added correct refund logic and points for sales

android/app/src/main/java/com/example/petstoremobile/dtos/SaleDTO.java

@@ -18,6 +18,7 @@ public class SaleDTO {
     private BigDecimal couponDiscountAmount;
     private BigDecimal employeeDiscountAmount;
     private BigDecimal loyaltyDiscountAmount;
+    private BigDecimal pointsDiscountAmount;
     private Integer pointsUsed;
     private String paymentMethod;
     private String channel;
@@ -144,6 +145,14 @@ public class SaleDTO {
         return customerName;
     }
 
+    public BigDecimal getPointsDiscountAmount() {
+        return pointsDiscountAmount;
+    }
+
+    public void setPointsDiscountAmount(BigDecimal pointsDiscountAmount) {
+        this.pointsDiscountAmount = pointsDiscountAmount;
+    }
+
     // Nested SaleItemDTO
     public static class SaleItemDTO {
         private Long saleItemId;

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/RefundFragment.java

@@ -302,11 +302,7 @@ public class RefundFragment extends Fragment {
     }
 
     private void updateRefundTotal() {
-        BigDecimal total = BigDecimal.ZERO;
+        BigDecimal total = viewModel.calculateRefundTotal();
-        List<RefundViewModel.RefundItem> cart = viewModel.getRefundCart().getValue();
-        if (cart != null) {
-            for (RefundViewModel.RefundItem item : cart) total = total.add(item.getTotal());
-        }
         binding.tvRefundTotal.setText("Refund Total: $" + total.setScale(2, RoundingMode.HALF_UP));
     }
 
@@ -321,9 +317,7 @@ public class RefundFragment extends Fragment {
         }
 
         String payment = PAYMENT_METHODS[binding.spinnerRefundPayment.getSelectedItemPosition()];
-        BigDecimal total = BigDecimal.ZERO;
+        final BigDecimal finalTotal = viewModel.calculateRefundTotal();
-        for (RefundViewModel.RefundItem item : viewModel.getRefundCart().getValue()) total = total.add(item.getTotal());
-        final BigDecimal finalTotal = total;
 
         DialogUtils.showConfirmDialog(requireContext(), "Confirm Refund", 
                 "Process refund for Sale #" + viewModel.getCurrentSale().getSaleId()

android/app/src/main/java/com/example/petstoremobile/fragments/listfragments/detailfragments/SaleDetailFragment.java

@@ -205,7 +205,13 @@ public class SaleDetailFragment extends Fragment {
                     binding.llEmployeeDiscount.setVisibility(View.GONE);
                 }
 
-                if (sale.getLoyaltyDiscountAmount() != null && sale.getLoyaltyDiscountAmount().compareTo(BigDecimal.ZERO) > 0) {
+                if (sale.getPointsDiscountAmount() != null && sale.getPointsDiscountAmount().compareTo(BigDecimal.ZERO) > 0) {
+                    binding.llLoyaltyDiscount.setVisibility(View.VISIBLE);
+                    binding.tvSaleLoyaltyDiscount.setText("-$" + String.format(Locale.getDefault(), "%.2f", sale.getPointsDiscountAmount()));
+                    if (sale.getPointsUsed() != null) {
+                        binding.tvLoyaltyDiscountLabel.setText("Loyalty Discount (" + sale.getPointsUsed() + " pts):");
+                    }
+                } else if (sale.getLoyaltyDiscountAmount() != null && sale.getLoyaltyDiscountAmount().compareTo(BigDecimal.ZERO) > 0) {
                     binding.llLoyaltyDiscount.setVisibility(View.VISIBLE);
                     binding.tvSaleLoyaltyDiscount.setText("-$" + String.format(Locale.getDefault(), "%.2f", sale.getLoyaltyDiscountAmount()));
                 } else {
@@ -437,7 +443,6 @@ public class SaleDetailFragment extends Fragment {
         
         if (Boolean.TRUE.equals(viewModel.getUseLoyaltyPoints().getValue())) {
             dto.setPointsUsed(viewModel.calculatePointsToUse());
-            dto.setLoyaltyDiscountAmount(viewModel.calculateLoyaltyDiscount());
         }
 
         viewModel.createSale(dto).observe(getViewLifecycleOwner(), resource -> {

android/app/src/main/java/com/example/petstoremobile/viewmodels/RefundViewModel.java

@@ -10,6 +10,7 @@ import com.example.petstoremobile.repositories.SaleRepository;
 import com.example.petstoremobile.utils.Resource;
 
 import java.math.BigDecimal;
+import java.math.RoundingMode;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -125,6 +126,33 @@ public class RefundViewModel extends ViewModel {
         refundCart.setValue(cart);
     }
 
+    public BigDecimal calculateRefundTotal() {
+        SaleDTO sale = currentSale.getValue();
+        List<RefundItem> cart = refundCart.getValue();
+        if (sale == null || cart == null || cart.isEmpty()) return BigDecimal.ZERO;
+
+        BigDecimal cartSubtotal = BigDecimal.ZERO;
+        for (RefundItem item : cart) cartSubtotal = cartSubtotal.add(item.getTotal());
+
+        BigDecimal originalSubtotal = sale.getSubtotalAmount();
+        if (originalSubtotal == null || originalSubtotal.compareTo(BigDecimal.ZERO) == 0) {
+            if (sale.getItems() != null) {
+                originalSubtotal = BigDecimal.ZERO;
+                for (SaleDTO.SaleItemDTO item : sale.getItems()) {
+                    if (item.getUnitPrice() != null && item.getQuantity() != null)
+                        originalSubtotal = originalSubtotal.add(item.getUnitPrice().multiply(BigDecimal.valueOf(Math.abs(item.getQuantity()))));
+                }
+            }
+        }
+        if (originalSubtotal == null || originalSubtotal.compareTo(BigDecimal.ZERO) == 0) return cartSubtotal;
+
+        BigDecimal originalTotal = sale.getTotalAmount();
+        if (originalTotal == null) return cartSubtotal;
+
+        BigDecimal ratio = cartSubtotal.divide(originalSubtotal, 10, RoundingMode.HALF_UP);
+        return originalTotal.abs().multiply(ratio).setScale(2, RoundingMode.HALF_UP);
+    }
+
     public LiveData<Resource<SaleDTO>> submitRefund(String paymentMethod) {
         SaleDTO sale = currentSale.getValue();
         List<RefundItem> cart = refundCart.getValue();