using Microsoft.AspNet.SignalR.Client;
using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Tango.Core;

namespace Tango.Transport.Adapters
{
    /// <summary>
    /// Represents an adapter for communicating via SignalR protocol.
    /// </summary>
    /// <seealso cref="Tango.Transport.TransportAdapterBase" />
    public class SignalRTransportAdapter : TransportAdapterBase
    {
        private IHubProxy _proxy;
        private HubConnection _connection;
        private Thread _pushThread;
        private ProducerConsumerQueue<byte[]> _pushQueue;
        private object _writeSyncObject = new object();

        /// <summary>
        /// Gets or sets the URL of the SignalR service.
        /// </summary>
        public String Url { get; set; }

        /// <summary>
        /// Gets or sets the SignalR hub name.
        /// </summary>
        public String Hub { get; set; }

        /// <summary>
        /// Gets or sets the serial number of the remote machine (Use only for <see cref="SignalRTransportAdapterMode.CreateSession"/>) mode.
        /// </summary>
        public String SerialNumber { get; set; }

        /// <summary>
        /// Gets or sets the remote session identifier.
        /// </summary>
        public String SessionID { get; private set; }

        /// <summary>
        /// Gets or sets the interval of write operation.
        /// Unlike other adapters, the SignalR adapter accumulates multiple write operations into one chunk.
        /// </summary>
        public TimeSpan WriteInterval { get; set; }

        /// <summary>
        /// Gets or sets the adapter mode.
        /// </summary>
        public SignalRTransportAdapterMode Mode { get; set; }

        /// <summary>
        /// Gets or sets the adapter connection timeout.
        /// </summary>
        public TimeSpan ConnectionTimeout { get; set; }

        /// <summary>
        /// Initializes a new instance of the <see cref="SignalRTransportAdapter"/> class.
        /// </summary>
        public SignalRTransportAdapter() : base()
        {
            ConnectionTimeout = TimeSpan.FromSeconds(30);
            WriteInterval = TimeSpan.FromMilliseconds(1);
            ComponentName = $"SignalR Adapter {_component_counter++}";
        }

        /// <summary>
        /// Initializes a new instance of the <see cref="SignalRTransportAdapter"/> class.
        /// </summary>
        /// <param name="url">The service address.</param>
        /// <param name="hub">The hub name.</param>
        /// <param name="mode">The adapter mode.</param>
        /// <param name="serialNumber">The machine serial number (when creating session).</param>
        /// <param name="sessionID">The session identifier (when joining session).</param>
        public SignalRTransportAdapter(String url, String hub, SignalRTransportAdapterMode mode, String serialNumber = null, String sessionID = null, String ipAddress = null) : this()
        {
            Url = url;
            Hub = hub;
            Mode = mode;
            SerialNumber = serialNumber;
            SessionID = sessionID;
            Address = sessionID;

            if (!String.IsNullOrWhiteSpace(ipAddress))
            {
                Address = ipAddress;
            }
        }

        /// <summary>
        /// Writes the specified data to the stream.
        /// </summary>
        /// <param name="data">The data.</param>
        /// <param name="immidiate">Writes the data as soon as possible while ignoring any message queuing and batching.</param>
        public override void Write(byte[] data, bool immidiate = false)
        {
            TotalBytesSent += data.Length;
            _totalBytes += data.Length;

            AppendTransferRateBytes(data.Length);

            if (!immidiate)
            {
                _pushQueue.BlockEnqueue(data);
            }
            else
            {
                try
                {
                    lock (_writeSyncObject)
                    {
                        _proxy.Invoke("Write", new List<byte[]>() { data }).GetAwaiter().GetResult();
                    }
                }
                catch (Exception ex)
                {
                    OnFailed(LogManager.Log(ex, $"{ComponentName}: Error writing to SignalR adapter ({Address})."));
                    return;
                }
            }
        }

        /// <summary>
        /// Connects the transport component.
        /// </summary>
        /// <returns></returns>
        public override Task Connect()
        {
            if (State != TransportComponentState.Connected)
            {
                LogManager.Log($"{ComponentName}: Connecting SignalR adapter...");

                bool completed = false;

                TaskCompletionSource<object> completionSource = new TaskCompletionSource<object>();

                _connection = new HubConnection(Url);
                _proxy = _connection.CreateHubProxy(Hub);

                Core.Threading.TimeoutTask.StartNew(() =>
                {
                    if (!completed)
                    {
                        completed = true;
                        completionSource.SetException(new TimeoutException("Could not reach the remote machine after the given timeout."));
                    }

                }, ConnectionTimeout);

                if (Mode == SignalRTransportAdapterMode.CreateSession)
                {
                    _proxy.On("SessionCreated", () =>
                    {
                        try
                        {
                            if (!completed)
                            {
                                completed = true;

                                LogManager.Log($"{ComponentName}: SignalR adapter session created ({SessionID})...");
                                LogManager.Log($"{ComponentName}: SingalR adapter connected.");
                                State = TransportComponentState.Connected;

                                StartPushThread();

                                completionSource.SetResult(true);
                            }
                        }
                        catch (Exception ex)
                        {
                            if (!completed)
                            {
                                LogManager.Log(ex, $"{ComponentName}: Error occurred after session created.");
                                completed = true;
                                completionSource.SetException(ex);
                            }
                        }
                    });
                }

                _connection.StateChanged += async (x) =>
                {
                    try
                    {
                        if (x.NewState == ConnectionState.Connected)
                        {
                            if (Mode == SignalRTransportAdapterMode.CreateSession)
                            {
                                LogManager.Log($"{ComponentName}: Creating SignalR adapter Session...");
                                SessionID = await _proxy.Invoke<String>("CreateSession", SerialNumber);
                            }
                            else
                            {
                                LogManager.Log($"{ComponentName}: Joining SignalR adapter session ({SessionID})...");
                                await _proxy.Invoke("JoinSession", SessionID);
                                LogManager.Log($"{ComponentName}: SingalR adapter connected.");
                            }

                            if (Mode == SignalRTransportAdapterMode.JoinSession)
                            {
                                if (!completed)
                                {
                                    completed = true;
                                    State = TransportComponentState.Connected;
                                    StartPushThread();
                                    completionSource.SetResult(true);
                                }
                            }
                        }
                    }
                    catch (Exception ex)
                    {
                        if (!completed)
                        {
                            completed = true;
                            LogManager.Log(ex, $"{ComponentName}: Error occurred on connection state changed event.");
                            completionSource.SetException(ex);
                        }
                    }
                };

                _proxy.On<List<byte[]>>("DataAvailable", (dataCollection) => { OnDataAvailable(dataCollection); });
                _connection.Start();

                return completionSource.Task;
            }

            return Task.FromResult(true);
        }

        /// <summary>
        /// Disconnects the transport component.
        /// </summary>
        /// <returns></returns>
        public override Task Disconnect()
        {
            return Task.Factory.StartNew(() =>
            {
                if (State == TransportComponentState.Connected)
                {
                    LogManager.Log($"{ComponentName}: Disconnecting SignalR adapter...");
                    Core.Threading.TimeoutTask.StartNew(() =>
                    {
                        try
                        {
                            _connection.Stop();
                            _connection.Dispose();

                            try
                            {
                                if (_pushThread != null)
                                {
                                    _pushThread.Abort();
                                }
                            }
                            catch { }
                        }
                        catch (Exception ex)
                        {
                            LogManager.Log(ex, $"{ComponentName}: Error disposing SignalR adapter connection.");
                        }
                    }, TimeSpan.FromSeconds(5));

                    LogManager.Log($"{ComponentName}: SignalR adapter disconnected.");
                    State = TransportComponentState.Disconnected;
                }
            });
        }

        /// <summary>
        /// Handles the write operation.
        /// </summary>
        private void PushThreadMethod()
        {
            try
            {
                while (State == TransportComponentState.Connected)
                {
                    List<byte[]> dataCollection = new List<byte[]>();

                    var data = _pushQueue.BlockDequeue();
                    var first = true;

                    while (_pushQueue.Count > 0 || first)
                    {
                        if (!first)
                        {
                            data = _pushQueue.BlockDequeue();
                        }
                        else
                        {
                            first = false;
                        }

                        if (EnableCompression)
                        {
                            var compressed = Compression.GZipHelper.Compress(data);
                            dataCollection.Add(compressed);
                        }
                        else
                        {
                            dataCollection.Add(data);
                        }
                    }

                    if (dataCollection.Count > 0)
                    {
                        try
                        {
                            lock (_writeSyncObject)
                            {
                                _proxy.Invoke("Write", dataCollection).GetAwaiter().GetResult();
                            }
                        }
                        catch (Exception ex)
                        {
                            OnFailed(LogManager.Log(ex, $"{ComponentName}: Error writing to SignalR adapter ({Address})."));
                            return;
                        }
                    }

                    Thread.Sleep(WriteInterval);
                }
            }
            catch (ThreadAbortException) { }
        }

        /// <summary>
        /// Called when new data is available.
        /// </summary>
        /// <param name="dataCollection">The data collection.</param>
        private void OnDataAvailable(List<byte[]> dataCollection)
        {
            try
            {
                foreach (var data in dataCollection)
                {
                    if (EnableCompression)
                    {
                        try
                        {
                            var decompressed = Compression.GZipHelper.Decompress(data);
                            OnDataAvailable(decompressed);
                        }
                        catch (Exception ex)
                        {
                            if (ex.Message.Contains("GZip"))
                            {
                                //Temporarily ignore, probably switching protocol definitions...
                                OnDataAvailable(data);
                            }
                            else
                            {
                                throw ex;
                            }
                        }
                    }
                    else
                    {
                        OnDataAvailable(data);
                    }
                }
            }
            catch (Exception ex)
            {
                OnFailed(ex);
            }
        }

        private void StartPushThread()
        {
            _pushQueue = new ProducerConsumerQueue<byte[]>();
            _pushThread = new Thread(PushThreadMethod);
            _pushThread.IsBackground = true;
            _pushThread.Name = $"{ComponentName} Push Thread";
            _pushThread.Start();
        }
    }
}