/*
 * 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.        
 */
/* LDCONTEXT.C -----------------------------------------
 * @doc
 * @module LDCONTEXT.C |
 *
 * Handling of CONTEXT-File
 *
 * Loads CONTEXT-File into main memory and does a qsort
 * of the Data by TopicOffset-Values to support
 * Generation of #-Footnotes
 *
 * Help Access Library Project.
 *
 *-----------------------------------------------------*/

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


void LOCAL nEnumeratePage(NPIFSFILE ifsfile, int PageCount, int CurrentLevel, int PageSize, int CurrPage, LPCONTEXTARRAY lpContextArray);


int  _USERENTRY ContextSort(const void *a, const void *b);

/* iContextLoad
 *
 * Load the Table of Context ID Entries
 */
void iContextLoad(NPTOPIC topic)                   /* Load Fonts-Table */
{ BTREEHEADER     BTreeHdr;
  UINT            PageCount;

  NPIFSFILE ifsfile = IFSOpenFile(topic->ifs, "|CONTEXT");
  if (ifsfile)
  {
     //--------- Read Title B-Tree header ------------------
     IFSReadFile(ifsfile, &BTreeHdr, sizeof(BTreeHdr));

     PageCount           = (UINT) (IFSSeekFile(ifsfile, 0L, 2)/leword(BTreeHdr.PageSize));
     topic->ContextArray = (LPCONTEXTARRAY) Hlpcalloc(sizeof(CONTEXTARRAY),1);

     if (topic->ContextArray &&
         NULL!=(topic->ContextArray->Context=Hlpmalloc(ledword(BTreeHdr.TotalBtreeEntries) * sizeof(CONTEXTREC)))
        )
     {
        topic->ContextArray->ContextAllocated=ledword(BTreeHdr.TotalBtreeEntries);
        nEnumeratePage(ifsfile, PageCount, leword(BTreeHdr.NLevels)-1, leword(BTreeHdr.PageSize), leword(BTreeHdr.RootPage), topic->ContextArray);
     }

     IFSCloseFile(ifsfile);

     qsort(topic->ContextArray->Context, topic->ContextArray->ContextCount, sizeof(CONTEXTREC), ContextSort);

     topic->contents = iReadContentsFile(topic->ifs);
  }
}


int _USERENTRY ContextSort(const void *va, const void *vb)
{
  CONTEXTREC FAR *a=(CONTEXTREC FAR *)va,
             FAR *b=(CONTEXTREC FAR *)vb;

# ifdef __WIN32__
  return ledword(a->TopicOffset) - ledword(b->TopicOffset);
# else
  return ledword(a->TopicOffset) >  ledword(b->TopicOffset) ? 1 :
         ledword(a->TopicOffset) == ledword(b->TopicOffset) ? 0 :
                                                             -1 ;
# endif
}



int _USERENTRY ContextFind(const void *va, const void *vb)
{
  CONTEXTREC FAR *a=(CONTEXTREC FAR *)va,
             FAR *b=(CONTEXTREC FAR *)vb;

  DWORD toa = ledword(a->TopicOffset);
  DWORD tob = ledword(b->TopicOffset);

  return
    abs(toa-tob)<3
    ? 0
    : ContextSort(va, vb);
}




/* iContextFree
 *
 * Free up memory allocates for Context-table
 */
void iContextFree(NPTOPIC topic)                   /* Free Memory used by Fonts-Table */
{
   if (topic->ContextArray)
   {
      if (topic->ContextArray->Context!=NULL)
         Hlpfree(topic->ContextArray->Context);

      Hlpfree(topic->ContextArray);
      topic->ContextArray=NULL;

      if (topic->contents != NULL)
        {
          iFreeContentsFile(topic->contents);
        }
   }
}







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


void LOCAL nEnumeratePage(NPIFSFILE ifsfile, int PageCount, int CurrentLevel, int PageSize, int CurrPage, LPCONTEXTARRAY lpContextArray)
{ DWORD                 loc        = sizeof(BTREEHEADER) + PageSize * (DWORD) CurrPage;
  NPSTR                 page       = (NPSTR) LocalAlloc(LPTR, PageSize);
  BTREENODEHEADER       NodeHeader;
  BTREEINDEXENTRY NEAR *CurrIndexEntry;
  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 --
         for (i=0,                  CurrIndexEntry = (BTREEINDEXENTRY NEAR *) (page+sizeof(BTREEINDEXHEADER));
              i<leword(NodeHeader.NEntries)+1;
              ++i                  ,++CurrIndexEntry)
            //------- We're currently in a node, so recurse down... ----
            nEnumeratePage(ifsfile, PageCount, CurrentLevel-1, PageSize, leword(CurrIndexEntry->PageNo), lpContextArray);
       }

       else
       {
         //--------- Copy Page Contents ---- --------------------------
            memcpy(lpContextArray->Context + lpContextArray->ContextCount, page+sizeof(BTREENODEHEADER), leword(NodeHeader.NEntries) * sizeof(CONTEXTREC));
                                             lpContextArray->ContextCount +=                             leword(NodeHeader.NEntries);
       }
     }

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






/* iContextFind
 *
 * Look if there is a Context-Id connected to this TopicOffset
 *
 * Returns a Pointer to a strdup-ed memory Buffer
 */
LPSTR iContextFind(NPTOPIC topic, DWORD TopicOffset)
{
  CONTEXTREC FAR *lpContextRec,
                  SearchForRec;
  LPSTR           lpszResult=NULL;

  if (topic->ContextArray)
  {
    //    SearchForRec.TopicOffset = TopicOffset;
    SearchForRec.TopicOffset.d1 = (TopicOffset >> 0) & 0xff;
    SearchForRec.TopicOffset.d2 = (TopicOffset >> 8) & 0xff;
    SearchForRec.TopicOffset.d3 = (TopicOffset >> 16) & 0xff;
    SearchForRec.TopicOffset.d4 = (TopicOffset >> 24) & 0xff;

    lpContextRec = bsearch(&SearchForRec, topic->ContextArray->Context, topic->ContextArray->ContextCount, sizeof(CONTEXTREC), ContextFind);

    if (lpContextRec)
    {
      /* WOW! found a Context-Record ... */

      /* Try to find a context ID matching this hash value */
      if (topic->contents)
        {
          lpszResult = iContentsFromHash(topic->contents, ledword(lpContextRec->HashValue));
        }

      /* Nothing available in the .cnt file, use a generated hash-value */
      if (!lpszResult)
        {
          char buf[500];
          HlpCreateStringForHashValue(ledword(lpContextRec->HashValue), buf);
          lpszResult = Hlpstrdup(buf);
        }
    }
  }

  return lpszResult;
}



/* HlpTopicFindContextIdForTopicOffset
 *
 * Find a context Id matching the given Topic Offset
 *
 * @param htopic      Handle to the topic file opened using the HTO_CONTEXT flag
 * @param TopicOffset TopicOffset we need a name for
 *
 * @return String with the context-ID retrieved. NULL if none found.
 *         The string needs to be released with a call to Hlpfree(...)
 */
LPSTR
WINAPI
HlpTopicFindContextIdForTopicOffset(HTOPIC htopic, DWORD TopicOffset)
{
  return iContextFind(htopic, TopicOffset);
}