using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Compression;
using System.Text;
using System.Text.RegularExpressions;


namespace RobvanderWoude
{
	internal class ODT2Txt
	{
		static string progver = "1.00";


		static int Main( string[] args )
		{
			string odtfile = string.Empty;
			Encoding encoding = null;
			bool usexmlencoding = false;

			#region Parse Command Line

			if ( args.Length == 0 || args.Length > 2 )
			{
				return ShowHelp( );
			}

			foreach ( string arg in args )
			{
				if ( arg[0] == '/' )
				{
					if ( arg == "/?" )
					{
						return ShowHelp( );
					}
					else if ( arg.ToUpper( ).StartsWith( "/D", StringComparison.OrdinalIgnoreCase ) )
					{
						usexmlencoding = true;
					}
					else if ( arg.ToUpper( ) == "/E" )
					{
						return ListEncodings( );
					}
					else
					{
						return ShowHelp( "Invalid command line switch {0}", arg );
					}
				}
				else
				{
					if ( string.IsNullOrWhiteSpace( odtfile ) )
					{
						odtfile = arg;
						if ( !File.Exists( odtfile ) )
						{
							return ShowHelp( "File \"{0}\" not found", odtfile );
						}
						if ( Path.GetExtension( odtfile ).ToLower( ) != ".odt" )
						{
							return ShowHelp( "This program can extract text from .ODT files only" );
						}
					}
					else if ( encoding == null )
					{
						encoding = GetEncoding( arg );
						if ( encoding == null )
						{
							return ShowHelp( "Invalid encoding \"{0}\"", args[1] );
						}
					}
					else
					{
						return ShowHelp( "Too many command line arguments" );
					}
				}
			}

			if ( string.IsNullOrWhiteSpace( odtfile ) )
			{
				return ShowHelp( );
			}

			#endregion Parse Command Line


			#region Extract Text

			string tempfile = Path.GetTempFileName( );
			string content = string.Empty;
			bool success = false;

			using ( ZipArchive archive = ZipFile.OpenRead( odtfile ) )
			{
				foreach ( ZipArchiveEntry entry in archive.Entries )
				{
					if ( entry.Name.ToLower( ) == "content.xml" )
					{
						entry.ExtractToFile( tempfile, true );
						success = true;
					}
				}
			}

			if ( success )
			{
				StreamReader sr = new StreamReader( tempfile );
				content = sr.ReadToEnd( );
				sr.Close( );
			}

			File.Delete( tempfile );

			#endregion Extract Text


			if ( success )
			{
				// The first 100 characters of the extracted XML usually contain its encoding;
				// this encoding will be used if the /D command line switch was used
				Regex regex = new Regex( " encoding=\"([^\"]+)\"" );
				string xmlencoding = regex.Match( content, 0, 100 ).Groups[1].Value;

				
				#region Cleanup Text
				
				// insert newlines after header, paragraph or list-item
				regex = new Regex( "</text:(h|list-item|p)>" );
				string plaintext = regex.Replace( content, "\n\n" );
				// remove all XML tags
				regex = new Regex( "<[^>]+>" );
				plaintext = regex.Replace( plaintext, "" );
				// reduce maximum number of censecutive newlines to two
				regex = new Regex( "\n{3,}" );
				plaintext = regex.Replace( plaintext, "\n\n" );
				// convert stray carriage returns to carriage return/linefeed pairs
				plaintext = ConvertStrayCarriageReturns( plaintext ).Trim( "\n\r\t ".ToCharArray( ) );

				#endregion Cleanup Text


				#region Display Text

				if ( usexmlencoding )
				{
					encoding = GetEncoding( xmlencoding );
				}

				if ( encoding == null )
				{
					// send text to console using default output encoding
					Console.WriteLine( plaintext );
				}
				else
				{
					// temporarily change output encoding and send text to console
					Encoding oldencoding = Console.OutputEncoding;
					Console.OutputEncoding = encoding;
					Console.WriteLine( plaintext );
					Console.OutputEncoding = oldencoding;
				}

				#endregion Display Text


				return 0;
			}
			return ShowHelp( "An error occurred while trying to read \"{0}\"", odtfile );
		}



		static string ConvertStrayCarriageReturns( string text )
		{
			// convert stray carriage returns to carriage return/linefeed pairs
			// search for stray carriage returns (\r), i.e. the ones NOT followed by linefeeds (\n)
			Regex regex = new Regex( "\r(?!\n)" );
			// replace each matching stray carriage return by a carriage return/linefeed pair
			text = regex.Replace( text, Environment.NewLine );
			return text;
		}


		static Encoding GetEncoding( string myencoding )
		{
			if ( string.IsNullOrEmpty( myencoding ) )
			{
				return null;
			}
			// Get a list of available encodings
			EncodingInfo[] encodings = Encoding.GetEncodings( );
			// Try correctly spelled encodings first
			foreach ( EncodingInfo encoding in encodings )
			{
				if ( encoding.Name.ToLower( ) == myencoding.ToLower( ) )
				{
					return Encoding.GetEncoding( encoding.CodePage );
				}
			}
			// No direct match found, try again, ignoring dashes
			foreach ( EncodingInfo encoding in encodings )
			{
				if ( encoding.Name.Replace( "-", "" ).ToLower( ) == myencoding.Replace( "-", "" ).ToLower( ) )
				{
					return Encoding.GetEncoding( encoding.CodePage );
				}
			}
			// Still no match, try codepages
			foreach ( EncodingInfo encoding in encodings )
			{
				if ( encoding.CodePage.ToString( ) == myencoding )
				{
					return Encoding.GetEncoding( encoding.CodePage );
				}
			}
			// Still no match, giving up
			return null;
		}


		static int ListEncodings( )
		{
			try
			{
				Console.Clear( );
			}
			catch
			{
				// Console.Clear( ) throws an IO exception if the output is redirected
			}
			int columnwidth = 8;
			EncodingInfo[] allencodings = Encoding.GetEncodings( );
			List<string> allencodingnames = new List<string>( );
			foreach ( EncodingInfo enc in allencodings )
			{
				allencodingnames.Add( enc.Name );
			}
			allencodingnames.Sort( );
			foreach ( string enc in allencodingnames )
			{
				columnwidth = Math.Max( columnwidth, enc.Length );
			}
			Console.WriteLine( "{0,-" + columnwidth + "}   {1}", "Encoding", "CodePage" );
			Console.WriteLine( "{0,-" + columnwidth + "}   {1}", "========", "========" );
			foreach ( string enc in allencodingnames )
			{
				Console.WriteLine( "{0,-" + columnwidth + "}   {1}", enc, GetEncoding( enc ).CodePage );
			}
			return 0;
		}


		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

			/*
			ODT2Txt.exe,  Version 1.00
			Return plain text content of an OpenOffice file without requiring OpenOffice
 
			Usage:    ODT2Txt.exe  odtfile  [ encoding | /D ]
 
			or:       ODT2Txt.exe  /E
 
			Where:    odtfile      is the path of the OpenOffice file to be read
			                       (no wildcards, only .odt extension allowed)
			          encoding     is the output encoding, e.g. UTF-8 to preserve
			                       Unicode characters, or IBM437 to convert Unicode
			                       doublequotes to ASCII
			          /D           use the encoding specified in the document file
			          /E           list all available encodings
			
			Notes:    If the specified encoding does not match any available encoding
			          name, the program will try again, ignoring dashes; if that does
			          not provide a match, the program will try matching the specified
			          encoding with the available encodings' codepages.
			          This program requires .NET 4.5.
			          Return code ("errorlevel") 1 in case of errors, 0 on success.
 
			Written by Rob van der Woude
			https://www.robvanderwoude.com
			*/

			#endregion Help Text


			#region Display Help Text

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "ODT2Txt.exe,  Version {0}", progver );

			Console.Error.WriteLine( "Return plain text content of an OpenOffice file without requiring OpenOffice" );

			Console.Error.WriteLine( );

			Console.Error.Write( "Usage:    " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.WriteLine( "ODT2Txt.exe  odtfile  [ encoding | /D ]" );
			Console.ResetColor( );

			Console.Error.WriteLine( );

			Console.Error.Write( "or:       " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.WriteLine( "ODT2Txt.exe  /E" );
			Console.ResetColor( );

			Console.Error.WriteLine( );

			Console.Error.Write( "Where:    " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "odtfile" );
			Console.ResetColor( );
			Console.Error.WriteLine( "      is the path of the OpenOffice file to be read" );

			Console.Error.WriteLine( "                       (no wildcards, only .odt extension allowed)" );

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "          encoding" );
			Console.ResetColor( );
			Console.Error.Write( "     is the output encoding, e.g. " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "UTF-8" );
			Console.ResetColor( );
			Console.Error.WriteLine( " to preserve" );

			Console.Error.Write( "                       Unicode characters, or " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "IBM437" );
			Console.ResetColor( );
			Console.Error.WriteLine( " to convert Unicode" );

			Console.Error.WriteLine( "                       doublequotes to ASCII" );

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "         /D" );
			Console.ResetColor( );
			Console.Error.WriteLine( "            use the encoding specified in the document file" );

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "         /E" );
			Console.ResetColor( );
			Console.Error.WriteLine( "            list all available encodings" );

			Console.Error.WriteLine( );

			Console.Error.WriteLine( "Notes:   If the specified encoding does not match any available encoding" );

			Console.Error.WriteLine( "         name, the program will try again, ignoring dashes; if that does" );

			Console.Error.WriteLine( "         not provide a match, the program will try matching the specified" );

			Console.Error.WriteLine( "         encoding with the available encodings' codepages." );

			Console.Error.WriteLine( "         This program requires .NET 4.5." );

			Console.Error.WriteLine( "         Return code (\"errorlevel\") 1 in case of errors, 0 on success." );
			
			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;
		}
	}
}