Worms2server/src/Syroot.OnlineWorms.Server/Net/PacketHandler.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Sockets;
using System.Reflection;

namespace Syroot.Worms.OnlineWorms.Server.Net
{
    /// <summary>
    /// Represents a class capable of dispatching received <see cref="Packet"/> instances to a corresponding method.
    /// </summary>
    internal class PacketHandler : IDisposable
    {
        // ---- FIELDS -------------------------------------------------------------------------------------------------

        private static readonly Dictionary<Type, Dictionary<Type, MethodInfo>> _packetHandlers
            = new Dictionary<Type, Dictionary<Type, MethodInfo>>();

        private readonly TcpClient _tcpClient;
        private readonly Dictionary<Type, MethodInfo> _handlerMethods;
        private readonly GameConnection _connection;
        private bool _disposed;

        // ---- CONSTRUCTORS & DESTRUCTOR ------------------------------------------------------------------------------

        internal PacketHandler(TcpClient tcpClient)
        {
            Console.WriteLine($"{tcpClient.Client.RemoteEndPoint} connected");
            _tcpClient = tcpClient;
            _handlerMethods = GetHandlerMethods();
            _connection = new GameConnection(_tcpClient);
        }

        // ---- METHODS (PUBLIC) ---------------------------------------------------------------------------------------

        public void Dispose()
        {
            // Do not change this code. Put cleanup code in Dispose(bool disposing).
            Dispose(true);
        }

        // ---- METHODS (INTERNAL) -------------------------------------------------------------------------------------

        /// <summary>
        /// Starts handling packets incoming from this client and calls corresponding methods.
        /// </summary>
        internal void Accept()
        {
            Packet packet;
            while ((packet = _connection.ReceivePacket()) != null)
                HandlePacket(packet);
        }

        // ---- METHODS (PROTECTED) ------------------------------------------------------------------------------------

        protected virtual void Dispose(bool disposing)
        {
            if (!_disposed)
            {
                if (disposing)
                    _tcpClient.Dispose();

                _disposed = true;
            }
        }

        // ---- METHODS (PRIVATE) --------------------------------------------------------------------------------------

        private Dictionary<Type, MethodInfo> GetHandlerMethods()
        {
            Type classType = GetType();
            if (!_packetHandlers.TryGetValue(classType, out Dictionary<Type, MethodInfo> handlerMethods))
            {
                handlerMethods = new Dictionary<Type, MethodInfo>();
                // Find all packet handling methods which are methods accepting and returning a specific packet.
                foreach (MethodInfo method in classType.GetMethods(BindingFlags.NonPublic | BindingFlags.Instance))
                {
                    Type inPacket = method.GetParameters().FirstOrDefault()?.ParameterType;
                    if (typeof(Packet).IsAssignableFrom(inPacket) && typeof(Packet).IsAssignableFrom(method.ReturnType))
                        handlerMethods.Add(inPacket, method);
                }
                _packetHandlers.Add(classType, handlerMethods);
            }
            return handlerMethods;
        }

        private void HandlePacket(Packet inPacket)
        {
            Type packetType = inPacket.GetType();
            Console.WriteLine($"{_tcpClient.Client.RemoteEndPoint} >> {packetType.Name}");

            // Invoke the handler and send back any packet resulting from it.
            if (_handlerMethods[packetType].Invoke(this, new[] { inPacket }) is Packet outPacket)
            {
                Console.WriteLine($"{_tcpClient.Client.RemoteEndPoint} << {outPacket.GetType().Name}");
                _connection.SendPacket(outPacket);
            }
        }
    }
}