Add shopping cart and related models

src/allmende_payment_system/models.py

@@ -2,8 +2,15 @@ import datetime
 import decimal
 import typing
 
-from sqlalchemy import Column, ForeignKey, Numeric, Table
-from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column, relationship
+from sqlalchemy import Column, ForeignKey, Numeric, Table, select
+from sqlalchemy.exc import NoResultFound
+from sqlalchemy.orm import (
+    DeclarativeBase,
+    Mapped,
+    mapped_column,
+    object_session,
+    relationship,
+)
 
 TABLE_PREFIX = "aps_"
 
@@ -46,6 +53,20 @@ class User(Base):
     accounts: Mapped[list["Account"]] = relationship(
         "Account", secondary=user_account_association, back_populates="users"
     )
+    orders: Mapped[list["Order"]] = relationship("Order", back_populates="user")
+
+    @property
+    def shopping_cart(self):
+        for order in self.orders:
+            if order.account_id is None:
+                cart = order
+                break
+        else:
+            cart = Order(user=self)
+            session = object_session(self)
+            session.add(cart)
+
+        return cart
 
 
 class Area(Base):
@@ -81,6 +102,40 @@ class Product(Base):
     image_path: Mapped[str] = mapped_column(nullable=True)
 
 
+class Order(Base):
+    __tablename__ = TABLE_PREFIX + "order"
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey(TABLE_PREFIX + "user.id"))
+    user: Mapped[User] = relationship("User", back_populates="orders")
+
+    account_id: Mapped[int] = mapped_column(
+        ForeignKey(TABLE_PREFIX + "account.id"), nullable=True
+    )
+    account: Mapped[Account | None] = relationship("Account")
+
+    items: Mapped[list["OrderItem"]] = relationship(
+        "OrderItem", cascade="all, delete-orphan", back_populates="order"
+    )
+
+    @property
+    def is_in_shopping_cart(self):
+        return self.account is None
+
+
+class OrderItem(Base):
+    __tablename__ = TABLE_PREFIX + "order_item"
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    order_id: Mapped[int] = mapped_column(ForeignKey(TABLE_PREFIX + "order.id"))
+    order: Mapped[Order] = relationship("Order", back_populates="items")
+
+    product_id: Mapped[int] = mapped_column(ForeignKey(TABLE_PREFIX + "product.id"))
+    product: Mapped[Product] = relationship("Product")
+    quantity: Mapped[int] = mapped_column(nullable=False)
+    total_amount: Mapped[decimal.Decimal] = mapped_column(
+        Numeric(10, 2), nullable=False
+    )
+
+
 TransactionTypes = typing.Literal[
     "product",
     "deposit",