/*
 * $Id$
 */

/*
 * Harbour Project source code:
 *   STRDIFF() CT3 string function
 *
 * Copyright 2002 IntTec GmbH, Neunlindenstr 32, 79106 Freiburg, Germany
 *        Author: Martin Vogel <vogel@inttec.de>
 *
 * www - http://www.harbour-project.org
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this software; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307 USA (or visit the web site http://www.gnu.org/).
 *
 * As a special exception, the Harbour Project gives permission for
 * additional uses of the text contained in its release of Harbour.
 *
 * The exception is that, if you link the Harbour libraries with other
 * files to produce an executable, this does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * Your use of that executable is in no way restricted on account of
 * linking the Harbour library code into it.
 *
 * This exception does not however invalidate any other reasons why
 * the executable file might be covered by the GNU General Public License.
 *
 * This exception applies only to the code released by the Harbour
 * Project under the name Harbour.  If you copy code from other
 * Harbour Project or Free Software Foundation releases into a copy of
 * Harbour, as the General Public License permits, the exception does
 * not apply to the code that you add in this way.  To avoid misleading
 * anyone as to the status of such modified files, you must delete
 * this exception notice from them.
 *
 * If you write modifications of your own for Harbour, it is your choice
 * whether to permit this exception to apply to your modifications.
 * If you do not wish that, delete this exception notice.
 *
 */


#include "ct.h"
#include <limits.h>


/*  $DOC$
 *  $FUNCNAME$
 *      STRDIFF()
 *  $CATEGORY$
 *      CT3 string functions
 *  $ONELINER$
 *      Evaluate the "Edit (Levensthein) Distance" of two strings
 *  $SYNTAX$
 *      STRDIFF (<cString1>, <cString2>, [<nReplacementPenalty>], [<nDeletionPenalty>], 
 *               [<nInsertionPenalty>]) -> <nDistance>
 *  $ARGUMENTS$
 *      <cString1>              string at the "starting point" of the transformation process, default is ""
 *      <cString2>              string at the "end point" of the transformation process, default is ""
 *      <nReplacementPenalty>   penalty points for a replacement of one character, default is 3
 *      <nDeletionPenalty>      penalty points for a deletion of one character, default is 6
 *      <nInsertionPenalty>     penalty points for an insertion of one character, default is 1
 *  $RETURNS$
 *      <nDistance>             penalty point sum of all operations needed to transform <cString1> to <cString2>
 *  $DESCRIPTION$
 *      The STRDIFF() functions calculates the so called "Edit" or "Levensthein" distance of two strings. 
 *      This distance is a measure for the number of single character replace/insert/delete operations (so called
 *      "point mutations") required to transform <cString1> into <cString2> and its value will be the smallest sum of
 *      the penalty points of the required operations.
 *
 *      Be aware that this function is both quite time - O(len(cString1)*len(cString2)) - and memory consuming - 
 *      O((len(cString1)+1)*(len(cString2)+1)*sizeof(int)) - so keep the strings as short as possible. 
 *      E.g., on common 32 bit systems (sizeof(int) == 4), calling strdiff() with two strings of 1024 bytes 
 *      in length will consume 4 MB of memory. To not impose unneeded restrictions, the function will only check if
 *      (len(cString1)+1)*(len(cString2)+1)*sizeof(int) <= UINT_MAX, although allocing UINT_MAX bytes will not
 *      work on most systems. If this simple check fails, -1 is returned.
 *
 *      Also, be aware that there can be an overflow when the penalty points are summed up: Assuming that the
 *      number of transformation operations is in the order of max(len(cString1),len(cString2)), the penalty point 
 *      sum, that is internally stored in an "int" variable, is in the order of 
 *      (max(len(cString1),len(cString2))*max(nReplacementPenalty,nDeletionPenalty,nInsertionPentaly). 
 *      The STRDIFF() does not do an overflow check due to time performance reasons. Future versions of STRDIFF() 
 *      could use a type different to "int" to store the penalty point sum to save memory or to avoid overflows.
 *
 *      The function is aware of the settings done by SETATLIKE(), that means that the wildchar character
 *      is considered equal to ALL characters.
 * 
 *  $EXAMPLES$
 *      ? strdiff("ABC", "ADC") // 3, one character replaced
 *      ? strdiff("ABC", "AEC") // 3, dito
 *      ? strdiff("CBA", "ABC") // 6, two characters replaced
 *      ? strdiff("ABC", "AXBC") // 1, one character inserted
 *      ? strdiff("AXBC", "ABC") // 6, one character removed
 *      ? strdiff("AXBC", "ADC") // 9, one character removed and one replaced
 *  $TESTS$
 *      strdiff("ABC", "ADC") == 3 
 *      strdiff("ABC", "AEC") == 3 
 *      strdiff("CBA", "ABC") == 6 
 *      strdiff("ABC", "AXBC") == 1 
 *      strdiff("AXBC", "ABC") == 6 
 *      strdiff("AXBC", "ADC") == 9
 *  $STATUS$
 *      Ready
 *  $COMPLIANCE$
 *      STRDIFF() is compatible with CT3's STRDIFF().
 *  $PLATFORMS$
 *      All
 *  $FILES$
 *      Source is strdiff.c, library is libct.
 *  $SEEALSO$
 *      SETATLIKE()
 *  $END$
 */

#define MATRIXELEMENT(__row,__col) *(piPenalty+((__row)*(sStrLen2+1))+(__col))

static int min3( int a, int b, int c )
{
   if( a < b )
   {
      return ( ( a < c ? a : c ) );
   }
   return ( ( b < c ? b : c ) );
}

HB_FUNC( STRDIFF )
{
   /* param check */
   if( ISCHAR( 1 ) || ISCHAR( 2 ) )
   {
      /* get parameters */
      char *pcStr1, *pcStr2;
      size_t sStrLen1, sStrLen2;
      int iReplace, iDelete, iInsert;
      int iAtLike = ct_getatlike();
      char cAtLike = ct_getatlikechar();
      int *piPenalty;
      size_t sRowCnt, sColCnt;

      if( ISCHAR( 1 ) )
      {
         pcStr1 = ( char * ) hb_parc( 1 );
         sStrLen1 = ( size_t ) hb_parclen( 1 );
      }
      else
      {
         pcStr1 = ( char * ) "";
         sStrLen1 = 0;
      }

      if( ISCHAR( 2 ) )
      {
         pcStr2 = ( char * ) hb_parc( 2 );
         sStrLen2 = ( size_t ) hb_parclen( 2 );
      }
      else
      {
         pcStr2 = ( char * ) "";
         sStrLen2 = 0;
      }

      /* check for memory consumption */
      if( ( ( double ) sStrLen1 + 1.0 ) *
          ( ( double ) sStrLen2 + 1.0 ) *
          ( ( double ) sizeof( int ) ) >= ( double ) UINT_MAX )
      {
         int iArgErrorMode = ct_getargerrormode();

         if( iArgErrorMode != CT_ARGERR_IGNORE )
         {
            ct_error( ( USHORT ) iArgErrorMode, EG_ARG, CT_ERROR_STRDIFF, NULL,
                      "STRDIFF", 0, EF_CANDEFAULT, HB_ERR_ARGS_BASEPARAMS );
         }
         hb_retni( -1 );
         return;
      }

      /* get penalty points */
      if( ISNUM( 3 ) )
         iReplace = hb_parni( 3 );
      else
         iReplace = 3;

      if( ISNUM( 4 ) )
         iDelete = hb_parni( 4 );
      else
         iDelete = 6;

      if( ISNUM( 5 ) )
         iInsert = hb_parni( 5 );
      else
         iInsert = 1;

      piPenalty = ( int * ) hb_xgrab( ( sStrLen1 + 1 ) *
                                      ( sStrLen2 + 1 ) * sizeof( int ) );

      MATRIXELEMENT( 0, 0 ) = 0;
      for( sColCnt = 0; sColCnt <= sStrLen2 - 1; sColCnt++ )
      {
         MATRIXELEMENT( 0, sColCnt + 1 ) = MATRIXELEMENT( 0, sColCnt ) + iInsert;
      }

      for( sRowCnt = 0; sRowCnt <= sStrLen1 - 1; sRowCnt++ )
      {
         MATRIXELEMENT( sRowCnt + 1, 0 ) = MATRIXELEMENT( sRowCnt, 0 ) + iDelete;
         for( sColCnt = 0; sColCnt <= sStrLen2 - 1; sColCnt++ )
         {
            int iReplaceCost;

            if( pcStr1[sRowCnt] == pcStr2[sColCnt] ||
                ( iAtLike == CT_SETATLIKE_WILDCARD &&
                  ( pcStr1[sRowCnt] == cAtLike ||
                    pcStr2[sColCnt] == cAtLike ) ) )
               iReplaceCost = 0;
            else
               iReplaceCost = iReplace;

            MATRIXELEMENT( sRowCnt + 1, sColCnt + 1 ) =
               min3( MATRIXELEMENT( sRowCnt, sColCnt ) + iReplaceCost,
                     MATRIXELEMENT( sRowCnt, sColCnt + 1 ) + iDelete,
                     MATRIXELEMENT( sRowCnt + 1, sColCnt ) + iInsert );
         }
      }

      hb_retni( MATRIXELEMENT( sStrLen1, sStrLen2 ) );
      hb_xfree( piPenalty );
   }
   else  /* ISCHAR( 1 ) || ISCHAR( 2 ) */
   {
      PHB_ITEM pSubst = NULL;
      int iArgErrorMode = ct_getargerrormode();

      if( iArgErrorMode != CT_ARGERR_IGNORE )
      {
         pSubst = ct_error_subst( ( USHORT ) iArgErrorMode, EG_ARG,
                                  CT_ERROR_STRDIFF, NULL, "STRDIFF", 0,
                                  EF_CANSUBSTITUTE, HB_ERR_ARGS_BASEPARAMS );
      }

      if( pSubst != NULL )
         hb_itemReturnRelease( pSubst );
      else
         hb_retni( 0 );
   }
}