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

namespace ConsoleApp.TelnetSamples
{
    internal class AsyncStreamTelnetClient : IAsyncTelnetClient
	{
		private CancellationTokenSource _cts = new CancellationTokenSource();

		public event EventHandler<string> MessageCallback;
        public event EventHandler<Exception> ErrorCallback;

        private TcpClient _client;
		private NetworkStream _stream; 

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

				_client = new TcpClient();
				await _client.ConnectAsync(ip, port);
				_stream = _client.GetStream();

				_cts = new CancellationTokenSource();
                Task.Run(ReadAsync, _cts.Token);		
			}
			catch (Exception)
			{
				throw;
			}
		}

		private async void ReadAsync()
		{
			try
			{
				StringBuilder sb = new StringBuilder();
				byte[] readBuffer = new byte[1024];
				while (true)
				{
					Thread.Sleep(50);
					if (_cts.IsCancellationRequested)
						break;

					int bytesRead = await this._stream.ReadAsync(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 _stream.WriteAsync(sendBytes);
			}
			catch (Exception)
			{
				throw;
			}
		}

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

				if (_stream != null)
				{
					_stream.Flush();
					_stream.Close();
				}

				_cts.Cancel();

				_client.Close();
				_client.Dispose();
			}
			catch (Exception)
			{
				throw;
			}
		}
	}
}