using Microsoft.AspNet.SignalR.Client;
using System.Collections.Concurrent;
using System.Threading;
using System.Threading.Tasks.Dataflow;

namespace Communicator
{
    public class UISignalRClient : ICommunicator
    {
        private string _connectionUrl;
        private string _hubName;
        private HubConnection? _hubConnection;
        private IHubProxy? _hubProxy;

        private readonly BufferBlock<KeyValuePair<string, object>> _changedDataItems;
        private readonly CancellationTokenSource _cancellationTokenSource;

        private readonly ConcurrentDictionary<string,List<Action<object>>> _subscribedKeys;

        private bool disposedValue;

        public UISignalRClient()
        {
            _connectionUrl = "http://localhost:9999/NewUI";
            _hubName = "UIHub";

            _changedDataItems = new BufferBlock<KeyValuePair<string, object>>();
            _cancellationTokenSource = new CancellationTokenSource();
            _subscribedKeys = new ConcurrentDictionary<string, List<Action<object>>>();
            Task.Run(() =>
            {
                ProcessReceivedData();
            });
        }

        public bool Initialize()
        {
            try
            {
                if (_hubConnection is not null)
                {
                    return true;
                }

                _hubConnection = new HubConnection(_connectionUrl);
                _hubConnection.StateChanged += OnStateChanged;

                _hubProxy = _hubConnection.CreateHubProxy(_hubName);
                _hubProxy.On<Dictionary<string, object>>("ReceiveChangedDataItems", items =>
                {
                    if(items.Count<=0)
                    {
                        return;
                    }

                    foreach (var item in items)
                    {
                        _changedDataItems.Post(item);
                    }
                });


                return true;
            }
            catch (Exception)
            {
                return false;
            }
        }

        public void SubscribeDataItem(string dataKey, Action<object> callback)
        {
            if(!_subscribedKeys.ContainsKey(dataKey))
            {
                _subscribedKeys.TryAdd(dataKey, new List<Action<object>>());
            }
            _subscribedKeys[dataKey].Add(callback);
        }

        public void UnsubscribeDataItem(string dataKey, Action<object> callback)
        {
            if( _subscribedKeys.ContainsKey(dataKey))
            {
                _subscribedKeys[dataKey].Remove(callback);
            }
        }

        private async void ProcessReceivedData()
        {
            while (await _changedDataItems.OutputAvailableAsync() && !_cancellationTokenSource.IsCancellationRequested)
            {
                var item = await _changedDataItems.ReceiveAsync();
                if (!_subscribedKeys.ContainsKey(item.Key))
                {
                    continue;
                }

                foreach (var action in _subscribedKeys[item.Key])
                {
                    action?.Invoke(item.Value);
                }
            }
        }

        private void OnStateChanged(StateChange obj)
        {
            //TODO:
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!disposedValue)
            {
                if (disposing)
                {
                    // TODO: dispose managed state (managed objects)
                    if (_hubConnection is not null)
                    {
                        _hubConnection.StateChanged -= OnStateChanged;
                        _hubConnection.Dispose();

                        _changedDataItems.Complete();
                        _cancellationTokenSource.Cancel();
                        _cancellationTokenSource.Dispose();
                    }
                }

                // TODO: free unmanaged resources (unmanaged objects) and override finalizer
                // TODO: set large fields to null
                disposedValue = true;
            }
        }

        // // TODO: override finalizer only if 'Dispose(bool disposing)' has code to free unmanaged resources
        // ~SignalRClient()
        // {
        //     // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
        //     Dispose(disposing: false);
        // }

        public void Dispose()
        {
            // Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
            Dispose(disposing: true);
            GC.SuppressFinalize(this);
        }
    }
}