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


namespace RobvanderWoude
{
	internal class CompareFiles
	{
		static string progver = "1.01";


		static int Main( string[] args )
		{
			#region Parse Command Line

			if ( args.Length < 2 || args.Length > 3 || args.Contains( "/?" ) )
			{
				return ShowHelp( );
			}

			string file1 = args[0];
			if ( !File.Exists( file1 ) )
			{
				ShowHelp( "File not found: \"{0}\"", file1 );
				return -2;
			}
			string file2 = args[1];
			if ( !File.Exists( file2 ) )
			{
				ShowHelp( "File not found: \"{0}\"", file2 );
				return -3;
			}

			bool ignoretimestamps = false;
			if ( args.Length == 3 )
			{
				if ( args[2].ToUpper( ) == "/IT" )
				{
					ignoretimestamps = true;
				}
				else
				{
					return ShowHelp( "Invalid command line argument \"{0}\"", args[2] );
				}
			}

			#endregion Parse Command Line


			#region Compare File Sizes

			long file1size = new FileInfo( file1 ).Length;
			long file2size = new FileInfo( file2 ).Length;
			if ( file1size > file2size )
			{
				Console.WriteLine( "\"{0}\" is bigger", file1 );
				return 1;
			}
			else if ( file1size < file2size )
			{
				Console.WriteLine( "\"{0}\" is bigger", file2 );
				return 2;
			}
			else
			{
				Console.WriteLine( "File sizes match" );
			}

			#endregion Compare File Sizes


			#region Compare Timestamps

			DateTime file1timestamp = File.GetLastWriteTime( file1 );
			DateTime file2timestamp = File.GetLastWriteTime( file2 );
			if ( file1timestamp > file2timestamp )
			{
				Console.WriteLine( "\"{0}\" is newer", file1 );
				if ( !ignoretimestamps )
				{
					return 3;
				}
			}
			else if ( file1timestamp < file2timestamp )
			{
				Console.WriteLine( "\"{0}\" is newer", file2 );
				if ( !ignoretimestamps )
				{
					return 4;
				}
			}
			else
			{
				Console.WriteLine( "Timestamps match" );
			}

			#endregion Compare Timestamps


			#region Compare MD5 Checksums

			string file1md5;
			string file2md5;
			using ( var md5 = MD5.Create( ) )
			{
				using ( var stream = File.OpenRead( file1 ) )
				{
					file1md5 = BitConverter.ToString( md5.ComputeHash( stream ) ).Replace( "-", "" ).ToLowerInvariant( );
				}
				using ( var stream = File.OpenRead( file2 ) )
				{
					file2md5 = BitConverter.ToString( md5.ComputeHash( stream ) ).Replace( "-", "" ).ToLowerInvariant( );
				}
			}
			if ( file1md5 == file2md5 )
			{
				Console.WriteLine( "MD5 checksums match" );
			}
			else
			{
				Console.WriteLine( "Files have different MD5 checksums" );
				return 5;
			}

			#endregion Compare MD5 Checksums


			Console.WriteLine( "Files are identical" );
			return 0;
		}


		#region Error handling

		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


			#region Help Text

			/*
			CompareFiles.exe,  Version 1.00
			Check if two files are identical
 
			Usage:        CompareFiles.exe  file1  file2  [ /IT ]
 
			Where:        file1 and file2 are the files to compare
			              /IT  Ignore Timestamps (continue even if timestamps differ)

			Return code:  0    files are identical
			              1    file1 is bigger
			              2    file1 is smaller
			              3    sizes match but file1 is newer
			              4    sizes match but file1 is older
			              5    MD5 checksums are different
			             -1    command line error
			             -2    file1 not found
			             -3    file2 not found

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

			#endregion Help Text


			#region Display Help Text

			Console.Error.WriteLine( );

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

			Console.Error.WriteLine( "Check if two files are identical" );

			Console.Error.WriteLine( );

			Console.Error.Write( "Usage:        " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.WriteLine( "CompareFiles.exe  file1  file2  [ /IT ]" );
			Console.ResetColor( );

			Console.Error.WriteLine( );

			Console.Error.Write( "Where:        " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "file1" );
			Console.ResetColor( );
			Console.Error.Write( " and " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "file2" );
			Console.ResetColor( );
			Console.Error.WriteLine( " are the files to compare" );

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "              /IT  I" );
			Console.ResetColor( );
			Console.Error.Write( "gnore " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "T" );
			Console.ResetColor( );
			Console.Error.WriteLine( "imestamps (continue even if timestamps differ)" );

			Console.Error.WriteLine( );


			Console.Error.WriteLine( "Return code:  0   files are identical" );

			Console.Error.WriteLine( "              1   file1 is bigger" );

			Console.Error.WriteLine( "              2   file1 is smaller" );

			Console.Error.WriteLine( "              3   sizes match but file1 is newer" );

			Console.Error.WriteLine( "              4   sizes match but file1 is older" );

			Console.Error.WriteLine( "              5   MD5 checksums are different" );

			Console.Error.WriteLine( "             -1   command line error" );

			Console.Error.WriteLine( "             -2   file1 not found" );

			Console.Error.WriteLine( "             -3   file2 not found" );

			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;
		}

		#endregion Error handling
	}
}