package com.ssm.manage.utils;

import com.alibaba.fastjson.JSONObject;
import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import javax.management.openmbean.InvalidKeyException;
import java.io.UnsupportedEncodingException;
import java.security.AlgorithmParameters;
import java.security.InvalidAlgorithmParameterException;
import java.security.NoSuchAlgorithmException;
import java.security.Security;
import java.security.spec.InvalidParameterSpecException;
import java.util.Arrays;

/**
 * 解密工具类
 */
public class AesCbcUtil {

    /**
     * AES解密
     *
     * @param encryptedData  包括敏感数据在内的完整用户信息的加密数据，
     * @param sessionKey    seccess_key秘钥
     * @param iv     加密算法的初始向量，
     * @return JSONObject
     * @see  Exception
     */
    public static JSONObject decrypt(String encryptedData, String sessionKey, String iv) throws Exception {

        //被加密的数据
        byte[] dataByte = Base64.decode(encryptedData);
        //加密秘钥
        byte[] keyByte = Base64.decode(sessionKey);
        //偏移量
        byte[] ivByte = Base64.decode(iv);

        // 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 (keyByte.length % base != 0) {
            int groups = keyByte.length / base + (keyByte.length % base != 0 ? 1 : 0);
            byte[] temp = new byte[groups * base];
            Arrays.fill(temp, (byte) 0);
            System.arraycopy(keyByte, 0, temp, 0, keyByte.length);
            keyByte = temp;
        }

        try {
            // 初始化
            Security.addProvider(new BouncyCastleProvider());
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS7Padding","BC");
            SecretKeySpec spec = new SecretKeySpec(keyByte, "AES");
            AlgorithmParameters parameters = AlgorithmParameters.getInstance("AES");
            parameters.init(new IvParameterSpec(ivByte));
            cipher.init(Cipher.DECRYPT_MODE, spec, parameters);// 初始化
            byte[] resultByte = cipher.doFinal(dataByte);
            if (null != resultByte && resultByte.length > 0) {
                String result = new String(resultByte, "UTF-8");
                return JSONObject.parseObject(result);
            }
            return null;
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        } catch (InvalidParameterSpecException e) {
            e.printStackTrace();
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return null;
    }

}
