using System;
using System.Text;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.Utilities.Encoders;
// ReSharper disable InconsistentNaming

namespace UFIDA.U8.Framework.Api.Common.Unit.GM
{
    /// <summary>
    /// GM工具类
    /// </summary>
    public class GMUtil
    {
        /// <summary>
        /// SM2加密
        /// </summary>
        /// <param name="publicKeyHex"></param>
        /// <param name="data_string"></param>
        /// <returns></returns>
        public static string SM2Encrypt(string publicKeyHex, string data_string)
        {
            // 如果是130位公钥，.NET使用的话，把开头的04截取掉
            if (publicKeyHex.Length == 130)
            {
                publicKeyHex = publicKeyHex.Substring(2, 128);
            }
            // 公钥X，前64位
            var x = publicKeyHex.Substring(0, 64);
            // 公钥Y，后64位
            var y = publicKeyHex.Substring(64);
            // 获取公钥对象
            AsymmetricKeyParameter publicKey1 = GM.GetPublickeyFromXY(new BigInteger(x, 16), new BigInteger(y, 16));
            // Sm2Encrypt: C1C3C2
            // Sm2EncryptOld: C1C2C3
            var digestByte = GM.Sm2Encrypt(Encoding.UTF8.GetBytes(data_string), publicKey1);
            var strSM2 = Hex.ToHexString(digestByte);
            return strSM2;
        }

        /// <summary>
        /// SM2解密
        /// </summary>
        /// <param name="privateKey_string"></param>
        /// <param name="encryptedData_string"></param>
        /// <returns></returns>
        public static string SM2Decrypt(string privateKey_string, string encryptedData_string)
        {
            if (!encryptedData_string.StartsWith("04"))
                encryptedData_string = "04" + encryptedData_string;
            var d = new BigInteger(privateKey_string, 16);
            // 先拿到私钥对象，用ECPrivateKeyParameters 或 AsymmetricKeyParameter 都可以
            // ECPrivateKeyParameters bcecPrivateKey = GmUtil.GetPrivatekeyFromD(d);
            AsymmetricKeyParameter bcecPrivateKey = GM.GetPrivatekeyFromD(d);
            var byToDecrypt = Hex.Decode(encryptedData_string);
            var byDecrypted = GM.Sm2Decrypt(byToDecrypt, bcecPrivateKey);
            var strDecrypted = Encoding.UTF8.GetString(byDecrypted);
            return strDecrypted;
        }

        /// <summary>
        /// SM4加密（ECB）
        /// </summary>
        /// <param name="key_string"></param>
        /// <param name="plainText"></param>
        /// <returns></returns>
        public static string SM4EncryptECB(string key_string, string plainText)
        {
            var key = Hex.Decode(key_string);
            var bs = GM.Sm4EncryptECB(key, Encoding.UTF8.GetBytes(plainText), GM.SM4_ECB_PKCS7PADDING);//NoPadding 的情况下需要校验数据长度是16的倍数. 使用 HandleSm4Padding 处理
            return Hex.ToHexString(bs);
        }

        /// <summary>
        /// SM4解密（ECB）
        /// </summary>
        /// <param name="key_string"></param>
        /// <param name="cipherText"></param>
        /// <returns></returns>
        public static string SM4DecryptECB(string key_string, string cipherText)
        {
            var key = Hex.Decode(key_string);
            var bs = GM.Sm4DecryptECB(key, Hex.Decode(cipherText), GM.SM4_ECB_PKCS7PADDING);
            return Encoding.UTF8.GetString(bs);
        }

        /// <summary>
        /// SM4加密（CBC）
        /// </summary>
        /// <param name="key_string"></param>
        /// <param name="iv_string"></param>
        /// <param name="plainText"></param>
        /// <returns></returns>
        public static string SM4EncryptCBC(string key_string, string iv_string, string plainText)
        {
            var key = Hex.Decode(key_string);
            var iv = Hex.Decode(iv_string);
            var bs = GM.Sm4EncryptCBC(key, Encoding.UTF8.GetBytes(plainText), iv, GM.SM4_CBC_PKCS7PADDING);
            return Hex.ToHexString(bs);
        }

        /// <summary>
        /// SM4解密（CBC）
        /// </summary>
        /// <param name="key_string"></param>
        /// <param name="iv_string"></param>
        /// <param name="cipherText"></param>
        /// <returns></returns>
        public static string SM4DecryptCBC(string key_string, string iv_string, string cipherText)
        {
            var key = Hex.Decode(key_string);
            var iv = Hex.Decode(iv_string);
            var bs = GM.Sm4DecryptCBC(key, Hex.Decode(cipherText), iv, GM.SM4_CBC_PKCS7PADDING);
            return Encoding.UTF8.GetString(bs);
        }

        /// <summary>
        /// 补足 16 进制字符串的 0 字符，返回不带 0x 的16进制字符串
        /// </summary>
        /// <param name="input"></param>
        /// <param name="mode">1表示加密，0表示解密</param>
        /// <returns></returns>
        private static byte[] HandleSm4Padding(byte[] input, int mode)
        {
            if (input == null)
            {
                return null;
            }
            byte[] ret;
            if (mode == 1)
            {
                var p = 16 - input.Length % 16;
                ret = new byte[input.Length + p];
                Array.Copy(input, 0, ret, 0, input.Length);
                for (var i = 0; i < p; i++)
                {
                    ret[input.Length + i] = (byte)p;
                }
            }
            else
            {
                int p = input[input.Length - 1];
                ret = new byte[input.Length - p];
                Array.Copy(input, 0, ret, 0, input.Length - p);
            }
            return ret;
        }
    }
}