package com.example.bankcards.util;

import java.util.Base64;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class CardEncryptionUtil {

    @Value("${app.card.encryption-key}")
    private String encryptionKey;

    private static final String ALGORITHM = "AES";

    public String encrypt(String cardNumber) {
        try {
            SecretKeySpec keySpec = new SecretKeySpec(
                encryptionKey.getBytes(),
                ALGORITHM
            );
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, keySpec);
            byte[] encrypted = cipher.doFinal(cardNumber.getBytes());
            return Base64.getEncoder().encodeToString(encrypted);
        } catch (Exception e) {
            throw new RuntimeException("Failed to encrypt card number", e);
        }
    }

    public String decrypt(String encryptedCardNumber) {
        try {
            SecretKeySpec keySpec = new SecretKeySpec(
                encryptionKey.getBytes(),
                ALGORITHM
            );
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, keySpec);
            byte[] decoded = Base64.getDecoder().decode(encryptedCardNumber);
            byte[] decrypted = cipher.doFinal(decoded);
            return new String(decrypted);
        } catch (Exception e) {
            throw new RuntimeException("Failed to decrypt card number", e);
        }
    }

    public String mask(String cardNumber) {
        if (cardNumber == null || cardNumber.length() < 4) {
            return "****";
        }
        String lastFour = cardNumber.substring(cardNumber.length() - 4);
        return "**** **** **** " + lastFour;
    }
}