using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Tango.Core;
using Tango.Core.Threading;
using Tango.Logging;
using Tango.Transport;
using Tango.Transport.Adapters;
using Tango.Transport.Compression;
using Tango.WebRTC.Network;

namespace Tango.WebRTC
{
    public class WebRtcTransportAdapter : TransportAdapterBase
    {
        private WebRtcClient _client;
        private bool _answerReceived;
        private List<IceCandidate> _queuedIceCandidates;

        public event EventHandler Ready;

        public ITransporter SignalingTransporter { get; set; }

        public WebRtcTransportAdapterMode Mode { get; set; }

        public String DataChannelName { get; set; }

        public WebRtcTransportAdapter(ITransporter signalingTransporter, WebRtcTransportAdapterMode mode) : this(signalingTransporter, mode, null)
        {

        }

        public WebRtcTransportAdapter(ITransporter signalingTransporter, WebRtcTransportAdapterMode mode, String dataChannelName)
        {
            SignalingTransporter = signalingTransporter;
            Mode = mode;
            DataChannelName = dataChannelName;
            Address = dataChannelName;
            ComponentName = $"WebRTC Adapter {_component_counter++}";

            SignalingTransporter.RegisterRequestHandler<IceCandidateRequest>(OnIceCandidateRequestReceived);
            SignalingTransporter.RegisterRequestHandler<OfferRequest>(OnOfferRequestReceived);
        }

        public override void Write(byte[] data, bool immidiate = false)
        {
            ThrowIfDisposed();

            try
            {
                if (EnableCompression)
                {
                    data = GZipHelper.Compress(data);
                }

                _client.SendBinary(data);
            }
            catch (Exception ex)
            {
                OnFailed(ex);
            }
        }

        public override Task Connect()
        {
            ThrowIfDisposed();

            TaskCompletionSource<object> completionSource = new TaskCompletionSource<object>();
            bool completed = false;

            _queuedIceCandidates = new List<IceCandidate>();
            _answerReceived = false;

            ThreadFactory.StartNew(async () =>
            {
                if (State != TransportComponentState.Connected)
                {
                    try
                    {
                        _client = new WebRtcClient();

                        if (DataChannelName != null)
                        {
                            _client.DataChannelName = DataChannelName;
                        }

                        Address = _client.DataChannelName;

                        _client.NewIceCandidate += WebRtc_NewIceCandidate;
                        _client.Disconnected += WebRtc_Disconnected;
                        _client.BinaryMessageReceived += WebRtc_BinaryMessageReceived;
                        _client.Ready += (x, e) =>
                        {
                            if (!completed)
                            {
                                LogManager.Log($"{ComponentName}: WebRTC Active Transport Adapter is ready.");
                                completed = true;
                                State = TransportComponentState.Connected;
                                completionSource.SetResult(true);
                                Ready?.Invoke(this, new EventArgs());
                            }

                            if (Mode == WebRtcTransportAdapterMode.Passive)
                            {
                                LogManager.Log($"{ComponentName}: WebRTC Passive Transport Adapter is ready.");
                                Ready?.Invoke(this, new EventArgs());
                            }
                        };

                        LogManager.Log($"{ComponentName}: Initializing WebRTC client...");
                        await _client.Init();

                        if (Mode == WebRtcTransportAdapterMode.Active)
                        {
                            LogManager.Log($"{ComponentName}: Creating WebRTC offer...", LogCategory.Debug);
                            var offer = await _client.CreateOffer();

                            LogManager.Log($"{ComponentName}: Sending WebRTC offer via signaling transporter...", LogCategory.Debug);
                            var response = await SignalingTransporter.SendGenericRequest<OfferRequest, OfferResponse>(new OfferRequest() { Offer = offer }, new TransportRequestConfig()
                            {
                                Timeout = TimeSpan.FromSeconds(30),
                            });

                            LogManager.Log($"{ComponentName}: WebRTC offer sent and responded with an answer. Setting WebRTC answer...", LogCategory.Debug);
                            _client.SetAnswer(response.Answer);
                            _answerReceived = true;

                            foreach (var ice in _queuedIceCandidates.ToList())
                            {
                                LogManager.Log($"{ComponentName}: Sending existing ice candidate '{ice.Sdp}'...", LogCategory.Debug);

                                try
                                {
                                    await SignalingTransporter.SendGenericRequest<IceCandidateRequest, IceCandidateResponse>(new IceCandidateRequest() { IceCandidate = ice }, new TransportRequestConfig()
                                    {
                                        Timeout = TimeSpan.FromSeconds(30),
                                    });
                                }
                                catch (Exception ex)
                                {
                                    LogManager.Log(ex, $"{ComponentName}: Error sending ice candidate.");
                                }
                            }
                        }
                        else
                        {
                            LogManager.Log($"{ComponentName}: Waiting for offer...", LogCategory.Debug);
                            State = TransportComponentState.Connected;

                            if (!completed)
                            {
                                completed = true;
                                completionSource.SetResult(true);
                            }
                        }
                    }
                    catch (Exception ex)
                    {
                        if (!completed)
                        {
                            completed = true;
                            completionSource.SetException(ex);
                        }
                    }
                }
                else
                {
                    if (!completed)
                    {
                        completed = true;
                        completionSource.SetResult(true);
                    }
                }
            });

            if (Mode == WebRtcTransportAdapterMode.Active)
            {
                TimeoutTask.StartNew(() =>
                {
                    if (!completed)
                    {
                        completed = true;
                        completionSource.SetException(new TimeoutException("Could not reach the remote peer using the WebRTC adapter."));
                    }

                }, TimeSpan.FromSeconds(30));
            }

            return completionSource.Task;
        }

        private void WebRtc_BinaryMessageReceived(object sender, DataMessageReceivedEventArgs<byte[]> e)
        {
            if (EnableCompression)
            {
                try
                {
                    var decompressed = GZipHelper.Decompress(e.Data);
                    OnDataAvailable(decompressed);
                }
                catch (Exception ex)
                {
                    if (ex.Message.Contains("GZip"))
                    {
                        //Temporarily ignore, probably switching protocol definitions...
                    }
                    else
                    {
                        //Do nothing... ?
                    }
                }
            }
            else
            {
                OnDataAvailable(e.Data);
            }
        }

        private async void OnOfferRequestReceived(ITransporter transporter, OfferRequest request, string token)
        {
            if (Mode == WebRtcTransportAdapterMode.Passive)
            {
                try
                {
                    var answer = await _client.CreateAnswer(request.Offer);
                    await SignalingTransporter.SendGenericResponse(new OfferResponse() { Answer = answer }, token);
                    _answerReceived = true;

                    foreach (var ice in _queuedIceCandidates.ToList())
                    {
                        LogManager.Log($"{ComponentName}: Sending existing ice candidate '{ice.Sdp}'...", LogCategory.Debug);

                        try
                        {
                            await SignalingTransporter.SendGenericRequest<IceCandidateRequest, IceCandidateResponse>(new IceCandidateRequest() { IceCandidate = ice }, new TransportRequestConfig()
                            {
                                Timeout = TimeSpan.FromSeconds(30),
                            });
                        }
                        catch (Exception ex)
                        {
                            LogManager.Log(ex, $"{ComponentName}: Error sending ice candidate to remote peer.");
                        }
                    }
                }
                catch (Exception ex)
                {
                    LogManager.Log(ex, $"{ComponentName}: Error occurred while trying to return WebRTC answer.");
                }
            }
        }

        private async void WebRtc_NewIceCandidate(object sender, NewIceCandidateEventArgs e)
        {
            try
            {
                if (_answerReceived)
                {
                    LogManager.Log($"{ComponentName}: New WebRTC candidate available. Sending ice to remote peer...", LogCategory.Debug);

                    await SignalingTransporter.SendGenericRequest<IceCandidateRequest, IceCandidateResponse>(new IceCandidateRequest() { IceCandidate = e.IceCandidate }, new TransportRequestConfig()
                    {
                        Timeout = TimeSpan.FromSeconds(30),
                    });
                }
                else
                {
                    if (Mode == WebRtcTransportAdapterMode.Active)
                    {
                        LogManager.Log($"{ComponentName}: New WebRTC candidate available. Will be sent after an answer is received...", LogCategory.Debug);
                    }
                    else
                    {
                        LogManager.Log($"{ComponentName}: New WebRTC candidate available. Will be sent after an offer is received...", LogCategory.Debug);
                    }

                    _queuedIceCandidates.Add(e.IceCandidate);
                }
            }
            catch (Exception ex)
            {
                LogManager.Log(ex, $"{ComponentName}: Error sending ice candidate to remote peer.");
            }
        }

        private async void OnIceCandidateRequestReceived(ITransporter transporter, IceCandidateRequest request, string token)
        {
            try
            {
                LogManager.Log($"{ComponentName}: Ice candidate request received from the remote peer.", LogCategory.Debug);
                await SignalingTransporter.SendGenericResponse(new IceCandidateResponse() { }, token);

                LogManager.Log($"{ComponentName}: Adding ice candidate '{request.IceCandidate.Sdp}'...", LogCategory.Debug);
                _client.AddIceCandidate(request.IceCandidate);
                LogManager.Log($"{ComponentName}: Ice candidate added.", LogCategory.Debug);
            }
            catch (Exception ex)
            {
                LogManager.Log(ex, $"{ComponentName}: Error occurred on ice candidate received handling.");
            }
        }

        private void WebRtc_Disconnected(object sender, EventArgs e)
        {
            OnFailed(new WebRtcTransportAdapterDisconnectedException("WebRtc Transport Adapter RTC client has disconnected."));
        }

        public override Task Disconnect()
        {
            TaskCompletionSource<object> completionSource = new TaskCompletionSource<object>();

            ThreadFactory.StartNew(() =>
            {
                if (State != TransportComponentState.Disconnected)
                {
                    if (_client != null)
                    {
                        LogManager.Log($"{ComponentName}: Disposing WebRTC client...");

                        _client.NewIceCandidate -= WebRtc_NewIceCandidate;
                        _client.Disconnected -= WebRtc_Disconnected;
                        _client.BinaryMessageReceived -= WebRtc_BinaryMessageReceived;

                        try
                        {
                            _client.Dispose();
                            _client = null;
                            SignalingTransporter.UnregisterRequestHandler<IceCandidateRequest>(OnIceCandidateRequestReceived);
                            SignalingTransporter.UnregisterRequestHandler<OfferRequest>(OnOfferRequestReceived);
                            LogManager.Log($"{ComponentName}: WebRTC client disposed.");
                        }
                        catch (Exception ex)
                        {
                            LogManager.Log(ex, $"{ComponentName}: Error disposing WebRTC client.");
                        }
                    }

                    State = TransportComponentState.Disconnected;
                    completionSource.SetResult(true);
                }
                else
                {
                    completionSource.SetResult(true);
                }
            });

            return completionSource.Task;
        }
    }
}