clean-architecture

# Clean Architecture, DDD & Hexagonal Architecture for NestJS ## Overview This skill provides comprehensive guidance for implementing Clean Architecture, Domain-Driven Design (DDD), and Hexagonal Architecture patterns in NestJS/TypeScript applications. It covers the architectural layers, tactical patterns, and practical implementation examples for building maintainable, testable, and loosely-coupled backend systems. ## When to Use - Architecting complex NestJS applications with long-term maintainability - Refactoring from tightly-coupled MVC to layered architecture - Implementing rich domain models with business logic encapsulation - Designing testable systems with swappable infrastructure - Creating microservices with clear bounded contexts - Separating business rules from framework code - Implementing event-driven architectures with domain events ## Instructions ### 1. Understand the Architectural Layers Clean Architecture organizes code into concentric layers where dependencies flow inward. Inner layers have no knowledge of outer layers: ``` +-------------------------------------+ | Infrastructure (Frameworks, DB) | Outer layer - volatile +-------------------------------------+ | Adapters (Controllers, Repositories)| Interface adapters +-------------------------------------+ | Application (Use Cases) | Business rules +-------------------------------------+ | Domain (Entities, Value Objects) | Core - most stable +-----------------------------...