nestjs-event-sourcing-lib/CHANGELOG.md

A comprehensive Event Sourcing and CQRS library for NestJS applications

# Changelog

All notable changes to this project will be documented in this file.

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## [1.0.0] - 2025-07-18

### Added
- Initial release of nest-event-sourcing
- Core Event Sourcing abstractions:
  - `Event` base class with metadata and serialization
  - `Command` base class with validation support
  - `AggregateRoot` abstract class with event application and snapshot support
  - `Projection` base class for read models
  - `EventStore` interface with comprehensive functionality

### Features
- **PostgreSQL Event Store**: Full implementation with TypeORM integration
  - Event persistence with optimistic concurrency control
  - Snapshot support for performance optimization
  - Transaction support for atomic operations
  - Comprehensive indexing for efficient queries
  - Connection pooling and health checks

- **MongoDB Event Store**: Complete implementation with MongoDB driver
  - Document-based event storage
  - Aggregation pipeline support for complex queries
  - Automatic indexing for optimal performance
  - Built-in error handling and retry mechanisms

- **Decorator System**: Rich metadata decoration system
  - `@AggregateRoot` for aggregate registration
  - `@CommandHandler` and `@Command` for CQRS integration
  - `@OnEvent` and `@Event` for event handling
  - `@Projection` for read model registration

- **Service Layer**: Production-ready service implementations
  - `CommandHandler` service with transaction management
  - `EventBus` service with local event publishing
  - Comprehensive error handling and logging
  - Built-in retry policies and optimistic locking

- **NestJS Integration**: Seamless framework integration
  - `EventSourcingModule` with `forRoot` and `forRootAsync` methods
  - Dependency injection support
  - Global module configuration
  - Feature module support with `forFeature`

### Technical Features
- **TypeScript First**: Strict typing throughout the library
- **Modular Architecture**: Support for multiple Event Store backends
- **Error Handling**: Comprehensive error types and handling
- **Performance**: Snapshot support and query optimization
- **Testing**: Full test suite with unit and integration tests
- **Documentation**: Comprehensive README with examples

### Dependencies
- Core dependencies: `@nestjs/common`, `@nestjs/core`, `@nestjs/cqrs`
- Validation: `class-validator`, `class-transformer`
- Utilities: `uuid` for ID generation
- Optional peer dependencies:
  - `typeorm` and `pg` for PostgreSQL support
  - `mongodb` for MongoDB support

### Breaking Changes
- None (initial release)

### Migration Guide
- None (initial release)

## [Unreleased]

### Planned Features
- EventStoreDB integration
- Kafka event bus integration
- RabbitMQ event bus integration
- Advanced projection capabilities
- Event replay functionality
- Saga pattern support
- Event versioning and migration tools
- Performance monitoring and metrics
- Distributed event sourcing support

### Known Issues
- None reported

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## Contributing

Please read [CONTRIBUTING.md](CONTRIBUTING.md) for details on our code of conduct and the process for submitting pull requests.

## License

This project is licensed under the MIT License - see the [LICENSE](LICENSE) file for details.