using System.Net;
using System.Net.Sockets;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;
using RPG.Services.Core.Session;
using RPG.Services.Gateserver.Options;
using RPG.Services.Gateserver.Session;

namespace RPG.Services.Gateserver.Network.Tcp;
internal class TcpGateway
{
    private readonly IOptions<GatewayOptions> _options;
    private readonly SessionManager _sessionManager;
    private readonly ILogger _logger;

    private Socket? _socket;

    private CancellationTokenSource? _acceptCancellation;
    private Task? _acceptTask;

    private ulong _sessionIdCounter;

    public TcpGateway(IOptions<GatewayOptions> options, SessionManager sessionManager, ILogger<TcpGateway> logger)
    {
        _options = options;
        _sessionManager = sessionManager;
        _logger = logger;
    }

    public void Start()
    {
        IPEndPoint bindEndPoint = _options.Value.BindEndPoint;

        _socket = new(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        _socket.Bind(bindEndPoint);
        _socket.Listen(100);

        _acceptCancellation = new();
        _acceptTask = RunAcceptLoopAsync(_acceptCancellation.Token);

        _logger.LogInformation("Listening at tcp://{endPoint}", bindEndPoint);
    }

    public async Task StopAsync()
    {
        if (_acceptCancellation != null && _acceptTask != null)
        {
            await _acceptCancellation.CancelAsync();
            await _acceptTask;
        }

        _socket?.Close();
    }

    private async Task RunAcceptLoopAsync(CancellationToken cancellationToken)
    {
        try
        {
            while (!cancellationToken.IsCancellationRequested)
            {
                Socket clientSocket = await _socket!.AcceptAsync(cancellationToken);

                _logger.LogInformation("New TCP connection from {remoteEndPoint}", clientSocket.RemoteEndPoint);
                _ = RunSessionAsync(clientSocket);
            }
        }
        catch (Exception exception) when (exception is not OperationCanceledException)
        {
            throw;
        }
        catch { /* Operation canceled */ }
    }

    private async Task RunSessionAsync(Socket socket)
    {
        NetworkSession? session = _sessionManager.Create<NetworkSession>(Interlocked.Increment(ref _sessionIdCounter));
        if (session == null) return;

        try
        {
            session.Socket = socket;
            await session.RunAsync();
        }
        catch (Exception exception) when (exception is not OperationCanceledException)
        {
            _logger.LogError("Unhandled exception occurred: {exception}", exception);
        }
        catch { /* Operation canceled */ }
        finally
        {
            _sessionManager.Remove(session);
        }
    }
}