@invoicing-sdk/domain/README.md

Core domain logic for the invoicing system including entities, value objects, services, and events

# Invoicing SDK: Domain Layer

Core domain logic for the invoicing system following Domain-Driven Design (DDD) principles.

## Overview

This package contains the pure business logic of the invoicing system, including:

- **Entities**: Core business objects like Invoice
- **Value Objects**: Immutable objects like Money, CustomerInfo, OrderItem
- **Domain Services**: Business logic that doesn't belong to a specific entity
- **Domain Events**: Events that represent important business occurrences
- **Policies**: Business rules and constraints
- **Types**: Shared type definitions

## Features

- Pure domain logic with no external dependencies
- TypeScript-first with full type safety
- Domain events for decoupled communication
- Rich value objects for data integrity
- Comprehensive business rule validation

## Installation

```bash
npm install @invoicing-sdk/domain
# or
pnpm add @invoicing-sdk/domain
# or
bun add @invoicing-sdk/domain
```

## Usage

```typescript
import { Invoice, Money, CustomerInfo } from '@invoicing-sdk/domain'

// Create value objects
const amount = new Money(100, 'EUR')
const customer = new CustomerInfo({
  name: 'John Doe',
  email: 'john@example.com',
  address: '123 Main St'
})

// Work with domain entities
const invoice = new Invoice({
  customerId: 'customer-123',
  items: [/* order items */],
  // ... other properties
})
```

## Architecture

This package follows Domain-Driven Design principles:

- **Entity**: Objects with identity that can change over time
- **Value Object**: Immutable objects defined by their attributes
- **Domain Service**: Stateless services that implement business logic
- **Domain Event**: Events that capture business-relevant occurrences
- **Policy**: Business rules and constraints

## Development

```bash
# Build the package
pnpm build

# Watch for changes during development
pnpm dev

# Run tests
pnpm test
```

## License

MIT