Supercell.GUT/Supercell.GUT.Server/Network/Connection/ClientConnection.cs

using Supercell.GUT.Logic;
using Supercell.GUT.Server.Protocol;
using Supercell.GUT.Titan.Logic.Message;

namespace Supercell.GUT.Server.Network.Connection;
internal class ClientConnection
{
    private const int ReceiveBufferSize = 16384;
    private const int ReceiveTimeoutMs = 30000;

    private readonly IConnectionListener _listener;
    private readonly MessageManager _messageManager;

    private readonly byte[] _receiveBuffer;
    private IProtocolEntity? _protocolEntity;
    private DateTime _lastKeepAliveTime;

    public bool IsAlive => (DateTime.Now - _lastKeepAliveTime).TotalSeconds < 30.0f;

    public ClientConnection(IConnectionListener listener, MessageManager messageManager)
    {
        _listener = listener;
        _listener.OnSend = SendAsync;
        _listener.RecvCallback = OnMessage;

        _messageManager = messageManager;

        _receiveBuffer = GC.AllocateUninitializedArray<byte>(ReceiveBufferSize);
        _lastKeepAliveTime = DateTime.Now;
    }

    public async Task RunAsync()
    {
        int receiveBufferIndex = 0;
        Memory<byte> receiveBufferMem = _receiveBuffer.AsMemory();

        while (true)
        {
            int readAmount = await ReceiveAsync(receiveBufferMem[receiveBufferIndex..], ReceiveTimeoutMs);
            if (readAmount == 0) break;

            receiveBufferIndex += readAmount;
            int consumedBytes = await _listener.OnReceive(receiveBufferMem, receiveBufferIndex);

            if (consumedBytes > 0)
            {
                Buffer.BlockCopy(_receiveBuffer, consumedBytes, _receiveBuffer, 0, receiveBufferIndex -= consumedBytes);
            }
            else if (consumedBytes < 0) break;
        }
    }

    public async Task SendMessage(PiranhaMessage message)
    {
        await _listener.Send(message);
    }

    public void RefreshKeepAliveTime()
    {
        _lastKeepAliveTime = DateTime.Now;
    }

    public void SetProtocolEntity(IProtocolEntity protocolEntity)
    {
        _protocolEntity = protocolEntity;
    }

    public IProtocolEntity ProtocolEntity
    {
        get
        {
            return _protocolEntity ?? throw new InvalidOperationException("Trying to access _protocolEntity when it's NULL!");
        }
    }

    private async Task OnMessage(PiranhaMessage message)
    {
        await _messageManager.ReceiveMessage(message);
    }

    private async ValueTask<int> ReceiveAsync(Memory<byte> buffer, int timeoutMs)
    {
        CancellationTokenSource cts = new(TimeSpan.FromMilliseconds(timeoutMs));
        return await ProtocolEntity.ReceiveAsync(buffer, cts.Token);
    }

    private async ValueTask SendAsync(Memory<byte> buffer)
    {
        await ProtocolEntity.SendAsync(buffer, default);
    }

    public void SetNonce(string nonce)
    {
        _listener.InitEncryption(LogicVersion.GetKey(), nonce);
    }
}