package com.schisandra.system.common.utils;

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

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * @ClassName RSAUtils
 * @Description TODO
 * @Author L
 * @Date 2024/1/26 17:28
 */
public class RSAUtils {

    /**
     * 加密算法RSA
     */
    private static final String KEY_ALGORITHM = "RSA";

    /**
     * 算法名称/加密模式/数据填充方式
     * 默认：RSA/ECB/PKCS1Padding
     */
    private static final String ALGORITHMS = "RSA/ECB/PKCS1Padding";

    /**
     * RSA最大加密明文大小
     */
    private static final int MAX_ENCRYPT_BLOCK = 245;

    /**
     * RSA最大解密密文大小
     */
    private static final int MAX_DECRYPT_BLOCK = 256;

    /**
     * RSA 位数 如果采用2048 上面最大加密和最大解密则须填写:  245 256
     */
    private static final int INITIALIZE_LENGTH = 2048;

    /**
     * 后端RSA的密钥对(公钥和私钥)Map，由静态代码块赋值
     */
    private static final Map<String, String> map = new LinkedHashMap<>(2);

    /**
     * 生成密钥对(公钥和私钥)
     */

    public static Map<String,String> genKeyPair() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(INITIALIZE_LENGTH);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        // 获取公钥
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        // 获取私钥
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        // 得到公钥字符串
        String publicKeyString = Base64.encodeBase64String(publicKey.getEncoded());
        // 得到私钥字符串
        String privateKeyString = Base64.encodeBase64String((privateKey.getEncoded()));
        map.put("publicKey",publicKeyString);
        map.put("privateKey",privateKeyString);
        return map;
    }
    public static  String getPrivateKey(){
        return map.get("privateKey");
    }
    public  static  String getPublicKey(){
        return  map.get("publicKey");
    }
    /**
     * RSA私钥解密
     * @param data BASE64编码过的密文
     * @param privateKey 私钥(BASE64编码)
     * @return utf-8编码的明文
     */
    public static byte[] decryptByPrivateKey(byte[] data, String privateKey) throws Exception {
        //base64格式的key字符串转Key对象
        Key privateK = KeyFactory.getInstance(KEY_ALGORITHM).generatePrivate(new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKey)));
        Cipher cipher = Cipher.getInstance(ALGORITHMS);
        cipher.init(Cipher.DECRYPT_MODE, privateK);

        //分段进行解密操作
        return encryptAndDecryptOfSubsection(data, cipher, MAX_DECRYPT_BLOCK);
    }

    /**
     * RSA公钥加密
     * @param data BASE64编码过的密文
     * @param publicKey 公钥(BASE64编码)
     * @return utf-8编码的明文
     */
    public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
        //base64格式的key字符串转Key对象
        Key publicK = KeyFactory.getInstance(KEY_ALGORITHM).generatePublic(new X509EncodedKeySpec(Base64.decodeBase64(publicKey)));
        Cipher cipher = Cipher.getInstance(ALGORITHMS);
        cipher.init(Cipher.ENCRYPT_MODE, publicK);
        //分段进行加密操作
        return encryptAndDecryptOfSubsection(data, cipher, MAX_ENCRYPT_BLOCK);
    }

    /**
     * RSA公钥解密
     * @param data BASE64编码过的密文
     * @param publicKey RSA公钥
     * @return utf-8编码的明文
     */
    public static byte[] pubKeyDec(byte[] data, String publicKey) throws Exception {
        //base64格式的key字符串转Key对象
        Key privateK = KeyFactory.getInstance(KEY_ALGORITHM).generatePublic(new X509EncodedKeySpec(Base64.decodeBase64(publicKey)));
        Cipher cipher = Cipher.getInstance(ALGORITHMS);
        cipher.init(Cipher.DECRYPT_MODE, privateK);

        //分段进行解密操作
        return encryptAndDecryptOfSubsection(data, cipher, MAX_DECRYPT_BLOCK);
    }


    /**
     * RSA私钥加密
     * @param data 待加密的明文
     * @param privateKey RSA私钥
     * @return  经BASE64编码后的密文
     */
    public static byte[] privKeyEnc(byte[] data, String privateKey) throws Exception {

        //base64格式的key字符串转Key对象
        Key publicK = KeyFactory.getInstance(KEY_ALGORITHM).generatePrivate(new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKey)));
        Cipher cipher = Cipher.getInstance(ALGORITHMS);
        cipher.init(Cipher.ENCRYPT_MODE, publicK);

        //分段进行加密操作
        return encryptAndDecryptOfSubsection(data, cipher, MAX_ENCRYPT_BLOCK);
    }

    /**
     * 分段进行加密、解密操作
     */
    private static byte[] encryptAndDecryptOfSubsection(byte[] data, Cipher cipher, int encryptBlock) throws Exception {
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > encryptBlock) {
                cache = cipher.doFinal(data, offSet, encryptBlock);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * encryptBlock;
        }
        out.close();
        return out.toByteArray();
    }

}
