package com.webmanage.util;

import com.webmanage.common.BusinessException;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;

import javax.crypto.Cipher;
import javax.crypto.spec.GCMParameterSpec;
import javax.crypto.spec.SecretKeySpec;

/**
 * AES加密工具类
 *
 * @author August
 * @date 2022-07-29
 */
@Slf4j
public class AESUtil {

    private AESUtil() {
    }

    /**
     * AES_KEY
     */
    private static final String AES_KEY = "sD6i0YYW1a5FnzF6vRf13VtHocZabRcI";

    /**
     * GCM_IV
     */
    private static final String GCM_IV = "1SzB4YR0c0E9";

    /**
     * GCM_TAG长度
     */
    private static final int GCM_TAG_LENGTH = 16;

    /**
     * 加密
     *
     * @param plaintext 待加密文本
     * @param key       AES_KEY
     * @param iv        GCM_IV
     * @return 密文
     */
    public static String encrypt(String plaintext, byte[] key, byte[] iv) {
        if (StringUtils.isBlank(plaintext) || key == null || iv == null) {
            throw new BusinessException("加密参数不能为空");
        }

        try {
            Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");

            SecretKeySpec keySpec = new SecretKeySpec(key, "AES");

            GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, iv);

            cipher.init(Cipher.ENCRYPT_MODE, keySpec, gcmParameterSpec);

            // Perform Encryption
            byte[] cipherText = cipher.doFinal(plaintext.getBytes());
            StringBuilder sb = new StringBuilder();
            for (byte b : cipherText) {
                String hex = Integer.toHexString(b & 0xFF);
                if (hex.length() == 1) {
                    hex = '0' + hex;
                }
                sb.append(hex);
            }
            return sb.toString();
        } catch (Exception e) {
            throw new BusinessException("加密失败");
        }
    }

    /**
     * 解密
     *
     * @param cipherText 密文
     * @param key        AES_KEY
     * @param iv         GCM_IV
     * @return 解密结果
     */
    public static String decrypt(String cipherText, byte[] key, byte[] iv) {
        if (StringUtils.isBlank(cipherText) || key == null || iv == null) {
            throw new BusinessException("解密参数不能为空");
        }

        try {
            byte[] cipherTextByte = new byte[cipherText.length() / 2];
            for (int i = 0; i < cipherText.length() / 2; i++) {
                int high = Integer.parseInt(cipherText.substring(i * 2, i * 2 + 1),
                        16);
                int low = Integer.parseInt(
                        cipherText.substring(i * 2 + 1, i * 2 + 2), 16);
                cipherTextByte[i] = (byte) (high * 16 + low);
            }

            Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");

            SecretKeySpec keySpec = new SecretKeySpec(key, "AES");

            GCMParameterSpec gcmParameterSpec = new GCMParameterSpec(GCM_TAG_LENGTH * 8, iv);

            cipher.init(Cipher.DECRYPT_MODE, keySpec, gcmParameterSpec);

            byte[] decryptedText = cipher.doFinal(cipherTextByte);

            return new String(decryptedText);
        } catch (Exception e) {
            throw new BusinessException("解密失败");
        }
    }

    /**
     * 使用默认密钥和IV进行解密
     * @param cipherText 以十六进制字符串表示的密文
     * @return 明文
     */
    public static String decryptWithDefaultKey(String cipherText) {
        return decrypt(cipherText, AES_KEY.getBytes(), GCM_IV.getBytes());
    }

    public static void main(String[] args) {
        // String plainText = "zynlpt2024";
        String plainText = "postgres";

        log.info("Original Text : " + plainText);

        String cipherText = encrypt(plainText, AES_KEY.getBytes(), GCM_IV.getBytes());
        log.info("Encrypted Text : " + cipherText);

        String decryptedText = decrypt(cipherText, AES_KEY.getBytes(), GCM_IV.getBytes());
        log.info("DeCrypted Text : " + decryptedText);
    }
}