//	Spludlow Software
//	Copyright © Samuel P. Ludlow 2020 All Rights Reserved
//	Distributed under the terms of the GNU General Public License version 3
//	Distributed WITHOUT ANY WARRANTY; without implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE
//	https://www.spludlow.co.uk/LICENCE.TXT
//	The Spludlow logo is a registered trademark of Samuel P. Ludlow and may not be used without permission
//	v1.14

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

using System.Data;
using System.Net.Sockets;

namespace Spludlow.Net
{
	public class PortScanner
	{
		public static void Scan(string[] addresses, int threads, int timeoutSeconds)
		{
			int[] portNumbers = new int[] { 21, 22, 23, 25, 53, 80, 110, 139, 443, 445, 465, 587, 993, 995, 1433, 5060, 9100 };

			Scan(addresses, threads, timeoutSeconds, portNumbers);
		}

		public static void Scan(string[] addresses, int threads, int timeoutSeconds, int[] portNumbers)
		{
			DataTable table = Spludlow.Data.TextTable.ReadText(new string[]
			{
				"Address	PortNumber	ThreadId	ConnectStart	ConnectFinish	Connectable",
				"String		Int32		Int32		DateTime		DateTime		Boolean",
			});

			foreach (string address in addresses)
			{
				foreach (int portNumber in portNumbers)
					table.Rows.Add(address, portNumber, -1);
			}

			Task[] tasks = new Task[threads];
			for (int index = 0; index < threads; ++index)
			{
				int threadId = index;

				tasks[threadId] = new Task(() => ScanWorker(table, threadId, timeoutSeconds));
			}

			foreach (Task task in tasks)
				task.Start();

			Task.WaitAll(tasks);

			DataView view = new DataView(table);
			view.RowFilter = "Connectable = true";

			Spludlow.Log.Report("PortScanner Scan", view, table);
		}

		private static void ScanWorker(DataTable table, int threadId, int timeoutSeconds)
		{
			DataRow row;

			string address;
			int portNumber;

			while (true)
			{
				lock (table)
				{
					DataRow[] rows = table.Select("ThreadId = -1");
					if (rows.Length == 0)
						return;

					row = rows[0];
					row["ThreadId"] = threadId;

					address = (string)row["Address"];
					portNumber = (int)row["PortNumber"];
				}

				DateTime start = DateTime.Now;
				bool connectable = CanTcpConnect(address, portNumber, timeoutSeconds);
				DateTime end = DateTime.Now;

				lock (table)
				{
					row["ConnectStart"] = start;
					row["Connectable"] = connectable;
					row["ConnectFinish"] = end;
				}
			}

		}

		public static bool CanTcpConnect(string address, int portNumber, int waitSeconds)
		{
			using (TcpClient client = new TcpClient())
			{
				IAsyncResult asyncResult = client.BeginConnect(address, portNumber, null, null);

				if (asyncResult.AsyncWaitHandle.WaitOne(waitSeconds * 1000) == true)
					client.EndConnect(asyncResult);

				return client.Connected;
			}
		}
	}
}