using System;
using System.Collections.Generic;


namespace RobvanderWoude
{
	class isDST
	{
		static string progver = "1.03";


		static int Main( string[] args )
		{
			// Defaults
			bool verbose = false;
			int rc = 1;
			DateTime checkDate = DateTime.Now;


			#region Parse Command Line

			if ( args.Length > 2 )
			{
				return ShowHelp( "Invalid command line argument(s)." );
			}

			foreach ( string arg in args )
			{
				switch ( arg.ToLower( ) )
				{
					case "/?":
					case "/h":
					case "-h":
					case "--h":
					case "/help":
					case "-help":
					case "--help":
						return ShowHelp( );
					case "/v":
					case "-v":
					case "--v":
					case "/verbose":
					case "-verbose":
					case "--verbose":
						verbose = true;
						break;
					default:
						// Check if the argument is a valid date/time
						try
						{
							checkDate = Convert.ToDateTime( arg );
						}
						catch ( FormatException )
						{
							return ShowHelp( "Invalid date \"{0}\"", arg );
						}
						break;
				}
			}

			// Two command line arguments are allowed, but only if one of these is the /Verbose switch
			if ( args.Length == 2 && !verbose )
			{
				return ShowHelp( "Invalid command line argument(s)." );
			}

			#endregion Parse Command Line


			// Check if date is in DST
			bool result = TimeZone.CurrentTimeZone.IsDaylightSavingTime( checkDate );

			// Display result on screen
			if ( verbose )
			{
				Console.Write( checkDate.ToLongDateString( ).ToString( ) );
				if ( result )
				{
					rc = 0;
					Console.ForegroundColor = ConsoleColor.Red;
					Console.Write( " IS" );
					Console.ResetColor( );
				}
				else
				{
					rc = 2;
					Console.Write( " is" );
					Console.ForegroundColor = ConsoleColor.Green;
					Console.Write( " NOT" );
					Console.ResetColor( );
				}
				Console.WriteLine( " in Daylight Saving Time" );
			}

			// Return result as 'errorlevel'
			return rc;
		}


		public static int ShowHelp( params string[] errmsg )
		{
			#region Help Text

			/*
			isDST,  Version 1.03
			Check if a date is in Daylight Saving Time

			Usage:  ISDST  [ date ]  [ /Verbose ]

			Where:  date       is an optional date/time to check (default: today/now)
					/Verbose   tells the program to display the result on screen

			Notes:  An "errorlevel" 0 is returned if the date is in DST, 2 if the date
					is not in DST, or 1 in case of (command line) errors.
					This program uses local date/time formats and timezone settings.
			        /Verbose switch may be abbreviated to /V.

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

			#endregion Help Text


			#region Error Message

			if ( errmsg.Length > 0 )
			{
				List<string> errargs = new List<string>( errmsg );
				errargs.RemoveAt( 0 );
				Console.Error.WriteLine( );
				Console.ForegroundColor = ConsoleColor.Red;
				Console.Error.Write( "ERROR:\t" );
				Console.ForegroundColor = ConsoleColor.White;
				Console.Error.WriteLine( errmsg[0], errargs.ToArray( ) );
				Console.ResetColor( );
			}

			#endregion Error Message


			#region Display Help Text

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "isDST,  Version {0}", progver );

			Console.Error.WriteLine( "Check if a date is in Daylight Saving Time" );

			Console.Error.WriteLine( );

			Console.Error.Write( "Usage:  " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.WriteLine( "ISDST  [ date ]  [ /Verbose ]" );
			Console.ResetColor( );

			Console.Error.WriteLine( );

			Console.Error.Write( "Where:  " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "date" );
			Console.ResetColor( );
			Console.Error.WriteLine( "       is an optional date/time to check (default: today/now)" );

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "        /V" );
			Console.ResetColor( );
			Console.Error.WriteLine( "erbose   tells the program to display the result on screen" );

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "Notes:  An \"errorlevel\" 0 is returned if the date is in DST, 2 if the date" );

			Console.Error.WriteLine( "        is not in DST, or 1 in case of (command line) errors." );

			Console.Error.WriteLine( "        This program uses local date/time formats and timezone settings." );

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "        /Verbose" );
			Console.ResetColor( );
			Console.Error.Write( " switch may be abbreviated to " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "/V" );
			Console.ResetColor( );
			Console.Error.WriteLine( "." );

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "Written by Rob van der Woude" );

			Console.Error.WriteLine( "https://www.robvanderwoude.com" );

			#endregion Display Help Text


			return 1;
		}

	}
}