01_backend_systems - ERP-Style Backend

Production-grade ERP backend demonstrating Domain-Driven Design, Clean Architecture, and enterprise patterns.

🎯 Overview

This module implements a comprehensive ERP-style backend with:

• Domain-Driven Design (DDD) - Entities, Value Objects, Aggregates
• Clean Architecture - Layered separation of concerns
• RBAC - Role-based access control
• RESTful APIs - OpenAPI 3.0 documented
• PostgreSQL - With Alembic migrations

📁 Structure

01_backend_systems/
├── src/
│   ├── domain/           # Business logic & entities
│   │   ├── entities/     # Core domain models
│   │   └── value_objects/# Immutable value types
│   ├── application/      # Use cases & services
│   │   └── services/     # Application services
│   ├── infrastructure/   # External concerns
│   │   ├── database/     # DB connection & session
│   │   └── repositories/ # Data access layer
│   └── presentation/     # API layer
│       ├── routes/       # API endpoints
│       └── schemas/      # Pydantic models
├── alembic/              # Database migrations
├── tests/                # Unit & integration tests
└── example_data/         # Sample data for testing

🚀 Quick Start

Prerequisites

• Python 3.11+
• PostgreSQL 14+ (or use SQLite for development)

Installation

# Create virtual environment
python -m venv venv
source venv/bin/activate  # or `venv\Scripts\activate` on Windows

# Install dependencies
pip install -e .

# Set environment variables
cp .env.example .env
# Edit .env with your database credentials

# Run migrations
alembic upgrade head

# Start the server
uvicorn src.main:app --reload --port 8000

API Documentation

Once running, visit:

• Swagger UI: http://localhost:8000/docs
• ReDoc: http://localhost:8000/redoc

🏗️ Architecture

┌─────────────────────────────────────────────────────────────┐
│                     PRESENTATION LAYER                      │
│  (FastAPI Routes, Pydantic Schemas, Request/Response DTOs)  │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│                     APPLICATION LAYER                       │
│     (Use Cases, Application Services, Business Logic)       │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│                       DOMAIN LAYER                          │
│   (Entities, Value Objects, Domain Services, Aggregates)    │
└─────────────────────────────────────────────────────────────┘
                              │
                              ▼
┌─────────────────────────────────────────────────────────────┐
│                   INFRASTRUCTURE LAYER                      │
│    (Repositories, Database, External APIs, Messaging)       │
└─────────────────────────────────────────────────────────────┘

📋 Domain Model

The ERP system manages:

• Organizations - Multi-tenant company management
• Users - Authentication and authorization
• Inventory - Product and stock management
• Orders - Sales order processing
• Invoices - Billing and payment tracking

🔒 RBAC Roles

🧪 Testing

# Run all tests
pytest tests/

# Run with coverage
pytest tests/ --cov=src --cov-report=html

# Run specific test file
pytest tests/unit/test_entities.py -v

📊 API Endpoints

🔧 Configuration

Environment variables (.env):

DATABASE_URL=postgresql://user:pass@localhost:5432/erp_db
SECRET_KEY=your-secret-key-here
DEBUG=true
ALLOWED_HOSTS=localhost,127.0.0.1

📄 License

MIT