Improve the frontend modals

services/inventory/app/repositories/ingredient_repository.py

@@ -398,11 +398,80 @@ class IngredientRepository(BaseRepository[Ingredient, IngredientCreate, Ingredie
             from app.schemas.inventory import IngredientUpdate
             update_data = IngredientUpdate(last_purchase_price=price)
             return await self.update(ingredient_id, update_data)
-            
+
         except Exception as e:
             logger.error("Failed to update last purchase price", error=str(e), ingredient_id=ingredient_id)
             raise
 
+    async def update_weighted_average_cost(
+        self,
+        ingredient_id: UUID,
+        current_stock_quantity: float,
+        new_purchase_quantity: float,
+        new_unit_cost: float
+    ) -> Optional[Ingredient]:
+        """
+        Update the average cost using weighted average calculation.
+
+        Formula:
+        new_average_cost = (current_stock_qty × current_avg_cost + new_qty × new_cost) / (current_stock_qty + new_qty)
+
+        Args:
+            ingredient_id: ID of the ingredient
+            current_stock_quantity: Current stock quantity before this purchase
+            new_purchase_quantity: Quantity being purchased
+            new_unit_cost: Unit cost of the new purchase
+
+        Returns:
+            Updated ingredient or None if not found
+        """
+        try:
+            # Get current ingredient data
+            ingredient = await self.get_by_id(ingredient_id)
+            if not ingredient:
+                logger.warning("Ingredient not found for average cost update", ingredient_id=ingredient_id)
+                return None
+
+            from decimal import Decimal
+
+            # Get current average cost (default to new cost if not set)
+            current_avg_cost = float(ingredient.average_cost) if ingredient.average_cost else float(new_unit_cost)
+
+            # Calculate weighted average
+            # If no current stock, just use the new purchase price
+            if current_stock_quantity <= 0:
+                new_average_cost = Decimal(str(new_unit_cost))
+            else:
+                # Weighted average formula
+                total_cost = (current_stock_quantity * current_avg_cost) + (new_purchase_quantity * new_unit_cost)
+                total_quantity = current_stock_quantity + new_purchase_quantity
+                new_average_cost = Decimal(str(total_cost / total_quantity))
+
+            # Update the ingredient
+            from app.schemas.inventory import IngredientUpdate
+            update_data = IngredientUpdate(average_cost=new_average_cost)
+            updated_ingredient = await self.update(ingredient_id, update_data)
+
+            logger.info(
+                "Updated weighted average cost",
+                ingredient_id=ingredient_id,
+                old_average_cost=current_avg_cost,
+                new_average_cost=float(new_average_cost),
+                current_stock_qty=current_stock_quantity,
+                new_purchase_qty=new_purchase_quantity,
+                new_unit_cost=new_unit_cost
+            )
+
+            return updated_ingredient
+
+        except Exception as e:
+            logger.error(
+                "Failed to update weighted average cost",
+                error=str(e),
+                ingredient_id=ingredient_id
+            )
+            raise
+
     async def get_ingredients_by_category(self, tenant_id: UUID, category: str) -> List[Ingredient]:
         """Get all ingredients in a specific category"""
         try: