using System;

namespace Spider
{
	/// <summary>
	/// Base class for parseing tag based files, such as HTML, HTTP headers
	/// or XML.
	/// 
	/// 
	/// This spider is copyright 2003 by Jeff Heaton. However, it is
	/// released under a Limited GNU Public License (LGPL). You may 
	/// use it freely in your own programs. For the latest version visit
	/// http://www.jeffheaton.com.
	///	
	/// </summary>
	public class Parse:AttributeList 
	{		/// <summary>
		/// The source text that is being parsed.
		/// </summary>		private string m_source;		/// <summary>
		/// The current position inside of the text that
		/// is being parsed.
		/// </summary>		private int m_idx;		/// <summary>
		/// The most reciently parsed attribute delimiter.
		/// </summary>		private char m_parseDelim;		/// <summary>
		/// This most receintly parsed attribute name.
		/// </summary>		private string m_parseName;		/// <summary>
		/// The most reciently parsed attribute value.
		/// </summary>		private string m_parseValue;		/// <summary>
		/// The most reciently parsed tag.
		/// </summary>		public string m_tag;		/// <summary>
		/// Determine if the specified character is whitespace or not.
		/// </summary>
		/// <param name="ch">A character to check</param>
		/// <returns>true if the character is whitespace</returns>		public static bool IsWhiteSpace(char ch)		{			return( "\t\n\r ".IndexOf(ch) != -1 );		}		/// <summary>
		/// Advance the index until past any whitespace.
		/// </summary>		public void EatWhiteSpace()		{			while ( !Eof() ) 
			{				if ( !IsWhiteSpace(GetCurrentChar()) )					return;				m_idx++;			}		}		/// <summary>
		/// Determine if the end of the source text has been
		/// reached. 
		/// </summary>
		/// <returns>True if the end of the source text has been		/// reached.</returns>		public bool Eof()		{			return(m_idx>=m_source.Length );		}		/// <summary>
		/// Parse the attribute name.
		/// </summary>		public void ParseAttributeName()		{			EatWhiteSpace();			// get attribute name			while ( !Eof() ) 
			{				if ( IsWhiteSpace(GetCurrentChar()) ||					(GetCurrentChar()=='=') ||					(GetCurrentChar()=='>') )					break;				m_parseName+=GetCurrentChar();				m_idx++;			}			EatWhiteSpace();		}		/// <summary>
		/// Parse the attribute value
		/// </summary>		public void ParseAttributeValue()		{			if ( m_parseDelim!=0 )				return;			if ( GetCurrentChar()=='=' ) 
			{				m_idx++;				EatWhiteSpace();				if ( (GetCurrentChar()=='\'') ||					(GetCurrentChar()=='\"') ) 
				{					m_parseDelim = GetCurrentChar();					m_idx++;					while ( GetCurrentChar()!=m_parseDelim ) 
					{						m_parseValue+=GetCurrentChar();						m_idx++;					}					m_idx++;				} 
				else 
				{					while ( !Eof() &&						!IsWhiteSpace(GetCurrentChar()) &&						(GetCurrentChar()!='>') ) 
					{						m_parseValue+=GetCurrentChar();						m_idx++;					}				}				EatWhiteSpace();			}		}		/// <summary>
		/// Add a parsed attribute to the collection.
		/// </summary>		public void AddAttribute()		{			Attribute a = new Attribute(m_parseName,				m_parseValue,m_parseDelim);			Add(a);		}
		/// <summary>
		/// Get the current character that is being parsed.
		/// </summary>
		/// <returns></returns>
		public char GetCurrentChar()
		{
			return GetCurrentChar(0);
		}

		/// <summary>
		/// Get a few characters ahead of the current character.
		/// </summary>
		/// <param name="peek">How many characters to peek ahead for.</param>
		/// <returns>The character that was retrieved.</returns>
		public char GetCurrentChar(int peek)
		{
			if( (m_idx+peek)<m_source.Length )
				return m_source[m_idx+peek];
			else
				return (char)0;
		}

		/// <summary>
		/// Obtain the next character and advance the index by one.
		/// </summary>
		/// <returns>The next character</returns>
		public char AdvanceCurrentChar()
		{
			return m_source[m_idx++];
		}

		/// <summary>
		/// Move the index forward by one.
		/// </summary>		public void Advance()		{			m_idx++;		}		/// <summary>
		/// The last attribute name that was encountered.
		/// </summary>		public string ParseName		{			get 			{				return m_parseName;			}			set 			{				m_parseName = value;			}		}		/// <summary>
		/// The last attribute value that was encountered.
		/// </summary>		public string ParseValue		{			get 			{				return m_parseValue;			}			set 			{				m_parseValue = value;			}		}		/// <summary>
		/// The last attribute delimeter that was encountered.
		/// </summary>		public char ParseDelim		{			get 			{				return m_parseDelim;			}			set 			{				m_parseDelim = value;			}		}		/// <summary>
		/// The text that is to be parsed.
		/// </summary>		public string Source		{			get 			{				return m_source;			}			set 			{				m_source = value;			}		}	}
}