Shogi/Shogi.Api/Services/SocketService.cs

using FluentValidation;
using Shogi.Contracts.Socket;
using Shogi.Contracts.Types;
using Shogi.Api.Extensions;
using Shogi.Api.Managers;
using System.Net;
using System.Net.WebSockets;
using System.Text.Json;

namespace Shogi.Api.Services
{
    public interface ISocketService
    {
        Task HandleSocketRequest(HttpContext context);
    }

    /// <summary>
    /// Services a single websocket connection. Authenticates the socket connection, accepts messages, and sends messages.
    /// </summary>
    public class SocketService : ISocketService
    {
        private readonly ILogger<SocketService> logger;
        private readonly ISocketConnectionManager communicationManager;
        private readonly ISocketTokenCache tokenManager;

        public SocketService(
          ILogger<SocketService> logger,
          ISocketConnectionManager communicationManager,
          ISocketTokenCache tokenManager) : base()
        {
            this.logger = logger;
            this.communicationManager = communicationManager;
            this.tokenManager = tokenManager;
        }

        public async Task HandleSocketRequest(HttpContext context)
        {
            if (!context.Request.Query.Keys.Contains("token"))
            {
                context.Response.StatusCode = (int)HttpStatusCode.Unauthorized;
                return;
            }
            var token = Guid.Parse(context.Request.Query["token"][0] ?? throw new InvalidOperationException("Token expected during socket connection request, but was not sent."));
            var userName = tokenManager.GetUsername(token);

            if (string.IsNullOrEmpty(userName))
            {
                context.Response.StatusCode = (int)HttpStatusCode.Unauthorized;
                return;
            }
            var socket = await context.WebSockets.AcceptWebSocketAsync();

            communicationManager.Subscribe(socket, userName);
            // TODO: I probably don't need this while-loop anymore? Perhaps unsubscribe when a disconnect is detected instead.
            while (socket.State.HasFlag(WebSocketState.Open))
            {
                try
                {
                    var message = await socket.ReceiveTextAsync();
                    if (string.IsNullOrWhiteSpace(message)) continue;
                    logger.LogInformation("Request \n{0}\n", message);
                    var request = JsonSerializer.Deserialize<ISocketMessage>(message);
                    if (request == null || !Enum.IsDefined(typeof(SocketAction), request.Action))
                    {
                        await socket.SendTextAsync("Error: Action not recognized.");
                        continue;
                    }
                    switch (request.Action)
                    {
                        default:
                            await socket.SendTextAsync($"Received your message with action {request.Action}, but did no work.");
                            break;
                    }
                }
                catch (OperationCanceledException ex)
                {
                    logger.LogError(ex.Message);
                }
                catch (WebSocketException ex)
                {
                    logger.LogInformation($"{nameof(WebSocketException)} in {nameof(SocketConnectionManager)}.");
                    logger.LogInformation("Probably tried writing to a closed socket.");
                    logger.LogError(ex.Message);
                }
                communicationManager.Unsubscribe(userName);

                if (!socket.State.HasFlag(WebSocketState.Closed) && !socket.State.HasFlag(WebSocketState.Aborted))
                {
                    try
                    {
                        await socket.CloseAsync(WebSocketCloseStatus.NormalClosure,
                            "Socket closed",
                            CancellationToken.None);
                    }
                    catch (Exception ex)
                    {
                        Console.WriteLine($"Ignored exception during socket closing. {ex.Message}");
                    }
                }

            }
        }
    }
}