using CommonSocketLibrary.Backoff;
using Serilog;
using System.Collections;
using System.Net.WebSockets;
using System.Text.Json;

namespace CommonSocketLibrary.Abstract
{
    public abstract class SocketClient<Message> : IDisposable where Message : class
    {
        protected ClientWebSocket? _socket;
        protected CancellationTokenSource? _cts;

        private readonly int ReceiveBufferSize = 8192;
        protected readonly ILogger _logger;
        protected readonly JsonSerializerOptions _options;
        private bool _disposed;

        public event EventHandler<EventArgs> OnConnected;
        public event EventHandler<SocketDisconnectionEventArgs> OnDisconnected;


        public SocketClient(ILogger logger, JsonSerializerOptions options)
        {
            _logger = logger;
            _options = options;
            _disposed = false;
        }

        protected async Task ConnectAsync(string url)
        {
            if (_socket != null)
            {
                if (_socket.State == WebSocketState.Open) return;
                else if (!_disposed) _socket.Dispose();
            }

            _socket = new ClientWebSocket();
            _socket.Options.RemoteCertificateValidationCallback = (o, c, ch, er) => true;
            _socket.Options.UseDefaultCredentials = false;
            _disposed = false;
            if (_cts != null) _cts.Dispose();
            _cts = new CancellationTokenSource();
            await _socket.ConnectAsync(new Uri(url), _cts.Token);
            await Task.Factory.StartNew(ReceiveLoop, _cts.Token, TaskCreationOptions.LongRunning, TaskScheduler.Default);
            OnConnected?.Invoke(this, EventArgs.Empty);
        }

        public async Task DisconnectAsync(SocketDisconnectionEventArgs args)
        {
            if (_disposed || _socket == null || _cts == null)
                return;
            
            if (_socket.State == WebSocketState.Open)
            {
                _cts.CancelAfter(TimeSpan.FromMilliseconds(500));
                await _socket.CloseOutputAsync(WebSocketCloseStatus.Empty, "", CancellationToken.None);
                await _socket.CloseAsync(WebSocketCloseStatus.NormalClosure, "", CancellationToken.None);
            }

            OnDisconnected?.Invoke(this, args);
            _socket.Dispose();
            _socket = null;
            _cts.Dispose();
            _cts = null;
        }

        public void Dispose()
        {
            if (_disposed)
                return;

            _disposed = true;
        }

        private async Task ReceiveLoop()
        {
            if (_socket == null || _cts == null) return;

            var loopToken = _cts.Token;
            MemoryStream? outputStream = null;
            WebSocketReceiveResult? receiveResult = null;
            var buffer = new byte[ReceiveBufferSize];
            try
            {
                while (!loopToken.IsCancellationRequested)
                {
                    outputStream = new MemoryStream(ReceiveBufferSize);
                    do
                    {
                        receiveResult = await _socket.ReceiveAsync(buffer, _cts.Token);
                        if (receiveResult.MessageType != WebSocketMessageType.Close)
                            outputStream.Write(buffer, 0, receiveResult.Count);
                    }
                    while (!receiveResult.EndOfMessage);
                    if (receiveResult.MessageType == WebSocketMessageType.Close) break;
                    outputStream.Position = 0;
                    await ResponseReceived(outputStream);
                }
            }
            catch (WebSocketException wse)
            {
                string data = string.Join(string.Empty, wse.Data.Cast<DictionaryEntry>().Select(e => e.Key + "=" + e.Value));
                _logger.Error($"Websocket connection problem while receiving data [state: {_socket.State}][code: {wse.ErrorCode}][data: {data}]");
            }
            catch (TaskCanceledException)
            {
                _logger.Error($"Socket's receive loop got canceled forcefully [state: {_socket.State}]");
            }
            finally
            {
                if (_socket.State.ToString().Contains("Close") || _socket.State == WebSocketState.Aborted)
                    await DisconnectAsync(new SocketDisconnectionEventArgs(_socket.CloseStatus.ToString()!, _socket.CloseStatusDescription ?? string.Empty));
            }
        }

        protected async Task Reconnect(IBackoff backoff, Action reconnect)
        {
            while (true)
            {
                try
                {
                    TimeSpan delay = backoff.GetNextDelay();
                    await Task.Delay(delay);
                    reconnect.Invoke();
                    backoff.Reset();
                    break;
                }
                catch (Exception)
                {
                    _logger.Error("Unable to reconnect to server.");
                }
            }
        }

        private async Task ResponseReceived(Stream stream)
        {
            Message? data = null;
            try
            {
                data = await JsonSerializer.DeserializeAsync<Message>(stream, _options);
            }
            catch (Exception ex)
            {
                _logger.Error(ex, "Failed to read a websocket message.");
            }
            finally
            {
                stream.Dispose();
            }
            if (data == null)
            {
                _logger.Error("Failed to read a websocket message.");
                return;
            }

            try
            {
                await OnResponseReceived(data);
            }
            catch (Exception ex)
            {
                _logger.Error(ex, "Failed to execute a websocket message.");
            }
        }

        protected abstract Task OnResponseReceived(Message? content);
    }

    public class SocketDisconnectionEventArgs : EventArgs
    {
        public string Status { get; }
        public string Reason { get; }

        public SocketDisconnectionEventArgs(string status, string reason)
        {
            Status = status;
            Reason = reason;
        }
    }
}