/**
 * @cond doxygen-libsbml-internal
 *
 * @file    FormulaTokenizer.c
 * @brief   Tokenizes an SBML formula string
 * @author  Ben Bornstein
 *
 * $Id: FormulaTokenizer.c 8704 2009-01-04 02:26:05Z mhucka $
 * $HeadURL: https://sbml.svn.sourceforge.net/svnroot/sbml/trunk/libsbml/src/math/FormulaTokenizer.c $
 *
 *<!---------------------------------------------------------------------------
 * This file is part of libSBML.  Please visit http://sbml.org for more
 * information about SBML, and the latest version of libSBML.
 *
 * Copyright 2005-2009 California Institute of Technology.
 * Copyright 2002-2005 California Institute of Technology and
 *                     Japan Science and Technology Corporation.
 * 
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation.  A copy of the license agreement is provided
 * in the file named "LICENSE.txt" included with this software distribution and
 * also available online as http://sbml.org/software/libsbml/license.html
 *----------------------------------------------------------------------- -->*/

#include <ctype.h>
#include <sbml/common/common.h>

#include <sbml/math/FormulaTokenizer.h>


/* Forward references */

void Token_convertNaNInf (Token_t *t);


/**
 * Creates a new FormulaTokenizer for the given formula string and returns
 * a pointer to it.
 */
LIBSBML_EXTERN
FormulaTokenizer_t *
FormulaTokenizer_createFromFormula (const char *formula)
{
  FormulaTokenizer_t *ft;


  ft = (FormulaTokenizer_t *) safe_malloc( sizeof(FormulaTokenizer_t) );

  ft->formula = safe_strdup(formula);
  ft->pos     = 0;

  return ft;
}


/**
 * Frees the given FormulaTokenizer.
 */
LIBSBML_EXTERN
void
FormulaTokenizer_free (FormulaTokenizer_t *ft)
{
  if (ft == NULL) return;


  safe_free(ft->formula);
  safe_free(ft);
}


/**
 * Reads a TT_NAME from the FormulaTokenizer into the given Token.  This is
 * a supporting function for FormulaTokenizer_nextToken().
 *
 * A TT_NAME is an SName:
 *
 *   letter ::=  a .. z, A .. Z
 *   digit  ::=  0 .. 9
 *   SName  ::= ( letter |  _  ) ( letter | digit |  _  )*
 *
 * This function assumes the character ft->formula[ft->pos] is either a
 * letter or an underscore.  FormulaTokenizer_nextToken() ensures this
 * precondition before calling this function.
 */
void
FormulaTokenizer_getName (FormulaTokenizer_t *ft, Token_t *t)
{
  char c;
  int  start, stop, len;


  t->type = TT_NAME;

  start = ft->pos;
  c     = ft->formula[ ++ft->pos ];

  while (isalpha(c) || isdigit(c) || c == '_')
  {
    c = ft->formula[ ++ft->pos ];
  }

  stop = ft->pos;
  len  = stop - start;

  t->value.name      = (char *) safe_malloc(len + 1);
  t->value.name[len] = '\0';
  strncpy(t->value.name, ft->formula + start, len);
}


/**
 * Reads either a TT_INTEGER or a TT_REAL from the FormulaTokenizer into
 * the given Token.  This is a supporting function for
 * FormulaTokenizer_nextToken().
 *
 * This function assumes the character ft->formula[ft->pos] is either a
 * period or a digit.  FormulaTokenizer_nextToken() ensures this
 * precondition before calling this function.
 *
 * Sign characters preceding the number are not recognized, but sign
 * characters in the exponent are recognized.
 *
 * A subtle error case:
 *
 * If the string starting with ft->formula[ft->pos] is some combination of
 * a '.', 'e|E' or '+|-' with no intervening digits, the token will be
 * marked as TT_UNKNOWN and t->value.ch set to ft->formula[ft->pos]
 * (a '.').
 */
void
FormulaTokenizer_getNumber (FormulaTokenizer_t *ft, Token_t *t)
{
  char c;
  char endchar;
  char *endptr;

  unsigned int start, stop, len;

  unsigned int exppos = 0;
  unsigned int endpos = 0;

  unsigned int seendot = 0;
  unsigned int seenexp = 0;
  unsigned int seensgn = 0;


  start = ft->pos;
  c     = ft->formula[ start ];

  /**
   * ([0-9]+\.?[0-9]*|\.[0-9]+)([eE][-+]?[0-9]+)?
   */
  while (1)
  {
    if (c == '.' && seendot == 0)
    {
      seendot = 1;
    }
    else if ((c == 'e' || c == 'E') && seenexp == 0)
    {
      seenexp = 1;
      exppos  = ft->pos;
    }
    else if ((c == '+' || c == '-') && seenexp == 1 && seensgn == 0)
    {
      seensgn = 1;
    }
    else if (c < '0' || c > '9')
    {
      endchar = c;
      endpos  = ft->pos;
      break;
    }

    c = ft->formula[ ++ft->pos ];
  }

  /**
   * Temporarily terminate ft->formula will a NULL at the character just
   * beyond the end of the number.  This prevents strtod() and strtol()
   * (below) from reading past the end of the number.
   *
   * This prevents at least one obscure bug where something like '3e 4' is
   * understood as one token 3e4 instead of two: 3e0 and 4.
   */
  ft->formula[ endpos ] = '\0';

  stop = ft->pos;
  len  = stop - start;

  /**
   * If the token is composed only of some combination of '.', 'e|E' or
   * '+|-' mark it as TT_UNKNOWN.  Otherwise, strtod() or strtol() should
   * be able to convert it, as all the syntax checking was performed above.
   */
  if (len == (seendot + seenexp + seensgn))
  {
    t->type     = TT_UNKNOWN;
    t->value.ch = ft->formula[start];
  }
  else if (seendot || seenexp)
  {
    /**
     * Temporarily "hide" the exponent part, so strtod below will convert
     * only the mantissa part.
     */
    if (seenexp)
    {
      c                     = ft->formula[ exppos ];
      ft->formula[ exppos ] = '\0';
    }

    t->type       = TT_REAL;
    t->value.real = c_locale_strtod(ft->formula + start, &endptr);

    /**
     * Convert the exponent part and "unhide" it.
     */
    if (seenexp)
    {
      t->type     = TT_REAL_E;
      t->exponent = strtol(ft->formula + exppos + 1, &endptr, 10);

      ft->formula[ exppos ] = c;
    }
  }
  else
  {
    t->type          = TT_INTEGER;
    t->value.integer = strtol(ft->formula + start, &endptr, 10);
  }

  /**
   * Restore the character overwritten above.
   */
  ft->formula[ endpos ] = endchar;
}


/**
 * @return the next token in the formula string.  If no more tokens are
 * available, the token type will be TT_END.
 */
LIBSBML_EXTERN
Token_t *
FormulaTokenizer_nextToken (FormulaTokenizer_t *ft)
{
  char     c = ft->formula[ ft->pos ];
  Token_t *t = Token_create();


  /**
   * Skip whitespace
   */
  while (isspace(c))
  {
    c = ft->formula[ ++ft->pos ];
  }


  if (c == '\0')
  {
    t->type     = TT_END;
    t->value.ch = c;
  }
  else if (c == '+' || c == '-' || c == '*' || c == '/' ||
           c == '^' || c == '(' || c == ')' || c == ',' )
  {
    t->type     = (TokenType_t) c;
    t->value.ch = c;
    ft->pos++;
  }
  else if (isalpha(c) || c == '_')
  {
    FormulaTokenizer_getName(ft, t);
  }
  else if (c == '.' || isdigit(c))
  {
    FormulaTokenizer_getNumber(ft, t);
  }
  else
  {
    t->type     = TT_UNKNOWN;
    t->value.ch = c;
    ft->pos++;
  }

  if (t->type == TT_NAME)
  {
    Token_convertNaNInf(t);
  }

  return t;
}


/**
 * Creates a new Token and returns a point to it.
 */
LIBSBML_EXTERN
Token_t *
Token_create (void)
{
  Token_t *t = (Token_t *) safe_calloc(1, sizeof(Token_t));


  t->type = TT_UNKNOWN;

  return t;
}


/**
 * Frees the given Token
 */
LIBSBML_EXTERN
void
Token_free (Token_t *t)
{
  if (t == NULL) return;


  if (t->type == TT_NAME)
  {
    safe_free(t->value.name);
  }

  safe_free(t);
}


/**
 * Converts the given Token (which must be of type TT_NAME) to a TT_REAL
 * NaN or Inf as appropriate.
 */
void
Token_convertNaNInf (Token_t *t)
{
  if ( !strcmp_insensitive(t->value.name, "NaN") )
  {
    safe_free(t->value.name);
    t->type       = TT_REAL;
    t->value.real = util_NaN();
  }
  else if ( !strcmp_insensitive(t->value.name, "Inf") )
  {
    safe_free(t->value.name);
    t->type       = TT_REAL;
    t->value.real = util_PosInf();
  }
}


/**
 * @return the value of this Token as a (long) integer.  This function
 * should be called only when the Token's type is TT_INTEGER.  If the type
 * is TT_REAL or TT_REAL_E, the function will cope by truncating the
 * number's fractional part.
 */
long
Token_getInteger (const Token_t *t)
{
  TokenType_t type   = t->type;
  long        result = 0;


  if (type == TT_INTEGER)
  {
    result = t->value.integer;
  }
  else if (type == TT_REAL || type == TT_REAL_E)
  {
    result = (int) Token_getReal(t);
  }

  return result;
}


/**
 * @return the value of this Token as a real (double).  This function
 * should be called only when the Token's is a number (TT_REAL, TT_REAL_E
 * or TT_INTEGER).
 */
double
Token_getReal (const Token_t *t)
{
  TokenType_t type   = t->type;
  double      result = 0.0;


  if (type == TT_REAL || type == TT_REAL_E)
  {
    result = t->value.real;
  
    if (type == TT_REAL_E)
    {
      result *= pow(10,  t->exponent);
    }
  }
  else if (type == TT_INTEGER)
  {
    result = (double) t->value.integer;
  }

  return result;
}


/**
 * Negates the value of this Token.  This operation is only valid if the
 * Token's type is TT_INTEGER, TT_REAL, or TT_REAL_E.
 */
void
Token_negateValue (Token_t *t)
{
  TokenType_t type = t->type;


  if (type == TT_INTEGER)
  {
    t->value.integer = - (t->value.integer);
  }
  else if (type == TT_REAL || type == TT_REAL_E)
  {
    t->value.real = - (t->value.real);
  }
}


/** @endcond doxygen-libsbml-internal */
