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// Public domain, by Christopher Diggins
// http://www.cdiggins.com
//
// This file defines the core YARD grammar rules for text parsing.
// Each type in this file represents a separate BNF grammar production
// (parsing rule). 

#ifndef YARD_TEXT_GRAMMAR_HPP
#define YARD_TEXT_GRAMMAR_HPP

namespace yard 
{
namespace text_grammar 
{
	// accepts a single char, returns false only if at the end of the file
	struct AnyChar
	{
		template<typename ParserState_T>
		static bool Match(ParserState_T& p) {
			if (p.AtEnd()) { 
				return false; 
			};
			p.GotoNext();
			return true;
		}
	};

	// accepts a single char as specified by the template parameter
	template<char C>
	struct Char
	{
	    template<typename ParserState_T>
		static bool Match(ParserState_T& p) {
			if (p.AtEnd()) { return false; }
			if (p.GetElem() == C) { p.GotoNext(); return true; }
			return false;
		}
	};
  
	// consume a single character but prints an error message and throws an exception,
	// if the character is not found in the input stream.
	template<char C>
	struct ExpectChar {
		template<typename ParserState_T>
		static bool Match(ParserState_T& p) {   
			if (p.AtEnd() || p.GetElem() != C) 
			{ 
				printf("expected character: %c\n", C);
				throw 0;
			}
			p.GotoNext();
			return true;
		}
	};

  // accepts anything except a specific Char
  // equivalent to Seq<Not<Char<C>, AnyChar> > but more efficient
  template<char C>
  struct NotChar
  {
    template<typename ParserState_T>
    static bool Match(ParserState_T& p) {
      if (p.AtEnd()) { return false; }
      if (p.GetElem() != C) { p.GotoNext(); return true; }
      return false;
    }
  };    
  
   // CharSetParser matches a single character in the character set 
	template<typename CharSet_T>
	struct CharSetParser
	{ 
		static const CharSet_T cs; 

		template<typename ParserState_T>
		static bool Match(ParserState_T& p) {
			if (p.AtEnd()) return false;
			if (cs.a[p.GetElem()]) {
				p.GotoNext();
				return true;
			}
			return false;
		}
	};

	template<typename CharSet_T>
	const CharSet_T CharSetParser<CharSet_T>::cs;

	// accepts any single char, except for the specified character set
	template<typename CharSet_T>
	struct AnyCharExcept
		: Seq<NotAt<CharSetParser<CharSet_T> >, AnyChar>
	{ };

	// CharSetRangeParser is a shorthand for CharSetParser<char_set_range>
	template<char C0, char C1>
	struct CharRange : CharSetParser<CharSetRange<C0, C1> > { };

	// decimal digit parser
	struct Digit : CharSetParser<DigitCharSet> { };          

	// binary digit parser
	struct BinDigit : Or<Char<'0'>, Char<'1'> > { };          

	// hexadecimal digit parser
	struct HexDigit : CharSetParser<HexDigitCharSet> { };

	// octal digit parser
	struct OctDigit : CharSetParser<OctDigitCharSet> { };

	// parses letters and underscores
	struct IdentFirstChar : CharSetParser<IdentFirstCharSet> { };

	// parses letters and underscores and numbers
	struct IdentNextChar : CharSetParser<IdentNextCharSet> { };

	// parses letters
	struct Letter : CharSetParser<LetterCharSet> { };

	// parses letters or numbers
	struct AlphaNum : CharSetParser<AlphaNumCharSet> { };

	// Not an alpha numeric character or underscore
	struct NotAlphaNum : NotAt<IdentNextChar> { };

	// parses lower case letters
	struct LowerCaseLetter : CharSetParser<LowerCaseLetterCharSet> { };

	// parses upper case letters 
	struct UpperCaseLetter : CharSetParser<UpperCaseLetterCharSet> { };

	// Ident matches C/C++/Java/etc. identifiers. A letter or underscore followed
	// by a sequence of letters, underscores and numbers of arbitrary length
	struct Ident 
	{      
		template<typename ParserState_T>
		static bool Match(ParserState_T& p) {        
		  if (p.AtEnd()) { return false; }
		  if (IdentFirstChar::template Match(p)) 
		  {            
			while (IdentNextChar::template Match(p)) { }
			return true;
		  }
		  return false;
		}
	};

	// this represents the NULL string 
	struct NS {
		static char GetChar(int n) {
		  return '\0';
		}
	};

	// this matches a sequence of characters
	template
	<
		char C0 = '\0', char C1 = '\0', char C2 = '\0', char C3 = '\0',
		char C4 = '\0', char C5 = '\0', char C6 = '\0', char C7 = '\0',
		char C8 = '\0', char C9 = '\0', char C10 = '\0', char C11 = '\0',
		char C12 = '\0', char C13 = '\0', char C14 = '\0', char C15 = '\0' 
	>  
	struct CharSeq 
	{
	static char GetChar(int n) {
	  switch(n) {
		case (0) : return C0;
		case (1) : return C1;
		case (2) : return C2;
		case (3) : return C3;
		case (4) : return C4;
		case (5) : return C5;
		case (6) : return C6;
		case (7) : return C7;
		case (8) : return C8;
		case (9) : return C9;
		case (10) : return C10;
		case (11) : return C11;
		case (12) : return C12;
		case (13) : return C13;
		case (14) : return C14;
		case (15) : return C15;
		default : assert(false && "maximum length of strings is 16 chars");
	  }
	  return '\0';
	}

	template<typename ParserState_T>
	static bool Match(ParserState_T& p) {
		typename ParserState_T::Iterator pos = p.GetPos();              		
			int n = 0;
			char ch = GetChar(n);		
			while (ch != '\0') 
			{
				if (p.AtEnd() || p.GetElem() != ch) 
				{
					p.SetPos(pos);
					return false;
				}
				p.GotoNext();
				ch = GetChar(++n);
			}
			return true;    
		}
	};

	// this matches sequences of lower case characters, ignoring the case
	// of the input
	template
	<
		char C0 = '\0', char C1 = '\0', char C2 = '\0', char C3 = '\0',
		char C4 = '\0', char C5 = '\0', char C6 = '\0', char C7 = '\0',
		char C8 = '\0', char C9 = '\0', char C10 = '\0', char C11 = '\0',
		char C12 = '\0', char C13 = '\0', char C14 = '\0', char C15 = '\0' 
	>  
	struct CharSeqIgnoreCase 
	{
	static char GetChar(int n) {
	  switch(n) {
		case (0) : return C0;
		case (1) : return C1;
		case (2) : return C2;
		case (3) : return C3;
		case (4) : return C4;
		case (5) : return C5;
		case (6) : return C6;
		case (7) : return C7;
		case (8) : return C8;
		case (9) : return C9;
		case (10) : return C10;
		case (11) : return C11;
		case (12) : return C12;
		case (13) : return C13;
		case (14) : return C14;
		case (15) : return C15;
		default : assert(false && "maximum length of strings is 16 chars");
	  }
	  return '\0';
	}

	static char ToLowercase(char x)
	{
		if (x >= 'A' && x <= 'Z')
			return 'a' + (x - 'A');
		return x;
	}

	template<typename ParserState_T>
	static bool Match(ParserState_T& p) {
		typename ParserState_T::Iterator pos = p.GetPos();              
		for (int n = 0; GetChar(n) != '\0'; ++n) {
			if (p.AtEnd()) 
			{
				p.SetPos(pos);
				return false;
			}
			if (ToLowercase(p.GetElem()) != GetChar(n)) 
			{
				p.SetPos(pos);
				return false;
			}
			p.GotoNext();
		}
		return true;    
		}
	};

	// this matches parser types which end a word boundary
	template<typename T>
	struct Word :
	Seq<
	  T, 
	  NotAt<IdentNextChar>
	>
	{ };  

	template<typename T>
	struct DoubleQuoted : 
		Seq<Char<'\"'>, T, Char<'\"'> >
	{ };

	template<typename T>
	struct SingleQuoted : 
		Seq<Char<'\''>, T, Char<'\''> >
	{ };		

	template<typename T>
	struct SingleOrDoubleQuoted : 
		Or<SingleQuoted<T>, DoubleQuoted<T> > 
	{ };		

} // text_grammar
} // yard

#endif // #ifndef YARD_TEXT_GRAMMAR_HPP