Features: 1) Add discount_price field to ProductDetailSerializer, PromotionDetailSerializer, and Product GraphQL type; 2) Introduce promos and discount_price properties in the Product model;

Fixes: None;

Extra: 1) Update field inclusion lists and methods in serializers to reflect the new `discount_price` field; 2) Add model property caching for `discount_price`;

core/graphene/object_types.py

@@ -481,6 +481,7 @@ class ProductType(DjangoObjectType):  # type: ignore [misc]
     personal_orders_only = Boolean(description=_("only available for personal orders"))
     seo_meta = Field(SEOMetaType, description=_("SEO Meta snapshot"))
     rating = Float(description=_("rating value from 1 to 10, inclusive, or 0 if not set."))
+    discount_price = Float(description=_("discount price"))
 
     class Meta:
         model = Product
@@ -577,6 +578,9 @@ class ProductType(DjangoObjectType):  # type: ignore [misc]
             "hreflang": info.context.LANGUAGE_CODE,
         }
 
+    def resolve_discount_price(self: Product, _info) -> float | None:
+        return self.discount_price
+
 
 class AttributeValueType(DjangoObjectType):  # type: ignore [misc]
     value = String(description=_("attribute value"))

core/models.py

@@ -658,6 +658,17 @@ class Product(ExportModelOperationsMixin("product"), NiceModel):  # type: ignore
     def __str__(self):
         return self.name
 
+    @property
+    def promos(self) -> QuerySet["Promotion"]:
+        return Promotion.objects.filter(
+            is_active=True,
+            products__in=[self.pk],
+        ).order_by("-discount_percent")
+
+    @cached_property
+    def discount_price(self) -> float | None:
+        return self.promos.first().discount_percent if self.promos.exists() else None  # type: ignore [union-attr]
+
     @property
     def rating(self) -> float:
         feedbacks = Feedback.objects.filter(order_product__product_id=self.pk)

core/serializers/detail.py

@@ -286,6 +286,7 @@ class ProductDetailSerializer(ModelSerializer):
     price = SerializerMethodField()
     quantity = SerializerMethodField()
     feedbacks_count = SerializerMethodField()
+    discount_price = SerializerMethodField()
 
     class Meta:
         model = Product
@@ -308,6 +309,7 @@ class ProductDetailSerializer(ModelSerializer):
             "price",
             "created",
             "modified",
+            "discount_price",
         ]
 
     def get_rating(self, obj: Product) -> float:
@@ -322,6 +324,9 @@ class ProductDetailSerializer(ModelSerializer):
     def get_quantity(self, obj: Product) -> int:
         return obj.quantity
 
+    def get_discount_price(self, obj: Product) -> float | None:
+        return obj.discount_price
+
 
 class PromotionDetailSerializer(ModelSerializer):
     products = ProductDetailSerializer(

core/serializers/simple.py

@@ -157,6 +157,7 @@ class ProductSimpleSerializer(ModelSerializer):  # type: ignore [type-arg]
     quantity = SerializerMethodField()
     feedbacks_count = SerializerMethodField()
     personal_orders_only = SerializerMethodField()
+    discount_price = SerializerMethodField()
 
     class Meta:
         model = Product
@@ -178,6 +179,7 @@ class ProductSimpleSerializer(ModelSerializer):  # type: ignore [type-arg]
             "rating",
             "price",
             "quantity",
+            "discount_price",
         ]
 
     def get_rating(self, obj: Product) -> float:
@@ -195,6 +197,9 @@ class ProductSimpleSerializer(ModelSerializer):  # type: ignore [type-arg]
     def get_personal_orders_only(self, obj: Product) -> bool:
         return obj.personal_orders_only
 
+    def get_discount_price(self, obj: Product) -> float | None:
+        return obj.discount_price
+
 
 class VendorSimpleSerializer(ModelSerializer):  # type: ignore [type-arg]
     class Meta: