/*
 * Help Access Library 
 * A Library to access the contents of Windows Help files.
 *
 * Copyright (C) 1995-2000 Bernd Herd, http://www.herdsoft.com
 *                                                                  
 * 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 of   
 * the License.              
 *                                                                  
 * 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 program; if not, write to the Free Software      
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.        
 */
/* GETTTL.C -------------------------------------------
 * @doc
 * @module GETTTL.C |
 * Gets Topic Title for any valid TopicOffset Value
 *
 * Help Access Library Project.
 *
 *-----------------------------------------------------*/

#include <windows.h>
#include <windowsx.h>
#include <time.h>
#include <stdio.h>
#include <string.h>
#include "hlpacces.h"


BOOL LOCAL nEnumerateTopics(NPIFSFILE ifsfile, DWORD dwTopicOffset, LPSTR lpszBuffer, UINT uBufferSize, LPDWORD lpdwTopicOffsetStart);
BOOL LOCAL nEnumeratePage(NPIFSFILE ifsfile, int PageCount, int CurrentLevel, int PageSize, int CurrPage, DWORD dwTopicOffset, LPSTR lpszBuffer, UINT uBufferSize, LPDWORD lpdwTopicOffsetStart);


/* @func BOOL | HlpGetTopicTitle |
 *
 * Retrieves the Topic Title for a given TopicOffset Value.
 * The TopicOffset does not neccessarily need to point directly
 * to the start of the Topic.
 *
 * @rdesc
 * TRUE if the Function was Successfull
 * FALSE else
 */
BOOL FAR PASCAL DLLEXP HlpGetTopicTitle(
                HIFS ifs,                       // @parm Handle to a opened File-System opened by <f IFSOpen>
                DWORD dwTopicOffset,            // @parm TopicOffset to search for
                LPSTR lpszBuffer,               // @parm Pointer to a Buffer to copy the retrieved Title String or NULL if not needed
                UINT uBufferSize,               // @parm Size of the Bufffer in Bytes
                LPDWORD lpdwTopicOffsetStart)   // @parm Pointer to a DWORD that will contain the TopicOffset value for the begin of the Topic or NULL if this is not needed
{ BOOL      Success=FALSE;
  NPIFSFILE ifsfile = IFSOpenFile(ifs, "|TTLBTREE");
  if (ifsfile)
  {
    Success = nEnumerateTopics(ifsfile, dwTopicOffset, lpszBuffer, uBufferSize, lpdwTopicOffsetStart);

    IFSCloseFile(ifsfile);
  }
  return Success;
}


/* nEnumerateTopic
 *
 * Does the buch of Work to do enumeration
 */
BOOL LOCAL nEnumerateTopics(NPIFSFILE ifsfile, DWORD dwTopicOffset, LPSTR lpszBuffer, UINT uBufferSize, LPDWORD lpdwTopicOffsetStart)
{ BOOL            Success;

  BTREEHEADER     BTreeHdr;
  DWORD           dwSize;
  UINT            PageCount;


  //--------- Read Title B-Tree header ------------------
  IFSReadFile(ifsfile, &BTreeHdr, sizeof(BTreeHdr));
  dwSize = IFSSeekFile(ifsfile, 0L, 2);

  PageCount = (UINT) (dwSize/leword(BTreeHdr.PageSize));

//  printf("# PageCount:%u NLevels: %u NSplits: %u PageSize: %u Total Entries:%ld\n\n", PageCount, BTreeHdr.NLevels, BTreeHdr.NSplits, BTreeHdr.PageSize, BTreeHdr.TotalBtreeEntries);

  Success = nEnumeratePage(ifsfile, PageCount, leword(BTreeHdr.NLevels)-1, leword(BTreeHdr.PageSize), leword(BTreeHdr.RootPage), dwTopicOffset, lpszBuffer, uBufferSize, lpdwTopicOffsetStart);

  return Success;
}


#pragma pack(1)
typedef struct
{ 
  LEWORD   PageNo;
  LEDWORD  TopicOffset;
} PACKED BTREEINDEXENTRY;
#pragma pack()



BOOL LOCAL nEnumeratePage(NPIFSFILE ifsfile, int PageCount, int CurrentLevel, int PageSize, int CurrPage, DWORD dwTopicOffset, LPSTR lpszBuffer, UINT uBufferSize, LPDWORD lpdwTopicOffsetStart)
{ 
  BOOL                           Success    = FALSE;
 DWORD                           loc       = sizeof(BTREEHEADER) + PageSize * (DWORD) CurrPage;
 NPSTR                          page       = (NPSTR) LocalAlloc(LPTR, PageSize);
  NPSTR                 next;
  BTREENODEHEADER       NodeHeader;
  BTREEINDEXENTRY NEAR *CurrIndexEntry,
                  NEAR *DownIndexEntry;
  int                   i;

  if (page)
  {
     //----------- Read Page ----------------------------------------
     IFSSeekFile(ifsfile, loc, 0);
     if (PageSize == IFSReadFile(ifsfile, page, PageSize))
     { memcpy(&NodeHeader, page, sizeof(NodeHeader));

       //--------- Are we in a Node or in a leaf? -------------------
       if (CurrentLevel > 0)
       { //-- We're in a node, search for next sub-node or leaf --
         DownIndexEntry = NULL;

         for (i=0,                  CurrIndexEntry = (BTREEINDEXENTRY NEAR *) (page+sizeof(BTREEINDEXHEADER));
              i<leword(NodeHeader.NEntries)+1 && !DownIndexEntry;
              ++i                  ,++CurrIndexEntry)
            //------- We're currently in a node, so recurse down... ----
            if (ledword(CurrIndexEntry->TopicOffset)>dwTopicOffset ||
                i==leword(NodeHeader.NEntries))
              DownIndexEntry = CurrIndexEntry;


         if (DownIndexEntry)
            Success = nEnumeratePage(ifsfile, PageCount, CurrentLevel-1, PageSize, leword(DownIndexEntry->PageNo), dwTopicOffset, lpszBuffer, uBufferSize, lpdwTopicOffsetStart);
       }

       else

       //--------- Enumerate Page contents --------------------------
       for (Success=TRUE, next=page+sizeof(BTREENODEHEADER), i=0;
            Success                                        &&i<leword(NodeHeader.NEntries);
                          next+=5+lstrlen(next+4)          , i++)
          if (ledword(*((LEDWORD NEAR *) next)) <= dwTopicOffset)
          {
            Success=TRUE;
            if (lpszBuffer)
               lstrcpyn(lpszBuffer, next+4, uBufferSize);
            if (lpdwTopicOffsetStart)
               *lpdwTopicOffsetStart=ledword(*((LEDWORD NEAR *) next));
          }
     }

     //----------- Free Page data except Header ---------------------
     LocalFree((HLOCAL) page);
  }

  return Success;
}