Kavita/API/SignalR/MessageHub.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using API.Data;
using API.Extensions;
using API.SignalR.Presence;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.SignalR;

namespace API.SignalR
{
    /// <summary>
    /// Generic hub for sending messages to UI
    /// </summary>
    [Authorize]
    public class MessageHub : Hub
    {
        private readonly IPresenceTracker _tracker;

        public MessageHub(IPresenceTracker tracker)
        {
            _tracker = tracker;
        }

        public override async Task OnConnectedAsync()
        {
            await _tracker.UserConnected(Context.User.GetUsername(), Context.ConnectionId);

            var currentUsers = await PresenceTracker.GetOnlineUsers();
            await Clients.All.SendAsync(MessageFactory.OnlineUsers, currentUsers);


            await base.OnConnectedAsync();
        }

        public override async Task OnDisconnectedAsync(Exception exception)
        {
            await _tracker.UserDisconnected(Context.User.GetUsername(), Context.ConnectionId);

            var currentUsers = await PresenceTracker.GetOnlineUsers();
            await Clients.All.SendAsync(MessageFactory.OnlineUsers, currentUsers);


            await base.OnDisconnectedAsync(exception);
        }
    }
}