/* This file is (c) 2008-2012 Konstantin Isakov <ikm@goldendict.org>
 * Part of GoldenDict. Licensed under GPLv3 or later, see the LICENSE file */

#include "aard.hh"
#include "btreeidx.hh"
#include "folding.hh"
#include "utf8.hh"
#include "chunkedstorage.hh"
#include "langcoder.hh"
#include "fsencoding.hh"
#include "decompress.hh"
#include "gddebug.hh"
#include "ftshelpers.hh"
#include "htmlescape.hh"

#include <map>
#include <set>
#include <string>

#ifdef _MSC_VER
#include <stub_msvc.h>
#endif

#include <QString>
#include <QSemaphore>
#include <QThreadPool>
#include <QAtomicInt>
#include <QDomDocument>
#include <QUrl>
#include <QtEndian>

#include "ufile.hh"
#include "wstring_qt.hh"

namespace Aard {

using std::map;
using std::multimap;
using std::pair;
using std::set;
using std::string;
using gd::wstring;

using BtreeIndexing::WordArticleLink;
using BtreeIndexing::IndexedWords;
using BtreeIndexing::IndexInfo;

namespace {

DEF_EX_STR( exNotAardFile, "Not an AARD file", Dictionary::Ex )
DEF_EX_STR( exCantReadFile, "Can't read file", Dictionary::Ex )
DEF_EX_STR( exWordIsTooLarge, "Enountered a word that is too large:", Dictionary::Ex )
DEF_EX_STR( exSuddenEndOfFile, "Sudden end of file", Dictionary::Ex )

#pragma pack( push, 1 )

/// AAR file header
struct AAR_header
{
    char signature[4];
    char checksum[40];
    quint16 version;
    char uuid[16];
    quint16 volume;
    quint16 totalVolumes;
    quint32 metaLength;
    quint32 wordsCount;
    quint32 articleOffset;
    char indexItemFormat[4];
    char keyLengthFormat[2];
    char articleLengthFormat[2];
}
#ifndef _MSC_VER
__attribute__((packed))
#endif
;

struct IndexElement
{
    quint32 wordOffset;
    quint32 articleOffset;
}
#ifndef _MSC_VER
__attribute__((packed))
#endif
;

struct IndexElement64
{
    quint32 wordOffset;
    quint64 articleOffset;
}
#ifndef _MSC_VER
__attribute__((packed))
#endif
;

enum
{
  Signature = 0x58524141, // AARX on little-endian, XRAA on big-endian
  CurrentFormatVersion = 4 + BtreeIndexing::FormatVersion + Folding::Version
};

struct IdxHeader
{
  quint32 signature; // First comes the signature, AARX
  quint32 formatVersion; // File format version (CurrentFormatVersion)
  quint32 chunksOffset; // The offset to chunks' storage
  quint32 indexBtreeMaxElements; // Two fields from IndexInfo
  quint32 indexRootOffset;
  quint32 wordCount;
  quint32 articleCount;
  quint32 langFrom;  // Source language
  quint32 langTo;    // Target language
}
#ifndef _MSC_VER
__attribute__((packed))
#endif
;

#pragma pack( pop )

bool indexIsOldOrBad( string const & indexFile )
{
  File::Class idx( indexFile, "rb" );

  IdxHeader header;

  return idx.readRecords( &header, sizeof( header ), 1 ) != 1 ||
         header.signature != Signature ||
         header.formatVersion != CurrentFormatVersion;
}

void readJSONValue( string const & source, string & str, string::size_type & pos)
{
    int level = 1;
    char endChar;
    str.push_back( source[pos] );
    if( source[pos] == '{')
        endChar = '}';
    else if( source[pos] == '[' )
        endChar = ']';
    else if( source[pos] == '\"' )
    {
        str.clear();
        endChar = '\"';
    }
    else
        endChar = ',';

    pos++;
    char ch = 0;
    char lastCh = 0;
    while( !( ch == endChar && lastCh != '\\' && level == 0 )
           && pos < source.size() )
    {
        lastCh = ch;
        ch = source[ pos++ ];
        if( ( ch == '{' || ch == '[' ) && lastCh != '\\' )
          level++;
        if( ( ch == '}' || ch == ']' ) && lastCh != '\\' )
          level--;

        if( ch == endChar &&
            ( ( ch == '\"' && lastCh != '\\' ) || ch == ',' )
            && level == 1)
          break;
        str.push_back( ch );
    }
}

map< string, string > parseMetaData( string const & metaData )
{
// Parsing JSON string
    map< string, string > data;
    string name, value;
    string::size_type n = 0;

    while( n < metaData.length() && metaData[n] != '{' )
        n++;
    while( n < metaData.length() )
    {
        // Skip to '"'
        while( n < metaData.length() && metaData[n] != '\"' )
            n++;
        if( ++n >= metaData.length() )
            break;

        // Read name
        while(  n < metaData.length() &&
                !( ( metaData[n] == '\"' || metaData[n] == '{' ) && metaData[n-1] != '\\' ) )
            name.push_back( metaData[n++]);

        // Skip to ':'
        if( ++n >= metaData.length() )
            break;
        while( n < metaData.length() && metaData[n] != ':' )
            n++;
        if( ++n >= metaData.length() )
            break;

        // Find value start after ':'
        while( n < metaData.length()
               && !( ( metaData[n] == '\"'
                       || metaData[n] == '{'
                       || metaData[n] == '['
                       || ( metaData[n] >= '0' && metaData[n] <= '9' ) )
               && metaData[n-1] != '\\' ) )
            n++;
        if( n >= metaData.length() )
            break;

        readJSONValue( metaData, value, n);

        data[name] = value;

        name.clear();
        value.clear();
        if( ++n >= metaData.length() )
            break;
    }
    return data;
}

class AardDictionary: public BtreeIndexing::BtreeDictionary
{
    Mutex idxMutex;
    Mutex aardMutex;
    File::Class idx;
    IdxHeader idxHeader;
    ChunkedStorage::Reader chunks;
    string dictionaryName;
    File::Class df;

  public:

    AardDictionary( string const & id, string const & indexFile,
                     vector< string > const & dictionaryFiles );

    ~AardDictionary();

    virtual string getName() throw()
    { return dictionaryName; }

    virtual map< Dictionary::Property, string > getProperties() throw()
    { return map< Dictionary::Property, string >(); }

    virtual unsigned long getArticleCount() throw()
    { return idxHeader.articleCount; }

    virtual unsigned long getWordCount() throw()
    { return idxHeader.wordCount; }

    inline virtual quint32 getLangFrom() const
    { return idxHeader.langFrom; }

    inline virtual quint32 getLangTo() const
    { return idxHeader.langTo; }

    virtual sptr< Dictionary::DataRequest > getArticle( wstring const &,
                                                        vector< wstring > const & alts,
                                                        wstring const & )
      throw( std::exception );

    virtual QString const& getDescription();

    virtual sptr< Dictionary::DataRequest > getSearchResults( QString const & searchString,
                                                              int searchMode, bool matchCase,
                                                              int distanceBetweenWords,
                                                              int maxResults );
    virtual void getArticleText( uint32_t articleAddress, QString & headword, QString & text );

    virtual void makeFTSIndex(QAtomicInt & isCancelled, bool firstIteration );

    virtual void setFTSParameters( Config::FullTextSearch const & fts )
    {
      can_FTS = fts.enabled
                && !fts.disabledTypes.contains( "AARD", Qt::CaseInsensitive )
                && ( fts.maxDictionarySize == 0 || getArticleCount() <= fts.maxDictionarySize );
    }

protected:

    virtual void loadIcon() throw();

private:

    /// Loads the article.
    void loadArticle( quint32 address,
                      string & articleText,
                      bool rawText = false );
    string convert( string const & in_data );

    friend class AardArticleRequest;
};

AardDictionary::AardDictionary( string const & id,
                                string const & indexFile,
                                vector< string > const & dictionaryFiles ):
    BtreeDictionary( id, dictionaryFiles ),
    idx( indexFile, "rb" ),
    idxHeader( idx.read< IdxHeader >() ),
    chunks( idx, idxHeader.chunksOffset ),
    df( dictionaryFiles[ 0 ], "rb" )
{
    // Read dictionary name

    idx.seek( sizeof( idxHeader ) );
    vector< char > dName( idx.read< quint32 >() );
    if( dName.size() )
    {
        idx.read( &dName.front(), dName.size() );
        dictionaryName = string( &dName.front(), dName.size() );
    }

    // Initialize the index

    openIndex( IndexInfo( idxHeader.indexBtreeMaxElements,
                          idxHeader.indexRootOffset ),
               idx, idxMutex );

    // Full-text search parameters

    can_FTS = true;

    ftsIdxName = indexFile + "_FTS";

    if( !Dictionary::needToRebuildIndex( dictionaryFiles, ftsIdxName )
        && !FtsHelpers::ftsIndexIsOldOrBad( ftsIdxName ) )
      FTS_index_completed.ref();
}

AardDictionary::~AardDictionary()
{
    df.close();
}

void AardDictionary::loadIcon() throw()
{
  if ( dictionaryIconLoaded )
    return;

  QString fileName =
    QDir::fromNativeSeparators( FsEncoding::decode( getDictionaryFilenames()[ 0 ].c_str() ) );

  // Remove the extension
  fileName.chop( 3 );

  if( !loadIconFromFile( fileName ) )
  {
    // Load failed -- use default icons
    dictionaryNativeIcon = dictionaryIcon = QIcon(":/icons/icon32_aard.png");
  }

  dictionaryIconLoaded = true;
}

string AardDictionary::convert( const string & in )
{
    string inConverted;
    char inCh, lastCh = 0;
    bool afterEol = false;

    for( string::const_iterator i = in.begin(), j = in.end(); i != j; ++i )
    {
        inCh = *i;
        if( lastCh == '\\' )
        {
            inConverted.erase( inConverted.size() - 1 );
            lastCh = 0;
            if( inCh == 'n' )
            {
                inConverted.append( "<br/>");
                afterEol = true;
                continue;
            }
            else if( inCh == 'r')
                continue;
        }
        else if( inCh == ' ' && afterEol )
        {
            inConverted.append( "&nbsp;" );
            continue;
        } else
            lastCh = inCh;
        afterEol = false;
        inConverted.push_back( inCh );
    }

    QString text = QString::fromUtf8( inConverted.c_str() );
    text.replace( QRegExp( "<\\s*a\\s*href\\s*=\\s*[\\\"'](w:|s:){0,1}([^#](?!ttp://)[^\\\"']*)(.)" ),
                  "<a href=\"bword:\\2\"");

    static QRegExp self_closing_divs( "(<div\\s[^>]*)/>", Qt::CaseInsensitive );  // <div ... />
    text.replace( self_closing_divs, "\\1></div>" );

    // Fix outstanding elements
    text += "<br style=\"clear:both;\" />";

    return text.toUtf8().data();
}

void AardDictionary::loadArticle( quint32 address,
                                  string & articleText,
                                  bool rawText )
{
    quint32 articleOffset = address;
    quint32 articleSize;
    quint32 size;

    vector< char > articleBody;

    articleText.clear();


    while( 1 )
    {
      articleText = string( QObject::tr( "Article loading error" ).toUtf8().constData() );
      try
      {
        Mutex::Lock _( aardMutex );
        df.seek( articleOffset );
        df.read( &size, sizeof(size) );
        articleSize = qFromBigEndian( size );

        // Don't try to read and decode too big articles,
        // it is most likely error in dictionary
        if( articleSize > 1048576 )
          break;

        articleBody.resize( articleSize );
        df.read( &articleBody.front(), articleSize );
      }
      catch( std::exception &ex )
      {
        gdWarning( "AARD: Failed loading article from \"%s\", reason: %s\n", getName().c_str(), ex.what() );
        break;
      }
      catch(...)
      {
        break;
      }

      if ( articleBody.empty() )
        break;

      articleText.clear();

      string text = decompressBzip2( articleBody.data(), articleSize );
      if( text.empty() )
        text = decompressZlib( articleBody.data(), articleSize );
      if( text.empty() )
        text = string( articleBody.data(), articleSize );

      if( text.empty() || text[ 0 ] != '[' )
        break;

      string::size_type n = text.find( '\"' );
      if( n == string::npos )
        break;

      readJSONValue( text, articleText, n );

      if( articleText.empty() )
      {
        n = text.find( "\"r\"" );
        if( n != string::npos && n + 3 < text.size() )
        {
          n = text.find( '\"', n + 3 );
          if( n == string::npos )
            break;

          string link;
          readJSONValue( text, link, n );
          if( !link.empty() )
          {
            string encodedLink;
            encodedLink.reserve( link.size() );
            bool prev = false;
            for( string::const_iterator i = link.begin(); i != link.end(); ++i )
            {
              if( *i == '\\' )
              {
                if( !prev )
                {
                  prev = true;
                  continue;
                }
              }
              encodedLink.push_back( *i );
              prev = false;
            }
            encodedLink = string( QUrl( QString::fromUtf8( encodedLink.data(), encodedLink.size() ) ).toEncoded().data() );
            articleText = "<a href=\"" + encodedLink + "\">" + link + "</a>";
          }
        }
      }

      break;
    }

    if( !articleText.empty() )
    {
      if( rawText )
        return;

      articleText = convert( articleText );
    }
    else
      articleText = string( QObject::tr( "Article decoding error" ).toUtf8().constData() );

    // See Issue #271: A mechanism to clean-up invalid HTML cards.
    string cleaner = "</font>""</font>""</font>""</font>""</font>""</font>"
                     "</font>""</font>""</font>""</font>""</font>""</font>"
                     "</b></b></b></b></b></b></b></b>"
                     "</i></i></i></i></i></i></i></i>"
                     "</a></a></a></a></a></a></a></a>";

    string prefix( "<div class=\"aard\"" );
    if( isToLanguageRTL() )
      prefix += " dir=\"rtl\"";
    prefix += ">";

    articleText = prefix + articleText + cleaner + "</div>";
}

QString const& AardDictionary::getDescription()
{
    if( !dictionaryDescription.isEmpty() )
        return dictionaryDescription;

    AAR_header dictHeader;
    quint32 size;
    vector< char > data;

    {
        Mutex::Lock _( aardMutex );
        df.seek( 0 );
        df.read( &dictHeader, sizeof(dictHeader) );
        size = qFromBigEndian( dictHeader.metaLength );
        data.resize( size );
        df.read( &data.front(), size );
    }

    string metaStr = decompressBzip2( data.data(), size );
    if( metaStr.empty() )
        metaStr = decompressZlib( data.data(), size );

    map< string, string > meta = parseMetaData( metaStr );

    if( !meta.empty() )
    {
        map< string, string >::const_iterator iter = meta.find( "copyright" );
        if( iter != meta.end() )
          dictionaryDescription = "Copyright: " + QString::fromUtf8( iter->second.c_str() ) + "\n\n";

        iter = meta.find( "version" );
        if( iter != meta.end() )
          dictionaryDescription = "Version: " + QString::fromUtf8( iter->second.c_str() ) + "\n\n";

        iter = meta.find( "description" );
        if( iter != meta.end() )
        {
          QString desc = QString::fromUtf8( iter->second.c_str() );
          desc.replace( "\\n", "\n" );
          desc.replace( "\\t", "\t" );
          dictionaryDescription += desc;
        }
    }

    if( dictionaryDescription.isEmpty() )
      dictionaryDescription = "NONE";

    return dictionaryDescription;
}

void AardDictionary::makeFTSIndex( QAtomicInt & isCancelled, bool firstIteration )
{
  if( !( Dictionary::needToRebuildIndex( getDictionaryFilenames(), ftsIdxName )
         || FtsHelpers::ftsIndexIsOldOrBad( ftsIdxName ) ) )
    FTS_index_completed.ref();

  if( haveFTSIndex() )
    return;

  if( ensureInitDone().size() )
    return;

  if( firstIteration && getArticleCount() > FTS::MaxDictionarySizeForFastSearch )
    return;

  gdDebug( "Aard: Building the full-text index for dictionary: %s\n",
           getName().c_str() );

  try
  {
    FtsHelpers::makeFTSIndex( this, isCancelled );
    FTS_index_completed.ref();
  }
  catch( std::exception &ex )
  {
    gdWarning( "Aard: Failed building full-text search index for \"%s\", reason: %s\n", getName().c_str(), ex.what() );
    QFile::remove( FsEncoding::decode( ftsIdxName.c_str() ) );
  }
}

void AardDictionary::getArticleText( uint32_t articleAddress, QString & headword, QString & text )
{
  try
  {
    headword.clear();
    string articleText;

    loadArticle( articleAddress, articleText );

    text = Html::unescape( QString::fromUtf8( articleText.data(), articleText.size() ) );
  }
  catch( std::exception &ex )
  {
    gdWarning( "Aard: Failed retrieving article from \"%s\", reason: %s\n", getName().c_str(), ex.what() );
  }
}

sptr< Dictionary::DataRequest > AardDictionary::getSearchResults( QString const & searchString,
                                                                  int searchMode, bool matchCase,
                                                                  int distanceBetweenWords,
                                                                  int maxResults )
{
  return new FtsHelpers::FTSResultsRequest( *this, searchString,searchMode, matchCase, distanceBetweenWords, maxResults );
}

/// AardDictionary::getArticle()

class AardArticleRequest;

class AardArticleRequestRunnable: public QRunnable
{
  AardArticleRequest & r;
  QSemaphore & hasExited;

public:

  AardArticleRequestRunnable( AardArticleRequest & r_,
                              QSemaphore & hasExited_ ): r( r_ ),
                                                         hasExited( hasExited_ )
  {}

  ~AardArticleRequestRunnable()
  {
    hasExited.release();
  }

  virtual void run();
};

class AardArticleRequest: public Dictionary::DataRequest
{
  friend class AardArticleRequestRunnable;

  wstring word;
  vector< wstring > alts;
  AardDictionary & dict;

  QAtomicInt isCancelled;
  QSemaphore hasExited;

public:

  AardArticleRequest( wstring const & word_,
                      vector< wstring > const & alts_,
                      AardDictionary & dict_ ):
    word( word_ ), alts( alts_ ), dict( dict_ )
  {
    QThreadPool::globalInstance()->start(
      new AardArticleRequestRunnable( *this, hasExited ) );
  }

  void run(); // Run from another thread by DslArticleRequestRunnable

  virtual void cancel()
  {
    isCancelled.ref();
  }

  ~AardArticleRequest()
  {
    isCancelled.ref();
    hasExited.acquire();
  }
};

void AardArticleRequestRunnable::run()
{
  r.run();
}

void AardArticleRequest::run()
{
  if ( isCancelled )
  {
    finish();
    return;
  }

  vector< WordArticleLink > chain = dict.findArticles( word );

  for( unsigned x = 0; x < alts.size(); ++x )
  {
    /// Make an additional query for each alt

    vector< WordArticleLink > altChain = dict.findArticles( alts[ x ] );

    chain.insert( chain.end(), altChain.begin(), altChain.end() );
  }

  multimap< wstring, pair< string, string > > mainArticles, alternateArticles;

  set< quint32 > articlesIncluded; // Some synonims make it that the articles
                                    // appear several times. We combat this
                                    // by only allowing them to appear once.

  wstring wordCaseFolded = Folding::applySimpleCaseOnly( word );

  for( unsigned x = 0; x < chain.size(); ++x )
  {
    if ( isCancelled )
    {
      finish();
      return;
    }

    if ( articlesIncluded.find( chain[ x ].articleOffset ) != articlesIncluded.end() )
      continue; // We already have this article in the body.

    // Now grab that article

    string headword, articleText;

    headword = chain[ x ].word;
    try
    {
      dict.loadArticle( chain[ x ].articleOffset, articleText );
    }
    catch(...)
    {
    }

    // Ok. Now, does it go to main articles, or to alternate ones? We list
    // main ones first, and alternates after.

    // We do the case-folded comparison here.

    wstring headwordStripped =
      Folding::applySimpleCaseOnly( Utf8::decode( headword ) );

    multimap< wstring, pair< string, string > > & mapToUse =
      ( wordCaseFolded == headwordStripped ) ?
        mainArticles : alternateArticles;

    mapToUse.insert( pair< wstring, pair< string, string > >(
      Folding::applySimpleCaseOnly( Utf8::decode( headword ) ),
      pair< string, string >( headword, articleText ) ) );

    articlesIncluded.insert( chain[ x ].articleOffset );
  }

  if ( mainArticles.empty() && alternateArticles.empty() )
  {
    // No such word
    finish();
    return;
  }

  string result;

  multimap< wstring, pair< string, string > >::const_iterator i;

  for( i = mainArticles.begin(); i != mainArticles.end(); ++i )
  {
      result += "<h3>";
      result += i->second.first;
      result += "</h3>";
      result += i->second.second;
  }

  for( i = alternateArticles.begin(); i != alternateArticles.end(); ++i )
  {
      result += "<h3>";
      result += i->second.first;
      result += "</h3>";
      result += i->second.second;
  }

  Mutex::Lock _( dataMutex );

  data.resize( result.size() );

  memcpy( &data.front(), result.data(), result.size() );

  hasAnyData = true;

  finish();
}

sptr< Dictionary::DataRequest > AardDictionary::getArticle( wstring const & word,
                                                            vector< wstring > const & alts,
                                                            wstring const & )
  throw( std::exception )
{
  return new AardArticleRequest( word, alts, *this );
}

} // anonymous namespace

vector< sptr< Dictionary::Class > > makeDictionaries(
                                      vector< string > const & fileNames,
                                      string const & indicesDir,
                                      Dictionary::Initializing & initializing )
  throw( std::exception )
{
  vector< sptr< Dictionary::Class > > dictionaries;

  for( vector< string >::const_iterator i = fileNames.begin(); i != fileNames.end();
       ++i )
  {
      // Skip files with the extensions different to .aar to speed up the
      // scanning
      if ( i->size() < 4 ||
          strcasecmp( i->c_str() + ( i->size() - 4 ), ".aar" ) != 0 )
        continue;

      // Got the file -- check if we need to rebuid the index

      vector< string > dictFiles( 1, *i );

      string dictId = Dictionary::makeDictionaryId( dictFiles );

      string indexFile = indicesDir + dictId;

      if ( Dictionary::needToRebuildIndex( dictFiles, indexFile ) ||
           indexIsOldOrBad( indexFile ) )
      {
        try
        {

          gdDebug( "Aard: Building the index for dictionary: %s\n", i->c_str() );

          {
            QFileInfo info( FsEncoding::decode( i->c_str() ) );
            if( info.size() > ULONG_MAX )
            {
              gdWarning( "File %s is too large\n", i->c_str() );
              continue;
            }
          }

          File::Class df( *i, "rb" );

          AAR_header dictHeader;

          df.read( &dictHeader, sizeof(dictHeader) );
          bool has64bitIndex = !strncmp( dictHeader.indexItemFormat, ">LQ", 4 );
          if( strncmp( dictHeader.signature, "aard", 4 )
              || ( !has64bitIndex && strncmp( dictHeader.indexItemFormat, ">LL", 4 ) )
              || strncmp( dictHeader.keyLengthFormat, ">H", 2 )
              || strncmp( dictHeader.articleLengthFormat, ">L", 2) )
          {
              gdWarning( "File %s is not in supported aard format\n", i->c_str() );
              continue;
          }

          vector< char > data;
          quint32 size = qFromBigEndian( dictHeader.metaLength );

          if( size == 0 )
          {
              gdWarning( "File %s has invalid metadata", i->c_str() );
              continue;
          }

          data.resize( size );
          df.read( &data.front(), size );
          string metaStr = decompressBzip2( data.data(), size );
          if( metaStr.empty() )
              metaStr = decompressZlib( data.data(), size );

          map< string, string > meta = parseMetaData( metaStr );

          if( meta.empty() )
          {
              gdWarning( "File %s has invalid metadata", i->c_str() );
              continue;
          }

          string dictName;
          map< string, string >::const_iterator iter = meta.find( "title" );
          if( iter != meta.end() )
              dictName = iter->second;

          string langFrom;
          iter = meta.find( "index_language" );
          if( iter != meta.end() )
              langFrom = iter->second;

          string langTo;
          iter = meta.find( "article_language" );
          if( iter != meta.end() )
              langTo = iter->second;

          if( ( dictName.compare( "Wikipedia") == 0 || dictName.compare( "Wikiquote" ) == 0 || dictName.compare( "Wiktionary" ) == 0 )
              && !langTo.empty() )
          {
            string capitalized = langTo.c_str();
            capitalized[0] = toupper( capitalized[0] );
            dictName = dictName + " (" + capitalized + ")";
          }

          quint16 volumes = qFromBigEndian( dictHeader.totalVolumes );
          if( volumes > 1 )
          {
            QString ss;
            ss.sprintf( " (%i/%i)", qFromBigEndian( dictHeader.volume ), volumes );
            dictName += ss.toLocal8Bit().data();
          }

          initializing.indexingDictionary( dictName );

          File::Class idx( indexFile, "wb" );
          IdxHeader idxHeader;
          memset( &idxHeader, 0, sizeof( idxHeader ) );

          // We write a dummy header first. At the end of the process the header
          // will be rewritten with the right values.

          idx.write( idxHeader );

          idx.write( (quint32) dictName.size() );
          if( !dictName.empty() )
              idx.write( dictName.data(), dictName.size() );

          IndexedWords indexedWords;

          ChunkedStorage::Writer chunks( idx );

          quint32 wordCount = qFromBigEndian( dictHeader.wordsCount );
          set< quint32 > articleOffsets;

          quint32 pos = df.tell();
          quint32 wordsBase = pos + wordCount * ( has64bitIndex ? sizeof( IndexElement64 ) : sizeof( IndexElement ) );
          quint32 articlesBase = qFromBigEndian( dictHeader.articleOffset );

          data.clear();
          for( quint32 j = 0; j < wordCount; j++ )
          {
            quint32 articleOffset;
            quint32 wordOffset;

            if( has64bitIndex )
            {
              IndexElement64 el64;

              df.seek( pos );
              df.read( &el64, sizeof(el64) );
              articleOffset = articlesBase + qFromBigEndian( el64.articleOffset );
              wordOffset = wordsBase + qFromBigEndian( el64.wordOffset );
            }
            else
            {
              IndexElement el;

              df.seek( pos );
              df.read( &el, sizeof(el) );
              articleOffset = articlesBase + qFromBigEndian( el.articleOffset );
              wordOffset = wordsBase + qFromBigEndian( el.wordOffset );
            }

            df.seek( wordOffset );

            quint16 sizeBE;
            df.read( &sizeBE, sizeof(sizeBE) );
            quint16 wordSize = qFromBigEndian( sizeBE );
            if( data.size() < wordSize )
              data.resize( wordSize );
            df.read( &data.front(), wordSize );

            if( articleOffsets.find( articleOffset ) == articleOffsets.end() )
                articleOffsets.insert( articleOffset );

            // Insert new entry
            indexedWords.addWord( Utf8::decode( string( data.data(), wordSize ) ), articleOffset);

            pos += has64bitIndex ? sizeof( IndexElement64 ) : sizeof( IndexElement );
          }
          data.clear();

          idxHeader.articleCount = articleOffsets.size();
          articleOffsets.clear();

          // Finish with the chunks

          idxHeader.chunksOffset = chunks.finish();

          // Build index

          IndexInfo idxInfo = BtreeIndexing::buildIndex( indexedWords, idx );

          idxHeader.indexBtreeMaxElements = idxInfo.btreeMaxElements;
          idxHeader.indexRootOffset = idxInfo.rootOffset;

          indexedWords.clear(); // Release memory -- no need for this data

          // That concludes it. Update the header.

          idxHeader.signature = Signature;
          idxHeader.formatVersion = CurrentFormatVersion;

          idxHeader.wordCount = wordCount;

          if( langFrom.size() == 3)
              idxHeader.langFrom = LangCoder::code3toInt( langFrom.c_str() );
          else if( langFrom.size() == 2 )
              idxHeader.langFrom = LangCoder::code2toInt( langFrom.c_str() );

          if( langTo.size() == 3)
              idxHeader.langTo = LangCoder::code3toInt( langTo.c_str() );
          else if( langTo.size() == 2 )
              idxHeader.langTo = LangCoder::code2toInt( langTo.c_str() );

          idx.rewind();

          idx.write( &idxHeader, sizeof( idxHeader ) );
        }
        catch( std::exception & e )
        {
          gdWarning( "Aard dictionary indexing failed: %s, error: %s\n",
                    i->c_str(), e.what() );
          continue;
        }
        catch( ... )
        {
          gdWarning( "Aard dictionary indexing failed\n" );
          continue;
        }
      } // if need to rebuild
      try
      {
        dictionaries.push_back( new AardDictionary( dictId,
                                                    indexFile,
                                                    dictFiles ) );
      }
      catch( std::exception & e )
      {
        gdWarning( "Aard dictionary initializing failed: %s, error: %s\n",
                  i->c_str(), e.what() );
        continue;
      }
  }
  return dictionaries;
}

}