using System;
using System.Collections.Concurrent;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using ZeroLevel.Services.Serialization;

namespace ZeroLevel.Network
{
    public class SocketClient
        : BaseSocket, ISocketClient
    {
        #region Private

        private readonly IRouter _router;
        private Socket _clientSocket;
        private NetworkStream _stream;
        private FrameParser _parser = new FrameParser();
        private Thread _sendThread;
        private long _heartbeat_key = -1;
        private long _last_rw_time = DateTime.UtcNow.Ticks;
        private readonly byte[] _buffer = new byte[DEFAULT_RECEIVE_BUFFER_SIZE];
        private readonly object _reconnection_lock = new object();
        private readonly BlockingCollection<SendInfo> _send_queue = new BlockingCollection<SendInfo>();
        private readonly RequestBuffer _requests = new RequestBuffer();
        private int _current_heartbeat_period_in_ms = 0;
        private bool _socket_freezed = false; // используется для связи сервер-клиент, запрещает пересоздание сокета

        private struct SendInfo
        {
            public bool isRequest;
            public int identity;
            public byte[] data;
        }
        #endregion Private

        public IRouter Router { get { return _router; } }

        public bool IsEmptySendQueue { get { return _send_queue.Count == 0; } }

        public SocketClient(IPEndPoint ep, IRouter router)
        {
            _router = router;
            Endpoint = ep;
            _parser.OnIncoming += _parser_OnIncoming;
            _sendThread = new Thread(SendFramesJob);
            _sendThread.IsBackground = true;
            _sendThread.Start();
            EnsureConnection();
        }

        public SocketClient(Socket socket, IRouter router)
        {
            _router = router;
            _socket_freezed = true;
            _clientSocket = socket;
            _stream = new NetworkStream(_clientSocket, true);
            Endpoint = (IPEndPoint)_clientSocket.RemoteEndPoint;
            _parser.OnIncoming += _parser_OnIncoming;
            _sendThread = new Thread(SendFramesJob);
            _sendThread.IsBackground = true;
            _sendThread.Start();
            Working();

            _stream.BeginRead(_buffer, 0, DEFAULT_RECEIVE_BUFFER_SIZE, ReceiveAsyncCallback, null);
        }

        #region API
        public event Action<ISocketClient> OnConnect = (_) => { };
        public event Action<ISocketClient> OnDisconnect = (_) => { };
        public event Action<ISocketClient, byte[], int> OnIncomingData = (_, __, ___) => { };
        public IPEndPoint Endpoint { get; }

        public void Request(Frame frame, Action<byte[]> callback, Action<string> fail = null)
        {
            if (frame == null) throw new ArgumentNullException(nameof(frame));
            if (frame != null && !_send_queue.IsAddingCompleted)
            {
                while (_send_queue.Count >= MAX_SEND_QUEUE_SIZE)
                {
                    Thread.Sleep(50);
                }
                var sendInfo = new SendInfo
                {
                    isRequest = true,
                    data = NetworkPacketFactory.Reqeust(MessageSerializer.Serialize(frame), out int id)
                };
                sendInfo.identity = id;
                _requests.RegisterForFrame(id, callback, fail);
                _send_queue.Add(sendInfo);
                frame.Release();
            }
        }

        public void ForceConnect()
        {
            EnsureConnection();
        }

        public void Send(Frame frame)
        {
            if (frame == null) throw new ArgumentNullException(nameof(frame));
            if (frame != null && !_send_queue.IsAddingCompleted)
            {
                while (_send_queue.Count >= MAX_SEND_QUEUE_SIZE)
                {
                    Thread.Sleep(50);
                }
                _send_queue.Add(new SendInfo
                {
                    isRequest = false,
                    identity = 0,
                    data = NetworkPacketFactory.Message(MessageSerializer.Serialize(frame))
                });
                frame.Release();
            }
        }

        public void Response(byte[] data, int identity)
        {
            if (data == null) throw new ArgumentNullException(nameof(data));
            if (!_send_queue.IsAddingCompleted)
            {
                while (_send_queue.Count >= MAX_SEND_QUEUE_SIZE)
                {
                    Thread.Sleep(50);
                }
                _send_queue.Add(new SendInfo
                {
                    isRequest = false,
                    identity = 0,
                    data = NetworkPacketFactory.Response(data, identity)
                });
            }
        }

        public void UseKeepAlive(TimeSpan period)
        {
            if (_heartbeat_key != -1)
            {
                Sheduller.Remove(_heartbeat_key);
            }
            if (period != TimeSpan.Zero && period.TotalMilliseconds > MINIMUM_HEARTBEAT_UPDATE_PERIOD_MS)
            {
                _current_heartbeat_period_in_ms = (int)period.TotalMilliseconds;
                _heartbeat_key = Sheduller.RemindEvery(period, Heartbeat);
            }
            else
            {
                _current_heartbeat_period_in_ms = 0;
            }
        }
        #endregion

        #region Private methods
        private void _parser_OnIncoming(FrameType type, int identity, byte[] data)
        {
            try
            {
                switch (type)
                {
                    case FrameType.KeepAlive:
                        // Nothing
                        return;
                    case FrameType.Message:
                        _router?.HandleMessage(MessageSerializer.Deserialize<Frame>(data), this);
                        break;
                    case FrameType.Request:
                        var response = _router?.HandleRequest(MessageSerializer.Deserialize<Frame>(data), this);
                        if (response != null)
                        {
                            this.Response(response, identity);
                        }
                        break;
                    case FrameType.Response:
                        _requests.Success(identity, data);
                        break;
                }
                OnIncomingData(this, data, identity);
            }
            catch (Exception ex)
            {
                Log.Error(ex, $"[SocketClient._parser_OnIncoming]");
            }
        }

        private bool TryConnect()
        {
            if (Status == SocketClientStatus.Working)
            {
                return true;
            }
            if (Status == SocketClientStatus.Disposed)
            {
                return false;
            }
            if (_clientSocket != null)
            {
                try
                {
                    _stream?.Close();
                    _stream?.Dispose();
                    _clientSocket.Dispose();
                }
                catch
                {
                    /* ignore */
                }
                _clientSocket = null;
                _stream = null;
            }
            try
            {
                _clientSocket = MakeClientSocket();
                _clientSocket.Connect(Endpoint);
                _stream = new NetworkStream(_clientSocket, true);
                _stream.BeginRead(_buffer, 0, DEFAULT_RECEIVE_BUFFER_SIZE, ReceiveAsyncCallback, null);
            }
            catch (Exception ex)
            {
                Log.SystemError(ex, "[SocketClient.TryConnect] Connection fault");
                Broken();
                return false;
            }
            Working();
            OnConnect(this);
            return true;
        }

        public void EnsureConnection()
        {
            if (_socket_freezed)
            {
                return;
            }
            lock (_reconnection_lock)
            {
                if (Status == SocketClientStatus.Disposed)
                {
                    throw new ObjectDisposedException("connection");
                }
                if (Status != SocketClientStatus.Working)
                {
                    if (false == TryConnect())
                    {
                        throw new Exception("No connection");
                    }
                }
            }
        }

        private void Heartbeat()
        {
            try
            {
                EnsureConnection();
            }
            catch (Exception ex)
            {
                Log.SystemError(ex, "[SocketClient.Heartbeat.EnsureConnection]");
                Broken();
                OnDisconnect(this);
                return;
            }
            _requests.TestForTimeouts();
            try
            {
                _send_queue.Add(new SendInfo
                {
                    identity = 0,
                    isRequest = false,
                    data = NetworkPacketFactory.KeepAliveMessage()
                });
            }
            catch (Exception ex)
            {
                Log.SystemError(ex, "[SocketClient.Heartbeat.Request]");
            }
            var diff_request_ms = ((DateTime.UtcNow.Ticks - _last_rw_time) / TimeSpan.TicksPerMillisecond);
            if (diff_request_ms > (_current_heartbeat_period_in_ms * 2))
            {
                var port = (_clientSocket.LocalEndPoint as IPEndPoint)?.Port;
                Log.Debug($"[SocketClient.Heartbeat] server disconnected, because last data was more thas {diff_request_ms} ms ago. Client port {port}");
                Broken();
            }
        }

        private void ReceiveAsyncCallback(IAsyncResult ar)
        {
            try
            {
                EnsureConnection();
                var count = _stream.EndRead(ar);
                if (count > 0)
                {
                    _parser.Push(_buffer, count);
                    _last_rw_time = DateTime.UtcNow.Ticks;
                }
                else
                {
                    // TODO!!!!!
                    Thread.Sleep(1);
                }
                if (Status == SocketClientStatus.Working
                    || Status == SocketClientStatus.Initialized)
                {
                    _stream.BeginRead(_buffer, 0, DEFAULT_RECEIVE_BUFFER_SIZE, ReceiveAsyncCallback, null);
                }
            }
            catch (ObjectDisposedException)
            {
                /// Nothing
            }
            catch (Exception ex)
            {
                Log.SystemError(ex, $"[SocketClient.ReceiveAsyncCallback] Error read data");
                Broken();
                OnDisconnect(this);
            }
        }

        private void SendFramesJob()
        {
            SendInfo frame;
            while (Status != SocketClientStatus.Disposed)
            {
                if (_send_queue.IsCompleted)
                {
                    return;
                }
                if (Status != SocketClientStatus.Working)
                {
                    Thread.Sleep(100);
                    try
                    {
                        EnsureConnection();
                    }
                    catch (Exception ex)
                    {
                        Log.SystemError(ex, "[SocketClient.SendFramesJob] Send next frame fault");
                    }
                    if (Status == SocketClientStatus.Disposed) return;
                    continue;
                }
                try
                {
                    frame = _send_queue.Take();
                    if (frame.isRequest)
                    {
                        _requests.StartSend(frame.identity);
                    }
                    _stream.Write(frame.data, 0, frame.data.Length);
                    _last_rw_time = DateTime.UtcNow.Ticks;
                }
                catch (Exception ex)
                {
                    Log.SystemError(ex, $"[SocketClient.SendFramesJob] Backward send error.");
                    Broken();
                    OnDisconnect(this);
                }
            }
        }

        #endregion

        #region Helper

        private static Socket MakeClientSocket()
        {
            var s = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            s.SetIPProtectionLevel(IPProtectionLevel.Unrestricted);
            s.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.DontLinger, true);
            return s;
        }

        #endregion Helper

        public override void Dispose()
        {
            if (Status == SocketClientStatus.Working)
            {
                OnDisconnect(this);
            }
            Disposed();
            Sheduller.Remove(_heartbeat_key);
            _stream?.Close();
            _stream?.Dispose();
        }
    }
}