Merge pull request #15 from mohamad-liyaghi/transactions-logic

Transactions logic

Author: mohamad-liyaghi

apps/orders/models.py

@@ -4,8 +4,9 @@
 from django.conf import settings
 from django.db.models import QuerySet
 from uuid import uuid4
-from orders.exceptions import EmptyCartException, InsufficientBalanceException
+from orders.exceptions import EmptyCartException
 from orders.enums import OrderStatus
+from transactions.models import Transaction
 from restaurants.models import Restaurant
 from products.models import Product
 
@@ -25,10 +26,11 @@ def __str__(self):
 
     def save(self, *args, **kwargs):
         if self.status == OrderStatus.PROCESSING and not self.is_removed_from_balance:
-            if self.user.balance < self.total_price:
-                raise InsufficientBalanceException
-            self.user.balance -= self.total_price
-            self.user.save()
+            Transaction.transfer(
+                sender=self.user,
+                receiver=self.restaurant.owner,
+                amount=self.total_price,
+            )
         return super().save(*args, **kwargs)
 
     @classmethod
@@ -64,6 +66,11 @@ def create_order(cls, user: settings.AUTH_USER_MODEL, cart: dict) -> QuerySet:
 
         with transaction.atomic():
             OrderItem.objects.bulk_create(order_items)
+
+            for item in order_items:
+                item.product.quantity -= item.quantity
+                item.product.save()
+
             for order in orders.values():
                 order.save()
 

apps/orders/views/customer.py

@@ -6,7 +6,7 @@
 from rest_framework import status
 from drf_spectacular.utils import extend_schema_view, OpenApiResponse, extend_schema
 from orders.enums import OrderStatus
-from orders.exceptions import InsufficientBalanceException
+from transactions.exceptions import InsufficientBalanceError
 from orders.models import Order
 from orders.serializers import OrderSerializer
 
@@ -80,7 +80,7 @@ def post(self, request, *args, **kwargs):
             order.save()
             return Response({"message": "Order is being processed"}, status=status.HTTP_200_OK)
 
-        except InsufficientBalanceException:
+        except InsufficientBalanceError:
             return Response({"error": "Insufficient balance"}, status=status.HTTP_400_BAD_REQUEST)
 
 

apps/products/views.py

@@ -39,7 +39,7 @@ def get_queryset(self):
         restaurant = self._get_restaurant()
         return Product.objects.select_related("restaurant", "restaurant__owner").filter(
             restaurant=restaurant, is_deleted=False
-        )  # TODO: make this single query
+        )
 
     def _get_restaurant(self, for_creation=False):
         if not for_creation:

apps/transactions/exceptions.py

@@ -0,0 +1,2 @@
+class InsufficientBalanceError(Exception):
+    pass

apps/transactions/models.py

@@ -3,6 +3,7 @@
 from decimal import Decimal
 from uuid import uuid4
 from transactions.enums import TransactionType, TransactionStatus
+from transactions.exceptions import InsufficientBalanceError
 from transactions.tasks import do_withdraw
 
 
@@ -21,18 +22,46 @@ def __str__(self):
 
     def save(self, *args, **kwargs):
         if self.status == TransactionStatus.SUCCESS and not self.is_processed:
-            if self.type == TransactionType.DEPOSIT:
-                self._handle_deposit()
-            elif self.type == TransactionType.WITHDRAWAL:
-                self._handle_withdrawal()
-            self.is_processed = True
-        return super().save(*args, **kwargs)
-
-    def _handle_deposit(self):
-        self.user.balance += Decimal(self.amount)
-        self.user.save()
+            self._process_transaction()
+        super().save(*args, **kwargs)
+
+    def _process_transaction(self):
+        amount = Decimal(self.amount)
+
+        if self.type == TransactionType.DEPOSIT:
+            self._adjust_balance(amount)
+        elif self.type in {TransactionType.WITHDRAWAL, TransactionType.COST}:
+            self._adjust_balance(-amount)
+        elif self.type == TransactionType.CHARGE:
+            self._adjust_balance(amount)
+
+        self.is_processed = True
 
-    def _handle_withdrawal(self):
-        self.user.balance -= Decimal(self.amount)
+        if self.type == TransactionType.WITHDRAWAL:
+            do_withdraw.delay(self.user.id, self.id)
+
+    def _adjust_balance(self, amount):
+        if amount < 0 and self.user.balance < abs(amount):
+            raise InsufficientBalanceError
+        self.user.balance += amount
         self.user.save()
-        do_withdraw.delay(self.user.id, self.id)
+
+    @classmethod
+    def transfer(cls, sender, receiver, amount) -> tuple:
+        """Transfer money from sender to receiver."""
+        if sender.balance < amount:
+            raise InsufficientBalanceError
+
+        sender_transaction = cls.objects.create(
+            user=sender,
+            amount=amount,
+            type=TransactionType.COST,
+            status=TransactionStatus.SUCCESS,
+        )
+        receiver_transaction = cls.objects.create(
+            user=receiver,
+            amount=amount,
+            type=TransactionType.CHARGE,
+            status=TransactionStatus.SUCCESS,
+        )
+        return sender_transaction, receiver_transaction

apps/transactions/tests/test_models.py

@@ -25,3 +25,13 @@ def test_user_balance_decreased_after_successful_withdrawal(self, user):
             status=TransactionStatus.SUCCESS,
         )
         assert user.balance == user_balance - Decimal(successful_withdrawal.amount)
+
+    def test_transfer_money_between_users(self, user, another_user):
+        user_balance = user.balance
+        another_user_balance = another_user.balance
+        amount = Decimal(100.00)
+        Transaction.transfer(user, another_user, amount)
+        user.refresh_from_db()
+        another_user.refresh_from_db()
+        assert user.balance == user_balance - amount
+        assert another_user.balance == another_user_balance + amount

apps/users/tests/test_views/test_profile/test_retrieve.py

@@ -22,4 +22,3 @@ def test_retrieve_authorized_succeeds(self, user):
         assert response.data["email"] == user.email
         assert response.data["first_name"] == user.first_name
         assert response.data["last_name"] == user.last_name
-        assert Decimal(response.data["balance"]) == Decimal(user.balance)

docker/Dockerfile

@@ -25,4 +25,3 @@ COPY . /src/
 WORKDIR /src
 
 EXPOSE 8000
-# TODO: This Dockerfile is shit, clean it up