package org.springblade.pay.utils;


import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 * RSA加密工具
 * @author wb081
 * @version 1.0.0
 */
public class CzcbRasUtil{

    /**
     * 加密方式
     */
    public static final String KEY_ALGORITHM = "RSA";
    /**
     * 签名算法
     */
    public static final String SIGNATURE_ALGORITHM = "SHA256withRSA";
    /**
     * 公钥算法
     */
    public static final String PUBLIC_KEY = "RSAPublicKey";
    /**
     * 私钥算法
     */
    public static final String PRIVATE_KEY = "RSAPrivateKey";

    public static byte[] decryptBASE64(String key){
        return Base64.decodeBase64(key);
    }

    public static String encryptBASE64(byte[] bytes){
        return Base64.encodeBase64String(bytes);
    }

    /**
     * 用私钥对信息生成数字签名
     * @param data 待签名数据
     * @param privateKey 私钥
     * @throws Exception
     */
    public static String sign(byte[] data, String privateKey) throws Exception{
        // 解密由base64编码的私钥
        byte[] keyBytes = decryptBASE64(privateKey);
        // 构造PKCS8EncodedKeySpec对象
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        // KEY_ALGORITHM 指定的加密算法
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 取私钥匙对象
        PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);
        // 用私钥对信息生成数字签名
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(priKey);
        signature.update(data);

        return encryptBASE64(signature.sign());
    }

    /**
     * 校验数字签名
     * @param data 加密数据
     * @param publicKey 公钥
     * @param sign 数字签名
     * @return 校验成功返回true，失败返回false
     * @throws Exception
     */
    public static boolean verify(byte[] data, String publicKey, String sign) throws Exception{
        // 解密由base64编码的公钥
        byte[] keyBytes = decryptBASE64(publicKey);
        // 构造X509EncodedKeySpec对象
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        // KEY_ALGORITHM 指定的加密算法
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        // 取公钥匙对象
        PublicKey pubKey = keyFactory.generatePublic(keySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(pubKey);
        signature.update(data);
        // 验证签名是否正常
        return signature.verify(decryptBASE64(sign));
    }

    /**
     * 解密<br>
     * 私钥解密
     * @param data 加密数据
     * @param key 私钥
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(byte[] data, String key) throws Exception{
        // 对密钥解密
        byte[] keyBytes = decryptBASE64(key);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
        // 对数据解密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateKey);
        return cipher.doFinal(data);
    }

    /**
     * 解密 <br>
     * 用私钥解密
     * @param data 加密数据
     * @param key 私钥
     * @return 消息
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(String data, String key) throws Exception{
        return decryptByPrivateKey(decryptBASE64(data), key);
    }

    /**
     * 加密<br>
     * 用公钥加密
     * @param data 待加密消息
     * @param key 公钥
     * @return 密文
     * @throws Exception
     */
    public static String encryptByPublicKey(String data, String key) throws Exception{
        // 对公钥解密
        byte[] keyBytes = decryptBASE64(key);
        // 取得公钥
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicKey = keyFactory.generatePublic(x509KeySpec);
        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);
        return encryptBASE64(cipher.doFinal(data.getBytes()));
    }
}
