using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Security.Cryptography;
using System.Threading;

namespace UdPunching
{
    internal static class PeerProgram
    {
        private static RSACryptoServiceProvider _serverRsa;
        private static RSACryptoServiceProvider _peerRsa;
        private static IPEndPoint _serverEndPoint;

        private static int packetSeq;
        private static Socket _peerSocket;

        private static void ProcessPacket(SocketAsyncEventArgs sae)
        {
            ++packetSeq;
            Console.WriteLine($"Incoming packet#{packetSeq:0,000,000} from {sae.RemoteEndPoint}, BytesTransferred {sae.BytesTransferred}");

            var peerId = TransferCodec.ReadId(sae.Buffer);
            Console.WriteLine($"Incoming packet#{packetSeq:0,000,000} peer id {peerId}");

            if (sae.RemoteEndPoint.IpEndPointEqualsTo(_serverEndPoint))
            {
                if (TransferCodec.InvalidPeerId == peerId)
                {
                    Console.WriteLine($"Incoming packet#{packetSeq:0,000,000} Server FAILURE");
                }
                else if (Guid.Empty == peerId)
                {
                    var msgData = TransferCodec.DecodeData(_peerRsa, sae.Buffer);
                    Console.WriteLine($"Incoming packet#{packetSeq:0,000,000} data length {msgData.Length}");

                    var msg = new ExchangeMessage(msgData);

                    Console.WriteLine($"Incoming packet#{packetSeq:0,000,000} flag {msg.Flags}");
                    if (msg.Flags.HasFlag(ExchangeMessageFlags.EchoEndPoint)) Console.WriteLine($"Incoming packet#{packetSeq:0,000,000} **** echo endpoint {msg.PeerEndPoint}");
                }
                //TODO: handle server message
            }
            else
            {
                //TODO: handle peers message
            }
        }

        private static void DeadLoopKeepAlive()
        {
            var buf = new byte[7];// 1flag,1count,1section,4timestamp
            var msg = new ExchangeMessage();
            msg.Flags = ExchangeMessageFlags.PeerKeepAlive;

            while (true)
            {
                msg.PeerTimeStamp = DateTime.Now;
                msg.WriteToBuffer(buf);
                var encode = TransferCodec.Encode(_serverRsa, Properties.Settings.Default.PeerId, buf);

                Console.WriteLine($"Sending packet KeepAlive {msg.PeerTimeStamp}");
                _peerSocket.SendTo(encode, _serverEndPoint);

                Thread.Sleep(1000);
            }
        }

        private static void Main(string[] args)
        {
            Console.WriteLine("Init...");

            _serverRsa = new RSACryptoServiceProvider();
            _serverRsa.FromXmlString(File.ReadAllText("ServerPublicKey.txt"));
            _peerRsa = new RSACryptoServiceProvider();
            _peerRsa.FromXmlString(File.ReadAllText("PeerPrivateKey.txt"));

            _serverEndPoint = new IPEndPoint(IPAddress.Parse(Properties.Settings.Default.Host), Properties.Settings.Default.Port);

            _peerSocket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
            _peerSocket.Bind(new IPEndPoint(IPAddress.Any, 0));
            Console.WriteLine($"Peer Bind on {_peerSocket.LocalEndPoint}");

            const int receiveBufferSize = 1500;

            var sae = new SocketAsyncEventArgs();
            sae.SetBuffer(new byte[receiveBufferSize], 0, receiveBufferSize);
            sae.RemoteEndPoint = new IPEndPoint(IPAddress.Any, 0);

            Console.WriteLine($"Receive buffer:{receiveBufferSize}");

            void SaeOnCompleted(object sender, SocketAsyncEventArgs e)
            {
                if (e.SocketError == SocketError.Success)
                {
                    try
                    {
                        ProcessPacket(sae);
                    }
                    catch (Exception exception)
                    {
                        Console.WriteLine(exception);
                    }
                }
                else
                {
                    Console.WriteLine($"ERROR:{e.SocketError}");
                }

                sae.RemoteEndPoint = new IPEndPoint(IPAddress.Any, 0);
                if (false == _peerSocket.ReceiveFromAsync(sae)) SaeOnCompleted(null, null);
            }

            sae.Completed += SaeOnCompleted;

            if (false == _peerSocket.ReceiveFromAsync(sae))
            {
                SaeOnCompleted(null, null);
            }

            DeadLoopKeepAlive();
        }
    }
}