fix order model invoice genrator

backend/order/invoice_generator.py

@@ -9,7 +9,7 @@ from django.template.loader import render_to_string
 from weasyprint import HTML
 from django.conf import settings
 import jdatetime
-
+from django.conf import settings
 
 def generate_order_invoice(order_id):
     """
@@ -30,33 +30,26 @@ def generate_order_invoice(order_id):
     except OrderModel.DoesNotExist:
         raise ValueError(f"Order with ID {order_id} does not exist")
     
-    # Prepare items with calculated discount amounts
+    # Prepare items with calculated discount amounts using stored values
     items = order.items.all()
     items_with_discount = []
+    total_items_discount = 0
+    
     for item in items:
-        # Calculate the discount amount from the discount_percent
-        # price is after discount, so we need to calculate original price
-        # original_price = price / (1 - discount_percent/100)
-        # discount_amount = original_price - price
-        if item.discount_percent > 0:
-            discount_multiplier = (100 - item.discount_percent) / 100
-            price_after_discount = item.price
-            price_before_discount = int(price_after_discount / discount_multiplier) if discount_multiplier > 0 else price_after_discount
-            item_discount_amount = (price_before_discount - price_after_discount)
-        else:
-            item_discount_amount = 0
-            price_before_discount = item.price
+        total_items_discount += item.total_product_discount_amount() or 0
         
         items_with_discount.append({
             'item': item,
-            'discount_amount': item_discount_amount,
-            'price_before_discount': price_before_discount
+            'discount_amount': item.total_product_discount_amount() or 0,
+            'price_before_discount': item.total_price_before_discount(),
+            'unit_price': item.unit_price(),
+            'final_price': item.price_after_special_discount(),
         })
     
-    # Prepare context for the template
+    # Use stored model fields for accuracy and consistency
     context = {
         'order': order,
-        'order_number': order.pk + 1000,
+        'order_number': order.pk,
         'items': items,
         'items_with_discount': items_with_discount,
         'user': order.user,
@@ -64,11 +57,13 @@ def generate_order_invoice(order_id):
         'discount_code': order.discount_code,
         'created_at_jalali': jdatetime.datetime.fromgregorian(datetime=order.created_at) if order.created_at else None,
         'total_items': sum(item.quantity for item in items),
-        'subtotal': order.cart_total,
-        'discount_amount': order.discount_amount or 0,
-        'special_discount_total': order.special_discount_total or 0,
-        'tax': order.tax or 0,
-        'final_price': order.final_price,
+        'subtotal': order.cart_total or 0,  # Stored field: total before any discounts
+        'items_discount_amount': total_items_discount,
+        'discount_amount': order.discount_amount or 0,  # Stored field: discount code amount
+        'special_discount_total': order.special_discount_total or 0,  # Stored field: special discount total
+        'tax_rate': settings.DEFAULT_TAX_RATE,
+        'tax': order.tax or 0,  # Stored field: tax amount
+        'final_price': order.final_price or 0,  # Stored field: final price after all calculations
         'is_paid': order.is_paid,
         'status': order.get_status_display(),
     }
@@ -104,7 +99,32 @@ def generate_shop_order_invoice(shop_order_id):
     except ShopOrderModel.DoesNotExist:
         raise ValueError(f"ShopOrder with ID {shop_order_id} does not exist")
     
+    # Calculate total before any discount from shop order items
+    # shop_order.subtotal stores price AFTER product discount, so we need to recalculate
+    items = shop_order.items.select_related('order_item').all()
+    total_before_any_discount = 0
+    total_product_discount = 0
+    
+    for shop_item in items:
+        order_item = shop_item.order_item
+        # order_item.price is unit price AFTER product discount
+        if order_item.discount_percent > 0:
+            discount_multiplier = (100 - order_item.discount_percent) / 100
+            if discount_multiplier > 0:
+                price_before_discount_unit = int(order_item.price / discount_multiplier)
+            else:
+                price_before_discount_unit = order_item.price
+            
+            item_discount = (price_before_discount_unit - order_item.price) * shop_item.quantity
+            total_product_discount += item_discount
+        else:
+            price_before_discount_unit = order_item.price
+        
+        total_before_any_discount += price_before_discount_unit * shop_item.quantity
+    
     # Prepare context for the template
+    subtotal_after_discount = total_before_any_discount - (total_product_discount + shop_order.special_discount_amount) + shop_order.tax_amount
+    
     context = {
         'shop_order': shop_order,
         'order_number': shop_order.order.pk + 1000,
@@ -119,12 +139,13 @@ def generate_shop_order_invoice(shop_order_id):
         'address_city': shop_order.address_city,
         'address_province': shop_order.address_province,
         'address_recipient_name': shop_order.address_recipient_name,
-        'items': shop_order.items.all(),
+        'items': items,
         'created_at_jalali': jdatetime.datetime.fromgregorian(datetime=shop_order.order_created_at) if shop_order.order_created_at else None,
         'total_items': shop_order.items_count,
-        'subtotal': shop_order.subtotal,
-        'discount_amount': shop_order.discount_amount,
+        'subtotal': total_before_any_discount,  # Total BEFORE any discount
+        'discount_amount': total_product_discount,  # Product discount amount
         'special_discount_amount': shop_order.special_discount_amount,
+        'subtotal_after_discount': subtotal_after_discount,
         'tax_amount': shop_order.tax_amount,
         'commission_percent': shop_order.commission_percent,
         'commission_amount': shop_order.commission_amount,