Implement refund system for sales

Petstoredata.sql

@@ -132,8 +132,11 @@ CREATE TABLE sale (
     paymentMethod VARCHAR(50) NOT NULL,
     employeeId INT NOT NULL,
     storeId INT NOT NULL,
+    isRefund BOOLEAN DEFAULT FALSE NOT NULL,
+    originalSaleId INT NULL,
     FOREIGN KEY (employeeId) REFERENCES employee(employeeId),
-    FOREIGN KEY (storeId) REFERENCES storeLocation(storeId)
+    FOREIGN KEY (storeId) REFERENCES storeLocation(storeId),
+    FOREIGN KEY (originalSaleId) REFERENCES sale(saleId)
 );
 
 CREATE TABLE saleItem (

refund_migration.sql

@@ -0,0 +1,14 @@
+-- Database Migration Script for Refund System
+-- Run this on existing Petstoredb to add refund functionality
+
+USE Petstoredb;
+
+-- Add refund columns to sale table
+ALTER TABLE sale
+  ADD COLUMN isRefund BOOLEAN DEFAULT FALSE NOT NULL,
+  ADD COLUMN originalSaleId INT NULL,
+  ADD CONSTRAINT fk_original_sale
+    FOREIGN KEY (originalSaleId) REFERENCES sale(saleId);
+
+-- Verify the changes
+DESCRIBE sale;

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

@@ -5,6 +5,8 @@ import javafx.collections.ObservableList;
 import javafx.collections.transformation.FilteredList;
 import javafx.event.ActionEvent;
 import javafx.fxml.FXML;
+import javafx.fxml.FXMLLoader;
+import javafx.scene.Scene;
 import javafx.scene.control.Alert;
 import javafx.scene.control.Button;
 import javafx.scene.control.ComboBox;
@@ -17,6 +19,8 @@ import javafx.scene.control.TableView;
 import javafx.scene.control.TextField;
 import javafx.scene.control.cell.PropertyValueFactory;
 import javafx.scene.layout.VBox;
+import javafx.stage.Modality;
+import javafx.stage.Stage;
 import org.example.petshopdesktop.auth.UserSession;
 import org.example.petshopdesktop.database.InventoryDB;
 import org.example.petshopdesktop.database.ProductDB;
@@ -38,6 +42,9 @@ public class SaleController {
     @FXML
     private Button btnRefresh;
 
+    @FXML
+    private Button btnRefund;
+
     @FXML
     private Label lblModeNote;
 
@@ -319,6 +326,30 @@ public class SaleController {
         }
     }
 
+    @FXML
+    void btnRefund(ActionEvent event) {
+        openRefundDialog();
+    }
+
+    private void openRefundDialog() {
+        try {
+            FXMLLoader loader = new FXMLLoader(getClass().getResource(
+                "/org/example/petshopdesktop/dialogviews/refund-dialog-view.fxml"));
+            Stage dialog = new Stage();
+            dialog.initOwner(btnRefund.getScene().getWindow());
+            dialog.initModality(Modality.APPLICATION_MODAL);
+            dialog.setTitle("Process Refund");
+            dialog.setScene(new Scene(loader.load()));
+            dialog.setResizable(false);
+            dialog.showAndWait();
+
+            refreshInventory();
+            refreshSales(true);
+        } catch (Exception e) {
+            ActivityLogger.getInstance().logException("SaleController.openRefundDialog", e, "Opening refund dialog");
+        }
+    }
+
     private void updateCartTotal() {
         double total = cartItems.stream().mapToDouble(SaleCartItem::getTotal).sum();
         lblCartTotal.setText(currency.format(total));

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

@@ -0,0 +1,329 @@
+package org.example.petshopdesktop.controllers.dialogcontrollers;
+
+import javafx.collections.FXCollections;
+import javafx.collections.ObservableList;
+import javafx.event.ActionEvent;
+import javafx.fxml.FXML;
+import javafx.scene.control.*;
+import javafx.scene.control.cell.PropertyValueFactory;
+import javafx.stage.Stage;
+import org.example.petshopdesktop.auth.UserSession;
+import org.example.petshopdesktop.database.SaleDB;
+import org.example.petshopdesktop.models.SaleCartItem;
+import org.example.petshopdesktop.models.SaleDetail;
+import org.example.petshopdesktop.util.ActivityLogger;
+
+import java.sql.SQLException;
+import java.text.NumberFormat;
+import java.time.format.DateTimeFormatter;
+import java.util.Locale;
+import java.util.Optional;
+
+public class RefundDialogController {
+
+    @FXML
+    private TextField txtSaleId;
+
+    @FXML
+    private Button btnLoadSale;
+
+    @FXML
+    private Label lblSaleInfo;
+
+    @FXML
+    private TableView<SaleDetail.SaleDetailItem> tvOriginalItems;
+
+    @FXML
+    private TableColumn<SaleDetail.SaleDetailItem, String> colOriginalProduct;
+
+    @FXML
+    private TableColumn<SaleDetail.SaleDetailItem, Integer> colOriginalQuantity;
+
+    @FXML
+    private TableColumn<SaleDetail.SaleDetailItem, Double> colOriginalUnitPrice;
+
+    @FXML
+    private TableColumn<SaleDetail.SaleDetailItem, Double> colOriginalTotal;
+
+    @FXML
+    private Button btnAddToRefund;
+
+    @FXML
+    private TableView<RefundItem> tvRefundItems;
+
+    @FXML
+    private TableColumn<RefundItem, String> colRefundProduct;
+
+    @FXML
+    private TableColumn<RefundItem, Integer> colRefundQuantity;
+
+    @FXML
+    private TableColumn<RefundItem, Double> colRefundUnitPrice;
+
+    @FXML
+    private TableColumn<RefundItem, Double> colRefundTotal;
+
+    @FXML
+    private Button btnRemoveFromRefund;
+
+    @FXML
+    private ComboBox<String> cbPaymentMethod;
+
+    @FXML
+    private Label lblRefundTotal;
+
+    @FXML
+    private Button btnProcessRefund;
+
+    @FXML
+    private Button btnCancel;
+
+    private SaleDetail currentSale;
+    private final ObservableList<RefundItem> refundItems = FXCollections.observableArrayList();
+    private final NumberFormat currency = NumberFormat.getCurrencyInstance(Locale.CANADA);
+
+    @FXML
+    public void initialize() {
+        setupTables();
+        cbPaymentMethod.setItems(FXCollections.observableArrayList("Cash", "Card", "Debit"));
+        cbPaymentMethod.getSelectionModel().selectFirst();
+        updateRefundTotal();
+    }
+
+    private void setupTables() {
+        colOriginalProduct.setCellValueFactory(new PropertyValueFactory<>("productName"));
+        colOriginalQuantity.setCellValueFactory(new PropertyValueFactory<>("quantity"));
+        colOriginalUnitPrice.setCellValueFactory(new PropertyValueFactory<>("unitPrice"));
+        colOriginalTotal.setCellValueFactory(new PropertyValueFactory<>("total"));
+        tvOriginalItems.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
+
+        colRefundProduct.setCellValueFactory(new PropertyValueFactory<>("productName"));
+        colRefundQuantity.setCellValueFactory(new PropertyValueFactory<>("quantity"));
+        colRefundUnitPrice.setCellValueFactory(new PropertyValueFactory<>("unitPrice"));
+        colRefundTotal.setCellValueFactory(new PropertyValueFactory<>("total"));
+        tvRefundItems.setItems(refundItems);
+        tvRefundItems.getSelectionModel().setSelectionMode(SelectionMode.SINGLE);
+    }
+
+    @FXML
+    void btnLoadSaleClicked(ActionEvent event) {
+        String saleIdText = txtSaleId.getText().trim();
+        if (saleIdText.isEmpty()) {
+            showError("Load Sale", "Enter a transaction ID.");
+            return;
+        }
+
+        int saleId;
+        try {
+            saleId = Integer.parseInt(saleIdText);
+        } catch (NumberFormatException e) {
+            showError("Load Sale", "Invalid transaction ID.");
+            return;
+        }
+
+        try {
+            if (SaleDB.isRefunded(saleId)) {
+                showError("Load Sale", "This sale has already been refunded.");
+                return;
+            }
+
+            currentSale = SaleDB.getSaleById(saleId);
+
+            DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
+            String saleInfo = String.format("Sale Date: %s | Employee: %s | Original Total: %s | Payment: %s",
+                currentSale.getSaleDate().format(formatter),
+                currentSale.getEmployeeName(),
+                currency.format(currentSale.getTotalAmount()),
+                currentSale.getPaymentMethod());
+            lblSaleInfo.setText(saleInfo);
+
+            tvOriginalItems.setItems(currentSale.getItems());
+            cbPaymentMethod.getSelectionModel().select(currentSale.getPaymentMethod());
+
+            refundItems.clear();
+            updateRefundTotal();
+
+        } catch (SQLException e) {
+            ActivityLogger.getInstance().logException("RefundDialogController.btnLoadSaleClicked", e, "Loading sale");
+            showError("Load Sale", e.getMessage() != null ? e.getMessage() : "Could not load sale.");
+        }
+    }
+
+    @FXML
+    void btnAddToRefundClicked(ActionEvent event) {
+        if (currentSale == null) {
+            showError("Add to Refund", "Load a sale first.");
+            return;
+        }
+
+        SaleDetail.SaleDetailItem selected = tvOriginalItems.getSelectionModel().getSelectedItem();
+        if (selected == null) {
+            showError("Add to Refund", "Select an item from the original sale.");
+            return;
+        }
+
+        int alreadyRefunded = refundItems.stream()
+            .filter(r -> r.getProdId() == selected.getProdId())
+            .mapToInt(RefundItem::getQuantity)
+            .sum();
+
+        int available = selected.getQuantity() - alreadyRefunded;
+        if (available <= 0) {
+            showError("Add to Refund", "All items of this product are already in the refund list.");
+            return;
+        }
+
+        TextInputDialog dialog = new TextInputDialog(String.valueOf(available));
+        dialog.setTitle("Refund Quantity");
+        dialog.setHeaderText("Product: " + selected.getProductName());
+        dialog.setContentText("Enter quantity to refund (max " + available + "):");
+
+        Optional<String> result = dialog.showAndWait();
+        if (result.isPresent()) {
+            try {
+                int quantity = Integer.parseInt(result.get().trim());
+                if (quantity <= 0) {
+                    showError("Add to Refund", "Quantity must be at least 1.");
+                    return;
+                }
+                if (quantity > available) {
+                    showError("Add to Refund", "Cannot refund more than " + available + " items.");
+                    return;
+                }
+
+                refundItems.add(new RefundItem(
+                    selected.getProdId(),
+                    selected.getProductName(),
+                    quantity,
+                    selected.getUnitPrice()
+                ));
+                updateRefundTotal();
+
+            } catch (NumberFormatException e) {
+                showError("Add to Refund", "Invalid quantity.");
+            }
+        }
+    }
+
+    @FXML
+    void btnRemoveFromRefundClicked(ActionEvent event) {
+        RefundItem selected = tvRefundItems.getSelectionModel().getSelectedItem();
+        if (selected != null) {
+            refundItems.remove(selected);
+            updateRefundTotal();
+        }
+    }
+
+    @FXML
+    void btnProcessRefundClicked(ActionEvent event) {
+        if (currentSale == null) {
+            showError("Process Refund", "Load a sale first.");
+            return;
+        }
+
+        if (refundItems.isEmpty()) {
+            showError("Process Refund", "Add at least one item to refund.");
+            return;
+        }
+
+        Integer employeeId = UserSession.getInstance().getEmployeeId();
+        if (employeeId == null || employeeId <= 0) {
+            showError("Process Refund", "Employee is not set for this account.");
+            return;
+        }
+
+        String payment = cbPaymentMethod.getSelectionModel().getSelectedItem();
+        if (payment == null || payment.isBlank()) {
+            showError("Process Refund", "Select a payment method.");
+            return;
+        }
+
+        Alert confirm = new Alert(Alert.AlertType.CONFIRMATION);
+        confirm.setTitle("Confirm Refund");
+        confirm.setHeaderText("Process refund for sale ID " + currentSale.getSaleId() + "?");
+        confirm.setContentText("Refund amount: " + lblRefundTotal.getText());
+
+        Optional<ButtonType> confirmResult = confirm.showAndWait();
+        if (confirmResult.isEmpty() || confirmResult.get() != ButtonType.OK) {
+            return;
+        }
+
+        try {
+            ObservableList<SaleCartItem> cartItems = FXCollections.observableArrayList();
+            for (RefundItem item : refundItems) {
+                cartItems.add(new SaleCartItem(item.getProdId(), item.getProductName(), item.getQuantity(), item.getUnitPrice()));
+            }
+
+            int refundId = SaleDB.createRefund(currentSale.getSaleId(), employeeId, payment, cartItems);
+
+            Alert success = new Alert(Alert.AlertType.INFORMATION);
+            success.setTitle("Refund Processed");
+            success.setHeaderText(null);
+            success.setContentText("Refund ID " + refundId + " was created successfully.");
+            success.showAndWait();
+
+            closeDialog();
+
+        } catch (SQLException e) {
+            ActivityLogger.getInstance().logException("RefundDialogController.btnProcessRefundClicked", e, "Processing refund");
+            showError("Process Refund", e.getMessage() != null ? e.getMessage() : "Could not process refund.");
+        }
+    }
+
+    @FXML
+    void btnCancelClicked(ActionEvent event) {
+        closeDialog();
+    }
+
+    private void updateRefundTotal() {
+        double total = refundItems.stream().mapToDouble(RefundItem::getTotal).sum();
+        lblRefundTotal.setText(currency.format(total));
+    }
+
+    private void closeDialog() {
+        Stage stage = (Stage) btnCancel.getScene().getWindow();
+        stage.close();
+    }
+
+    private void showError(String title, String message) {
+        Alert alert = new Alert(Alert.AlertType.ERROR);
+        alert.setTitle(title);
+        alert.setHeaderText(null);
+        alert.setContentText(message);
+        alert.showAndWait();
+    }
+
+    public static class RefundItem {
+        private final int prodId;
+        private final String productName;
+        private final int quantity;
+        private final double unitPrice;
+
+        public RefundItem(int prodId, String productName, int quantity, double unitPrice) {
+            this.prodId = prodId;
+            this.productName = productName;
+            this.quantity = quantity;
+            this.unitPrice = unitPrice;
+        }
+
+        public int getProdId() {
+            return prodId;
+        }
+
+        public String getProductName() {
+            return productName;
+        }
+
+        public int getQuantity() {
+            return quantity;
+        }
+
+        public double getUnitPrice() {
+            return unitPrice;
+        }
+
+        public double getTotal() {
+            return quantity * unitPrice;
+        }
+    }
+}

src/main/java/org/example/petshopdesktop/database/SaleDB.java

@@ -4,6 +4,7 @@ import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
 import org.example.petshopdesktop.DTOs.SaleDTO;
 import org.example.petshopdesktop.models.SaleCartItem;
+import org.example.petshopdesktop.models.SaleDetail;
 import org.example.petshopdesktop.models.SaleLineItem;
 import org.example.petshopdesktop.models.analytics.*;
 import org.example.petshopdesktop.util.ActivityLogger;
@@ -129,7 +130,8 @@ public class SaleDB {
                 si.quantity,
                 si.unitPrice,
                 (si.quantity * si.unitPrice) as total,
-                s.paymentMethod
+                s.paymentMethod,
+                s.isRefund
             FROM sale s
             JOIN saleItem si ON s.saleId = si.saleId
             JOIN product p ON si.prodId = p.prodId
@@ -149,7 +151,8 @@ public class SaleDB {
                 rs.getInt("quantity"),
                 rs.getDouble("unitPrice"),
                 rs.getDouble("total"),
-                rs.getString("paymentMethod")
+                rs.getString("paymentMethod"),
+                rs.getBoolean("isRefund")
             ));
         }
 
@@ -397,4 +400,173 @@ public class SaleDB {
         conn.close();
         return summary;
     }
+
+    public static SaleDetail getSaleById(int saleId) throws SQLException {
+        Connection conn = ConnectionDB.getConnection();
+
+        String saleSql = """
+            SELECT s.saleId, s.saleDate, s.totalAmount, s.paymentMethod,
+                   CONCAT(e.firstName, ' ', e.lastName) as employeeName,
+                   s.isRefund
+            FROM sale s
+            JOIN employee e ON s.employeeId = e.employeeId
+            WHERE s.saleId = ?
+        """;
+
+        PreparedStatement saleStmt = conn.prepareStatement(saleSql);
+        saleStmt.setInt(1, saleId);
+        ResultSet saleRs = saleStmt.executeQuery();
+
+        if (!saleRs.next()) {
+            conn.close();
+            throw new SQLException("Sale not found with ID: " + saleId);
+        }
+
+        boolean isRefund = saleRs.getBoolean("isRefund");
+        if (isRefund) {
+            conn.close();
+            throw new SQLException("Cannot refund a refund transaction");
+        }
+
+        SaleDetail detail = new SaleDetail(
+            saleRs.getInt("saleId"),
+            saleRs.getTimestamp("saleDate").toLocalDateTime(),
+            saleRs.getDouble("totalAmount"),
+            saleRs.getString("paymentMethod"),
+            saleRs.getString("employeeName"),
+            FXCollections.observableArrayList()
+        );
+
+        String itemsSql = """
+            SELECT si.prodId, p.prodName, si.quantity, si.unitPrice,
+                   (si.quantity * si.unitPrice) as total
+            FROM saleItem si
+            JOIN product p ON si.prodId = p.prodId
+            WHERE si.saleId = ?
+        """;
+
+        PreparedStatement itemsStmt = conn.prepareStatement(itemsSql);
+        itemsStmt.setInt(1, saleId);
+        ResultSet itemsRs = itemsStmt.executeQuery();
+
+        while (itemsRs.next()) {
+            detail.getItems().add(new SaleDetail.SaleDetailItem(
+                itemsRs.getInt("prodId"),
+                itemsRs.getString("prodName"),
+                itemsRs.getInt("quantity"),
+                itemsRs.getDouble("unitPrice"),
+                itemsRs.getDouble("total")
+            ));
+        }
+
+        conn.close();
+        return detail;
+    }
+
+    public static boolean isRefunded(int saleId) throws SQLException {
+        Connection conn = ConnectionDB.getConnection();
+
+        String sql = """
+            SELECT COUNT(*) as refundCount
+            FROM sale
+            WHERE originalSaleId = ? AND isRefund = TRUE
+        """;
+
+        PreparedStatement pstmt = conn.prepareStatement(sql);
+        pstmt.setInt(1, saleId);
+        ResultSet rs = pstmt.executeQuery();
+
+        boolean refunded = false;
+        if (rs.next()) {
+            refunded = rs.getInt("refundCount") > 0;
+        }
+
+        conn.close();
+        return refunded;
+    }
+
+    public static int createRefund(int originalSaleId, int employeeId, String paymentMethod, ObservableList<SaleCartItem> refundItems) throws SQLException {
+        if (refundItems.isEmpty()) {
+            throw new SQLException("Cannot create refund with empty items");
+        }
+
+        Connection conn = ConnectionDB.getConnection();
+
+        SaleDetail originalSale = getSaleById(originalSaleId);
+        conn = ConnectionDB.getConnection();
+
+        if (isRefunded(originalSaleId)) {
+            throw new SQLException("This sale has already been refunded");
+        }
+
+        conn.setAutoCommit(false);
+
+        try {
+            double totalAmount = -refundItems.stream().mapToDouble(SaleCartItem::getTotal).sum();
+
+            String insertSale = """
+                INSERT INTO sale (saleDate, totalAmount, paymentMethod, employeeId, storeId, isRefund, originalSaleId)
+                VALUES (NOW(), ?, ?, ?, 1, TRUE, ?)
+            """;
+
+            PreparedStatement saleStmt = conn.prepareStatement(insertSale, Statement.RETURN_GENERATED_KEYS);
+            saleStmt.setDouble(1, totalAmount);
+            saleStmt.setString(2, paymentMethod);
+            saleStmt.setInt(3, employeeId);
+            saleStmt.setInt(4, originalSaleId);
+            saleStmt.executeUpdate();
+
+            ResultSet rs = saleStmt.getGeneratedKeys();
+            if (!rs.next()) {
+                throw new SQLException("Failed to get generated refund ID");
+            }
+            int refundId = rs.getInt(1);
+
+            String insertItem = """
+                INSERT INTO saleItem (saleId, prodId, quantity, unitPrice)
+                VALUES (?, ?, ?, ?)
+            """;
+
+            String updateInventory = """
+                UPDATE inventory
+                SET quantity = quantity + ?
+                WHERE prodId = ?
+            """;
+
+            PreparedStatement itemStmt = conn.prepareStatement(insertItem);
+            PreparedStatement invStmt = conn.prepareStatement(updateInventory);
+
+            for (SaleCartItem item : refundItems) {
+                itemStmt.setInt(1, refundId);
+                itemStmt.setInt(2, item.getProdId());
+                itemStmt.setInt(3, -item.getQuantity());
+                itemStmt.setDouble(4, item.getUnitPrice());
+                itemStmt.executeUpdate();
+
+                invStmt.setInt(1, item.getQuantity());
+                invStmt.setInt(2, item.getProdId());
+                int updated = invStmt.executeUpdate();
+
+                if (updated == 0) {
+                    throw new SQLException("Failed to update inventory for product ID " + item.getProdId());
+                }
+            }
+
+            conn.commit();
+
+            ActivityLogger.getInstance().logInsert("sale",
+                String.format("Refund ID: %d", refundId),
+                String.format("Created refund for sale ID %d with %d items, total: $%.2f", originalSaleId, refundItems.size(), Math.abs(totalAmount)));
+
+            return refundId;
+
+        } catch (SQLException e) {
+            conn.rollback();
+            ActivityLogger.getInstance().logException("SaleDB.createRefund", e, "Creating refund");
+            throw e;
+        } finally {
+            conn.setAutoCommit(true);
+            conn.close();
+        }
+    }
 }

src/main/java/org/example/petshopdesktop/models/SaleDetail.java

@@ -0,0 +1,82 @@
+package org.example.petshopdesktop.models;
+
+import javafx.collections.ObservableList;
+import java.time.LocalDateTime;
+
+public class SaleDetail {
+    private final int saleId;
+    private final LocalDateTime saleDate;
+    private final double totalAmount;
+    private final String paymentMethod;
+    private final String employeeName;
+    private final ObservableList<SaleDetailItem> items;
+
+    public SaleDetail(int saleId, LocalDateTime saleDate, double totalAmount, String paymentMethod, String employeeName, ObservableList<SaleDetailItem> items) {
+        this.saleId = saleId;
+        this.saleDate = saleDate;
+        this.totalAmount = totalAmount;
+        this.paymentMethod = paymentMethod;
+        this.employeeName = employeeName;
+        this.items = items;
+    }
+
+    public int getSaleId() {
+        return saleId;
+    }
+
+    public LocalDateTime getSaleDate() {
+        return saleDate;
+    }
+
+    public double getTotalAmount() {
+        return totalAmount;
+    }
+
+    public String getPaymentMethod() {
+        return paymentMethod;
+    }
+
+    public String getEmployeeName() {
+        return employeeName;
+    }
+
+    public ObservableList<SaleDetailItem> getItems() {
+        return items;
+    }
+
+    public static class SaleDetailItem {
+        private final int prodId;
+        private final String productName;
+        private final int quantity;
+        private final double unitPrice;
+        private final double total;
+
+        public SaleDetailItem(int prodId, String productName, int quantity, double unitPrice, double total) {
+            this.prodId = prodId;
+            this.productName = productName;
+            this.quantity = quantity;
+            this.unitPrice = unitPrice;
+            this.total = total;
+        }
+
+        public int getProdId() {
+            return prodId;
+        }
+
+        public String getProductName() {
+            return productName;
+        }
+
+        public int getQuantity() {
+            return quantity;
+        }
+
+        public double getUnitPrice() {
+            return unitPrice;
+        }
+
+        public double getTotal() {
+            return total;
+        }
+    }
+}

src/main/java/org/example/petshopdesktop/models/SaleLineItem.java

@@ -9,8 +9,9 @@ public class SaleLineItem {
     private final double unitPrice;
     private final double total;
     private final String paymentMethod;
+    private final boolean isRefund;
 
-    public SaleLineItem(int saleId, String saleDate, String employeeName, String itemName, int quantity, double unitPrice, double total, String paymentMethod) {
+    public SaleLineItem(int saleId, String saleDate, String employeeName, String itemName, int quantity, double unitPrice, double total, String paymentMethod, boolean isRefund) {
         this.saleId = saleId;
         this.saleDate = saleDate;
         this.employeeName = employeeName;
@@ -19,6 +20,7 @@ public class SaleLineItem {
         this.unitPrice = unitPrice;
         this.total = total;
         this.paymentMethod = paymentMethod;
+        this.isRefund = isRefund;
     }
 
     public int getSaleId() {
@@ -52,4 +54,8 @@ public class SaleLineItem {
     public String getPaymentMethod() {
         return paymentMethod;
     }
+
+    public boolean isRefund() {
+        return isRefund;
+    }
 }

src/main/resources/org/example/petshopdesktop/dialogviews/refund-dialog-view.fxml

@@ -0,0 +1,192 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<?import javafx.geometry.Insets?>
+<?import javafx.scene.control.Button?>
+<?import javafx.scene.control.ComboBox?>
+<?import javafx.scene.control.Label?>
+<?import javafx.scene.control.Separator?>
+<?import javafx.scene.control.TableColumn?>
+<?import javafx.scene.control.TableView?>
+<?import javafx.scene.control.TextField?>
+<?import javafx.scene.layout.HBox?>
+<?import javafx.scene.layout.Region?>
+<?import javafx.scene.layout.VBox?>
+<?import javafx.scene.text.Font?>
+
+<VBox minHeight="-Infinity" minWidth="-Infinity" prefHeight="700.0" prefWidth="900.0" spacing="20.0" style="-fx-font-size: 14px;" xmlns="http://javafx.com/javafx/17" xmlns:fx="http://javafx.com/fxml/1" fx:controller="org.example.petshopdesktop.controllers.dialogcontrollers.RefundDialogController">
+   <padding>
+      <Insets bottom="20.0" left="20.0" right="20.0" top="20.0" />
+   </padding>
+   <children>
+      <HBox alignment="CENTER_LEFT" spacing="20.0" style="-fx-background-color: #FF6b6b; -fx-background-radius: 14;">
+         <padding>
+            <Insets bottom="15.0" left="15.0" right="15.0" top="15.0" />
+         </padding>
+         <children>
+            <VBox alignment="CENTER_LEFT">
+               <children>
+                  <Label text="Process Refund" textFill="WHITE">
+                     <font>
+                        <Font name="Comic Sans MS Bold" size="30.0" />
+                     </font>
+                  </Label>
+               </children>
+            </VBox>
+            <Region HBox.hgrow="ALWAYS" />
+            <Button fx:id="btnCancel" mnemonicParsing="false" onAction="#btnCancelClicked" style="-fx-background-color: #E74c3c; -fx-cursor: hand; -fx-background-radius: 8;" text="Cancel" textFill="WHITE">
+               <font>
+                  <Font name="System Bold" size="14.0" />
+               </font>
+               <padding>
+                  <Insets bottom="12.0" left="24.0" right="24.0" top="12.0" />
+               </padding>
+            </Button>
+         </children>
+      </HBox>
+
+      <VBox spacing="15.0" style="-fx-background-color: white; -fx-background-radius: 14; -fx-border-width: 2; -fx-border-color: #FF6b6b; -fx-border-radius: 14;">
+         <padding>
+            <Insets bottom="15.0" left="15.0" right="15.0" top="15.0" />
+         </padding>
+         <children>
+            <Label text="Load Sale" textFill="#2c3e50">
+               <font>
+                  <Font name="System Bold" size="18.0" />
+               </font>
+            </Label>
+            <HBox alignment="CENTER_LEFT" spacing="10.0">
+               <children>
+                  <Label text="Transaction ID:" textFill="#2c3e50">
+                     <font>
+                        <Font name="System Bold" size="14.0" />
+                     </font>
+                  </Label>
+                  <TextField fx:id="txtSaleId" prefWidth="150.0" promptText="Enter sale ID" style="-fx-border-color: #E8EBED; -fx-border-width: 2; -fx-border-radius: 10; -fx-background-radius: 10;">
+                     <padding>
+                        <Insets bottom="7.0" left="10.0" right="10.0" top="7.0" />
+                     </padding>
+                  </TextField>
+                  <Button fx:id="btnLoadSale" mnemonicParsing="false" onAction="#btnLoadSaleClicked" style="-fx-background-color: #4ECDC4; -fx-cursor: hand; -fx-background-radius: 8;" text="Load Sale" textFill="WHITE">
+                     <font>
+                        <Font name="System Bold" size="13.0" />
+                     </font>
+                     <padding>
+                        <Insets bottom="8.0" left="18.0" right="18.0" top="8.0" />
+                     </padding>
+                  </Button>
+               </children>
+            </HBox>
+            <Label fx:id="lblSaleInfo" text="" textFill="#7f8c8d">
+               <font>
+                  <Font size="14.0" />
+               </font>
+            </Label>
+         </children>
+      </VBox>
+
+      <VBox spacing="10.0" style="-fx-background-color: white; -fx-background-radius: 14; -fx-border-width: 2; -fx-border-color: #FF6b6b; -fx-border-radius: 14;" VBox.vgrow="ALWAYS">
+         <padding>
+            <Insets bottom="15.0" left="15.0" right="15.0" top="15.0" />
+         </padding>
+         <children>
+            <HBox alignment="CENTER_LEFT" spacing="10.0">
+               <children>
+                  <Label text="Original Items" textFill="#2c3e50">
+                     <font>
+                        <Font name="System Bold" size="16.0" />
+                     </font>
+                  </Label>
+                  <Region HBox.hgrow="ALWAYS" />
+                  <Button fx:id="btnAddToRefund" mnemonicParsing="false" onAction="#btnAddToRefundClicked" style="-fx-background-color: #FF6b6b; -fx-cursor: hand; -fx-background-radius: 8;" text="Add to Refund" textFill="WHITE">
+                     <font>
+                        <Font name="System Bold" size="13.0" />
+                     </font>
+                     <padding>
+                        <Insets bottom="8.0" left="18.0" right="18.0" top="8.0" />
+                     </padding>
+                  </Button>
+               </children>
+            </HBox>
+            <TableView fx:id="tvOriginalItems" prefHeight="150.0" style="-fx-background-color: white; -fx-background-radius: 10;">
+               <columns>
+                  <TableColumn fx:id="colOriginalProduct" prefWidth="350.0" text="Product Name" />
+                  <TableColumn fx:id="colOriginalQuantity" prefWidth="120.0" text="Quantity" />
+                  <TableColumn fx:id="colOriginalUnitPrice" prefWidth="150.0" text="Unit Price" />
+                  <TableColumn fx:id="colOriginalTotal" prefWidth="150.0" text="Total" />
+               </columns>
+            </TableView>
+
+            <Separator />
+
+            <HBox alignment="CENTER_LEFT" spacing="10.0">
+               <children>
+                  <Label text="Refund Items" textFill="#2c3e50">
+                     <font>
+                        <Font name="System Bold" size="16.0" />
+                     </font>
+                  </Label>
+                  <Region HBox.hgrow="ALWAYS" />
+                  <Button fx:id="btnRemoveFromRefund" mnemonicParsing="false" onAction="#btnRemoveFromRefundClicked" style="-fx-background-color: #34495E; -fx-cursor: hand; -fx-background-radius: 8;" text="Remove Selected" textFill="WHITE">
+                     <font>
+                        <Font name="System Bold" size="13.0" />
+                     </font>
+                     <padding>
+                        <Insets bottom="8.0" left="18.0" right="18.0" top="8.0" />
+                     </padding>
+                  </Button>
+               </children>
+            </HBox>
+            <TableView fx:id="tvRefundItems" prefHeight="150.0" style="-fx-background-color: white; -fx-background-radius: 10;">
+               <columns>
+                  <TableColumn fx:id="colRefundProduct" prefWidth="350.0" text="Product Name" />
+                  <TableColumn fx:id="colRefundQuantity" prefWidth="120.0" text="Quantity" />
+                  <TableColumn fx:id="colRefundUnitPrice" prefWidth="150.0" text="Unit Price" />
+                  <TableColumn fx:id="colRefundTotal" prefWidth="150.0" text="Total" />
+               </columns>
+            </TableView>
+         </children>
+      </VBox>
+
+      <VBox spacing="12.0" style="-fx-background-color: white; -fx-background-radius: 14; -fx-border-width: 2; -fx-border-color: #FF6b6b; -fx-border-radius: 14;">
+         <padding>
+            <Insets bottom="15.0" left="15.0" right="15.0" top="15.0" />
+         </padding>
+         <children>
+            <HBox alignment="CENTER_LEFT" spacing="15.0">
+               <children>
+                  <Label text="Payment Method:" textFill="#2c3e50">
+                     <font>
+                        <Font name="System Bold" size="14.0" />
+                     </font>
+                  </Label>
+                  <ComboBox fx:id="cbPaymentMethod" prefWidth="160.0" style="-fx-border-color: #E8EBED; -fx-border-width: 2; -fx-border-radius: 10; -fx-background-radius: 10; -fx-background-color: white;">
+                     <padding>
+                        <Insets bottom="3.0" left="10.0" right="10.0" top="3.0" />
+                     </padding>
+                  </ComboBox>
+                  <Region HBox.hgrow="ALWAYS" />
+                  <Label text="Refund Total:" textFill="#2c3e50">
+                     <font>
+                        <Font name="System Bold" size="14.0" />
+                     </font>
+                  </Label>
+                  <Label fx:id="lblRefundTotal" text="\$0.00" textFill="#FF6b6b">
+                     <font>
+                        <Font name="System Bold" size="18.0" />
+                     </font>
+                  </Label>
+                  <Region prefWidth="20.0" />
+                  <Button fx:id="btnProcessRefund" mnemonicParsing="false" onAction="#btnProcessRefundClicked" style="-fx-background-color: #FF6b6b; -fx-cursor: hand; -fx-background-radius: 8;" text="Process Refund" textFill="WHITE">
+                     <font>
+                        <Font name="System Bold" size="14.0" />
+                     </font>
+                     <padding>
+                        <Insets bottom="12.0" left="24.0" right="24.0" top="12.0" />
+                     </padding>
+                  </Button>
+               </children>
+            </HBox>
+         </children>
+      </VBox>
+   </children>
+</VBox>

src/main/resources/org/example/petshopdesktop/modelviews/sale-view.fxml

@@ -38,6 +38,14 @@
                </padding>
             </Label>
             <Region prefHeight="200.0" prefWidth="200.0" HBox.hgrow="ALWAYS" />
+            <Button fx:id="btnRefund" mnemonicParsing="false" onAction="#btnRefund" prefHeight="44.0" style="-fx-background-color: #FF6b6b; -fx-cursor: hand; -fx-background-radius: 8;" text="Process Refund" textFill="WHITE">
+               <font>
+                  <Font name="System Bold" size="14.0" />
+               </font>
+               <padding>
+                  <Insets bottom="12.0" left="24.0" right="24.0" top="12.0" />
+               </padding>
+            </Button>
             <Button fx:id="btnRefresh" mnemonicParsing="false" onAction="#btnRefresh" prefHeight="44.0" prefWidth="118.0" style="-fx-background-color: #4ECDC4; -fx-cursor: hand; -fx-background-radius: 8;" text="Refresh" textFill="WHITE">
                <font>
                   <Font name="System Bold" size="14.0" />