using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Reactive.Subjects;
using System.Threading;
using System.Threading.Tasks;
using SocketIOClient.JsonSerializer;
using SocketIOClient.Messages;
using SocketIOClient.UriConverters;

namespace SocketIOClient.Transport
{
    public abstract class BaseTransport : IObserver<string>, IObserver<byte[]>, IObservable<IMessage>, IDisposable
    {
        public BaseTransport(SocketIOOptions options, IJsonSerializer jsonSerializer)
        {
            Options = options;
            MessageSubject = new Subject<IMessage>();
            JsonSerializer = jsonSerializer;
            UriConverter = new UriConverter();
            _messageQueue = new Queue<IMessage>();
        }

        DateTime _pingTime;
        readonly Queue<IMessage> _messageQueue;

        protected SocketIOOptions Options { get; }
        protected Subject<IMessage> MessageSubject { get; }

        protected IJsonSerializer JsonSerializer { get; }
        protected CancellationTokenSource PingTokenSource { get; private set; }
        protected OpenedMessage OpenedMessage { get; private set; }

        public string Namespace { get; set; }
        public IUriConverter UriConverter { get; set; }

        public async Task SendAsync(IMessage msg, CancellationToken cancellationToken)
        {
            msg.Eio = Options.EIO;
            msg.Protocol = Options.Transport;
            var payload = new Payload
            {
                Text = msg.Write()
            };
            if (msg.OutgoingBytes != null)
            {
                payload.Bytes = msg.OutgoingBytes;
            }
            await SendAsync(payload, cancellationToken).ConfigureAwait(false);
        }

        protected virtual async Task OpenAsync(OpenedMessage msg)
        {
            OpenedMessage = msg;
            if (Options.EIO == 3 && string.IsNullOrEmpty(Namespace))
            {
                return;
            }
            var connectMsg = new ConnectedMessage
            {
                Namespace = Namespace,
                Eio = Options.EIO,
                Query = Options.Query,
            };
            if (Options.EIO == 4)
            {
                if (Options.Auth != null)
                {
                    connectMsg.AuthJsonStr = JsonSerializer.Serialize(new[] { Options.Auth }).Json.TrimStart('[').TrimEnd(']');
                }
            }

            for (int i = 1; i <= 3; i++)
            {
                try
                {
                    await SendAsync(connectMsg, CancellationToken.None).ConfigureAwait(false);
                    break;
                }
                catch (Exception e)
                {
                    if (i == 3)
                        OnError(e);
                    else
                        await Task.Delay(TimeSpan.FromMilliseconds(Math.Pow(2, i) * 100));
                }
            }
        }

        /// <summary>
        /// <para>Eio3 ping is sent by the client</para>
        /// <para>Eio4 ping is sent by the server</para>
        /// </summary>
        /// <param name="cancellationToken"></param>
        private void StartPing(CancellationToken cancellationToken)
        {
            Debug.WriteLine($"[Ping] Interval: {OpenedMessage.PingInterval}");
            Task.Factory.StartNew(async () =>
            {
                while (!cancellationToken.IsCancellationRequested)
                {
                    await Task.Delay(OpenedMessage.PingInterval);
                    if (cancellationToken.IsCancellationRequested)
                    {
                        break;
                    }
                    try
                    {
                        var ping = new PingMessage();
                        Debug.WriteLine($"[Ping] Sending");
                        await SendAsync(ping, CancellationToken.None).ConfigureAwait(false);
                        Debug.WriteLine($"[Ping] Has been sent");
                        _pingTime = DateTime.Now;
                        MessageSubject.OnNext(ping);
                    }
                    catch (Exception e)
                    {
                        Debug.WriteLine($"[Ping] Failed to send, {e.Message}");
                        MessageSubject.OnError(e);
                        break;
                    }
                }
            }, TaskCreationOptions.LongRunning);
        }

        public abstract Task ConnectAsync(Uri uri, CancellationToken cancellationToken);

        public abstract Task DisconnectAsync(CancellationToken cancellationToken);

        public abstract void AddHeader(string key, string val);

        public virtual void Dispose()
        {
            MessageSubject.Dispose();
            _messageQueue.Clear();
            if (PingTokenSource != null)
            {
                PingTokenSource.Cancel();
                PingTokenSource.Dispose();
            }
        }

        public abstract Task SendAsync(Payload payload, CancellationToken cancellationToken);

        public void OnCompleted()
        {
            throw new NotImplementedException();
        }

        public void OnError(Exception error)
        {
            MessageSubject.OnError(error);
        }

        public void OnNext(string text)
        {
            Debug.WriteLine($"[Receive] {text}");
            var msg = MessageFactory.CreateMessage(Options.EIO, text);
            if (msg == null)
            {
                return;
            }
            if (msg.BinaryCount > 0)
            {
                msg.IncomingBytes = new List<byte[]>(msg.BinaryCount);
                _messageQueue.Enqueue(msg);
                return;
            }
            if (msg.Type == MessageType.Opened)
            {
                OpenAsync(msg as OpenedMessage).ConfigureAwait(false);
            }

            if (Options.EIO == 3)
            {
                if (msg.Type == MessageType.Connected)
                {
                    var connectMsg = msg as ConnectedMessage;
                    connectMsg.Sid = OpenedMessage.Sid;
                    if ((string.IsNullOrEmpty(Namespace) && string.IsNullOrEmpty(connectMsg.Namespace)) || connectMsg.Namespace == Namespace)
                    {
                        if (PingTokenSource != null)
                        {
                            PingTokenSource.Cancel();
                        }
                        PingTokenSource = new CancellationTokenSource();
                        StartPing(PingTokenSource.Token);
                    }
                    else
                    {
                        return;
                    }
                }
                else if (msg.Type == MessageType.Pong)
                {
                    var pong = msg as PongMessage;
                    pong.Duration = DateTime.Now - _pingTime;
                }
            }

            MessageSubject.OnNext(msg);

            if (msg.Type == MessageType.Ping)
            {
                _pingTime = DateTime.Now;
                try
                {
                    SendAsync(new PongMessage(), CancellationToken.None).ConfigureAwait(false);
                    MessageSubject.OnNext(new PongMessage
                    {
                        Eio = Options.EIO,
                        Protocol = Options.Transport,
                        Duration = DateTime.Now - _pingTime
                    });
                }
                catch (Exception e)
                {
                    OnError(e);
                }
            }
        }

        public void OnNext(byte[] bytes)
        {
            Debug.WriteLine($"[Receive] binary message");
            if (_messageQueue.Count > 0)
            {
                var msg = _messageQueue.Peek();
                msg.IncomingBytes.Add(bytes);
                if (msg.IncomingBytes.Count == msg.BinaryCount)
                {
                    MessageSubject.OnNext(msg);
                    _messageQueue.Dequeue();
                }
            }
        }

        public IDisposable Subscribe(IObserver<IMessage> observer)
        {
            return MessageSubject.Subscribe(observer);
        }
    }
}