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

namespace ConsoleApp.TelnetSamples
{
	internal class AsyncSocketTelnetClient : IAsyncTelnetClient
	{
		private readonly CancellationTokenSource CTS = new CancellationTokenSource();

		public event EventHandler<string> MessageCallback;

		private Socket _socket;

		public async void Connect(string ip, int port = 23)
		{
			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);

				Task.Run(ReadAsync);
			}
			catch (Exception)
			{
				throw;
			}
		}

		private async void ReadAsync()
		{
			try
			{

				StringBuilder sb = new StringBuilder();
				byte[] readBuffer = new byte[1024];
				while (true)
				{
					int bytesRead = await _socket.ReceiveAsync(readBuffer);
					if (bytesRead < 1)
						break;

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

		public async void SendCommand(string command)
		{
			try
			{
				command += "\r\n";
				byte[] sendBytes = Encoding.ASCII.GetBytes(command);
				await _socket.SendAsync(sendBytes);
			}
			catch (Exception)
			{
				throw;
			}
		}

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

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