package com.tofly.third.common.util;

import org.springframework.util.Base64Utils;

import java.security.SecureRandom;
import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.security.NoSuchAlgorithmException;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * @version V1.0
 * @desc AES 加密工具类
 * 使用说明 encrypt用于加密，decrypt用于解密,
 * notice:
 * NbiotJson需要进行两次解密，通过appName解密timeStamp，再通过已解密timeStamp解密data，
 * 同理，加密需要通过appName加密timeStamp，通过timeStamp加密data
 * <p>
 * timeStamp对应密码appName
 * data对应密码timeStamp
 */
public class AESUtil {

    private static final String KEY_ALGORITHM = "AES";
    //默认的加密算法
    private static final String DEFAULT_CIPHER_ALGORITHM = "AES/ECB/PKCS5Padding";


    /**
     * AES 加密操作
     *
     * @param content  待加密内容
     * @param password 加密密码
     * @return 返回Base64转码后的加密数据
     */
    public static String encrypt(String content, String password) {
        try {
            Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);// 创建密码器

            byte[] byteContent = content.getBytes("utf-8");

            cipher.init(Cipher.ENCRYPT_MODE, getSecretKey(password));// 初始化为加密模式的密码器

            byte[] result = cipher.doFinal(byteContent);// 加密

            return Base64Utils.encodeToString(result);//通过Base64转码返回
        } catch (Exception ex) {
            Logger.getLogger(AESUtil.class.getName()).log(Level.SEVERE, null, ex);
        }

        return null;
    }

    /**
     * AES 解密操作
     *
     * @param content
     * @param password
     * @return
     */
    public static String decrypt(String content, String password) {

        try {
            //实例化
            Cipher cipher = Cipher.getInstance(DEFAULT_CIPHER_ALGORITHM);

            //使用密钥初始化，设置为解密模式
            cipher.init(Cipher.DECRYPT_MODE, getSecretKey(password));

            //执行操作
            byte[] result = cipher.doFinal(Base64Utils.decodeFromString(content));
            String s = new String(result, "utf-8");
            return s;
        } catch (Exception ex) {
            ex.printStackTrace();
            Logger.getLogger(AESUtil.class.getName()).log(Level.SEVERE, null, ex);
        }

        return null;
    }

    /**
     * 生成加密秘钥
     *
     * @return
     */
    private static SecretKeySpec getSecretKey(String password) {
        //返回生成指定算法密钥生成器的 KeyGenerator 对象
        KeyGenerator kg = null;
        try {
            kg = KeyGenerator.getInstance(KEY_ALGORITHM);
            //使用SHA1PRNG算法生成随机数
            SecureRandom random = SecureRandom.getInstance("SHA1PRNG");
            //设置种子为固定值 从而能解密
            random.setSeed(password.getBytes());
            //AES 要求密钥长度为 128bit,相当于16bytes
            kg.init(128, random);
            //生成一个密钥
            SecretKey secretKey = kg.generateKey();
            //转换为AES专用密钥
            SecretKeySpec secretKeySpec = new SecretKeySpec(secretKey.getEncoded(), KEY_ALGORITHM);
            return secretKeySpec;
        } catch (NoSuchAlgorithmException ex) {
            Logger.getLogger(AESUtil.class.getName()).log(Level.SEVERE, null, ex);
        }
        return null;
    }


}

