using System;
using System.Media;
using System.Net;
using System.Threading;

namespace RobvanderWoude
{
	class PingSite
	{
		static bool beep = false;

		static int Main( string[] args )
		{
			try
			{

				// Default values
				bool varSpeed = false;
				bool verbose = true;
				bool changes = false;
				int interval = 0;
				int fastInt = 0;
				int slowInt = 0;
				int previous = 0;
				string expected = string.Empty;
				string url = string.Empty;

				#region Command Line Parsing

				// Custom error message
				string msgInvalid = "Invalid command line argument" + ( ( args.Length == 1 ) ? string.Empty : "(s)" );

				// No command line arguments? Display help
				if ( args.Length == 0 )
				{
					return WriteError( string.Empty );
				}

				foreach ( string arg in args )
				{
					// Check switches first
					switch ( arg.ToLower( ).Substring( 0, 2 ) )
					{
						case "/?":
						case "-?":
						case "/h":
						case "-h":
							// Display help
							return WriteError( string.Empty );
						case "--":
							if ( arg.ToLower( ) == "--help" )
							{
								// Display help
								return WriteError( string.Empty );
							}
							else
							{
								// Display error message
								return WriteError( msgInvalid );
							}
						case "/b":
							beep = true;
							break;
						case "/c":
							verbose = false;
							changes = true;
							break;
						case "/i":
							if ( arg.ToLower( ).StartsWith( "/i:" ) || arg.ToLower( ).StartsWith( "/interval:" ) )
							{
								slowInt = System.Convert.ToInt32( arg.Substring( arg.IndexOf( ":" ) + 1 ) );
								if ( slowInt < 1 )
								{
									return WriteError( "Interval must be 1 or greater" );
								}
							}
							else
							{
								return WriteError( msgInvalid );
							}
							break;
						case "/q":
							verbose = false;
							changes = false;
							break;
						case "/s":
							{
								if ( arg.IndexOf( ":" ) > 0 )
								{
									expected = arg.Substring( arg.IndexOf( ":" ) + 1 ).ToUpper( );
								}
								else
								{
									expected = "OK";
								}
								if ( expected == "OK" )
								{
									expected = "200,301,302,303,304,305,306,307";
								}
							}
							break;
						case "/v":
							varSpeed = true;
							break;
						default:
							url = arg;
							break;
					}
				}

				if ( string.IsNullOrEmpty( url ) )
				{
					return WriteError( "An URL must be specified" );
				}

				if ( slowInt < 1 && changes )
				{
					return WriteError( "To display status changes only, an interval must be specified" );
				}

				if ( slowInt > 0 && !( verbose || changes ) )
				{
					return WriteError( "/Quiet switch not allowed if an interval is specified" );
				}

				if ( varSpeed && ( string.IsNullOrEmpty( expected ) || slowInt < 1 ) )
				{
					return WriteError( "/Variable requires both /Status and /Interval" );
				}

				interval = slowInt;
				if ( slowInt >= 25 )
				{
					fastInt = slowInt / 5;
				}
				else if ( slowInt < 5 )
				{
					fastInt = slowInt;
				}
				else
				{
					fastInt = 5;
				}

				#endregion Command Line Parsing

				// Loop will be aborted if interval is less than 1
				while ( true )
				{
					HttpStatusCode status = GetResponse( url );
					string statusText = status.ToString( );
					int statusCode = (int) status;

					// Display result
					if ( ( ( previous != statusCode ) && changes ) || verbose )
					{
						ConsoleColor statusColor;
						if ( string.IsNullOrEmpty( expected ) || expected.Contains( statusCode.ToString( ) ) )
						{
							statusColor = ConsoleColor.White;
							interval = slowInt;
						}
						else
						{
							statusColor = ConsoleColor.Red;
							if ( varSpeed )
							{
								interval = fastInt;
							}
						}
						Console.Write( "[{0}]\t", DateTime.Now );
						Console.ForegroundColor = statusColor;
						Console.Write( "{0}\t{1}", statusCode, statusText );
						Console.ResetColor( );
						Console.WriteLine( "\t{0}", url );
						Console.Title = "PingSite: " + statusCode.ToString( );
						// Beep on changes, if requested
						if ( beep )
						{
							bool beepNow = false;
							if ( changes )
							{
								beepNow = true;
							}
							if ( string.IsNullOrEmpty( expected ) == false )
							{
								if ( expected.Contains( statusCode.ToString( ) ) == false )
								{
									beepNow = true;
								}
							}
							if ( beepNow )
							{
								Console.Beep( );
							}
						}
					}

					// Save the last status code to compare it in the next iteration of the loop
					previous = statusCode;

					// Break the loop if interval is less than 1
					if ( interval < 1 )
					{
						if ( string.IsNullOrEmpty( expected ) )
						{
							// Return the actual status code
							return statusCode;
						}
						else
						{
							// If we were monitoring for an expected code, return either 0 (match) or 2 (no match)
							return ( ( expected.Contains( statusCode.ToString( ) ) ) ? 0 : 2 );
						}
					}

					// Wait for the specified number of seconds
					Thread.Sleep( interval * 1000 );
				}
			}
			catch ( Exception e )
			{
				return WriteError( e.Message );
			}
		}

		public static HttpStatusCode GetResponse( string url )
		{
			// Returns the HTTP Status Code for the specified URL, or 0 on errors
			try
			{
				HttpWebRequest req = (HttpWebRequest) WebRequest.Create( url );
				req.AllowAutoRedirect = false;
				HttpWebResponse resp = (HttpWebResponse) req.GetResponse( );
				HttpStatusCode stat = resp.StatusCode;
				req.Abort( );
				return stat;
			}
			catch ( WebException e )
			{
				// Handle exceptions caused by the server response, e.g. 404
				try
				{
					HttpWebResponse httpResponse = (HttpWebResponse) e.Response;
					return httpResponse.StatusCode;
				}
				// Handle the "real" exceptions
				catch
				{
					WriteError( e.Message, false );
					return 0;
				}
			}
			catch ( Exception e )
			{
				WriteError( e.Message );
				return 0;
			}
		}

		#region Error Handling

		public static int WriteError( Exception e )
		{
			return WriteError( e == null ? null : e.Message );
		}

		public static int WriteError( string errorMessage, bool showHelp = true )
		{
			/*
			PingSite,  Version 1.21
			Check if a website is up and running

			Usage:  PINGSITE  url  [ /Status[:expected] ]  [ /Interval:seconds ]
			                       [ /Variable ]  [ /Beep ]  [ /Changes | /Quiet ]

			Where:  url        is the URL of the site or page to check (including http://)
			        /Beep      beep on changes or if response does not match expected
			        /Changes   display status changes only (requires /Interval)
			        /Interval  defines the optional interval in seconds between checks
			                   (default if not specified: terminate after 1 check)
			        /Quiet     no screen output, 'errorlevel' only
			        /Status    is either the expected numeric HTTP response code, or
			                   'OK' for 200, 301..307 (default)
			        /Variable  shorter interval on mismatch (requires /Interval & /Status)

			Notes:  If /Status was used, 'errorlevel' 0 is returned if status matches
			        expected, 2 if not; otherwise the actual status code is returned as
			        'errorlevel'; in case of (command line) errors 1 is returned.
			        Switches /Interval and /Quiet are mutually exclusive.
			        Switches may be abbreviated, e.g. /I instead of /Interval.

			Written by Rob van der Woude
			http://www.robvanderwoude.com
			*/

			if ( string.IsNullOrEmpty( errorMessage ) == false )
			{
				Console.Error.WriteLine( );
				Console.ForegroundColor = ConsoleColor.Red;
				Console.Error.Write( "ERROR:  " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.WriteLine( errorMessage );
				Console.ResetColor( );
				if ( beep )
				{
					Console.Beep( );
				}
			}
			if ( showHelp )
			{
				Console.Error.WriteLine( );
				Console.Error.WriteLine( "PingSite,  Version 1.21" );
				Console.Error.WriteLine( "Check if a website is up and running" );
				Console.Error.WriteLine( );
				Console.Error.Write( "Usage: " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.WriteLine( "PINGSITE  url  [ /Status[:expected] ]  [ /Interval:seconds ]" );
				Console.Error.WriteLine( "                      [ /Variable ]  [ /Beep ]  [ /Changes | /Quiet ]" );
				Console.ResetColor( );
				Console.Error.WriteLine( );
				Console.Error.WriteLine( "Where:  url        is the URL of the site or page to check (including http://)" );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "        /B" );
				Console.ResetColor( );
				Console.Error.WriteLine( "eep      beep on changes or if response does not match expected" );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "        /C" );
				Console.ResetColor( );
				Console.Error.Write( "hanges   display status changes only (requires " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "/I" );
				Console.ResetColor( );
				Console.Error.WriteLine( "nterval)" );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "        /I" );
				Console.ResetColor( );
				Console.Error.WriteLine( "nterval  defines the optional interval in seconds between checks" );
				Console.Error.WriteLine( "                   (default if not specified: terminate after 1 check)" );
				Console.ForegroundColor = ConsoleColor.White;
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "        /Q" );
				Console.ResetColor( );
				Console.Error.WriteLine( "uiet     no screen output, 'errorlevel' only" );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "        /S" );
				Console.ResetColor( );
				Console.Error.WriteLine( "tatus    is either the expected numeric HTTP response code, or" );
				Console.Error.WriteLine( "                   'OK' for 200, 301..307 (default)" );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "        /V" );
				Console.ResetColor( );
				Console.Error.Write( "ariable  shorter interval on mismatch (requires " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "/I" );
				Console.ResetColor( );
				Console.Error.Write( "nterval & " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "/S" );
				Console.ResetColor( );
				Console.Error.WriteLine( "tatus)" );
				Console.Error.WriteLine( );
				Console.Error.Write( "Notes: If " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "/S" );
				Console.ResetColor( );
				Console.Error.WriteLine( "tatus was used, 'errorlevel' 0 is returned if status matches" );
				Console.Error.WriteLine( "       expected, 2 if not; otherwise the actual status code is returned as" );
				Console.Error.WriteLine( "       'errorlevel'; in case of (command line) errors 1 is returned." );
				Console.Error.Write( "       Switches " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "/I" );
				Console.ResetColor( );
				Console.Error.Write( "nterval and " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "/Q" );
				Console.ResetColor( );
				Console.Error.WriteLine( "uiet are mutually exclusive." );
				Console.Error.Write( "       Switches may be abbreviated, e.g. " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "/I" );
				Console.ResetColor( );
				Console.Error.Write( " instead of " );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.Write( "/I" );
				Console.ResetColor( );
				Console.Error.WriteLine( "nterval." );
				Console.Error.WriteLine( );
				Console.Error.WriteLine( "Written by Rob van der Woude" );
				Console.Error.Write( "http://www.robvanderwoude.com" );
			}
			return 1;
		}

		#endregion Error Handling
	}
}