/*
 * $Id$
 */

/*
 * Harbour Project source code: 
 *   CT3 string function WORDREPL()
 *
 * Copyright 2001 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"


/*  $DOC$
 *  $FUNCNAME$
 *      WORDREPL()
 *  $CATEGORY$
 *      CT3 string functions
 *  $ONELINER$
 *      Replacement of double characters
 *  $SYNTAX$
 *      WORDREPL (<cDoubleCharacterSearchString>, <[@]cString>,
 *                <cDoubleCharacterReplaceString>, [<lMode>]) -> cString
 *  $ARGUMENTS$
 *      <cDoubleCharacterSearchString>   is a string of double characters
 *                                       that should be replaced
 *      <[@]cString>                     is the processed string
 *      <cDoubleCharacterReplaceString>  is a string of double characters that
 *                                       replace the one of <cSearchString>
 *      [<lMode>]                        sets the replacement method (see description)
 *                                       Default: .F.
 *  $RETURNS$
 *      cString                          the processed string
 *  $DESCRIPTION$
 *      The WORDREPL() takes the double characters of <cDoubleCharacterSearchString>
 *      one after the other and searches for them in <cString>.
 *      For <lMode> set to .F., this search is successful, if the double
 *      character sequence in <cString> starts at an odd position or at any
 *      position, if <lMode> is set to .T.
 *      If this happens, the double character sequence will be replaced with
 *      the corresponding double character sequence of <cDoubleCharacterReplaceString>.
 *      If <cDoubleCharacterReplaceString> is shorter than <cDoubleCharacterSearchString>
 *      the last double sequence of <cDoubleCharacterReplaceString> is used for
 *      the "rest" of <cDoubleCharacterSearchString>. Note that the last double
 *      character sequence in "AABBC" is "BB" in this context !!
 *      After the replacement the function restarts the search in <cString>
 *      BEHIND the replacement if the CSETATMUPA() switch is turned off, or
 *      BEHIND the first character of the replacement if the switch is turned on.
 *      (see examples for this !)
 *      One can omit the return value of this function by setting the CSETREF()
 *      to .T., but one must then pass <cString> by reference to get a result.
 *  $EXAMPLES$
 *      ? wordrepl("CC", "AABBCCDDEE", "XX") // "AABBXXDDEE"
 *      ? wordrepl("aa", "1aaaa", "ba")      // "1abaa" 
 *      ? wordrepl("aa", "1aaaa", "ba", .T.) // "1baba" 
 *      csetatmupa(.T.)
 *      ? wordrepl("aa", "1aaaa", "ba")      // "1abaa" 
 *      ? wordrepl("aa", "1aaaa", "ba", .T.) // "1bbba" 
 *  $TESTS$
 *      wordrepl("CC", "AABBCCDDEE", "XX") == "AABBXXDDEE"
 *      wordrepl("aa", "1aaaa", "ba")      == "1abaa" 
 *      wordrepl("aa", "1aaaa", "ba", .T.) == "1baba" 
 *      eval ({||csetatmupa(.T.),wordrepl("aa", "1aaaa", "ba")}) == "1abaa" 
 *      eval ({||csetatmupa(.T.),wordrepl("aa", "1aaaa", "ba", .T.)}) == "1bbba"
 *  $STATUS$
 *      Ready
 *  $COMPLIANCE$
 *      WORDREPL() is compatible with CT3's WORDREPL().
 *  $PLATFORMS$
 *      All
 *  $FILES$
 *      Source is wordrepl.c, library is ct3.
 *  $SEEALSO$
 *      CHARREPL(),RANGEREPL(),POSREPL(),CSETREF(),CSETATMUPA()
 *  $END$
 */

HB_FUNC( WORDREPL )
{
   int iNoRet;
   int iMultiPass;

   size_t sSearchLen, sReplaceLen;

   /* suppressing return value ? */
   iNoRet = ct_getref() && ISBYREF( 2 );
   iMultiPass = ct_getatmupa();

   /* param check */
   if( ( sSearchLen = ( size_t ) hb_parclen( 1 ) ) / 2 > 0 && ISCHAR( 2 ) &&
       ( sReplaceLen = ( size_t ) hb_parclen( 3 ) ) / 2 > 0 )
   {
      /* get parameters */
      char *pcSearch = hb_parc( 1 );
      char *pcString = hb_parc( 2 );
      size_t sStrLen = ( size_t ) hb_parclen( 2 );
      char *pcReplace = hb_parc( 3 );
      int iMode;
      char *pcRet;
      size_t sIndex;

      if( ISLOG( 4 ) )
         iMode = hb_parl( 4 );
      else
         iMode = 0;

      pcRet = ( char * ) hb_xgrab( sStrLen + 1 );
      hb_xmemcpy( pcRet, pcString, sStrLen );

      for( sIndex = 0; sIndex < ( sSearchLen & 0xFFFFFFFE ); sIndex += 2 )
      {

         size_t sMatchStrLen;
         char *pc;
         size_t sReplIndex = sIndex;

         if( sReplIndex > ( sReplaceLen & 0xFFFFFFFE ) )
         {
            sReplIndex = ( sReplaceLen & 0xFFFFFFFE );
         }

         pc = pcString;
         while( ( pc = ct_at_exact_forward( pc, sStrLen - ( pc - pcString ),
                                            pcSearch + sIndex, 2, &sMatchStrLen ) ) != NULL )
         {
            if( iMode )
            {
               /* always replace */
               *( pcRet + ( pc - pcString ) ) = *( pcReplace + sReplIndex );
               *( pcRet + ( pc - pcString ) + 1 ) = *( pcReplace + sReplIndex + 1 );

               if( iMultiPass )
                  pc++;
               else
                  pc += 2;
            }
            else
            {
               /* replace only if pc is an even position */
               if( ( ( pc - pcString ) % 2 ) == 0 )
               {
                  *( pcRet + ( pc - pcString ) ) = *( pcReplace + sReplIndex );
                  *( pcRet + ( pc - pcString ) + 1 ) = *( pcReplace + sReplIndex + 1 );
                  /* parse pcString in steps of two characters */
                  pc += 2;
               }
               else
               {
                  /* we are on an odd position, so add only 1 to pc */
                  pc++;
               }
            }
         }
      }

      /* return string */
      if( ISBYREF( 2 ) )
      {
         hb_storclen( pcRet, sStrLen, 2 );
      }

      if( iNoRet )
      {
         hb_retl( 0 );
         hb_xfree( pcRet );
      }
      else
      {
         hb_retclen_buffer( pcRet, sStrLen );
      }
   }
   else  /* ( sSearchLen = ( size_t ) hb_parclen( 1 ) ) / 2 > 0 && ISCHAR( 2 ) &&
            ( sReplaceLen = ( size_t ) hb_parclen( 3 ) ) / 2 > 0 */
   {
      PHB_ITEM pSubst = NULL;
      int iArgErrorMode = ct_getargerrormode();

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

      if( pSubst != NULL )
         hb_itemReturnRelease( pSubst );
      else if( iNoRet )
         hb_retl( 0 );
      else if( ISCHAR( 2 ) )
         hb_retclen( hb_parc( 2 ), hb_parclen( 2 ) );
      else
         hb_retc( NULL );
   }
}
