/** ********************************** */
/** Part of the QIParser.h declaration */
/** ********************************** */


#ifndef _qi_polynomial_parser_h_
#define _qi_polynomial_parser_h_

#include <libqi/rpl/bigint.h>
#include <libqi/io/QIParser.h>

unsigned short _current_symbol;

/** I. */
/** *************************** */
/** Input stream symbol reading */
/** *************************** */
#define CURRENT_SYMBOL _current_symbol
#define NEXT_SYMBOL    CURRENT_SYMBOL++
#define PREV_SYMBOL    --CURRENT_SYMBOL

#define GET_CURRENT_SYMBOL() ((_current_symbol < _string_length) ? (_quadricDesc.c_str()[CURRENT_SYMBOL]) : '\0')
#define GET_NEXT_SYMBOL()    ((_current_symbol < _string_length) ? (_quadricDesc.c_str()[NEXT_SYMBOL])    : '\0')
#define GET_PREV_SYMBOL()    ((_current_symbol > 0)              ? (_quadricDesc.c_str()[PREV_SYMBOL])    : _quadricDesc[0])


/** II. */
/** ***************************************************** */
/** Monomial parsing: see the file "monomial_parsing.txt" */
/** ***************************************************** */
short m_code[4];    /** Power of X,Y,Z,W */
short m_sum;        /** Value of X+Y+Z+W */    
short current_var;  /** Last encountered variable */

/** Current monomial's sign */
short m_sign;


/** Current monomial's coefficient value */
rpl::bigint m_coefficient;

  
/** Associate an indice inside m_code for each variable X,Y,Z,W */
#define VAR_X  3
#define VAR_Y  2
#define VAR_Z  1
#define VAR_W  0

/** Resets the code */
#define reset_code m_sum=m_code[0]=m_code[1]=m_code[2]=m_code[3]=0

/** Update each variable's power value as it is encountered */
#define raise_var ++(m_code[current_var])
#define raise_x   current_var = VAR_X; raise_var
#define raise_y   current_var = VAR_Y; raise_var
#define raise_z   current_var = VAR_Z; raise_var
#define raise_w   current_var = VAR_W; raise_var
  

/** Sums each digit of the code */
#define sum_code m_sum = m_code[0] + m_code[1] + m_code[2] + m_code[3]

/** Homogenises the code */
#define hom_code m_code[0] += (2 - m_sum)

/** A general purpose macro that checks the code
    and homogenises it if necessary */
#define check_code \
 sum_code; \
 if (m_sum > 2) { throw "Invalid monomial: " + decode(); }\
 else if (m_sum < 2) { \
   if (m_code[0] != 0) { throw "Invalid monomial: " + decode(); } \
   else hom_code; \
 }
 
/** Does W+2Z+4Y+8X  */
#define hash_code m_code[0] + (m_code[1]<<1) + (m_code[2]<<2) + (m_code[3]<<3)

/** Returns the indice inside the vector */
#define indice_vector m_hash[hash_code]

#define init() \
reset_code; \
m_coefficient = 1; \
m_sign = 1;

/** When a "+" or a "-" is encountered, we store the
    previously parsed monomial (if exists), then
    we reinit all to prepare for the next monomial, via
    the "init" macro */
#define next_coeff() \
try {check_code; } catch(string e) { throw e; }\
if (indice_vector >= 0 && indice_vector < 10) _vectorialDesc[indice_vector] = m_sign * m_coefficient; \
init()


/** III. */
/** ****************************************** */
/** Templates defining parsing functions for   */
/** each non terminal of the grammar.          */
/** ****************************************** */

/** Handy macros to define prototypes and skeletons */

/** Header */
#define PARSE_DECL(name) void parse_##name (void) throw (string) 

/** Declaration (used in the QIParser's implementation file */
#define PARSE_IMPL(name) void QIParser::parse_##name (void) throw (string)

/** Call to a non terminal checking function */
#define IS_A(name)  parse_##name();

/** Booleans used in logical expression */
#define decl_is_a(name)  bool is_a_##name = false 

/** Automatically declares a prototype for each
    non terminal symbol of the grammar. */
PARSE_DECL(poly);
PARSE_DECL(term);
PARSE_DECL(mono);
PARSE_DECL(var);
PARSE_DECL(coef);
PARSE_DECL(sign);
PARSE_DECL(eol);


/** IV. */
/** **************** */
/** Terminal parsing */
/** **************** */
/** Please note that if the read character doesn't match, we *don't*
 *  advance to the next character, i.e. "NEXT_SYMBOL" is skipped by
 *  the "throw" statement. */
#define PARSE_TERMINAL(character) \
  do { 				  \
      if ( ! (GET_CURRENT_SYMBOL() == character) ) { \
	stringstream s; \
	s << "Parse error: '" << GET_CURRENT_SYMBOL() << "' at position: " << CURRENT_SYMBOL+1; \
        throw s.str(); \
      } 	   \
      NEXT_SYMBOL; \
  }while(0)


/** V. */
/** *************************************** */
/** Debugging function                      */
/** Prints the current monomial as a string */
/** *************************************** */
inline string decode () {
  stringstream ss; 
  
  if (m_code[3] > 0) { ss << "x"; if (m_code[3] >= 2) ss << "^" << m_code[3]; ss << " "; } 
  if (m_code[2] > 0) { ss << "y"; if (m_code[2] >= 2) ss << "^" << m_code[2]; ss << " "; }  
  if (m_code[1] > 0) { ss << "z"; if (m_code[1] >= 2) ss << "^" << m_code[1]; ss << " "; }
  if (m_code[0] > 0) { ss << "w"; if (m_code[0] >= 2) ss << "^" << m_code[0]; }
  return ss.str();
}

#endif