MCP protocol implementation
│   ├── standards/        # Standards engine
│   ├── validation/       # Validation engine
│   └── cache/            # Caching layer
├── analyzers/            # Language analyzers
├── api/                  # REST API (optional)
├── cli/                  # Command-line interface
└── utils/                # Shared utilities
```

### 2. Testing Strategy

- **Unit Tests**: Individual component testing
- **Integration Tests**: Component interaction testing
- **End-to-End Tests**: Full workflow validation
- **Performance Tests**: Load and stress testing
- **Security Tests**: Vulnerability scanning

### 3. Development Workflow

```
1. Feature Development
   ↓
2. Unit Testing
   ↓
3. Integration Testing
   ↓
4. Code Review
   ↓
5. Performance Testing
   ↓
6. Security Scanning
   ↓
7. Deployment
```

## Technology Stack

### Core Technologies

- **Python 3.11+**: Main implementation language
- **FastAPI**: HTTP server framework
- **Pydantic**: Data validation and serialization
- **SQLAlchemy**: Database ORM (for analytics)
- **Redis**: Caching and session storage
- **asyncio**: Asynchronous programming

### External Dependencies

- **Git**: Standards repository management
- **Docker**: Containerization
- **NLTK**: Natural language processing
- **sentence-transformers**: Semantic search
- **ChromaDB**: Vector database for embeddings

### Development Tools

- **pytest**: Testing framework
- **black**: Code formatting
- **mypy**: Type checking
- **ruff**: Linting
- **pre-commit**: Git hooks

## Future Architecture Considerations

### 1. Planned Enhancements

- **GraphQL API**: More efficient data fetching
- **Event Streaming**: Real-time updates with Kafka
- **ML Models**: AI-powered standard recommendations
- **Blockchain**: Immutable standards versioning

### 2. Scalability Improvements

- **Kubernetes**: Container orchestration
- **Service Mesh**: Advanced networking
- **Distributed Caching**: Global cache coherence
- **Edge Computing**: Regional standard caching

### 3. Integration Expansion

- **IDE Plugins**: More editor support
- **Cloud Platforms**: AWS, GCP, Azure integration
- **CI/CD Tools**: Enhanced pipeline integration
- **Security Tools**: SAST/DAST integration

---

For implementation details, see the [Standards Engine](./standards-engine.md) and [Token Optimization](./token-optimization.md) documentation.
