// See https://aka.ms/new-console-template for more information
using System.Net;
using System.Net.Sockets;
using System.Numerics;
using System.Text;
using System.Text.RegularExpressions;
using static RemoteFrameBufferClientProtocol;

IPAddress tessia = new([192,168,16,253]);

IRemoteFrameBufferClientStreamProvider tessia6001vnc = new IRemoteFrameBufferClientStreamProvider.RemoteFrameBufferTcpClientStreamProvider(tessia, 5901);
RemoteFramebufferClient client = new(tessia6001vnc);

client.Start();
Console.ReadLine();
client.Stop();

public interface INetEndPoint
{
    public IPEndPoint EndPoint { get; }
    public IPAddress Address { get; }
    public Int32 Port { get; }

    public class NetEndPointFromIP : INetEndPoint
    {
        public IPEndPoint EndPoint { get; }
        public IPAddress Address => this.EndPoint.Address;
        public Int32 Port => this.EndPoint.Port;

        public NetEndPointFromIP(IPEndPoint endpoint)
        {
            this.EndPoint = endpoint;
        }

        public NetEndPointFromIP(IPAddress address, Int32 port) : this(new(address, port)) { }
    }

    public class NetEndPointFromHostname(String hostname, Int32 port) : INetEndPoint
    {
        public String Hostname { get; } = hostname;
        public IPEndPoint EndPoint => new(this.Address, this.Port);

        public IPAddress Address {
            get
            {
                IPHostEntry entry = Dns.GetHostEntry(this.Hostname);
                return entry.AddressList[0];
            }
        }
        public Int32 Port { get; } = port;
    }
}

public interface IRemoteFrameBufferClientStreamProvider
{
    public Stream GetRemoteFrameBufferClientStream();

    public class RemoteFrameBufferTcpClientStreamProvider : IRemoteFrameBufferClientStreamProvider
    {
        private readonly INetEndPoint remoteEndPoint;
        private readonly IPEndPoint localEndPoint;

        public RemoteFrameBufferTcpClientStreamProvider(INetEndPoint remoteEndPoint, IPEndPoint? localEndPoint)
        {
            this.remoteEndPoint = remoteEndPoint;
            this.localEndPoint = localEndPoint ?? new(IPAddress.Any, 0);
        }

        public Stream GetRemoteFrameBufferClientStream()
        {
            TcpClient tcpClient = new TcpClient(this.localEndPoint);
            tcpClient.Connect(this.remoteEndPoint.EndPoint);
            return tcpClient.GetStream();
        }

        public RemoteFrameBufferTcpClientStreamProvider(String hostname, Int16 port, IPEndPoint? localEndPoint = null) : this(new INetEndPoint.NetEndPointFromHostname(hostname, port), localEndPoint) { }
        public RemoteFrameBufferTcpClientStreamProvider(IPAddress address, Int32 port, IPEndPoint? localEndPoint = null) : this(new INetEndPoint.NetEndPointFromIP(address, port), localEndPoint) { }
        public RemoteFrameBufferTcpClientStreamProvider(IPEndPoint remoteEndPoint, IPEndPoint? localEndPoint = null) : this(new INetEndPoint.NetEndPointFromIP(remoteEndPoint), localEndPoint) { }
    }
}

public partial class RemoteFramebufferClient
{
    private static Dictionary<RfbProtoVersion, RemoteFrameBufferClientProtocol.IRemoteFramebufferClientProtocolFactory> _protocolHandlers;

    private readonly IRemoteFrameBufferClientStreamProvider _socketProvider;
    private Task? backgroundWorker;
    private CancellationTokenSource cancellationTokenSource = new();

    static RemoteFramebufferClient() {
        _protocolHandlers = new() {
            { new RfbProtoVersion(3, 3), new RemoteFrameBufferClientProtocolFactory<RemoteFrameBufferClientProtocol.RemoteFrameBufferClientProtocol_3_3>() },
        };
    }

    public RemoteFramebufferClient(IRemoteFrameBufferClientStreamProvider socketProvider)
    {
        this._socketProvider = socketProvider;
    }

    public void Start()
    {
        if (this.backgroundWorker == null)
        {
            Console.Error.WriteLine("VNC client starting");
            this.backgroundWorker = new Task(this.Worker, this.cancellationTokenSource.Token);
            this.backgroundWorker.ContinueWith(this.WorkerStopped);
            this.backgroundWorker.Start();
        }
    }

    public void Stop()
    {
        if (this.backgroundWorker != null)
        {
            this.cancellationTokenSource.Cancel();
            this.backgroundWorker.Wait();
        }
    }

    private void Worker()
    {
        Int32 failcount = 0;
        while (!this.cancellationTokenSource.Token.IsCancellationRequested)
        {
            Console.Error.WriteLine("Attempting to connect");
            Stream s = this._socketProvider.GetRemoteFrameBufferClientStream();
            using (s)
            {
                Byte[] buf = new Byte[12];
                CancellationTokenSource readTimeout = new CancellationTokenSource(TimeSpan.FromSeconds(5));
                CancellationTokenSource readTokenSource = CancellationTokenSource.CreateLinkedTokenSource(this.cancellationTokenSource.Token, readTimeout.Token);
                try
                {
                    s.ReadExactlyAsync(buf, 0, buf.Length, readTokenSource.Token).AsTask().Wait();
                }catch (AggregateException e)// TODO: go through InnerExceptions and only throw if we are left with unhandled ones
                {
                    if (e.InnerException is TaskCanceledException)
                    {
                        if (failcount++ >= 5)
                        {
                            break;
                        }
                        Task.Delay(1000).Wait();
                        continue;
                    }else
                    {
                        throw new Exception("Something broke. Yeah, I know, very useful message.", e);
                    }
                }
                failcount = 0;
                String protover = Encoding.ASCII.GetString(buf);
                Console.Error.Write($"Server protocol: {protover}");
                Match m = _rfbVersionRegex().Match(protover);
                if (!m.Success)
                {
                    throw new Exception("Cannot parse protocol version");
                }
                RfbProtoVersion serverVersion = new(Int16.Parse(m.Groups["major"].Value), Int16.Parse(m.Groups["minor"].Value));
                RfbProtoVersion maxProto = _protocolHandlers.Keys.Where((ph) => ph <= serverVersion).Max();
                RemoteFrameBufferClientProtocol proto = _protocolHandlers[maxProto].Construct(s);
                Console.Error.WriteLine($"Using client protocol {proto.Version.Major}.{proto.Version.Minor}");
            }

        }
    }

    private void WorkerStopped(Task t)
    {
        Console.Error.WriteLine("VNC client exited");
        this.backgroundWorker = null;
        if (!this.cancellationTokenSource.TryReset())
        {
            this.cancellationTokenSource = new();
        }
    }

    [GeneratedRegex(@"^RFB (?'major'\d{3}).(?'minor'\d{3})$")]
    private static partial Regex _rfbVersionRegex();
}
public struct RfbProtoVersion(Int16 major, Int16 minor)
{
    public Int16 Major = major;
    public Int16 Minor = minor;


    public static Boolean operator ==(RfbProtoVersion a, RfbProtoVersion b)
    {
        return (a.Major == b.Major) && (a.Minor == b.Minor);
    }
    public static Boolean operator !=(RfbProtoVersion a, RfbProtoVersion b)
    {
        return !(a == b);
    }
    public static Boolean operator <(RfbProtoVersion a, RfbProtoVersion b)
    {
        if (a.Major == b.Major)
        {
            return a.Minor < b.Minor;
        } else
        {
            return a.Major < b.Major;
        }
    }
    public static Boolean operator >(RfbProtoVersion a, RfbProtoVersion b)
    {
        return b < a;
    }
    public static Boolean operator <=(RfbProtoVersion a, RfbProtoVersion b)
    {
        return b < a;
    }
    public static Boolean operator >=(RfbProtoVersion a, RfbProtoVersion b)
    {
        return a < b;
    }
}
public abstract class RemoteFrameBufferClientProtocol
{
    protected readonly Stream vncStream;
    public abstract RfbProtoVersion Version { get; }

    public RemoteFrameBufferClientProtocol(Stream s)
    {
        this.vncStream = s;
    }

    public interface IRemoteFramebufferClientProtocolFactory {
        public abstract RemoteFrameBufferClientProtocol Construct(Stream s);
    }
    public class RemoteFrameBufferClientProtocolFactory<T> : IRemoteFramebufferClientProtocolFactory where T : RemoteFrameBufferClientProtocol
    {
        public RemoteFrameBufferClientProtocol Construct(Stream s)
        {
            return (RemoteFrameBufferClientProtocol)Activator.CreateInstance(typeof(T), s)!;
        }
    }

    public class RemoteFrameBufferClientProtocol_3_3 : RemoteFrameBufferClientProtocol
    {
        public override RfbProtoVersion Version => new(3,3);

        public RemoteFrameBufferClientProtocol_3_3(Stream s) : base(s)
        {
        }
    }
}