package io.nutz.nutzsite.common.utils;


import java.util.Base64;
import javax.crypto.Cipher;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
 * Java RSA 加密工具类
 * @Author: Haimming
 * @Date: 2019-10-12 10:12
 * @Version 1.0
 */
public class RSAUtils {

    public static final String KEY_ALGORITHM = "RSA";
    /**
     * 密钥长度 于原文长度对应 以及越长速度越慢
     */
    private final static int KEY_SIZE = 2048;
    /**
     * 用于封装随机产生的公钥与私钥
     */
    public static Map<String, String> keyMap = new HashMap<String, String>();

    public static final String PUBLIC_KEY = "RSAPublicKey";
    public static final String PRIVATE_KEY = "RSAPrivateKey";


    /**
     * 随机生成密钥对
     */
    public static void genKeyPair() throws NoSuchAlgorithmException {
        // KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        // 初始化密钥对生成器
        keyPairGen.initialize(KEY_SIZE, new SecureRandom());
        // 生成一个密钥对，保存在keyPair中
        KeyPair keyPair = keyPairGen.generateKeyPair();
        // 得到私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        // 得到公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        String publicKeyString = Base64.getEncoder().encodeToString(publicKey.getEncoded());
        // 得到私钥字符串
        String privateKeyString = Base64.getEncoder().encodeToString(privateKey.getEncoded());
        // 将公钥和私钥保存到Map
        keyMap.put(PUBLIC_KEY, publicKeyString);
        keyMap.put(PRIVATE_KEY, privateKeyString);
    }

    /**
     * RSA公钥加密
     *
     * @param str       加密字符串
     * @param publicKey 公钥
     * @return 密文
     * @throws Exception 加密过程中的异常信息
     */
    public static String encrypt(String str, String publicKey) throws Exception {
        //base64编码的公钥
        byte[] decoded = Base64.getDecoder().decode(publicKey);
        RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance(KEY_ALGORITHM).generatePublic(new X509EncodedKeySpec(decoded));
        //RSA加密
        Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, pubKey);
        String outStr = Base64.getEncoder().encodeToString(cipher.doFinal(str.getBytes("UTF-8")));
        return outStr;
    }

    /**
     * RSA私钥解密
     *
     * @param str        加密字符串
     * @param privateKey 私钥
     * @return 明文
     * @throws Exception 解密过程中的异常信息
     */
    public static String decrypt(String str, String privateKey) throws Exception {
        //64位解码加密后的字符串
        byte[] inputByte = Base64.getDecoder().decode(str);
        //base64编码的私钥
        byte[] decoded = Base64.getDecoder().decode(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance(KEY_ALGORITHM).generatePrivate(new PKCS8EncodedKeySpec(decoded));
        //RSA解密
        Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        String outStr = new String(cipher.doFinal(inputByte));
        return outStr;
    }


    public static void main(String[] args) throws Exception {

        long temp = System.currentTimeMillis();
        //生成公钥和私钥
        genKeyPair();
        String publicKey =  keyMap.get(PUBLIC_KEY);
        String privateKey = keyMap.get(PRIVATE_KEY);
        //加密字符串
        System.out.println("公钥:" +publicKey);
        System.out.println("私钥:" + privateKey);
        System.out.println("生成密钥消耗时间:" + (System.currentTimeMillis() - temp) / 1000.0 + "秒");


        String message = "RSA测试ABCD~!@#$";
        System.out.println("原文:" + message);

        temp = System.currentTimeMillis();
        String messageEn = encrypt(message, publicKey);
        System.out.println("密文:" + messageEn);
        System.out.println("加密消耗时间:" + (System.currentTimeMillis() - temp) / 1000.0 + "秒");

        temp = System.currentTimeMillis();

        String messageDe = decrypt(messageEn, privateKey);
        System.out.println("解密:" + messageDe);
        System.out.println("解密消耗时间:" + (System.currentTimeMillis() - temp) / 1000.0 + "秒");
    }
}