feat(order): Add finalize order functionality

src/allmende_payment_system/models.py

@@ -58,7 +58,7 @@ class User(Base):
     @property
     def shopping_cart(self):
         for order in self.orders:
-            if order.account_id is None:
+            if order.transaction is None:
                 cart = order
                 break
         else:
@@ -109,10 +109,7 @@ class Order(Base):
     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")
+    transaction: Mapped["Transaction | None"] = relationship("Transaction")
 
     items: Mapped[list["OrderItem"]] = relationship(
         "OrderItem", cascade="all, delete-orphan", back_populates="order"
@@ -120,12 +117,37 @@ class Order(Base):
 
     @property
     def is_in_shopping_cart(self):
-        return self.account is None
+        return self.transaction is None
 
     @property
     def total_amount(self):
         return sum(item.total_amount for item in self.items)
 
+    def finalize(self, account: Account):
+        """
+        Moves the order from the shopping cart to a given account
+        and adds a transaction to the account.
+
+        :param account: The account to which the order should be finalized
+        :raises ValueError: If the order is already finalized or empty"""
+        if not self.is_in_shopping_cart:
+            raise ValueError("Order is already finalized.")
+
+        if not self.items:
+            raise ValueError("Cannot finalize an empty order.")
+
+        assert account in self.user.accounts, "Account does not belong to user."
+
+        # create a transaction for the order
+        transaction = Transaction(
+            type="order",
+            total_amount=-self.total_amount,
+            order=self,
+            account=account,
+        )
+        session = object_session(self)
+        session.add(transaction)
+
 
 class OrderItem(Base):
     __tablename__ = TABLE_PREFIX + "order_item"
@@ -142,7 +164,7 @@ class OrderItem(Base):
 
 
 TransactionTypes = typing.Literal[
-    "product",
+    "order",
     "deposit",
     "withdrawal",
     "expense",
@@ -161,10 +183,10 @@ class Transaction(Base):
         Numeric(10, 2), nullable=False
     )
 
-    product_id: Mapped[int] = mapped_column(
-        ForeignKey(TABLE_PREFIX + "product.id"), nullable=True
+    order_id: Mapped[int] = mapped_column(
+        ForeignKey(TABLE_PREFIX + "order.id"), nullable=True
     )
-    product: Mapped["Product"] = relationship("Product")
+    order: Mapped["Order"] = relationship("Order", back_populates="transaction")
 
     account_id: Mapped[int] = mapped_column(ForeignKey(TABLE_PREFIX + "account.id"))
     account: Mapped["Account"] = relationship("Account", back_populates="transactions")