orion/docs/architecture/customer-orders-architecture.md

Customer-Orders Architecture

This document describes the consumer-agnostic customer architecture, following the same pattern as Media Architecture.

Overview

┌─────────────────────────────────────────────────────────────────────┐
│                        CONSUMER MODULES                              │
│                                                                      │
│   ┌─────────────┐    ┌─────────────┐    ┌─────────────┐            │
│   │   Orders    │    │   Loyalty   │    │   Future    │            │
│   │             │    │  (future)   │    │   Module    │            │
│   │ Order model │    │LoyaltyPoints│    │ XxxCustomer │            │
│   │ (customer_id)│   │(customer_id)│    │             │            │
│   └──────┬──────┘    └──────┬──────┘    └──────┬──────┘            │
│          │                  │                  │                    │
│          └──────────────────┼──────────────────┘                    │
│                             │                                       │
│                             ▼                                       │
│   ┌─────────────────────────────────────────────────────────────┐  │
│   │                    Customers Module                          │  │
│   │                                                              │  │
│   │   Customer (generic, consumer-agnostic storage)             │  │
│   │   CustomerService (CRUD, authentication, profile management) │  │
│   └─────────────────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────────────────────┘

Design Principles

1. Consumer-Agnostic Customer Storage

The customers module provides generic customer storage without knowing what entities will reference customers:

• Customer stores customer data (email, name, addresses, preferences)
• CustomerService handles CRUD, authentication, and profile management
• Customers module has no knowledge of orders, loyalty points, or any specific consumers

2. Consumer-Owned Relationships

Each module that references customers defines its own relationship:

• Orders: Order.customer_id links orders to customers
• Future Loyalty: Would define LoyaltyPoints.customer_id
• Future Subscriptions: Would define Subscription.customer_id

This follows the principle: The consumer knows what it needs, the provider doesn't need to know who uses it.

3. Correct Dependency Direction

WRONG (Hidden Dependency):
  Customers → Orders (customers imports Order model)

CORRECT:
  Orders → Customers (orders references Customer via FK)

Optional modules (orders) depend on core modules (customers), never the reverse.

Key Components

Customer Model (Customers Module)

# app/modules/customers/models/customer.py

class Customer(Base, TimestampMixin):
    """Generic customer - consumer-agnostic."""

    __tablename__ = "customers"

    id = Column(Integer, primary_key=True)
    store_id = Column(Integer, ForeignKey("stores.id"), nullable=False)

    # Authentication
    email = Column(String(255), nullable=False)
    hashed_password = Column(String(255))

    # Profile
    first_name = Column(String(100))
    last_name = Column(String(100))
    phone = Column(String(50))
    customer_number = Column(String(50), unique=True)

    # Preferences
    marketing_consent = Column(Boolean, default=False)
    preferred_language = Column(String(10))

    # Status
    is_active = Column(Boolean, default=True)

    # Note: Consumer-specific relationships (orders, loyalty points, etc.)
    # are defined in their respective modules. Customers module doesn't
    # know about specific consumers.

CustomerService (Customers Module)

The CustomerService provides generic operations:

# app/modules/customers/services/customer_service.py

class CustomerService:
    """Generic customer operations - consumer-agnostic."""

    def create_customer(self, db, store_id, customer_data):
        """Create a new customer."""
        ...

    def get_customer(self, db, store_id, customer_id):
        """Get a customer by ID."""
        ...

    def update_customer(self, db, store_id, customer_id, customer_data):
        """Update customer profile."""
        ...

    def login_customer(self, db, store_id, email, password):
        """Authenticate a customer."""
        ...

    # Note: Customer order methods have been moved to the orders module.
    # Use orders.services.customer_order_service for order-related operations.

Order Model (Orders Module)

# app/modules/orders/models/order.py

class Order(Base, TimestampMixin):
    """Order with customer reference - orders owns the relationship."""

    __tablename__ = "orders"

    id = Column(Integer, primary_key=True)
    store_id = Column(Integer, ForeignKey("stores.id"), nullable=False)

    # Customer reference - orders module owns this relationship
    customer_id = Column(Integer, ForeignKey("customers.id"))

    # Order data
    order_number = Column(String(50), unique=True)
    status = Column(String(20), default="pending")
    total_cents = Column(Integer)
    ...

    # Relationship to customer
    customer = relationship("Customer", lazy="joined")

CustomerOrderService (Orders Module)

# app/modules/orders/services/customer_order_service.py

class CustomerOrderService:
    """Customer-order operations - owned by orders module."""

    def get_customer_orders(self, db, store_id, customer_id, skip=0, limit=50):
        """Get orders for a specific customer."""
        ...

    def get_recent_orders(self, db, store_id, customer_id, limit=5):
        """Get recent orders for a customer."""
        ...

    def get_order_count(self, db, store_id, customer_id):
        """Get total order count for a customer."""
        ...

Customer Order Metrics (Orders Module)

Order statistics for customers use the MetricsProvider pattern:

# app/modules/orders/services/order_metrics.py

class OrderMetricsProvider:
    """Metrics provider including customer-level order metrics."""

    def get_customer_order_metrics(self, db, store_id, customer_id, context=None):
        """
        Get order metrics for a specific customer.

        Returns MetricValue objects for:
        - total_orders: Total orders placed
        - total_spent: Total amount spent
        - avg_order_value: Average order value
        - last_order_date: Date of most recent order
        - first_order_date: Date of first order
        """
        ...

API Endpoints

Customers Module Endpoints

Customer CRUD operations (no order data):

GET  /api/store/customers              → List customers
GET  /api/store/customers/{id}         → Customer details (no order stats)
PUT  /api/store/customers/{id}         → Update customer
PUT  /api/store/customers/{id}/status  → Toggle active status

Orders Module Endpoints

Customer order data (owned by orders):

GET  /api/store/customers/{id}/orders      → Customer's order history
GET  /api/store/customers/{id}/order-stats → Customer's order statistics

Adding Customer References to a New Module

When creating a module that references customers (e.g., a loyalty module):

Step 1: Reference Customer via Foreign Key

# app/modules/loyalty/models/loyalty_points.py

class LoyaltyPoints(Base):
    """Loyalty points - owned by loyalty module."""

    __tablename__ = "loyalty_points"

    id = Column(Integer, primary_key=True)
    store_id = Column(Integer, ForeignKey("stores.id"))

    # Reference to customer - loyalty module owns this
    customer_id = Column(Integer, ForeignKey("customers.id"))

    points_balance = Column(Integer, default=0)
    tier = Column(String(20), default="bronze")

    # Relationship
    customer = relationship("Customer", lazy="joined")

Step 2: Create Your Service

# app/modules/loyalty/services/customer_loyalty_service.py

class CustomerLoyaltyService:
    """Customer loyalty operations - owned by loyalty module."""

    def get_customer_points(self, db, store_id, customer_id):
        """Get loyalty points for a customer."""
        ...

    def add_points(self, db, store_id, customer_id, points, reason):
        """Add points to customer's balance."""
        ...

Step 3: Add Routes in Your Module

# app/modules/loyalty/routes/api/store.py

@router.get("/customers/{customer_id}/loyalty")
def get_customer_loyalty(customer_id: int, ...):
    """Get loyalty information for a customer."""
    return loyalty_service.get_customer_points(db, store_id, customer_id)

Benefits of This Architecture

1. Module Independence: Orders can be disabled without affecting customers
2. Extensibility: New modules easily reference customers
3. No Hidden Dependencies: Dependencies flow in one direction
4. Clean Separation: Customers handles identity, consumers handle their domain
5. Testability: Can test customers without any consumer modules
6. Single Responsibility: Each module owns its domain

Anti-Patterns to Avoid

Don't: Import Consumer Models in Customers

# BAD - Creates hidden dependency
class CustomerService:
    def get_customer_orders(self, db, customer_id):
        from app.modules.orders.models import Order  # Wrong!
        return db.query(Order).filter(Order.customer_id == customer_id).all()

Don't: Add Consumer-Specific Fields to Customer

# BAD - Customer shouldn't know about orders
class Customer(Base):
    # These create coupling to orders module
    total_orders = Column(Integer)  # Wrong approach
    last_order_date = Column(DateTime)  # Wrong approach

Instead, query order data from the orders module when needed.

Don't: Put Consumer Routes in Customers Module

# BAD - customers/routes shouldn't serve order data
@router.get("/customers/{id}/orders")
def get_customer_orders(customer_id: int):
    from app.modules.orders.models import Order  # Wrong!
    ...

Migration Note

Previously, the customers module had methods that imported from orders:

# OLD (removed)
class CustomerService:
    def get_customer_orders(self, db, store_id, customer_id):
        from app.modules.orders.models import Order  # Lazy import
        ...

    def get_customer_statistics(self, db, store_id, customer_id):
        from app.modules.orders.models import Order  # Lazy import
        ...

These have been moved to the orders module:

• get_customer_orders() → orders.services.customer_order_service
• get_customer_statistics() → orders.services.order_metrics.get_customer_order_metrics()

Related Documentation

• Media Architecture - Similar pattern for media files
• Module System Architecture - Module structure and dependencies
• Cross-Module Import Rules - Import restrictions
• Metrics Provider Pattern - Provider pattern for statistics