using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using Microsoft.Win32;


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


		static bool openwallpapers = false;
		static bool singlewallpaper = false;
		static bool verbosedisplay = false;


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

			foreach ( string arg in args )
			{
				switch ( arg.ToUpper( ) )
				{
					case "/?":
						return ShowHelp( );
					case "/O":
						if ( openwallpapers )
						{
							return ShowHelp( "Duplicate command line switch /O" );
						}
						openwallpapers = true;
						break;
					case "/S":
						if ( singlewallpaper )
						{
							return ShowHelp( "Duplicate command line switch /S" );
						}
						singlewallpaper = true;
						break;
					case "/V":
						if ( verbosedisplay )
						{
							return ShowHelp( "Duplicate command line switch /V" );
						}
						verbosedisplay = true;
						break;
					default:
						return ShowHelp( "Invalid command line argument \"{0}\"", arg );
				}
			}

			#endregion Parse Command Line


			Dictionary<string, string> wallpapers = new Dictionary<string, string>( );


			#region List Wallpapers
			
			try
			{
				using ( RegistryKey key = Registry.CurrentUser.OpenSubKey( @"Control Panel\\Desktop" ) )
				{
					byte[] imagebytes = (byte[])key.GetValue( "TranscodedImageCache" );
					string image = Bytes2Path( imagebytes );
					if ( !wallpapers.Keys.Contains( image ) )
					{
						wallpapers.Add( image, @"HKEY_CURRENT_USER\Control Panel\Desktop\TranscodedImageCache" );
					}

					if ( !singlewallpaper )
					{
						// Check if more cached values are available
						foreach ( string valuename in key.GetValueNames( ) )
						{
							if ( valuename.StartsWith( "TranscodedImageCache_" ) )
							{
								imagebytes = (byte[])key.GetValue( valuename );
								image = Bytes2Path( imagebytes );
								if ( image != null && !wallpapers.Keys.Contains( image ) )
								{
									wallpapers.Add( image, @"HKEY_CURRENT_USER\Control Panel\Desktop\" + valuename );
								}
							}
						}
					}
				}
			}
			catch { } // ignore errors

			#endregion List Wallpapers


			#region Return Results

			int maxlen = 0;
			if ( verbosedisplay )
			{
				foreach ( string wallpaper in wallpapers.Keys )
				{
					maxlen = Math.Max( maxlen, wallpaper.Length );
				}
				foreach ( string wallpaper in wallpapers.Keys )
				{
					Console.WriteLine( "{0,-" + maxlen + "}\t{1}", wallpaper, wallpapers[wallpaper] );
					if ( openwallpapers )
					{
						Process.Start( wallpaper );
					}
				}
			}
			else
			{
				foreach ( string wallpaper in wallpapers.Keys )
				{
					Console.WriteLine( wallpaper );
					if ( openwallpapers )
					{
						Process.Start( wallpaper );
					}
				}
			}

			#endregion Return Results


			return wallpapers.Count;
		}


		static string Bytes2Path( byte[] bytesarray )
		{
			string imageraw = Encoding.Unicode.GetString( bytesarray ).Replace( "\0", "" );
			string image = imageraw.Substring( imageraw.IndexOf( ":\\" ) - 1 );
			string pattern = @"(?<=\.[a-z0-9]+)[^a-z0-9].*";
			image = Regex.Replace( image, pattern, "" );
			if ( File.Exists( image ) )
			{
				return image;
			}
			return null;
		}


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

			/*
			GetCurrentWallpapers,  Version 1.01
			Get the path(s) of the current wallpaper(s)
 
			Usage:   GetCurrentWallpapers  [ /O ]  [ /S ]  [ /V ]
 
			Where:   /O    tells the program to open each wallpaper found
			         /S    tells the program to get only the first wallpaper it finds
			         /V    tells the program to display the registry keys for each
			               wallpaper found (Verbose mode)

			Notes:   Without /S the listed wallpapers may include previous ones too.
			         Return code ("errorlevel") equals the number of wallpapers found,
			         or -1 in case of (command line) errors.

			Credits: Based on PowerShell code by Ramesh Srinivasan on GitHub:
			         https://gist.github.com/winhelponline/4dc635770d5b123f6c1a719326037880

			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( "GetCurrentWallpapers,  Version {0}", progver );

			Console.Error.WriteLine( "Get the path(s) of the current wallpaper(s)" );

			Console.Error.WriteLine( );

			Console.Error.Write( "Usage:   " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.WriteLine( "GetCurrentWallpapers  [ /O ]  [ /S ]  [ /V ]" );
			Console.ResetColor( );

			Console.Error.WriteLine( );

			Console.Error.Write( "Where:   " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "/O" );
			Console.ResetColor( );
			Console.Error.WriteLine( "    tells the program to open each wallpaper found" );

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "         /S" );
			Console.ResetColor( );
			Console.Error.WriteLine( "    tells the program to get only the first wallpaper it finds" );

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "         /V" );
			Console.ResetColor( );
			Console.Error.WriteLine( "    tells the program to display the registry keys for each" );

			Console.Error.Write( "               wallpaper found (" );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "V" );
			Console.ResetColor( );
			Console.Error.WriteLine( "erbose mode)" );

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "Notes:   Without /S the listed wallpapers may include previous ones too." );
			
			Console.Error.WriteLine( "         Return code (\"errorlevel\") equals the number of wallpapers found," );

			Console.Error.WriteLine( "         or -1 in case of (command line) errors." );

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "Credits: Based on PowerShell code by Ramesh Srinivasan on GitHub:" );

			Console.ForegroundColor = ConsoleColor.DarkGray;
			Console.Error.WriteLine( "         https://gist.github.com/winhelponline/4dc635770d5b123f6c1a719326037880" );
			Console.ResetColor( );

			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;
		}
	}
}