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


namespace RobvanderWoude
{
	internal class Epub2Txt
	{
		static string progver = "1.01";


		static int Main( string[] args )
		{
			string epub = string.Empty;
			Encoding encoding = null;


			#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( ) == "/E" )
					{
						return ListEncodings( );
					}
					else
					{
						return ShowHelp( "Invalid command line switch {0}", arg );
					}
				}
				else
				{
					if ( string.IsNullOrWhiteSpace( epub ) )
					{
						epub = arg;
						if ( !File.Exists( epub ) )
						{
							return ShowHelp( "File \"{0}\" not found", epub );
						}
						if ( Path.GetExtension( epub ).ToLower( ) != ".epub" )
						{
							return ShowHelp( "This program can handle .EPUB 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( epub ) )
			{
				return ShowHelp( );
			}

			#endregion Parse Command Line


			#region Extract Text

			string content = string.Empty;
			string doctitle = string.Empty;
			SortedDictionary<int, string> textcontent = new SortedDictionary<int, string>( );

			// Open document as ZIP file and extract the XML file containing the text content
			using ( ZipArchive archive = ZipFile.OpenRead( epub ) )
			{
				foreach ( ZipArchiveEntry entry in archive.Entries )
				{
					if ( entry.Name.ToLower( ) == "toc.ncx" )
					{
						string toc = Path.GetTempFileName( );
						entry.ExtractToFile( toc, true );

						XDocument xml = XDocument.Load( toc );
						if ( encoding == null )
						{
							encoding = GetEncoding( xml.Declaration.Encoding );
						}
						foreach ( XElement el in xml.Elements( ).Elements( ) )
						{
							if ( el.Name.LocalName == "docTitle" )
							{
								doctitle = el.Value;
							}
						}
						foreach ( XElement el in xml.Elements( ).Elements( ).Elements( ) )
						{
							if ( el.Name.LocalName == "navPoint" )
							{
								string header = el.Value;
								int playorder = int.Parse( el.Attribute( "playOrder" ).Value );
								string chaptersrc = string.Empty;
								foreach ( XElement el2 in el.Elements( ) )
								{
									if ( el2.Name.LocalName == "content" )
									{
										chaptersrc = el2.Attribute( "src" ).Value;
										if ( chaptersrc.Contains( "#" ) )
										{
											chaptersrc = chaptersrc.Split( "#".ToCharArray( ) )[0];
										}
									}
								}
								string chapter = Path.GetTempFileName( );
								string text = string.Empty;
								foreach ( ZipArchiveEntry entry2 in archive.Entries )
								{
									if ( entry2.Name == chaptersrc )
									{
										entry2.ExtractToFile( chapter, true );
										text = File.ReadAllText( chapter );
										File.Delete( chapter );
										text = Regex.Replace( text, "<title>[^<]*</title>", string.Empty, RegexOptions.IgnoreCase );
										text = Regex.Replace( text, "<br( /)?>", Environment.NewLine, RegexOptions.IgnoreCase );
										text = Regex.Replace( text, "(</p>|</h\\d+>)", Environment.NewLine + Environment.NewLine, RegexOptions.IgnoreCase );
										text = Regex.Replace( text, "<[^>]+>", string.Empty );
									}
								}
								textcontent.Add( playorder, text );
							}
						}
						File.Delete( toc );
					}
				}
			}

			#endregion Extract Text

			
			int textlength = 0;
			Encoding oldencoding = Console.OutputEncoding;
			Console.OutputEncoding = encoding;
			foreach ( int key in textcontent.Keys )
			{
				Console.WriteLine( textcontent[key] );
				textlength += textcontent[key].Length;
			}
			Console.OutputEncoding = oldencoding;

			if ( textlength > 1000 )
			{
				return 0;
			}
			else
			{
				return 1;
			}
		}


		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 Help Text

			/*
			Epub2Txt,  Version 1.01
			Extract plain text from an EPUB file and send it to the screen
 
			Usage:   Epub2Txt    "epubfile"  [ encoding ]
 
			or:      Epub2Txt    /E
 
			Where:   epubfile    is the path of the EPUB file to be read
			                     (no wildcards allowed, only .epub extension)
			         encoding    force use of alternative encoding for plain
			                     text, e.g. UTF-8 to preserve accented characters
			                     or IBM437 to convert unicode quotes to ASCII
			                     (default: encoding of EPUB 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") 0 means no errors were encountered and
			         extracted text exceeds 1KB; otherwise the return code will be 1.

			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( "Epub2Txt,  Version {0}", progver );

			Console.Error.WriteLine( "Extract plain text from an EPUB file and send it to the screen" );

			Console.Error.WriteLine( );

			Console.Error.Write( "Usage:   " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.WriteLine( "Epub2Txt    \"epubfile\"  [ encoding ]" );
			Console.ResetColor( );

			Console.Error.WriteLine( );

			Console.Error.Write( "or:      " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.WriteLine( "Epub2Txt    /E" );
			Console.ResetColor( );

			Console.Error.WriteLine( );

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

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

			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "         encoding" );
			Console.ResetColor( );
			Console.Error.WriteLine( "    force use of alternative encoding for plain" );

			Console.Error.Write( "                     text, e.g. " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "UTF-8" );
			Console.ResetColor( );
			Console.Error.WriteLine( " to preserve accented characters" );

			Console.Error.Write( "                     or " );
			Console.ForegroundColor = ConsoleColor.White;
			Console.Error.Write( "IBM437" );
			Console.ResetColor( );
			Console.Error.WriteLine( " to convert unicode quotes to ASCII" );

			Console.Error.WriteLine( "                     (default: encoding of EPUB 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( "         Return code (\"errorlevel\") 0 means no errors were encounterd" );

			Console.Error.WriteLine( "         and some text was extracted from the file; otherwise the" );

			Console.Error.WriteLine( "         return code will be 1." );

			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;
		}
	}
}