feat(discounts): добавлено комбинирование скидок по режимам

Добавлено поле combine_mode с тремя режимами:
- stack - складывать с другими скидками
- max_only - применять только максимальную
- exclusive - отменяет все остальные скидки

Изменения:
- Модель Discount: добавлено поле combine_mode
- Calculator: новый класс DiscountCombiner, методы возвращают списки скидок
- Applier: создание нескольких DiscountApplication записей
- Admin: отображение combine_mode с иконками
- POS API: возвращает списки применённых скидок
- POS UI: отображение нескольких скидок с иконками режимов

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

myproject/discounts/services/applier.py

@@ -6,6 +6,7 @@ from django.core.exceptions import ValidationError
 class DiscountApplier:
     """
     Сервис для применения скидок к заказам.
+    Поддерживает комбинирование скидок по combine_mode.
     Все операции атомарны.
     """
 
@@ -14,6 +15,7 @@ class DiscountApplier:
     def apply_promo_code(order, promo_code, user=None):
         """
         Применить промокод к заказу.
+        Поддерживает комбинирование скидок.
 
         Args:
             order: Order
@@ -23,8 +25,8 @@ class DiscountApplier:
         Returns:
             dict: {
                 'success': bool,
-                'discount': Discount,
-                'discount_amount': Decimal,
+                'discounts': [{'discount': Discount, 'amount': Decimal}, ...],
+                'total_amount': Decimal,
                 'error': str
             }
         """
@@ -36,9 +38,7 @@ class DiscountApplier:
             DiscountApplier._remove_order_discount_only(order)
 
         # Рассчитываем скидку
-        result = DiscountCalculator.calculate_order_discount(
-            order, promo_code
-        )
+        result = DiscountCalculator.calculate_order_discount(order, promo_code)
 
         if result['error']:
             return {
@@ -46,15 +46,17 @@ class DiscountApplier:
                 'error': result['error']
             }
 
-        discount = result['discount']
         promo = result['promo_code']
-        discount_amount = result['discount_amount']
+        discounts_data = result['discounts']
+        total_amount = result['total_amount']
 
-        # Применяем к заказу
-        order.applied_discount = discount
-        order.applied_promo_code = promo.code
-        order.discount_amount = discount_amount
-        order.save(update_fields=['applied_discount', 'applied_promo_code', 'discount_amount'])
+        # Применяем первую скидку в applied_discount (для обратной совместимости с Order)
+        if discounts_data:
+            first_discount = discounts_data[0]['discount']
+            order.applied_discount = first_discount
+            order.applied_promo_code = promo.code
+            order.discount_amount = total_amount
+            order.save(update_fields=['applied_discount', 'applied_promo_code', 'discount_amount'])
 
         # Пересчитываем total_amount
         order.calculate_total()
@@ -62,27 +64,31 @@ class DiscountApplier:
         # Регистрируем использование промокода
         promo.record_usage(order.customer)
 
-        # Создаем запись о применении
-        DiscountApplication.objects.create(
-            order=order,
-            discount=discount,
-            promo_code=promo,
-            target='order',
-            base_amount=order.subtotal,
-            discount_amount=discount_amount,
-            final_amount=order.subtotal - discount_amount,
-            customer=order.customer,
-            applied_by=user or order.modified_by
-        )
+        # Создаем записи о применении для каждой скидки
+        for disc_data in discounts_data:
+            discount = disc_data['discount']
+            amount = disc_data['amount']
 
-        # Увеличиваем счетчик использований скидки
-        discount.current_usage_count += 1
-        discount.save(update_fields=['current_usage_count'])
+            DiscountApplication.objects.create(
+                order=order,
+                discount=discount,
+                promo_code=promo,
+                target='order',
+                base_amount=order.subtotal,
+                discount_amount=amount,
+                final_amount=order.subtotal - amount,
+                customer=order.customer,
+                applied_by=user or order.modified_by
+            )
+
+            # Увеличиваем счетчик использований скидки
+            discount.current_usage_count += 1
+            discount.save(update_fields=['current_usage_count'])
 
         return {
             'success': True,
-            'discount': discount,
-            'discount_amount': discount_amount
+            'discounts': discounts_data,
+            'total_amount': total_amount
         }
 
     @staticmethod
@@ -90,6 +96,7 @@ class DiscountApplier:
     def apply_auto_discounts(order, user=None):
         """
         Применить автоматические скидки к заказу и позициям.
+        Поддерживает комбинирование скидок.
 
         Args:
             order: Order
@@ -97,7 +104,7 @@ class DiscountApplier:
 
         Returns:
             dict: {
-                'order_discount': {...},
+                'order_discounts': [...],
                 'item_discounts': [...],
                 'total_discount': Decimal
             }
@@ -106,71 +113,35 @@ class DiscountApplier:
         from discounts.services.calculator import DiscountCalculator
 
         result = {
-            'order_discount': None,
+            'order_discounts': [],
             'item_discounts': [],
             'total_discount': Decimal('0')
         }
 
-        # 1. Применяем скидку на заказ (если есть)
+        # 1. Применяем скидки на заказ (может быть несколько)
         order_result = DiscountCalculator.calculate_order_discount(order)
-        if order_result['discount'] and not order_result['error']:
-            discount = order_result['discount']
-            discount_amount = order_result['discount_amount']
 
-            order.applied_discount = discount
-            order.discount_amount = discount_amount
+        if order_result['discounts'] and not order_result['error']:
+            total_order_amount = order_result['total_amount']
+
+            # Сохраняем первую скидку в applied_discount (для совместимости)
+            first_discount_data = order_result['discounts'][0]
+            order.applied_discount = first_discount_data['discount']
+            order.discount_amount = total_order_amount
             order.save(update_fields=['applied_discount', 'discount_amount'])
 
-            # Создаем запись о применении
-            DiscountApplication.objects.create(
-                order=order,
-                discount=discount,
-                target='order',
-                base_amount=order.subtotal,
-                discount_amount=discount_amount,
-                final_amount=order.subtotal - discount_amount,
-                customer=order.customer,
-                applied_by=user
-            )
+            # Создаем записи о применении для всех скидок
+            for disc_data in order_result['discounts']:
+                discount = disc_data['discount']
+                amount = disc_data['amount']
 
-            # Увеличиваем счетчик
-            discount.current_usage_count += 1
-            discount.save(update_fields=['current_usage_count'])
-
-            result['order_discount'] = {
-                'discount': discount,
-                'discount_amount': discount_amount
-            }
-            result['total_discount'] += discount_amount
-
-        # 2. Применяем скидки на позиции
-        available_discounts = list(DiscountCalculator.get_available_discounts(
-            scope='product',
-            auto_only=True
-        ))
-
-        for item in order.items.all():
-            item_result = DiscountCalculator.calculate_item_discount(
-                item, available_discounts
-            )
-
-            if item_result['discount']:
-                discount = item_result['discount']
-                discount_amount = item_result['discount_amount']
-
-                item.applied_discount = discount
-                item.discount_amount = discount_amount
-                item.save(update_fields=['applied_discount', 'discount_amount'])
-
-                # Создаем запись о применении
                 DiscountApplication.objects.create(
                     order=order,
-                    order_item=item,
                     discount=discount,
-                    target='order_item',
-                    base_amount=item.price * item.quantity,
-                    discount_amount=discount_amount,
-                    final_amount=item.get_total_price(),
+                    target='order',
+                    base_amount=order.subtotal,
+                    discount_amount=amount,
+                    final_amount=order.subtotal - amount,
                     customer=order.customer,
                     applied_by=user
                 )
@@ -179,12 +150,57 @@ class DiscountApplier:
                 discount.current_usage_count += 1
                 discount.save(update_fields=['current_usage_count'])
 
+            result['order_discounts'] = order_result['discounts']
+            result['total_discount'] += total_order_amount
+
+        # 2. Применяем скидки на позиции
+        available_product_discounts = list(DiscountCalculator.get_available_discounts(
+            scope='product',
+            auto_only=True
+        ))
+
+        for item in order.items.all():
+            item_result = DiscountCalculator.calculate_item_discount(
+                item, available_product_discounts
+            )
+
+            if item_result['discounts']:
+                total_item_amount = item_result['total_amount']
+
+                # Сохраняем первую скидку в applied_discount (для совместимости)
+                first_discount_data = item_result['discounts'][0]
+                item.applied_discount = first_discount_data['discount']
+                item.discount_amount = total_item_amount
+                item.save(update_fields=['applied_discount', 'discount_amount'])
+
+                # Создаем записи о применении для всех скидок
+                base_amount = item.price * item.quantity
+                for disc_data in item_result['discounts']:
+                    discount = disc_data['discount']
+                    amount = disc_data['amount']
+
+                    DiscountApplication.objects.create(
+                        order=order,
+                        order_item=item,
+                        discount=discount,
+                        target='order_item',
+                        base_amount=base_amount,
+                        discount_amount=amount,
+                        final_amount=item.get_total_price(),
+                        customer=order.customer,
+                        applied_by=user
+                    )
+
+                    # Увеличиваем счетчик
+                    discount.current_usage_count += 1
+                    discount.save(update_fields=['current_usage_count'])
+
                 result['item_discounts'].append({
                     'item': item,
-                    'discount': discount,
-                    'discount_amount': discount_amount
+                    'discounts': item_result['discounts'],
+                    'total_amount': total_item_amount
                 })
-                result['total_discount'] += discount_amount
+                result['total_discount'] += total_item_amount
 
         # Пересчитываем итоговую сумму
         order.calculate_total()
@@ -208,8 +224,9 @@ class DiscountApplier:
             discount_amount=Decimal('0')
         )
 
-        # Удаляем записи о применении (опционально - для истории можно оставить)
-        # DiscountApplication.objects.filter(order=order).delete()
+        # Удаляем записи о применении
+        from discounts.models import DiscountApplication
+        DiscountApplication.objects.filter(order=order).delete()
 
         # Пересчитываем
         order.calculate_total()
@@ -285,6 +302,11 @@ class DiscountApplier:
         Args:
             order: Order
         """
+        from discounts.models import DiscountApplication
+
+        # Удаляем записи о применении скидок к заказу
+        DiscountApplication.objects.filter(order=order, target='order').delete()
+
         order.applied_discount = None
         order.applied_promo_code = None
         order.discount_amount = Decimal('0')