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

namespace Naloga
{
    class Server
    {
        const int STD_PORT = 1234;
        const string STD_IP = "127.0.0.1";
        const int STD_BUFF = 256;
        

        static void Main()
        {
           
            TcpListener listener = new TcpListener(IPAddress.Parse(STD_IP), STD_PORT);
            listener.Start();

            TcpClient client = listener.AcceptTcpClient();
            NetworkStream tcpStream = client.GetStream();
            FileStream fileStream = new FileStream("video.mp4", FileMode.OpenOrCreate);

            

            int bufferCount = Convert.ToInt32(Math.Ceiling((double)fileStream.Length / (double)STD_BUFF));
            byte[] size = BitConverter.GetBytes(bufferCount);
            tcpStream.Write(size, 0, size.Length);
           

            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[myPublicKey.Length];
                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"); ;
                    //tcpStream.Write(aes.IV, 0, aes.IV.Length);
                    //Console.WriteLine(Encoding.UTF8.GetString(aes.IV));
                    aes.Mode = CipherMode.CBC;
                    aes.Padding = PaddingMode.PKCS7;
                    // Encrypt the message



                    using (CryptoStream cs = new CryptoStream(fileStream, aes.CreateEncryptor(), CryptoStreamMode.Read))
                    {
                        for(int i = 0; i < bufferCount+1; i++)
                        {
                            byte[] buffer = new byte[STD_BUFF];
                            int readBytes = cs.Read(buffer, 0, buffer.Length);
                            tcpStream.Write(buffer, 0, readBytes);
                        }
                        cs.Close();
                    }
                    aes.Dispose();
                }
                eCDiffieHellmanCng.Dispose();

            }



            Console.WriteLine("Finished");

            fileStream.Close();
            tcpStream.Close();
            client.Close();
            listener.Stop();
            Console.ReadKey();
        }
    }

}