package com.ruoyi.app.utils;

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

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.security.*;
import java.security.interfaces.RSAKey;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

public class RSAUtils {
    public static final String CHARSET = "UTF-8";
    public static final String RSA_ALGORITHM = "RSA";


    public static Map<String, String> createKeys(int keySize) {
        //为RSA算法创建一个KeyPairGenerator对象
        KeyPairGenerator kpg;
        try {
            kpg = KeyPairGenerator.getInstance(RSA_ALGORITHM);
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalArgumentException("No such algorithm-->[" + RSA_ALGORITHM + "]");
        }

        //初始化KeyPairGenerator对象,密钥长度
        kpg.initialize(keySize);
        //生成密匙对
        KeyPair keyPair = kpg.generateKeyPair();
        //得到公钥
        Key publicKey = keyPair.getPublic();
        String publicKeyStr = Base64.encodeBase64URLSafeString(publicKey.getEncoded());
        //得到私钥
        Key privateKey = keyPair.getPrivate();
        String privateKeyStr = Base64.encodeBase64URLSafeString(privateKey.getEncoded());
        Map<String, String> keyPairMap = new HashMap<String, String>();
        keyPairMap.put("publicKey", publicKeyStr);
        keyPairMap.put("privateKey", privateKeyStr);

        return keyPairMap;
    }

    /**
     * 得到公钥
     *
     * @param publicKey 密钥字符串（经过base64编码）
     * @throws Exception
     */
    public static RSAPublicKey getPublicKey(String publicKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
        //通过X509编码的Key指令获得公钥对象
        KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(Base64.decodeBase64(publicKey));
        RSAPublicKey key = (RSAPublicKey) keyFactory.generatePublic(x509KeySpec);
        return key;
    }

    /**
     * 得到私钥
     *
     * @param privateKey 密钥字符串（经过base64编码）
     * @throws Exception
     */
    public static RSAPrivateKey getPrivateKey(String privateKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
        //通过PKCS#8编码的Key指令获得私钥对象
        KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKey));
        RSAPrivateKey key = (RSAPrivateKey) keyFactory.generatePrivate(pkcs8KeySpec);
        return key;
    }

    public static byte[] encrypt(byte[] data, Key key) throws Exception {
        Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
        cipher.init(Cipher.ENCRYPT_MODE, key);
        return rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data
                , ((RSAKey) key).getModulus().bitLength());
    }

    public static byte[] decrypt(byte[] data, Key key) throws Exception {
        Cipher cipher = Cipher.getInstance(RSA_ALGORITHM);
        cipher.init(Cipher.DECRYPT_MODE, key);
        return rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, data, ((RSAKey) key)
                .getModulus()
                .bitLength());
    }

    private static byte[] rsaSplitCodec(Cipher cipher, int opmode, byte[] datas, int keySize) {
        int maxBlock;
        if (opmode == Cipher.DECRYPT_MODE) {
            maxBlock = keySize / 8;
        } else {
            maxBlock = keySize / 8 - 11;
        }
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] buff;
        int i = 0;
        try {
            while (datas.length > offSet) {
                if (datas.length - offSet > maxBlock) {
                    buff = cipher.doFinal(datas, offSet, maxBlock);
                } else {
                    buff = cipher.doFinal(datas, offSet, datas.length - offSet);
                }
                out.write(buff, 0, buff.length);
                i++;
                offSet = i * maxBlock;
            }
        } catch (Exception e) {
            throw new RuntimeException("加解密阀值为[" + maxBlock + "]的数据时发生异常", e);
        }
        byte[] resultDatas = out.toByteArray();
        try {
            out.close();
        } catch (IOException e) {
            throw new RuntimeException("关闭流失败", e);
        }

        return resultDatas;
    }

    public static String DoRSASha256(String input, RSAPrivateKey privateKey) throws Exception {
//        MessageDigest messageDigest = MessageDigest.getInstance("SHA-256");
//        messageDigest.update(input.getBytes(CHARSET));
//        byte[] digested = messageDigest.digest();

        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initSign(privateKey);
        signature.update(input.getBytes(CHARSET));
        return Base64.encodeBase64String(signature.sign());
    }

    public static boolean VerifyRSASha256(String input, String sign, RSAPublicKey publicKey) throws Exception {
        Signature signature = Signature.getInstance("SHA256withRSA");
        signature.initVerify(publicKey);
        signature.update(input.getBytes(CHARSET));
        return signature.verify(Base64.decodeBase64(sign));
    }
}
