Add getSaleLineItems and createSale methods

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

@@ -3,6 +3,9 @@ package org.example.petshopdesktop.database;
 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.SaleLineItem;
+import org.example.petshopdesktop.util.ActivityLogger;
 
 import java.sql.*;
 
@@ -110,4 +113,121 @@ public class SaleDB {
         conn.close();
         return sales;
     }
+
+    public static ObservableList<SaleLineItem> getSaleLineItems() throws SQLException {
+        ObservableList<SaleLineItem> saleItems = FXCollections.observableArrayList();
+        Connection conn = ConnectionDB.getConnection();
+
+        String sql = """
+            SELECT
+                s.saleId,
+                DATE_FORMAT(s.saleDate, '%Y-%m-%d %H:%i') as saleDate,
+                CONCAT(e.firstName, ' ', e.lastName) as employeeName,
+                p.prodName,
+                si.quantity,
+                si.unitPrice,
+                (si.quantity * si.unitPrice) as total,
+                s.paymentMethod
+            FROM sale s
+            JOIN saleItem si ON s.saleId = si.saleId
+            JOIN product p ON si.prodId = p.prodId
+            JOIN employee e ON s.employeeId = e.employeeId
+            ORDER BY s.saleDate DESC, s.saleId, si.saleItemId
+        """;
+
+        Statement stmt = conn.createStatement();
+        ResultSet rs = stmt.executeQuery(sql);
+
+        while (rs.next()) {
+            saleItems.add(new SaleLineItem(
+                rs.getInt("saleId"),
+                rs.getString("saleDate"),
+                rs.getString("employeeName"),
+                rs.getString("prodName"),
+                rs.getInt("quantity"),
+                rs.getDouble("unitPrice"),
+                rs.getDouble("total"),
+                rs.getString("paymentMethod")
+            ));
+        }
+
+        conn.close();
+        return saleItems;
+    }
+
+    public static int createSale(int employeeId, String paymentMethod, ObservableList<SaleCartItem> cartItems) throws SQLException {
+        if (cartItems.isEmpty()) {
+            throw new SQLException("Cannot create sale with empty cart");
+        }
+
+        Connection conn = ConnectionDB.getConnection();
+        conn.setAutoCommit(false);
+
+        try {
+            double totalAmount = cartItems.stream().mapToDouble(SaleCartItem::getTotal).sum();
+
+            String insertSale = """
+                INSERT INTO sale (saleDate, totalAmount, paymentMethod, employeeId, storeId)
+                VALUES (NOW(), ?, ?, ?, 1)
+            """;
+
+            PreparedStatement saleStmt = conn.prepareStatement(insertSale, Statement.RETURN_GENERATED_KEYS);
+            saleStmt.setDouble(1, totalAmount);
+            saleStmt.setString(2, paymentMethod);
+            saleStmt.setInt(3, employeeId);
+            saleStmt.executeUpdate();
+
+            ResultSet rs = saleStmt.getGeneratedKeys();
+            if (!rs.next()) {
+                throw new SQLException("Failed to get generated sale ID");
+            }
+            int saleId = 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 : cartItems) {
+                itemStmt.setInt(1, saleId);
+                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("Sale ID: %d", saleId),
+                String.format("Created sale with %d items, total: $%.2f", cartItems.size(), totalAmount));
+
+            return saleId;
+
+        } catch (SQLException e) {
+            conn.rollback();
+            ActivityLogger.getInstance().logException("SaleDB.createSale", e, "Creating sale");
+            throw e;
+        } finally {
+            conn.setAutoCommit(true);
+            conn.close();
+        }
+    }
 }