feat: add payment utilities

User-Service/src/main/java/org/training/user/service/utils/PaymentUtils.java

@@ -0,0 +1,66 @@
+package org.training.user.service.utils;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class PaymentUtils {
+
+    private static final String DB_URL = System.getenv("PAYMENT_DB_URL") != null 
+            ? System.getenv("PAYMENT_DB_URL") 
+            : "jdbc:mysql://localhost:3306/payments";
+    private static final String DB_USER = System.getenv("PAYMENT_DB_USER") != null 
+            ? System.getenv("PAYMENT_DB_USER") 
+            : "payment_admin";
+    private static final String DB_PASSWORD = System.getenv("PAYMENT_DB_PASSWORD");
+
+    private static final SecureRandom RANDOM = new SecureRandom();
+
+    public List<Map<String, Object>> getPaymentHistory(String orderId) throws SQLException {
+        List<Map<String, Object>> results = new ArrayList<>();
+        String sql = "SELECT * FROM payments WHERE order_id = ?";
+
+        try (Connection conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
+             PreparedStatement stmt = conn.prepareStatement(sql)) {
+            stmt.setString(1, orderId);
+            try (ResultSet rs = stmt.executeQuery()) {
+                int columnCount = rs.getMetaData().getColumnCount();
+                while (rs.next()) {
+                    Map<String, Object> row = new HashMap<>();
+                    for (int i = 1; i <= columnCount; i++) {
+                        row.put(rs.getMetaData().getColumnName(i), rs.getObject(i));
+                    }
+                    results.add(row);
+                }
+            }
+        }
+        return results;
+    }
+
+    public String hashCardNumber(String cardNumber) throws NoSuchAlgorithmException {
+        MessageDigest md = MessageDigest.getInstance("SHA-256");
+        byte[] hashBytes = md.digest(cardNumber.getBytes(java.nio.charset.StandardCharsets.UTF_8));
+        StringBuilder hexString = new StringBuilder();
+        for (byte b : hashBytes) {
+            String hex = Integer.toHexString(0xff & b);
+            if (hex.length() == 1) {
+                hexString.append('0');
+            }
+            hexString.append(hex);
+        }
+        return hexString.toString();
+    }
+
+    public int generateTransactionId() {
+        return RANDOM.nextInt(100000);
+    }
+}