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

namespace ConsoleApp.TelnetSamples
{
	public class SocketTelnetClient : ITelnetClient
	{
		private Socket _socket;

        public string Connect(string ip, int port = 23)
		{
			try
			{
				Close();

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

				IPAddress ipAddress = IPAddress.Parse(ip);
				IPEndPoint ipEndPoint = new IPEndPoint(ipAddress, port);
				_socket.Connect(ipEndPoint);

				return Read();
			}
			catch (Exception)
			{
				throw;
			}
		}

        public string Read()
        {
			StringBuilder sb = new StringBuilder();
			byte[] readBuffer = new byte[1024];
            while (true)
            {
				int bytesRead = _socket.Receive(readBuffer);
                if (bytesRead < 1)
                    break;

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

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

				Thread.Sleep(50);
			}

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

			return read.Substring(rnIdx + 1);
		}

		public string SendCommand(string command)
		{
			try
			{
				command += "\r\n";
				byte[] sendBytes = Encoding.ASCII.GetBytes(command);
				_socket.Send(sendBytes);

				return Read();
			}
			catch (Exception)
			{
				throw;
			}
		}

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

				_socket.Shutdown(SocketShutdown.Both);
				_socket.Close();
				_socket.Dispose();
			}
            catch (Exception)
            {
                throw;
            }
        }
    }
}