using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;


namespace StringHash
{
	class StringHash
	{
		static readonly string progver = "1.01";


		static int Main( string[] args )
		{
			string hash = string.Empty;
			string str = string.Empty;


			#region Command Line Parsing

			if ( args.Contains( "/?" ) )
			{
				return ShowHelp( );
			}

			List<string> arguments = new List<string>( args );
				
			if ( Console.IsInputRedirected )
			{
				arguments.Insert( 0, "/S:" + Console.In.ReadToEnd( ) );
			}

			if ( arguments.Count != 2 )
			{
				return ShowHelp( "Missing or invalid command line arguments" );
			}

			foreach ( string arg in arguments )
			{
				switch ( arg.Substring( 0, 3 ).ToUpper( ) )
				{
					case "/A:":
						if ( !string.IsNullOrWhiteSpace( hash ) )
						{
							return ShowHelp( "Duplicate hash algorithm specification" );
						}
						hash = arg.Substring( 3 ).ToUpper( );
						if ( string.IsNullOrWhiteSpace( hash ) )
						{
							return ShowHelp( "Missing hash specification" );
						}
						break;
					case "/S:":
						if ( !string.IsNullOrWhiteSpace( str ) )
						{
							return ShowHelp( "Duplicate string specification" );
						}
						str = arg.Substring( 3 );
						if ( string.IsNullOrWhiteSpace( str ) )
						{
							return ShowHelp( "Empty string" );
						}
						break;
					default:
						return ShowHelp( "Invalid command line argument \"{0}\"", arg );
				}
			}

			#endregion Command Line Parsing


			HashAlgorithm hashalgorithm;
			switch ( hash )
			{
				case "MD5":
					hashalgorithm = new MD5CryptoServiceProvider( );
					break;
				case "SHA1":
				case "SHA-1":
					hashalgorithm = new SHA1CryptoServiceProvider( );
					break;
				case "SHA256":
				case "SHA-256":
					hashalgorithm = new SHA256CryptoServiceProvider( );
					break;
				case "SHA384":
				case "SHA-384":
					hashalgorithm = new SHA384CryptoServiceProvider( );
					break;
				case "SHA512":
				case "SHA-512":
					hashalgorithm = new SHA512CryptoServiceProvider( );
					break;
				default:
					return ShowHelp( "Invalid hash type \"{0}\"", hash );
			}
			string result = BitConverter.ToString( hashalgorithm.ComputeHash( StrToByteArray( str ) ) );
			hashalgorithm.Clear( );

			StringBuilder sb = new StringBuilder( result.ToLowerInvariant( ) );
			Console.WriteLine( sb.Replace( "-", "" ) );

			return 0;
		}


		// C# to convert a string to a byte array
		// http://www.chilkatsoft.com/faq/dotnetstrtobytes.html
		public static byte[] StrToByteArray( string instring )
		{
			ASCIIEncoding encoding = new ASCIIEncoding( );
			return encoding.GetBytes( instring );
		}


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

			/*			
			StringHash.exe,  Version 1.01
			Get the MD5 or SHA* hash value for the specified string

			Usage:  STRINGHASH.EXE  /A:hashAlgorithm  /S:"string"

			   or:  some_command  |  STRINGHASH.EXE  /A:hashAlgorithm

			Where:  hashAlgorithm  is either MD5, SHA1, SHA256, SHA384 or SHA512
					string         must be enclosed in doublequotes if it contains
			                       spaces or special characters
			        some_command   console program whose output serves as the string

			Note:   Return code ("ErrorLevel") -1 in case of errors, otherwise 0.

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

			#region Display Help Text

			Console.Error.WriteLine( );
			
			Console.Error.WriteLine( "StringHash.exe,  Version {0}", progver );
			
			Console.Error.WriteLine( "Get the MD5 or SHA* hash value for the specified string" );
			
			Console.Error.WriteLine( );

			Console.Error.WriteLine( "Usage:  STRINGHASH.EXE  /A:hashAlgorithm  /S:\"string\"" );

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "   or:  some_command  |  STRINGHASH.EXE  /A:hashAlgorithm" );

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "Where:  hashAlgorithm  is either MD5, SHA1, SHA256, SHA384 or SHA512" );
			
			Console.Error.WriteLine( "        string         must be enclosed in doublequotes if it contains" );

			Console.Error.WriteLine( "                       spaces or special characters" );

			Console.Error.WriteLine( "        some_command   console program whose output serves as the string" );

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "Note:   Return code (\"ErrorLevel\") -1 in case of errors, otherwise 0." );

			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;
		}
	}
}