using Networking.Pages;
using System;
using System.Threading;
using System.Windows.Forms;

namespace PortScanner
{
     public class ScannerManagerSingleton : IScannerManagerSingleton
     {
          // The instance variable - this is a singleton class
          private static ScannerManagerSingleton _instance;

          // The PortScanner used to scan ports
          private PortScannerBase portScanner;

          // Enumeration for scanning modes
          public enum ScanMode
          {
               TCP = 1,
               UDP = 2
          }

          // Private constructor - this is a singleton class
          private ScannerManagerSingleton()
          {
          }

          // Instance property - this is a singleton class
          public static ScannerManagerSingleton Instance
          {
               get
               {
                    if (_instance == null)
                         _instance = new ScannerManagerSingleton();

                    return _instance;
               }
          }

          // Instantiate the correct type of PortScanner
          private void InstantiatePortScanner(ScanMode scanMode)
          {
               switch (scanMode)
               {
                    case ScanMode.TCP:
                         portScanner = new TCPPortScanner();
                         break;

                    case ScanMode.UDP:
                         portScanner = new UDPPortScanner();
                         break;
               }
          }

          // Scan one port asynchronously
          public async void ExecuteOnceAsync(string hostname, int port, int timeout, ScanMode scanMode, WF_PortScanner.ExecuteOnceAsyncCallback callback, CancellationToken ct)
          {
               // Instantiate a PortScanner
               InstantiatePortScanner(scanMode);

               // Assign values
               portScanner.Hostname = hostname;
               portScanner.Port = port;
               portScanner.Timeout = timeout;

               // Await for the result of this operation
               var task = portScanner.CheckOpenAsync(ct);
               await task;

               // If a cancellation request has been triggered through CancellationToken ct, we must advise the callback function
               bool cancelled = ct.IsCancellationRequested;

               // Callback with the result and the port
               callback(port, task.Result, cancelled, true);
          }

          // Scan a range of ports asynchronously
          public async void ExecuteRangeAsync(string hostname, int portMin, int portMax, int timeout, ScanMode scanMode, ProgressBar progress, WF_PortScanner.ExecuteOnceAsyncCallback callback, CancellationToken ct)
          {
               // Instantiate a PortScanner
               InstantiatePortScanner(scanMode);

               // Assign first values
               portScanner.Hostname = hostname;
               portScanner.Timeout = timeout;

               bool isLast = false;
               bool cancelled = false;

               for (int i = portMin; i <= portMax && !cancelled; i++)
               {
                    if (i == portMax)
                    {
                         isLast = true;
                    }

                    portScanner.Port = i;
                    int percent = 100 * i / portMax;
                    progress.Value = percent;

                    var task = portScanner.CheckOpenAsync(ct);
                    await task;

                    cancelled = ct.IsCancellationRequested;

                    callback(i, task.Result, cancelled, isLast);
               }
          }
     }
}