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{
    "partnerOrderId": "202512XXXX031300011032631762517",
    "partnerOrderAmount": 52231,
    "currency": "MXN",
    "expireTime": "2025-12-09T01:11:33.000+08:00",
    "finishTime": "2025-12-08T01:12:08.000+08:00",
    "createTime": "2025-12-08T01:11:33.000+08:00",
    "updateTime": "2025-12-08T01:12:08.000+08:00",
    "rejectCode": "",
    "rejectMsg": "",
    "test": true
}

{
    "partnerOrderId": "16000227_20260XXXX796022901278864",
    "partnerRefundId": "16000227_KBOtXXXX20260127202943864",
    "refundAmount": 9999,
    "currency": "MXN",
    "rejectCode": "",
    "rejectMsg": "",
    "refundTime": "2026-01-27T20:29:43.000+08:00",
    "createTime": "2026-01-27T20:29:43.000+08:00",
    "updateTime": "2026-01-27T20:29:48.000+08:00",
    "test": true
}

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.time.Instant;

/**
 * HMAC-SHA512 Signature verification tools
 * Format: eventId:timestamp:data
 * Signature result: hexadecimal string
 */
public class HMACSHA512HexSignerVerify {

    private static final String HMAC_SHA512 = "HmacSHA512";
    private static final String DELIMITER = ":";

    /**
     * Verify signature
     *
     * @param eventId       event ID, value description: X-Event-ID in the request header
     * @param data          data, value description: The complete response of the request
     * @param signature     The signature to be verified (hexadecimal string), value description: X-Event-Signature in the request header
     * @param secretKey     key, value description: The unique signature key generated when a tenant adds a subscription
     * @param timestamp     timestamp (in seconds), take X-Event-Timestamp from the header
     * @param maxAgeSeconds signature maximum validity period (seconds), 0 indicates no validity period verification
     * @return verification result
     */
    public static boolean verifySignature(
            String eventId,
            String data,
            String signature,
            String secretKey,
            long timestamp,
            long maxAgeSeconds) {

        try {
            // Verify the validity period of the timestamp
            if (maxAgeSeconds > 0) {
                long currentTime = Instant.now().getEpochSecond();
                if (Math.abs(currentTime - timestamp) > maxAgeSeconds) {
                    return false; // The signature has expired.
                }
            }

            // Recalculate the signature
            String expectedSignature = generateSignature(eventId, data, secretKey, timestamp);

            // Security comparison of the signature
            return constantTimeEquals(expectedSignature.toLowerCase(), signature.toLowerCase());

        } catch (Exception e) {
            return false;
        }
    }

    /**
     * Generate a signature (hexadecimal string with a timestamp)
     *
     * @param eventId   event ID
     * @param data      data
     * @param secretKey key
     * @param timestamp Timestamp (in seconds)
     * @return hexadecimal string signature
     */
    public static String generateSignature(String eventId, String data, String secretKey, long timestamp) {
        try {
            // Build the payload
            String payload = eventId + DELIMITER + timestamp + DELIMITER + data;

            // Calculate HMAC-SHA512
            Mac mac = Mac.getInstance(HMAC_SHA512);
            SecretKeySpec secretKeySpec = new SecretKeySpec(
                    secretKey.getBytes(StandardCharsets.UTF_8),
                    HMAC_SHA512
            );
            mac.init(secretKeySpec);
            byte[] hashBytes = mac.doFinal(payload.getBytes(StandardCharsets.UTF_8));

            // Convert to a hexadecimal string
            return bytesToHex(hashBytes);

        } catch (NoSuchAlgorithmException | InvalidKeyException e) {
            throw new RuntimeException("Failed to generate the signature", e);
        }
    }

    /**
     * Convert a byte array to a hexadecimal string
     *
     * @param bytes byte array
     * @return hexadecimal string
     */
    private static String bytesToHex(byte[] bytes) {
        StringBuilder hexString = new StringBuilder();
        for (byte b : bytes) {
            String hex = Integer.toHexString(0xff & b);
            if (hex.length() == 1) {
                hexString.append('0');
            }
            hexString.append(hex);
        }
        return hexString.toString();
    }

    /**
     * Secure string comparison (preventing timing attacks)
     *
     * @param str1 string1
     * @param str2 string2
     * @return whether they are equal
     */
    private static boolean constantTimeEquals(String str1, String str2) {
        if (str1 == null || str2 == null) {
            return false;
        }

        if (str1.length() != str2.length()) {
            return false;
        }

        int result = 0;
        for (int i = 0; i < str1.length(); i++) {
            result |= str1.charAt(i) ^ str2.charAt(i);
        }
        return result == 0;
    }

}