Correctly changing deal currency (#2837)

Author: f213

Makefile

@@ -5,6 +5,8 @@ compilemessages:
 	$(manage) compilemessages
 
 fmt:
+	uv run ruff format src
+	# Run formatter for the second time to fix errors left after first fixing
 	uv run ruff format src
 	uv run ruff check src --fix --unsafe-fixes
 	uv run toml-sort pyproject.toml

src/apps/b2b/admin/deals/forms.py

@@ -4,7 +4,7 @@
 from django.utils.translation import gettext_lazy as _
 
 from apps.b2b.models import Deal
-from apps.b2b.services import BulkStudentCreator, DealCreator
+from apps.b2b.services import BulkStudentCreator, DealCreator, DealCurrencyChanger
 from core.admin import ModelForm
 
 
@@ -50,10 +50,20 @@ class Meta:
         fields = "__all__"
 
     def save(self, commit: bool = False) -> Deal:
+        self._change_currency(deal=self.instance)
+
         deal = super().save(commit=commit)
 
+        self._create_students(deal)
+
+        return deal
+
+    def _change_currency(self, deal: Deal) -> None:
+        currency = self.cleaned_data["currency"]
+        if self.initial["currency"] != currency:
+            DealCurrencyChanger(deal, new_currency_code=currency)()
+
+    def _create_students(self, deal: Deal) -> None:
         student_list = self.cleaned_data["students"]
         if len(student_list) > 0:
             BulkStudentCreator(user_input=student_list, deal=deal)()
-
-        return deal

src/apps/b2b/factory.py

@@ -2,6 +2,7 @@
 from typing import Any
 
 from apps.b2b.models import Customer, Deal
+from apps.banking import currency
 from apps.products.models import Course
 from apps.users.models import User
 from core.test.factory import FixtureFactory, register
@@ -14,21 +15,23 @@ def deal(
     author: User | None = None,
     course: Course | None = None,
     price: Decimal | None = None,
-    currency: str | None = None,
+    currency_code: str | None = None,
     student_count: int | None = 0,
     **kwargs: dict[str, Any],
 ) -> Deal:
     customer = self.mixer.blend("b2b.Customer") if customer is None else customer
     author = self.mixer.blend("users.User") if author is None else author
     course = self.course() if course is None else course
     price = price if price is not None else Decimal(self.price())
+    currency_code = currency_code if currency_code is not None else "RUB"
 
     deal = Deal.objects.create(
         customer=customer,
         course=course,
         price=price,
         author=author,
-        currency=currency if currency is not None else "RUB",
+        currency=currency_code,
+        currency_rate_on_creation=currency.get_rate_or_default(currency_code),
         **kwargs,
     )
 

src/apps/b2b/services/__init__.py

@@ -1,9 +1,11 @@
 from apps.b2b.services.bulk_student_creator import BulkStudentCreator
 from apps.b2b.services.deal_completer import DealCompleter
 from apps.b2b.services.deal_creator import DealCreator
+from apps.b2b.services.deal_currency_changer import DealCurrencyChanger
 
 __all__ = [
     "BulkStudentCreator",
     "DealCompleter",
     "DealCreator",
+    "DealCurrencyChanger",
 ]

src/apps/b2b/services/deal_currency_changer.py

@@ -0,0 +1,47 @@
+from dataclasses import dataclass
+from typing import Callable
+
+from django.contrib.admin.models import CHANGE
+
+from apps.b2b.models import Deal
+from apps.banking import currency
+from core.current_user import get_current_user
+from core.services import BaseService
+from core.tasks import write_admin_log
+
+
+@dataclass
+class DealCurrencyChanger(BaseService):
+    """Changes deal currency and currency rate on creation"""
+
+    deal: Deal
+    new_currency_code: str
+
+    def act(self) -> None:
+        self.deal.currency = self.new_currency_code.upper()
+        self.deal.currency_rate_on_creation = currency.get_rate_or_default(self.new_currency_code)
+        self.deal.save(update_fields=["currency", "currency_rate_on_creation", "modified"])
+
+        self.write_auditlog()
+
+    def get_validators(self) -> list[Callable]:
+        return [
+            self.validate_currency_code,
+        ]
+
+    def write_auditlog(self) -> None:
+        user = get_current_user()
+        if user is None:
+            raise RuntimeError("Cannot determine user")
+
+        write_admin_log.delay(
+            action_flag=CHANGE,
+            change_message=f"Deal currency changed to {self.deal.currency}",
+            model="b2b.Deal",
+            object_id=self.deal.id,
+            user_id=user.id,
+        )
+
+    def validate_currency_code(self) -> None:
+        if currency.get_rate(self.new_currency_code.upper()) is None:
+            raise TypeError("Non-existant currency code")

src/apps/b2b/tests/conftest.py

@@ -13,7 +13,7 @@ def course(factory):
 
 @pytest.fixture
 def deal(factory, customer, course):
-    return factory.deal(customer=customer, course=course)
+    return factory.deal(customer=customer, course=course, currency_code="RUB")
 
 
 @pytest.fixture

src/apps/b2b/tests/deal_completer/test_deal_completer_new_order_creation.py

@@ -66,15 +66,15 @@ def test_price_calculation(completer, factory, student_count, single_order_price
 
 @pytest.mark.usefixtures("usd")
 @pytest.mark.parametrize(
-    ("currency", "single_order_price"),
+    ("currency_code", "single_order_price"),
     [
         ("RUB", "50.00"),
         ("USD", "5000.00"),
         ("NNE", "50.00"),  # for nonexistant currencis the default rate is used
     ],
 )
-def test_currency_price_calculation(completer, factory, currency, single_order_price):
-    deal = factory.deal(student_count=2, price=Decimal("100.00"), currency=currency)
+def test_currency_price_calculation(completer, factory, currency_code, single_order_price):
+    deal = factory.deal(student_count=2, price=Decimal("100.00"), currency_code=currency_code)
 
     completer(deal=deal)()
     order = Order.objects.first()

src/apps/b2b/tests/test_deal_creator_service.py

@@ -6,15 +6,10 @@
 
 pytestmark = [
     pytest.mark.django_db,
-    pytest.mark.usefixtures("_set_current_user"),
+    pytest.mark.usefixtures("_set_current_user", "kzt"),
 ]
 
 
-@pytest.fixture(autouse=True)
-def _kzt(factory):
-    factory.currency(name="KZT", rate=Decimal("0.2"))
-
-
 def test_deal_is_created(customer, course):
     deal = DealCreator(
         customer=customer,
@@ -34,7 +29,7 @@ def test_deal_is_created(customer, course):
     [
         ("RUB", "1.0"),
         ("NNE", "1.0"),  # unknown currency
-        ("KZT", "0.2"),
+        ("KZT", "5.0"),
     ],
 )
 def test_currency_is_saved(customer, course, currency, expected_rate):

src/apps/b2b/tests/test_deal_currency_changer.py

@@ -0,0 +1,45 @@
+from decimal import Decimal
+
+import pytest
+from django.contrib.admin.models import CHANGE, LogEntry
+from django.contrib.contenttypes.models import ContentType
+
+from apps.b2b.services import DealCurrencyChanger
+
+pytestmark = [
+    pytest.mark.django_db,
+    pytest.mark.usefixtures("_set_current_user", "usd"),
+]
+
+
+@pytest.mark.parametrize("new_currency_code", ["usd", "UsD"])
+def test(deal, new_currency_code):
+    assert deal.currency == "RUB"
+
+    DealCurrencyChanger(deal=deal, new_currency_code=new_currency_code)()
+    deal.refresh_from_db()
+
+    assert deal.currency == "USD"
+    assert deal.currency_rate_on_creation == Decimal(100)
+
+
+def test_wrong_currency_code(deal):
+    with pytest.raises(TypeError):
+        DealCurrencyChanger(deal=deal, new_currency_code="NONEXISTANT-STUPID-CODE")()
+
+
+@pytest.mark.auditlog
+def test_auditlog(deal, user):
+    DealCurrencyChanger(deal=deal, new_currency_code="usd")()
+
+    log = LogEntry.objects.filter(
+        content_type=ContentType.objects.get_for_model(deal).id,
+    ).last()
+
+    assert log.action_flag == CHANGE
+    assert "currency" in log.change_message
+    assert "USD" in log.change_message
+
+    assert log.user == user
+    assert log.object_id == str(deal.id)
+    assert log.object_repr == str(deal)

src/apps/banking/currency.py

@@ -37,7 +37,7 @@ def get_rate(name: str) -> Decimal | None:
     Currency = apps.get_model("banking.Currency")
 
     with contextlib.suppress(Currency.DoesNotExist):
-        return Currency.objects.get(name=name).rate
+        return Currency.objects.get(name__iexact=name).rate
 
 
 def get_rate_or_default(name: str) -> Decimal: