using System;
using System.IO;
using System.Security.Cryptography;
using Org.BouncyCastle.OpenSsl;
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Operators;
using Org.BouncyCastle.Crypto.Engines;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Crypto.Parameters;
using System.Text;

public class RSAExample
{
    public static void Main()
    {
        // 讀取並載入私鑰和公鑰
        RSA rsaGen = RSA.Create();
        RSAParameters privateKeyParameters = rsaGen.ExportParameters(true);
        RSAParameters publicKeyParameters = rsaGen.ExportParameters(false);
        //RSAParameters privateKeyParameters = LoadPrivateKey("private_key.pem");
        //RSAParameters publicKeyParameters = LoadPublicKey("public_key.pem");

        var aes = Aes.Create();
        var buffer = new MemoryStream();
        CryptoStream cryptoStream = new CryptoStream(
                buffer,
                aes.CreateEncryptor(),
                CryptoStreamMode.Write);
        StreamWriter sw = new StreamWriter(cryptoStream);
        sw.Write("this is the message");
        sw.Close();
        var key = aes.Key;
        var iv = aes.IV;
        var encoded = buffer.ToArray();

        var aesDecrept = Aes.Create();
        aesDecrept.Key = key;
        aesDecrept.IV = iv;
        var toDecryptStream = new MemoryStream(encoded);
        CryptoStream deCryptoStream = new CryptoStream(
               toDecryptStream,
               aesDecrept.CreateDecryptor(),
               CryptoStreamMode.Read);
        StreamReader sr = new StreamReader(deCryptoStream);
        var deceypedString = sr.ReadToEnd();

        // 創建 RSA 實例
        using (RSA rsa = RSA.Create())
        {
            rsa.ImportParameters(privateKeyParameters);

            // 用私鑰加密數據
            byte[] dataToEncrypt = System.Text.Encoding.UTF8.GetBytes("This is a secret message");
            byte[] encryptedData = rsa.Encrypt(dataToEncrypt, RSAEncryptionPadding.OaepSHA256);

            Console.WriteLine("Encrypted Data (Base64): " + Convert.ToBase64String(encryptedData));

            rsa.ImportParameters(publicKeyParameters);

            // 用公鑰解密數據
            byte[] decryptedData = rsa.Decrypt(encryptedData, RSAEncryptionPadding.OaepSHA256);
            string decryptedMessage = System.Text.Encoding.UTF8.GetString(decryptedData);

            Console.WriteLine("Decrypted Message: " + decryptedMessage);
        }
    }

    private static RSAParameters LoadPrivateKey(string filePath)
    {
        using (StreamReader reader = new StreamReader(filePath))
        {
            PemReader pemReader = new PemReader(reader);
            AsymmetricCipherKeyPair keyPair = (AsymmetricCipherKeyPair)pemReader.ReadObject();
            RsaPrivateCrtKeyParameters privateKey = (RsaPrivateCrtKeyParameters)keyPair.Private;

            return DotNetUtilities.ToRSAParameters(privateKey);
        }
    }

    private static RSAParameters LoadPublicKey(string filePath)
    {
        using (StreamReader reader = new StreamReader(filePath))
        {
            PemReader pemReader = new PemReader(reader);
            RsaKeyParameters publicKey = (RsaKeyParameters)pemReader.ReadObject();

            return DotNetUtilities.ToRSAParameters(publicKey);
        }
    }
}

public static class DotNetUtilities
{
    public static RSAParameters ToRSAParameters(RsaPrivateCrtKeyParameters privateKey)
    {
        return new RSAParameters
        {
            Modulus = privateKey.Modulus.ToByteArrayUnsigned(),
            Exponent = privateKey.PublicExponent.ToByteArrayUnsigned(),
            D = privateKey.Exponent.ToByteArrayUnsigned(),
            P = privateKey.P.ToByteArrayUnsigned(),
            Q = privateKey.Q.ToByteArrayUnsigned(),
            DP = privateKey.DP.ToByteArrayUnsigned(),
            DQ = privateKey.DQ.ToByteArrayUnsigned(),
            InverseQ = privateKey.QInv.ToByteArrayUnsigned()
        };
    }

    public static RSAParameters ToRSAParameters(RsaKeyParameters publicKey)
    {
        return new RSAParameters
        {
            Modulus = publicKey.Modulus.ToByteArrayUnsigned(),
            Exponent = publicKey.Exponent.ToByteArrayUnsigned()
        };
    }
}