Don't allow duplicate coupon codes (#2888)

b2b_ecommerce/migrations/0011_alter_b2bcoupon_coupon_code.py

@@ -0,0 +1,23 @@
+# Generated by Django 3.2.23 on 2024-03-04 12:48
+
+from django.db import migrations, models
+import ecommerce.utils
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("b2b_ecommerce", "0010_b2bline"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="b2bcoupon",
+            name="coupon_code",
+            field=models.CharField(
+                max_length=50,
+                unique=True,
+                validators=[ecommerce.utils.CouponUtils.validate_unique_coupon_code],
+            ),
+        ),
+    ]

b2b_ecommerce/models.py

@@ -16,6 +16,7 @@
     Product,
     ProductVersion,
 )
+from ecommerce.utils import CouponUtils
 from mitxpro.models import AuditableModel, AuditModel, TimestampedModel
 from mitxpro.utils import serialize_model_object
 
@@ -66,7 +67,11 @@ class B2BCoupon(TimestampedModel, AuditableModel):
     """
 
     name = models.TextField()
-    coupon_code = models.CharField(max_length=50)
+    coupon_code = models.CharField(
+        max_length=50,
+        unique=True,
+        validators=[CouponUtils.validate_unique_coupon_code],
+    )
     discount_percent = models.DecimalField(
         decimal_places=5,
         max_digits=20,

ecommerce/api.py

@@ -14,7 +14,7 @@
 from urllib.parse import quote_plus, urljoin
 
 from django.conf import settings
-from django.db import transaction
+from django.db import IntegrityError, transaction
 from django.db.models import Count, F, Max, Prefetch, Q, Subquery
 from django.http import HttpRequest
 from django.urls import reverse
@@ -1322,7 +1322,27 @@ def create_coupons(
         )
         for _ in range(num_coupon_codes)
     ]
-    coupon_objs = Coupon.objects.bulk_create(coupons)
+
+    try:
+        with transaction.atomic():
+            coupon_objs = Coupon.objects.bulk_create(coupons)
+    except IntegrityError:
+        log.warning(
+            "Falling back to create Coupons for coupon payment {} and company {}".format(
+                name, company_id
+            )
+        )
+
+        new_coupon_codes = [coupon.coupon_code for coupon in coupons]
+        existing_coupon_codes = Coupon.objects.filter(
+            coupon_code__in=new_coupon_codes
+        ).values_list("coupon_code", flat=True)
+        if existing_coupon_codes:
+            for coupon in coupons:
+                if coupon.coupon_code in existing_coupon_codes:
+                    coupon.coupon_code = uuid.uuid4().hex
+        coupon_objs = Coupon.objects.bulk_create(coupons)
+
     versions = [
         CouponVersion(coupon=obj, payment_version=payment_version)
         for obj in coupon_objs

ecommerce/api_test.py

@@ -1473,14 +1473,19 @@ def test_fetch_and_serialize_unused_coupons_for_all_inactive_products(user):
     assert unused_coupons == []
 
 
-@pytest.mark.parametrize("use_defaults", [True, False])
-def test_create_coupons(use_defaults):
+@pytest.mark.parametrize(
+    "use_defaults,num_coupon_codes",
+    (
+        (True, 12),
+        (False, 1),
+    ),
+)
+def test_create_coupons(use_defaults, num_coupon_codes):
     """create_coupons should fill in good default parameters where necessary"""
     product = ProductVersionFactory.create().product
     name = "n a m e"
     coupon_type = CouponPaymentVersion.SINGLE_USE
     amount = Decimal("123")
-    num_coupon_codes = 12
 
     optional = (
         {}

ecommerce/migrations/0041_alter_coupon_coupon_code.py

@@ -0,0 +1,23 @@
+# Generated by Django 3.2.23 on 2024-03-04 12:48
+
+from django.db import migrations, models
+import ecommerce.utils
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("ecommerce", "0040_alter_taxrate_tax_rate"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="coupon",
+            name="coupon_code",
+            field=models.CharField(
+                max_length=50,
+                unique=True,
+                validators=[ecommerce.utils.CouponUtils.validate_unique_coupon_code],
+            ),
+        ),
+    ]

ecommerce/models.py

@@ -19,7 +19,11 @@
     ORDERED_VERSIONS_QSET_ATTR,
     REFERENCE_NUMBER_PREFIX,
 )
-from ecommerce.utils import get_order_id_by_reference_number, validate_amount
+from ecommerce.utils import (
+    get_order_id_by_reference_number,
+    validate_amount,
+    CouponUtils,
+)
 from mail.constants import MAILGUN_EVENT_CHOICES
 from mitxpro.models import (
     AuditableModel,
@@ -636,7 +640,11 @@ class Coupon(TimestampedModel):
     coupon information. Since the coupon_code is the identifier for the coupon, this should never be changed.
     """
 
-    coupon_code = models.CharField(max_length=50)
+    coupon_code = models.CharField(
+        max_length=50,
+        unique=True,
+        validators=[CouponUtils.validate_unique_coupon_code],
+    )
     payment = models.ForeignKey(CouponPayment, on_delete=models.PROTECT)
     is_global = models.BooleanField(default=False)
     enabled = models.BooleanField(default=True)

ecommerce/serializers.py

@@ -27,7 +27,7 @@
 )
 from ecommerce.constants import CYBERSOURCE_CARD_TYPES, DISCOUNT_TYPES
 from ecommerce.models import Basket, TaxRate
-from ecommerce.utils import validate_amount
+from ecommerce.utils import validate_amount, CouponUtils
 from mitxpro.serializers import WriteableSerializerMethodField
 from mitxpro.utils import now_in_utc
 from users.serializers import ExtendedLegalAddressSerializer
@@ -875,7 +875,7 @@ class PromoCouponSerializer(BaseCouponSerializer):
     num_coupon_codes = serializers.IntegerField(default=1, required=False)
     coupon_code = serializers.CharField(
         max_length=50,
-        validators=[UniqueValidator(queryset=models.Coupon.objects.all())],
+        validators=[CouponUtils.validate_unique_coupon_code],
     )
     payment_transaction = serializers.CharField(
         max_length=256, allow_null=True, required=False, allow_blank=True

ecommerce/utils.py

@@ -3,6 +3,7 @@
 from urllib.parse import urljoin, urlencode
 
 from django.conf import settings
+from django.core.exceptions import ValidationError
 from django.urls import reverse
 
 from courses.constants import ENROLLABLE_ITEM_ID_SEPARATOR
@@ -108,3 +109,26 @@ def validate_amount(discount_type, amount):
 def positive_or_zero(number):
     """Return 0 if a number is negative otherwise return number"""
     return 0 if number < 0 else number
+
+
+class CouponUtils:
+    @staticmethod
+    def validate_unique_coupon_code(value):
+        """
+        Validate the uniqueness of coupon codes in Coupon and B2BCoupon models.
+        """
+        if CouponUtils.is_existing_coupon_code(value):
+            raise ValidationError("Coupon code already exists in the platform.")
+
+    @staticmethod
+    def is_existing_coupon_code(value):
+        """
+        Check if the coupon code exists in either Coupon or B2BCoupon models.
+        """
+        from b2b_ecommerce.models import B2BCoupon
+        from ecommerce.models import Coupon
+
+        return (
+            Coupon.objects.filter(coupon_code=value).exists()
+            or B2BCoupon.objects.filter(coupon_code=value).exists()
+        )

ecommerce/views_test.py

@@ -1150,7 +1150,7 @@ def test_post_global_promo_coupon(admin_drf_client, promo_coupon_json):
             "At least one product must be selected or coupon should be global.",
         ],
         ["name", "AlreadyExists", "This field must be unique."],
-        ["coupon_code", "AlreadyExists", "This field must be unique."],
+        ["coupon_code", "AlreadyExists", "Coupon code already exists in the platform."],
     ],
 )
 @pytest.mark.parametrize(