package com.zhangyy3.tuantuan.common;

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.encoders.Base64;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.Key;
import java.security.Security;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public final class EncryptedUtil {
  
  private EncryptedUtil() {
  }

  private static final String KEY_ALGORITHM = "AES";
  private static final String ALGORITHM_STR = "AES/CBC/PKCS7Padding";
  private static Key key;
  private static Cipher cipher;
  private static final Logger LOGGER = LoggerFactory.getLogger(EncryptedUtil.class);

  public static String decryptData(String encryptDataB64, String sessionKeyB64, String ivB64) {
    return new String(
      decryptOfDiyIV(
        Base64.decode(encryptDataB64),
        Base64.decode(sessionKeyB64),
        Base64.decode(ivB64)
      )
    );
  }

  private static void init(byte[] keyBytes) {
    // 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
    int base = 16;
    if (keyBytes.length % base != 0) {
        int groups = keyBytes.length / base + (keyBytes.length % base != 0 ? 1 : 0);
        byte[] temp = new byte[groups * base];
        Arrays.fill(temp, (byte) 0);
        System.arraycopy(keyBytes, 0, temp, 0, keyBytes.length);
        keyBytes = temp;
    }
    // 初始化
    Security.addProvider(new BouncyCastleProvider());
    // 转化成JAVA的密钥格式
    key = new SecretKeySpec(keyBytes, KEY_ALGORITHM);
    try {
        // 初始化cipher
        cipher = Cipher.getInstance(ALGORITHM_STR, "BC");
    } catch (Exception e) {
        e.printStackTrace();
    }
  }

  /**
     * 解密方法
     *
     * @param encryptedData 要解密的字符串
     * @param keyBytes      解密密钥
     * @param ivs           自定义对称解密算法初始向量 iv
     * @return 解密后的字节数组
     */
    private static byte[] decryptOfDiyIV(byte[] encryptedData, byte[] keyBytes, byte[] ivs) {
      byte[] encryptedText = null;
      init(keyBytes);
      try {
          cipher.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(ivs));
          encryptedText = cipher.doFinal(encryptedData);
      } catch (Exception e) {
          e.printStackTrace();
      }
      return encryptedText;
  }
  

}

// 代码是这样的