using System;
using System.Collections.Generic;
using System.Windows.Forms;
using System.Diagnostics;
using System.Net.NetworkInformation;
using System.Threading;
using System.Net.Sockets;
using System.IO;
using System.Management;

namespace DirectToDesktop
{
	static class Program
	{
		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		/// <param name="args">The args.</param>
		[STAThread]
		static void Main(string[] args)
		{
			if (args.Length < 3 || args.Length > 4)
			{
				ShowHelp();
				return;
			}

			string vpnClientPath = args[0];
			string vpnClientArgs = args[1];
			string hostName = args[2];
			string lookAlivePath = (args.Length > 3) ? args[3] : string.Empty;

			if (!String.IsNullOrEmpty(lookAlivePath) &&
				File.Exists(lookAlivePath))
			{
				// Only start a new instance of LookAlive for the specified host
				// if one is not already running.  
				bool lookAliveRunning = false;

				string wmiQuery = string.Format("select CommandLine from Win32_Process where Name='{0}'", "LookAlive.exe");
				ManagementObjectSearcher searcher = new ManagementObjectSearcher(wmiQuery);
				ManagementObjectCollection retObjectCollection = searcher.Get();
				foreach (ManagementObject retObject in retObjectCollection)
				{
					string commandLine = retObject["CommandLine"] as string;
					if (commandLine != null)
					{
						if (commandLine.ToLower().Contains(hostName.ToLower()))
						{
							lookAliveRunning = true;
							break;
						}
					}
				}

				if (!lookAliveRunning)
				{
					Process.Start(lookAlivePath, hostName);
				}
			}

			if (!HostIsOnline(hostName))
			{
				Process.Start(vpnClientPath, vpnClientArgs);

				// In case the VPN client is a single-instance process, we
				// search for any process with a matching name rather than
				// use the Process.Exited event handler.
				string vpnProcessName = Path.GetFileNameWithoutExtension(vpnClientPath);

				// Wait for the host to become available, or the VPN client process to exit.
				while (!HostIsOnline(hostName) && ProcessIsRunning(vpnProcessName)) 
				{
					Thread.Sleep(250);
				}
			}

			// If the host is available at this point, start a remote desktop session to it.
			if (HostIsOnline(hostName))
			{
				Process.Start(Environment.ExpandEnvironmentVariables(@"%windir%\system32\mstsc.exe"), "/v:" + hostName);
			}
		}

		/// <summary>
		/// Checks if a hosts can be pinged.
		/// </summary>
		/// <param name="hostName">Name of the host.</param>
		/// <returns>True if the host can be pinged, otherwise false.</returns>
		private static bool HostIsOnline(string hostName)
		{
			bool online = false;
			Ping ping = new Ping();

			try
			{
				PingReply reply = ping.Send(hostName, 1000);	// 1 second timeout
				online = (reply.Status == IPStatus.Success);
			}
			catch (PingException)
			{
				// no reply received yet.
			}

			return online;
		}

		/// <summary>
		/// Returns true if a specified process is currently running.
		/// </summary>
		/// <param name="processName">The name of the process (e.g. 'devenv').</param>
		/// <returns>True if the process is found to be running, otherwise false.</returns>
		private static bool ProcessIsRunning(string processName)
		{
			Process[] processes = Process.GetProcessesByName(Path.GetFileNameWithoutExtension(processName));
			return (processes.Length > 0);
		}

		/// <summary>
		/// Shows the help.
		/// </summary>
		private static void ShowHelp()
		{
			Application.EnableVisualStyles();
			Application.SetCompatibleTextRenderingDefault(false);
			Application.Run(new FrmAbout());
		}
	}
}