package io.hmit.common.utils.sm.sm2;

import org.bouncycastle.asn1.gm.GMNamedCurves;
import org.bouncycastle.asn1.x9.X9ECParameters;
import org.bouncycastle.crypto.engines.SM2Engine;
import org.bouncycastle.crypto.params.ECDomainParameters;
import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.crypto.params.ParametersWithRandom;
import org.bouncycastle.jcajce.provider.asymmetric.ec.BCECPrivateKey;
import org.bouncycastle.jcajce.provider.asymmetric.ec.BCECPublicKey;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.jce.spec.ECParameterSpec;
import org.bouncycastle.jce.spec.ECPrivateKeySpec;
import org.bouncycastle.jce.spec.ECPublicKeySpec;
import org.bouncycastle.util.encoders.Hex;

import java.math.BigInteger;
import java.nio.charset.StandardCharsets;
import java.security.*;
import java.security.spec.ECGenParameterSpec;
import java.util.Objects;

/**
 * <h1>国标商密 SM2</h1>
 * @author Shen && syf0412@vip.qq.com
 * @since 2022/9/22 9:40
 */
public class SM2Utils {

    /**
     * @Description 生成秘钥对
     * @return KeyPair
     */
    public static KeyPair createECKeyPair() {
        //使用标准名称创建EC参数生成的参数规范
        final ECGenParameterSpec sm2Spec = new ECGenParameterSpec("sm2p256v1");

        // 获取一个椭圆曲线类型的密钥对生成器
        final KeyPairGenerator kpg;
        try {
            kpg = KeyPairGenerator.getInstance("EC", new BouncyCastleProvider());
            // 使用SM2算法域参数集初始化密钥生成器（默认使用以最高优先级安装的提供者的 SecureRandom 的实现作为随机源）
            // kpg.initialize(sm2Spec);

            // 使用SM2的算法域参数集和指定的随机源初始化密钥生成器
            kpg.initialize(sm2Spec, new SecureRandom());

            // 通过密钥生成器生成密钥对
            return kpg.generateKeyPair();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * @Description 公钥加密
     * @param publicKeyHex SM2十六进制公钥
     * @param data         明文数据
     * @return String
     */
    public static String encrypt(String publicKeyHex, String data) {
        return encrypt(getECPublicKeyByPublicKeyHex(publicKeyHex), data, 1);
    }

    /**
     * @Description 公钥加密
     * @param publicKey SM2公钥
     * @param data      明文数据
     * @param modeType  加密模式
     * @return String
     */
    public static String encrypt(BCECPublicKey publicKey, String data, int modeType) {
        //加密模式
        SM2Engine.Mode mode = SM2Engine.Mode.C1C3C2;
        if (modeType != 1) {
            mode = SM2Engine.Mode.C1C2C3;
        }
        //通过公钥对象获取公钥的基本域参数。
        ECParameterSpec ecParameterSpec = publicKey.getParameters();
        ECDomainParameters ecDomainParameters = new ECDomainParameters(ecParameterSpec.getCurve(),
                ecParameterSpec.getG(), ecParameterSpec.getN());
        //通过公钥值和公钥基本参数创建公钥参数对象
        ECPublicKeyParameters ecPublicKeyParameters = new ECPublicKeyParameters(publicKey.getQ(), ecDomainParameters);
        //根据加密模式实例化SM2公钥加密引擎
        SM2Engine sm2Engine = new SM2Engine(mode);
        //初始化加密引擎
        sm2Engine.init(true, new ParametersWithRandom(ecPublicKeyParameters, new SecureRandom()));
        byte[] arrayOfBytes = null;
        try {
            //将明文字符串转换为指定编码的字节串
            byte[] in = data.getBytes(StandardCharsets.UTF_8);
            //通过加密引擎对字节数串行加密
            arrayOfBytes = sm2Engine.processBlock(in, 0, in.length);
        } catch (Exception e) {
            System.out.println("SM2加密时出现异常:" + e.getMessage());
            e.printStackTrace();
        }
        //将加密后的字节串转换为十六进制字符串
        return Hex.toHexString(Objects.requireNonNull(arrayOfBytes));
    }

    /**
     * @Description 私钥解密
     * @param privateKeyHex SM2十六进制私钥
     * @param cipherData    密文数据
     * @return String
     */
    public static String decrypt(String privateKeyHex, String cipherData) {
        return decrypt(getBCECPrivateKeyByPrivateKeyHex(privateKeyHex), cipherData, 1);
    }

    /**
     * @Description 私钥解密
     * @param privateKey SM私钥
     * @param cipherData 密文数据
     * @param modeType   解密模式
     * @return
     */
    public static String decrypt(BCECPrivateKey privateKey, String cipherData, int modeType) {
        //解密模式
        SM2Engine.Mode mode = SM2Engine.Mode.C1C3C2;
        if (modeType != 1)
            mode = SM2Engine.Mode.C1C2C3;
        //将十六进制字符串密文转换为字节数组（需要与加密一致，加密是：加密后的字节数组转换为了十六进制字符串）
        byte[] cipherDataByte = Hex.decode(cipherData);
        //通过私钥对象获取私钥的基本域参数。
        ECParameterSpec ecParameterSpec = privateKey.getParameters();
        ECDomainParameters ecDomainParameters = new ECDomainParameters(ecParameterSpec.getCurve(),
                ecParameterSpec.getG(), ecParameterSpec.getN());
        //通过私钥值和私钥钥基本参数创建私钥参数对象
        ECPrivateKeyParameters ecPrivateKeyParameters = new ECPrivateKeyParameters(privateKey.getD(),
                ecDomainParameters);
        //通过解密模式创建解密引擎并初始化
        SM2Engine sm2Engine = new SM2Engine(mode);
        sm2Engine.init(false, ecPrivateKeyParameters);
        String result = null;
        try {
            //通过解密引擎对密文字节串进行解密
            byte[] arrayOfBytes = sm2Engine.processBlock(cipherDataByte, 0, cipherDataByte.length);
            //将解密后的字节串转换为utf8字符编码的字符串（需要与明文加密时字符串转换成字节串所指定的字符编码保持一致）
            result = new String(arrayOfBytes, StandardCharsets.UTF_8);
        } catch (Exception e) {
            System.out.println("SM2解密时出现异常" + e.getMessage());
        }
        return result;
    }
    //椭圆曲线ECParameters ASN.1 结构
    private static final X9ECParameters x9ECParameters = GMNamedCurves.getByName("sm2p256v1");
    //椭圆曲线公钥或私钥的基本域参数。
    private static final ECParameterSpec ecDomainParameters = new ECParameterSpec(x9ECParameters.getCurve(), x9ECParameters.getG(), x9ECParameters.getN());

    /**
     * @Description 公钥字符串转换为 BCECPublicKey 公钥对象
     * @param pubKeyHex 64字节十六进制公钥字符串(如果公钥字符串为65字节首个字节为0x04：表示该公钥为非压缩格式，操作时需要删除)
     * @return BCECPublicKey SM2公钥对象
     */
    public static BCECPublicKey getECPublicKeyByPublicKeyHex(String pubKeyHex) {
        //截取64字节有效的SM2公钥（如果公钥首个字节为0x04）
        if (pubKeyHex.length() > 128) {
            pubKeyHex = pubKeyHex.substring(pubKeyHex.length() - 128);
        }
        //将公钥拆分为x,y分量（各32字节）
        String stringX = pubKeyHex.substring(0, 64);
        String stringY = pubKeyHex.substring(stringX.length());
        //将公钥x、y分量转换为BigInteger类型
        BigInteger x = new BigInteger(stringX, 16);
        BigInteger y = new BigInteger(stringY, 16);
        //通过公钥x、y分量创建椭圆曲线公钥规范
        ECPublicKeySpec ecPublicKeySpec = new ECPublicKeySpec(x9ECParameters.getCurve().createPoint(x, y), ecDomainParameters);
        //通过椭圆曲线公钥规范，创建出椭圆曲线公钥对象（可用于SM2加密及验签）
        return new BCECPublicKey("EC", ecPublicKeySpec, BouncyCastleProvider.CONFIGURATION);
    }

    /**
     * @Description 私钥字符串转换为 BCECPrivateKey 私钥对象
     * @param privateKeyHex 32字节十六进制私钥字符串
     * @return BCECPrivateKey SM2私钥对象
     */
    public static BCECPrivateKey getBCECPrivateKeyByPrivateKeyHex(String privateKeyHex) {
        //将十六进制私钥字符串转换为BigInteger对象
        BigInteger d = new BigInteger(privateKeyHex, 16);
        //通过私钥和私钥域参数集创建椭圆曲线私钥规范
        ECPrivateKeySpec ecPrivateKeySpec = new ECPrivateKeySpec(d, ecDomainParameters);
        //通过椭圆曲线私钥规范，创建出椭圆曲线私钥对象（可用于SM2解密和签名）
        return new BCECPrivateKey("EC", ecPrivateKeySpec, BouncyCastleProvider.CONFIGURATION);
    }

    public static void main(String[] args) {
        String publicKeyHex = null;
        String privateKeyHex = null;
        KeyPair keyPair = createECKeyPair();
        PublicKey publicKey = keyPair.getPublic();
        if (publicKey instanceof BCECPublicKey) {
            //获取65字节非压缩缩的十六进制公钥串(0x04)
//            publicKeyHex = Hex.toHexString(((BCECPublicKey) publicKey).getQ().getEncoded(false));
            publicKeyHex = "04af48bcab50e9bd8696ef1fbf7c880b16451b5774ec313294adec6b620ae88d786eb9e5452af9302ad49999683e89963b84d0cb00dcfd145ad6bc30eb221e51b4";
            System.out.println("---->SM2公钥：" + publicKeyHex);
        }
        PrivateKey privateKey = keyPair.getPrivate();
        if (privateKey instanceof BCECPrivateKey) {
            //获取32字节十六进制私钥串
//            privateKeyHex = ((BCECPrivateKey) privateKey).getD().toString(16);
            privateKeyHex = "1946c9950c06b773a232abc866deaa920d0862fe1fdce3ea6ce963222068d3eb";
            System.out.println("---->SM2私钥：" + privateKeyHex);
        }

        /**
         * 公钥加密
         */
        String data = "=========待加密数据=========";

        //将十六进制公钥串转换为 BCECPublicKey 公钥对象
        String encryptData = encrypt(publicKeyHex, data);
        System.out.println("---->加密结果：" + encryptData);

        encryptData = "047b11abb349f69cc6bb099446aedf1faee1114fbcb5ad49493c39b12296e7ceb3919b3dfc3833af6383c7aa35bb01409641611e1ed894cd28e46984bb97bbc5a0c96a3ccbb9a2c939b1b005d2a51c9346e1b5a903cd61dac624784c6e8d19e5c4fcee348c3a45a2b04cbf8b47cc54e564";

        /**
         * 私钥解密
         */
        //将十六进制私钥串转换为 BCECPrivateKey 私钥对象
        data = decrypt(privateKeyHex, encryptData);
        System.out.println("---->解密结果：" + data);
    }

}
