using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Security.Cryptography;
using System.Reflection.Metadata;
using System;

namespace Naloga {
    class Client
    {
        const int STD_PORT = 1234;
        const string STD_IP = "127.0.0.1";
        const int STD_BUFF = 256;
        static void Main()
        {
          
            TcpClient client = new TcpClient();
            client.Connect(IPAddress.Parse(STD_IP), STD_PORT);
            NetworkStream tcpStream = client.GetStream();

            byte[] bytes = new byte[STD_BUFF];
            int lenght = tcpStream.Read(bytes, 0, bytes.Length);
            int bufferCount = BitConverter.ToInt32(bytes,0);

            using (ECDiffieHellmanCng eCDiffieHellmanCng = new ECDiffieHellmanCng())
            {

                eCDiffieHellmanCng.KeyDerivationFunction = ECDiffieHellmanKeyDerivationFunction.Hash;
                eCDiffieHellmanCng.HashAlgorithm = CngAlgorithm.Sha256;

                byte[] myPublicKey = eCDiffieHellmanCng.PublicKey.ToByteArray();
                tcpStream.Write(myPublicKey, 0, myPublicKey.Length);

                byte[] therePublicKey = new byte[STD_BUFF];
                int retLenght = tcpStream.Read(therePublicKey, 0, therePublicKey.Length);
                CngKey thereKey = CngKey.Import(therePublicKey, CngKeyBlobFormat.EccPublicBlob);
                byte[] myKey = eCDiffieHellmanCng.DeriveKeyMaterial(thereKey);

                using (Aes aes = Aes.Create())
                {
                    aes.Key = myKey;
                    aes.IV = Encoding.UTF8.GetBytes("sestnajst1616161");
                    //Console.WriteLine(Encoding.UTF8.GetString(aes.IV));
                    aes.Mode = CipherMode.CBC;
                    aes.Padding = PaddingMode.PKCS7;
                    // Encrypt the message

                    using(FileStream fileStream = new FileStream("video.mp4", FileMode.OpenOrCreate))
                    using (CryptoStream cs = new CryptoStream(tcpStream, aes.CreateDecryptor(), CryptoStreamMode.Read))
                    {
                        
                        for (int i = 0; i < bufferCount+1; i++)
                        {
                            byte[] bytes2 = new byte[STD_BUFF];
                            int len = cs.Read(bytes2, 0, bytes2.Length);

                            //Console.WriteLine(Encoding.UTF8.GetString(bytes2));
                            fileStream.Write(bytes2, 0, len);
                        }

                        cs.Close();
                        fileStream.Close();
                    }
                    aes.Dispose();
                }
            }

            


            
            tcpStream.Close();
            client.Close();


            Console.WriteLine("Finished");
            Console.ReadKey();
        }
    }
}