using XLua;
using System;
using System.Text;
//c#加解密库都存在于此
using System.Security.Cryptography;

namespace BF
{
    /// <summary>
    /// PKCS#1
    /// </summary>
    [LuaCallCSharp]
    public class RsaEncrypt
    {

        /// <summary>
        /// 基于Base64编码的RSA加密
        /// </summary>
        static public string Encrypt(string key, string value, bool tobase64 = false)
        {
            if (string.IsNullOrEmpty(key) || string.IsNullOrEmpty(value))
                return string.Empty;

            using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
            {
                rsa.ImportParameters(ConvertFromPemPublicKey(key));
                var rsaBytes = rsa.Encrypt(Encoding.UTF8.GetBytes(value), false);
                return tobase64 ? Convert.ToBase64String(rsaBytes) : Encoding.UTF8.GetString(rsaBytes);
            }
        }
        
        /// <summary>
        /// 基于Base64编码的RSA加密
        /// </summary>
        static public string Decrypt(string key, string value, bool frombase64 = false)
        {
            if (string.IsNullOrEmpty(key) || string.IsNullOrEmpty(value))
                return string.Empty;

            using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
            {
                rsa.ImportParameters(ConvertFromPemPublicKey(key));
                var rsaBytes = rsa.Decrypt(frombase64 ? Convert.FromBase64String(value) : Encoding.UTF8.GetBytes(value), false);
                return Encoding.UTF8.GetString(rsaBytes);
            }
        }

        /// <summary>
        /// 构造Parameters
        /// </summary>
        static public RSAParameters ConvertFromPemPublicKey(string pemFileConent)
        {
            if (string.IsNullOrEmpty(pemFileConent))
            {
                throw new ArgumentNullException("pemFileConent", "This arg cann't be empty.");
            }
            pemFileConent = pemFileConent.Replace("-----BEGIN PUBLIC KEY-----", "").
                                          Replace("-----END PUBLIC KEY-----", "").
                                          Replace("\n", "").
                                          Replace("\r", "");
            byte[] keyData = Convert.FromBase64String(pemFileConent);
            bool keySize512 = (keyData.Length == 94);
            bool keySize1024 = (keyData.Length == 162);
            bool keySize2048 = (keyData.Length == 294);
            //BFLog.Log("rsa keysize = {0}", keyData.Length);
            if (!(keySize1024 || keySize2048 || keySize512))
            {
                throw new ArgumentException("pem file content is incorrect, Only support the key size is 1024 or 2048");
            }

            var pemModulus = (keySize1024 ? new byte[128] : new byte[256]);

            //1024或者2048密钥
            if (keySize1024 || keySize2048)
            {
                Array.Copy(keyData, (keySize1024 ? 29 : 33), pemModulus, 0, (keySize1024 ? 128 : 256));
            }

            //512位长度密钥
            if (keySize512)
            {
                pemModulus = new byte[64];
                Array.Copy(keyData, 25, pemModulus, 0, pemModulus.Length);
            }

            var pemPublicExponent = new byte[3];
            Array.Copy(keyData, keyData.Length - 3, pemPublicExponent, 0, 3);

            var para = new RSAParameters { Modulus = pemModulus, Exponent = pemPublicExponent };
            return para;
        }

    }
}