using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace TelnetCommunicator.Telnet
{
    public enum TelnetMode
    {
        Continuously = 0,
        Once,
    }

    public class AsyncSocketTelnetClient
    {
        public event EventHandler<string> MessageCallback;

        private Socket _socket;
        private Thread _readThread;

        public async Task Connect(string ip, int port = 23, TelnetMode mode = TelnetMode.Continuously)
        {
            try
            {
                Close();

                _socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
                _socket.ReceiveTimeout = 1000;

                IPAddress ipAddress = Dns.GetHostAddresses(ip)[0];
                IPEndPoint ipEndPoint = new IPEndPoint(ipAddress, port);
                await _socket.ConnectAsync(ipEndPoint);

                switch (mode)
                {
                    case TelnetMode.Continuously:
                        _readThread = new Thread(ReadAsync);
                        break;
                    case TelnetMode.Once:
                        _readThread = new Thread(ReadAsyncOnce);
                        break;
                }

                _readThread.Start();
            }
            catch (Exception)
            {
                throw;
            }
        }

        private async void ReadAsync()
        {
            try
            {
                StringBuilder sb = new StringBuilder();
                byte[] readBuffer = new byte[1024];

                while (true)
                {
                    int readByte = _socket == null ? 0 : await _socket.ReceiveAsync(readBuffer, SocketFlags.None);
                    if (readByte < 1)
                        break;

                    string data = Encoding.ASCII.GetString(readBuffer, 0, readByte);
                    sb.Append(data);

                    if (!data.EndsWith("\r\n>"))
                        continue;

                    // 에코 삭제
                    string read = sb.ToString();
                    int rnIdx = read.IndexOf("\r\n");
                    read = read.Substring(rnIdx + 1);

                    if (this.MessageCallback != null)
                        this.MessageCallback(this, read);

                    sb.Clear();
                }
            }
            catch (Exception)
            {
                throw;
            }
        }

        private async void ReadAsyncOnce()
        {
            try
            {
                StringBuilder sb = new StringBuilder();
                byte[] readBuffer = new byte[1024];

                while (true)
                {
                    int readByte = _socket == null ? 0 : await _socket.ReceiveAsync(readBuffer, SocketFlags.None);
                    if (readByte < 1)
                    {
                        if (sb.Length > 0 && this.MessageCallback != null)
                            this.MessageCallback(this, sb.ToString());
                        break;
                    }

                    string data = Encoding.ASCII.GetString(readBuffer, 0, readByte);
                    sb.Append(data);

                    if (!data.EndsWith("\r\n>"))
                        continue;

                    // 에코 삭제
                    string read = sb.ToString();
                    int rnIdx = read.IndexOf("\r\n");
                    read = read.Substring(rnIdx + 1);

                    if (this.MessageCallback != null)
                        this.MessageCallback(this, read);

                    sb.Clear();
                }

                Close();
            }
            catch (Exception)
            {
                throw;
            }
        }

        public async Task SendMessage(string message)
        {
            if (_socket == null)
                return;

            try
            {
                message += "\r\n";
                byte[] sendBuffer = Encoding.ASCII.GetBytes(message);
                await _socket.SendAsync(sendBuffer, SocketFlags.None);
            }
            catch (Exception)
            {
                throw;
            }
        }

        public void Close()
        {
            if (_socket == null)
                return;

            try
            {
                _socket.Shutdown(SocketShutdown.Both);

                //_readThread.Abort();
                _socket.Close();
                _socket.Disconnect(true);
                _socket.Dispose();
            }
            catch (Exception)
            {
                throw;
            }
        }
    }
}