Fix refund flow

src/main/java/org/example/petshopdesktop/controllers/SaleController.java

@@ -372,6 +372,11 @@ public class SaleController {
     private void openRefundDialog() {
         try {
             SaleLineItem selectedSale = tvSales.getSelectionModel().getSelectedItem();
+            if (selectedSale != null && selectedSale.isRefund()) {
+                showError("Refund", "Select an original sale, not an existing refund.");
+                return;
+            }
+
             FXMLLoader loader = new FXMLLoader(getClass().getResource(
                 "/org/example/petshopdesktop/dialogviews/refund-dialog-view.fxml"));
             Stage dialog = new Stage();

src/main/java/org/example/petshopdesktop/controllers/dialogcontrollers/RefundDialogController.java

@@ -86,6 +86,8 @@ public class RefundDialogController {
     private Button btnCancel;
 
     private SaleResponse currentSale;
+    private final List<SaleItemResponse> baseOriginalItems = new ArrayList<>();
+    private final ObservableList<SaleItemResponse> originalItems = FXCollections.observableArrayList();
     private final ObservableList<RefundItem> refundItems = FXCollections.observableArrayList();
     private final NumberFormat currency = NumberFormat.getCurrencyInstance(Locale.CANADA);
 
@@ -102,6 +104,7 @@ public class RefundDialogController {
         colOriginalQuantity.setCellValueFactory(new PropertyValueFactory<>("quantity"));
         colOriginalUnitPrice.setCellValueFactory(new PropertyValueFactory<>("unitPrice"));
         colOriginalTotal.setCellValueFactory(new PropertyValueFactory<>("lineTotal"));
+        tvOriginalItems.setItems(originalItems);
         tvOriginalItems.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
 
         colRefundProduct.setCellValueFactory(new PropertyValueFactory<>("productName"));
@@ -143,6 +146,11 @@ public class RefundDialogController {
         try {
             List<SaleResponse> allSales = SaleApi.getInstance().listSales(0, 1000, null);
             currentSale = SaleApi.getInstance().getSale(saleId);
+            if (Boolean.TRUE.equals(currentSale.getIsRefund())) {
+                clearLoadedSale();
+                showError("Load Sale", "Select an original sale, not a refund record.");
+                return;
+            }
             List<SaleResponse> previousRefunds = allSales.stream()
                 .filter(s -> Boolean.TRUE.equals(s.getIsRefund()) && saleId.equals(s.getOriginalSaleId()))
                 .collect(Collectors.toList());
@@ -161,10 +169,13 @@ public class RefundDialogController {
                 return;
             }
 
-            tvOriginalItems.setItems(FXCollections.observableArrayList(refundableItems));
+            baseOriginalItems.clear();
+            baseOriginalItems.addAll(copySaleItems(refundableItems));
+            originalItems.setAll(copySaleItems(refundableItems));
             cbPaymentMethod.getSelectionModel().select(currentSale.getPaymentMethod());
 
             refundItems.clear();
+            updateOriginalItemAvailability();
             updateRefundTotal();
 
         } catch (Exception e) {
@@ -215,12 +226,8 @@ public class RefundDialogController {
                     return;
                 }
 
-                refundItems.add(new RefundItem(
-                    selected.getProdId().intValue(),
-                    selected.getProductName(),
-                    quantity,
-                    selected.getUnitPrice().doubleValue()
-                ));
+                addOrMergeRefundItem(selected, quantity);
+                updateOriginalItemAvailability();
                 updateRefundTotal();
 
             } catch (NumberFormatException e) {
@@ -234,6 +241,7 @@ public class RefundDialogController {
         RefundItem selected = tvRefundItems.getSelectionModel().getSelectedItem();
         if (selected != null) {
             refundItems.remove(selected);
+            updateOriginalItemAvailability();
             updateRefundTotal();
         }
     }
@@ -309,6 +317,83 @@ public class RefundDialogController {
         closeDialog();
     }
 
+    private void clearLoadedSale() {
+        currentSale = null;
+        lblSaleInfo.setText("");
+        baseOriginalItems.clear();
+        originalItems.clear();
+        refundItems.clear();
+        updateRefundTotal();
+    }
+
+    private void addOrMergeRefundItem(SaleItemResponse selected, int quantity) {
+        for (int i = 0; i < refundItems.size(); i++) {
+            RefundItem existing = refundItems.get(i);
+            if (existing.getProdId() == selected.getProdId().intValue()) {
+                refundItems.set(i, new RefundItem(
+                    existing.getProdId(),
+                    existing.getProductName(),
+                    existing.getQuantity() + quantity,
+                    existing.getUnitPrice()
+                ));
+                return;
+            }
+        }
+
+        refundItems.add(new RefundItem(
+            selected.getProdId().intValue(),
+            selected.getProductName(),
+            quantity,
+            selected.getUnitPrice().doubleValue()
+        ));
+    }
+
+    private void updateOriginalItemAvailability() {
+        if (currentSale == null) {
+            baseOriginalItems.clear();
+            originalItems.clear();
+            return;
+        }
+
+        Map<Long, Integer> pendingRefunds = new HashMap<>();
+        for (RefundItem refundItem : refundItems) {
+            pendingRefunds.merge((long) refundItem.getProdId(), refundItem.getQuantity(), Integer::sum);
+        }
+
+        List<SaleItemResponse> refreshedItems = new ArrayList<>();
+        for (SaleItemResponse originalItem : baseOriginalItems) {
+            SaleItemResponse refreshedItem = copySaleItem(originalItem);
+            int pending = pendingRefunds.getOrDefault(refreshedItem.getProdId(), 0);
+            refreshedItem.setQuantity(Math.max(0, refreshedItem.getQuantity() - pending));
+            if (refreshedItem.getQuantity() > 0) {
+                refreshedItems.add(refreshedItem);
+            }
+        }
+
+        originalItems.setAll(refreshedItems);
+        tvOriginalItems.getSelectionModel().clearSelection();
+        tvOriginalItems.refresh();
+        tvRefundItems.refresh();
+    }
+
+    private List<SaleItemResponse> copySaleItems(List<SaleItemResponse> items) {
+        List<SaleItemResponse> copies = new ArrayList<>();
+        for (SaleItemResponse item : items) {
+            copies.add(copySaleItem(item));
+        }
+        return copies;
+    }
+
+    private SaleItemResponse copySaleItem(SaleItemResponse source) {
+        SaleItemResponse copy = new SaleItemResponse();
+        copy.setSaleItemId(source.getSaleItemId());
+        copy.setProdId(source.getProdId());
+        copy.setProductName(source.getProductName());
+        copy.setQuantity(source.getQuantity());
+        copy.setUnitPrice(source.getUnitPrice());
+        return copy;
+    }
+
     private void updateRefundTotal() {
         double total = refundItems.stream().mapToDouble(RefundItem::getTotal).sum();
         lblRefundTotal.setText(currency.format(total));