WebAPISignalRChat/Backend/Diligent.WebAPI.Host/Hubs/ChatHub.cs

using Diligent.WebAPI.Data.Entities;
using Diligent.WebAPI.Host.DTOs.Notification;
using Diligent.WebAPI.Host.Mediator.Messages.Commands;
using Diligent.WebAPI.Host.Mediator.Notifications.Commands;
using MediatR;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.SignalR;

namespace Diligent.WebAPI.Host.Hubs
{
    public class ChatHub : Hub<IChatClient>
    {
        private readonly IDictionary<string, UserConnection> _connections;
        private readonly IMediator _mediator;

        public ChatHub(IDictionary<string, UserConnection> connections,IMediator mediator)
        {
            _connections = connections;
            _mediator = mediator;
        }

        //public override Task OnDisconnectedAsync(Exception? exception)
        //{
        //    if (_connections.TryGetValue(Context.ConnectionId, out UserConnection room))
        //    {
        //        _connections.Remove(Context.ConnectionId);
        //        Clients.Group(room.RoomId).ReceiveMessage(new ChatMessage { User = room.UserId, Message = $"{room.UserId} has left room" });
        //    }

        //    return base.OnDisconnectedAsync(exception);
        //}

        [HubMethodName("SendMessageToGroup")]
        public async Task SendMessageToGroup(ChatMessage message)
        {
            // Find user's room and send message to everyone
            // All other users will receive notification
            if (_connections.TryGetValue(message.ConnId, out UserConnection room))
            {
                await Clients.Group(room.RoomId).ReceiveMessage(new ChatMessage { User = room.UserId, Message = message.Message });
                await Clients.OthersInGroup(room.RoomId).ReceiveNotifications(room.UserId, room.RoomId);
                await _mediator.Send(new AddMessageCommand(room.RoomId, new Message { Content = message.Message, SenderId = message.UserId, Username = room.Username }));

                // Find other users in room and save notification in database
                foreach (KeyValuePair<string, UserConnection> conn in _connections)
                {
                    if (conn.Value.RoomId == room.RoomId && conn.Key != message.ConnId)
                    {
                        await _mediator.Send(new AddNotificationCommand(new NotificationSaveDTO { RoomId = room.RoomId, ReceiverId = conn.Value.UserId }));
                    }
                }
            }
        }

        [HubMethodName("JoinRoom")]
        public async Task JoinRoom(UserConnection userConnection)
        {
            // Check is user in requested room
            var result = _connections.Where(x => x.Value.UserId == userConnection.UserId && x.Value.RoomId == userConnection.RoomId).FirstOrDefault();

            // If user is not in room, add him
            // Return message "User has joined room" to all users in room
            if (result.Value == null)
            {
                await Groups.AddToGroupAsync(Context.ConnectionId, userConnection.RoomId);
                _connections[Context.ConnectionId] = userConnection;
                await Clients.Group(userConnection.RoomId).ReceiveMessage(new ChatMessage { User = userConnection.UserId, Message = $"{userConnection.Username} has joined room", ConnId = Context.ConnectionId });
            }
            else
            {
                await _mediator.Send(new DeleteNotificationCommand(new NotificationDeleteDTO { UserId = userConnection.UserId, RoomId = userConnection.RoomId }));
            }
        }
    }
}