using Networking.Pages;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace PortScanner
{
     class UDPPortScanner : PortScannerBase
     {
          // The UDP client used for scanning a port
          private UdpClient udpClient;

          // Constructor - use base constructor
          public UDPPortScanner() : base()
          {
          }

          // TODO:
          public async override Task<bool> CheckOpenAsync(CancellationToken ct)
          {
               // We are using a UDP client to see whether the port is open or not
               // Therefore, the absence of a response means that the port is open
               // If there is any respone, it is closed
               using (udpClient = new UdpClient())
               {
                    bool returnVal;
                    try
                    {
                         // Connect to the server
                         udpClient.Connect(Hostname, Port);

                         // Set the timeout
                         udpClient.Client.ReceiveTimeout = Timeout;

                         // Sends a message over UDP
                         Byte[] sendBytes = Encoding.ASCII.GetBytes("Are you open?");
                         udpClient.Send(sendBytes, sendBytes.Length);

                         // IPEndPoint object will allow us to read datagrams sent from any source.
                         // Port 0 means any available port
                         IPEndPoint RemoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);

                         // Asynchronously begin receiving
                         var result = udpClient.ReceiveAsync();
                         if (await Task.WhenAny(result, Task.Delay(Timeout, ct)) == result)
                         {
                              Console.WriteLine(Encoding.ASCII.GetString(result.Result.Buffer));
                              returnVal = false;
                         }
                         else
                         {
                              // There was no response, we will consider this port as open
                              returnVal = true;
                         }
                         udpClient.Close();
                         return returnVal;
                    }
                    catch (SocketException e)
                    {
                         Console.WriteLine("Error Code: " + e.ErrorCode);

                         switch (e.ErrorCode)
                         {
                              case 10054:
                                   returnVal = false;
                                   break;

                              case 11001:
                                   returnVal = false;

                                   // Display an error message on the main thread
                                   MessageBox.Show(
                                       "Hostname could not be resolved.",
                                       "Connection Error",
                                       MessageBoxButtons.OK,
                                       MessageBoxIcon.Error);
                                   break;
                              default:
                                   returnVal = true;
                                   break;
                         }
                    }
                    udpClient.Close();
                    return returnVal;
               }
          }
     }
}