uabh perhitungan tax

lib/Screens/Sales/provider/sales_cart_provider.dart

@@ -132,11 +132,26 @@ class CartNotifier extends ChangeNotifier {
       totalPayableAmount -= discountAmount;
     }
 
-    // Apply VAT
-    if (selectedVat?.rate != null) {
-      vatAmount = (totalPayableAmount * selectedVat!.rate!) / 100;
-      vatAmountController.text = vatAmount.toStringAsFixed(2);
+    // Apply Item-wise VAT
+    vatAmount = 0;
+    for (var element in cartItemList) {
+      num unitPrice = element.unitPrice ?? 0;
+      num quantity = element.quantity;
+      num taxRate = element.perItemTaxPercentage ?? 0;
+
+      // VAT Formula: (Price * Qty * Rate%)
+      // Note: We are calculating VAT on the base price, not discounted price if that's the requirement.
+      // But usually VAT is on the final price.
+      // The user request "QTY x Harga x % dari vat_id" implies Base Price.
+      // If it should be on discounted price, we would subtract productDiscount.
+      // Assuming "Harga" refers to the selling price.
+      
+      num itemVat = (unitPrice * quantity * taxRate) / 100;
+      vatAmount += itemVat;
     }
+    vatAmountController.text = vatAmount.toStringAsFixed(2);
+    
+    // Add Total VAT to Payable
     totalPayableAmount += vatAmount;
 
     // Apply Shipping