using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Net.Sockets;
using System.Threading;
using System.IO;
using System.Net;
using System.Collections;

namespace OpenRA.Server
{
	static class Server
	{
		static List<Connection> conns = new List<Connection>();
		static TcpListener listener = new TcpListener(IPAddress.Any, 1234);

		public static void Main(string[] args)
		{
			listener.Start();

			Console.WriteLine("Server started.");

			for (; ; )
			{
				var checkRead = new ArrayList();
				checkRead.Add(listener.Server);
				foreach (var c in conns) checkRead.Add(c.socket);

				Socket.Select(checkRead, null, null, 1000000 /* 1s */);

				Console.WriteLine("Select() completed with {0} sockets",
					checkRead.Count);

				foreach (Socket s in checkRead)
					if (s == listener.Server) AcceptConnection();
					else ReadData(conns.Single(c => c.socket == s));
			}
		}

		static void AcceptConnection()
		{
			var newConn = new Connection { socket = listener.AcceptSocket() };
			newConn.socket.Blocking = false;
			newConn.socket.NoDelay = true;
			conns.Add(newConn);

			/* todo: assign a player number, setup host behavior, etc */

			Console.WriteLine("Accepted connection from {0}.",
				newConn.socket.RemoteEndPoint);
		}

		static bool ReadDataInner(Connection conn)
		{
			var rx = new byte[1024];
			var len = 0;

			for (; ; )
			{
				try
				{
					if (0 < (len = conn.socket.Receive(rx)))
					{
						Console.WriteLine("Read {0} bytes", len);
						conn.data.AddRange(rx.Take(len));
					}
					else
						break;
				}
				catch (SocketException e)
				{
					if (e.SocketErrorCode == SocketError.WouldBlock) break;
					DropClient(conn, e); 
					return false; 
				}
			}

			return true;
		}

		static void ReadData(Connection conn)
		{
			Console.WriteLine("Start ReadData() for {0}",
				conn.socket.RemoteEndPoint);

			if (ReadDataInner(conn))
				while (conn.data.Count >= conn.ExpectLength)
				{
					var bytes = conn.PopBytes(conn.ExpectLength);
					switch (conn.State)
					{
						case ReceiveState.Header:
							{
								conn.ExpectLength = BitConverter.ToInt32(bytes, 0) - 4;
								conn.Frame = BitConverter.ToInt32(bytes, 4);
								conn.State = ReceiveState.Data;
							} break;

						case ReceiveState.Data:
							{
								DispatchOrders(conn, conn.Frame, bytes);
								conn.ExpectLength = 8;
								conn.State = ReceiveState.Header;
							} break;
					}
				}

			Console.WriteLine("End ReadData() for {0}",
				conn.socket.RemoteEndPoint);
		}

		static void DispatchOrders(Connection conn, int frame, byte[] data)
		{
			foreach (var c in conns.Except(conn).ToArray())
			{
				try
				{
					c.socket.Blocking = true;
					c.socket.Send(BitConverter.GetBytes(data.Length + 4));
					c.socket.Send(BitConverter.GetBytes(frame));
					c.socket.Send(data);
					c.socket.Blocking = false;
				}
				catch (Exception e) { DropClient(c, e); }
			}

			if (frame == 0)
				InterpretServerOrders(data);
		}

		static void InterpretServerOrders(byte[] data)
		{
			/* todo: handle all server orders! */
		}

		static void DropClient(Connection c, Exception e)
		{
			Console.WriteLine("Client dropped: {0}.", c.socket.RemoteEndPoint);
			Console.WriteLine(e.ToString());

			conns.Remove(c);

			/* todo: tell everyone else that `c` has dropped */
		}

		public static void Write(this Stream s, byte[] data) { s.Write(data, 0, data.Length); }
		public static byte[] Read(this Stream s, int len) { var data = new byte[len]; s.Read(data, 0, len); return data; }
		public static IEnumerable<T> Except<T>(this IEnumerable<T> ts, T t)
		{
			return ts.Except(new[] { t });
		}
	}
}