refactor(business): DRY‑up promo validation & optimize creation logic

- Apply DRY: extract shared validation rules into dedicated `PromoValidator`
  to eliminate duplication between `PromoCreateSerializer` and `PromoDetailSerializer`
- Implement atomic promo creation via `PromoManager.create_promo()`
  using `@transaction.atomic` for full rollback on error
- Move custom model managers into `managers.py` for cleaner structure

Author: RandomProgramm3r

promo_code/business/managers.py

@@ -0,0 +1,53 @@
+import django.contrib.auth.models
+import django.db.models
+
+import business.models
+
+
+class CompanyManager(django.contrib.auth.models.BaseUserManager):
+    def create_company(self, email, name, password=None, **extra_fields):
+        if not email:
+            raise ValueError('The Email must be set')
+
+        email = self.normalize_email(email)
+        company = self.model(
+            email=email,
+            name=name,
+            **extra_fields,
+        )
+        company.set_password(password)
+        company.save(using=self._db)
+        return company
+
+
+class PromoManager(django.db.models.Manager):
+    @django.db.transaction.atomic
+    def create_promo(
+        self,
+        user,
+        target_data,
+        promo_common,
+        promo_unique,
+        **kwargs,
+    ):
+        promo = self.create(
+            company=user,
+            target=target_data,
+            **kwargs,
+        )
+
+        if promo.mode == business.models.Promo.MODE_COMMON:
+            promo.promo_common = promo_common
+            promo.save(update_fields=['promo_common'])
+        elif promo.mode == business.models.Promo.MODE_UNIQUE and promo_unique:
+            self._create_unique_codes(promo, promo_unique)
+
+        return promo
+
+    def _create_unique_codes(self, promo, codes):
+        business.models.PromoCode.objects.bulk_create(
+            [
+                business.models.PromoCode(promo=promo, code=code)
+                for code in codes
+            ],
+        )

promo_code/business/models.py

@@ -3,21 +3,7 @@
 import django.contrib.auth.models
 import django.db.models
 
-
-class CompanyManager(django.contrib.auth.models.BaseUserManager):
-    def create_company(self, email, name, password=None, **extra_fields):
-        if not email:
-            raise ValueError('The Email must be set')
-
-        email = self.normalize_email(email)
-        company = self.model(
-            email=email,
-            name=name,
-            **extra_fields,
-        )
-        company.set_password(password)
-        company.save(using=self._db)
-        return company
+import business.managers
 
 
 class Company(django.contrib.auth.models.AbstractBaseUser):
@@ -37,7 +23,7 @@ class Company(django.contrib.auth.models.AbstractBaseUser):
     created_at = django.db.models.DateTimeField(auto_now_add=True)
     is_active = django.db.models.BooleanField(default=True)
 
-    objects = CompanyManager()
+    objects = business.managers.CompanyManager()
 
     USERNAME_FIELD = 'email'
     REQUIRED_FIELDS = ['name']
@@ -87,6 +73,8 @@ class Promo(django.db.models.Model):
 
     created_at = django.db.models.DateTimeField(auto_now_add=True)
 
+    objects = business.managers.PromoManager()
+
     def __str__(self):
         return f'Promo {self.id} ({self.mode})'
 

promo_code/business/serializers.py

@@ -246,104 +246,23 @@ class Meta:
         )
 
     def validate(self, data):
-        mode = data.get('mode')
-        promo_common = data.get('promo_common')
-        promo_unique = data.get('promo_unique')
-        max_count = data.get('max_count')
-
-        if mode == business_models.Promo.MODE_COMMON:
-            if not promo_common:
-                raise rest_framework.serializers.ValidationError(
-                    {
-                        'promo_common': (
-                            'This field is required for COMMON mode.'
-                        ),
-                    },
-                )
-
-            if promo_unique is not None:
-                raise rest_framework.serializers.ValidationError(
-                    {
-                        'promo_unique': (
-                            'This field is not allowed for COMMON mode.'
-                        ),
-                    },
-                )
-
-            if max_count < 0 or max_count > 100000000:
-                raise rest_framework.serializers.ValidationError(
-                    {
-                        'max_count': (
-                            'Must be between 0 and 100,000,000 '
-                            'for COMMON mode.'
-                        ),
-                    },
-                )
-
-        elif mode == business_models.Promo.MODE_UNIQUE:
-            if not promo_unique:
-                raise rest_framework.serializers.ValidationError(
-                    {
-                        'promo_unique': (
-                            'This field is required for UNIQUE mode.'
-                        ),
-                    },
-                )
-
-            if promo_common is not None:
-                raise rest_framework.serializers.ValidationError(
-                    {
-                        'promo_common': (
-                            'This field is not allowed for UNIQUE mode.'
-                        ),
-                    },
-                )
-
-            if max_count != 1:
-                raise rest_framework.serializers.ValidationError(
-                    {'max_count': 'Must be 1 for UNIQUE mode.'},
-                )
-
-        else:
-            raise rest_framework.serializers.ValidationError(
-                {'mode': 'Invalid mode.'},
-            )
-
-        active_from = data.get('active_from')
-        active_until = data.get('active_until')
-        if active_from and active_until and active_from > active_until:
-            raise rest_framework.serializers.ValidationError(
-                {'active_until': 'Must be after or equal to active_from.'},
-            )
-
-        return data
+        data = super().validate(data)
+        validator = business.validators.PromoValidator(data=data)
+        return validator.validate()
 
     def create(self, validated_data):
         target_data = validated_data.pop('target')
         promo_common = validated_data.pop('promo_common', None)
         promo_unique = validated_data.pop('promo_unique', None)
-        mode = validated_data['mode']
-
-        user = self.context['request'].user
-        validated_data['company'] = user
 
-        promo = business_models.Promo.objects.create(
+        return business_models.Promo.objects.create_promo(
+            user=self.context['request'].user,
+            target_data=target_data,
+            promo_common=promo_common,
+            promo_unique=promo_unique,
             **validated_data,
-            target=target_data,
         )
 
-        if mode == business_models.Promo.MODE_COMMON:
-            promo.promo_common = promo_common
-            promo.save()
-        elif mode == business_models.Promo.MODE_UNIQUE and promo_unique:
-            promo_codes = [
-                business_models.PromoCode(promo=promo, code=code)
-                for code in promo_unique
-            ]
-            business_models.PromoCode.objects.bulk_create(promo_codes)
-
-        return promo
-
     def to_representation(self, instance):
         data = super().to_representation(instance)
         data['target'] = instance.target
@@ -505,74 +424,12 @@ def update(self, instance, validated_data):
         return instance
 
     def validate(self, data):
-        instance = self.instance
-        full_data = {
-            'mode': instance.mode,
-            'promo_common': instance.promo_common,
-            'promo_unique': None,
-            'max_count': instance.max_count,
-            'active_from': instance.active_from,
-            'active_until': instance.active_until,
-            'target': instance.target if instance.target is not None else {},
-        }
-        full_data.update(data)
-        mode = full_data.get('mode')
-        promo_common = full_data.get('promo_common')
-        promo_unique = full_data.get('promo_unique')
-        max_count = full_data.get('max_count')
-
-        if mode == business_models.Promo.MODE_COMMON:
-            if not promo_common:
-                raise rest_framework.serializers.ValidationError(
-                    {
-                        'promo_common': (
-                            'This field is required for COMMON mode.'
-                        ),
-                    },
-                )
-
-            if promo_unique is not None:
-                raise rest_framework.serializers.ValidationError(
-                    {
-                        'promo_unique': (
-                            'This field is not allowed for COMMON mode.'
-                        ),
-                    },
-                )
-
-            if max_count < 0 or max_count > 100000000:
-                raise rest_framework.serializers.ValidationError(
-                    {'max_count': 'Must be between 0 and 100,000,000.'},
-                )
-
-        elif mode == business_models.Promo.MODE_UNIQUE:
-            if promo_common is not None:
-                raise rest_framework.serializers.ValidationError(
-                    {
-                        'promo_common': (
-                            'This field is not allowed for UNIQUE mode.'
-                        ),
-                    },
-                )
-
-            if max_count != 1:
-                raise rest_framework.serializers.ValidationError(
-                    {'max_count': 'Must be 1 for UNIQUE mode.'},
-                )
-        else:
-            raise rest_framework.serializers.ValidationError(
-                {'mode': 'Invalid mode.'},
-            )
-
-        active_from = full_data.get('active_from')
-        active_until = full_data.get('active_until')
-
-        if active_from and active_until and active_from > active_until:
-            raise rest_framework.serializers.ValidationError(
-                {'active_until': 'Must be after or equal to active_from.'},
-            )
-
-        return data
+        data = super().validate(data)
+        validator = business.validators.PromoValidator(
+            data=data,
+            instance=self.instance,
+        )
+        return validator.validate()
 
     def get_like_count(self, obj):
         return 0

promo_code/business/tests/promocodes/operations/test_detail.py

@@ -45,7 +45,6 @@ def setUpTestData(cls):
         cls.promo2_id = response2.data['id']
 
     def test_get_promo_company1(self):
-
         promo_detail_url = django.urls.reverse(
             'api-business:promo-detail',
             kwargs={'id': self.__class__.promo1_id},

promo_code/business/tests/promocodes/validations/test_create_validation.py

@@ -7,7 +7,6 @@
 class TestPromoCreate(
     business.tests.promocodes.base.BasePromoTestCase,
 ):
-
     def setUp(self):
         super().setUp()
         self.client.credentials(

promo_code/business/tests/promocodes/validations/test_detail_validation.py

@@ -5,7 +5,6 @@
 
 
 class TestPromoDetail(business.tests.promocodes.base.BasePromoTestCase):
-
     @classmethod
     def setUpClass(cls):
         super().setUpClass()