package org.apache.maven.index.context;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0    
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  import java.io.File;
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  import java.nio.channels.FileLock;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.nio.file.StandardOpenOption;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Date;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Set;
  
  import org.apache.lucene.analysis.Analyzer;
  import org.apache.lucene.document.Document;
  import org.apache.lucene.document.Field;
  import org.apache.lucene.document.StoredField;
  import org.apache.lucene.index.CorruptIndexException;
  import org.apache.lucene.index.DirectoryReader;
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.index.IndexWriter;
  import org.apache.lucene.index.IndexWriterConfig;
  import org.apache.lucene.index.MultiBits;
  import org.apache.lucene.index.Term;
  import org.apache.lucene.search.IndexSearcher;
  import org.apache.lucene.search.SearcherManager;
  import org.apache.lucene.search.TermQuery;
  import org.apache.lucene.search.TopDocs;
  import org.apache.lucene.search.TopScoreDocCollector;
  import org.apache.lucene.store.Directory;
  import org.apache.lucene.store.FSDirectory;
  import org.apache.lucene.store.FSLockFactory;
  import org.apache.lucene.store.Lock;
  import org.apache.lucene.store.LockObtainFailedException;
  import org.apache.lucene.util.Bits;
  import org.apache.maven.index.ArtifactInfo;
  import org.apache.maven.index.IndexerField;
  import org.apache.maven.index.artifact.GavCalculator;
  import org.apache.maven.index.artifact.M2GavCalculator;
  import org.codehaus.plexus.util.StringUtils;
  
  /**
   * The default {@link IndexingContext} implementation.
   * 
   * @author Jason van Zyl
   * @author Tamas Cservenak
   */
  public class DefaultIndexingContext
      extends AbstractIndexingContext
  {
      /**
       * A standard location for indices served up by a webserver.
       */
      private static final String INDEX_DIRECTORY = ".index";
  
      public static final String FLD_DESCRIPTOR = "DESCRIPTOR";
  
      public static final String FLD_DESCRIPTOR_CONTENTS = "NexusIndex";
  
      public static final String FLD_IDXINFO = "IDXINFO";
  
      public static final String VERSION = "1.0";
  
      private static final Term DESCRIPTOR_TERM = new Term( FLD_DESCRIPTOR, FLD_DESCRIPTOR_CONTENTS );
  
      private Directory indexDirectory;
  
      private TrackingLockFactory lockFactory;
  
      private File indexDirectoryFile;
  
      private String id;
  
      private boolean searchable;
  
      private String repositoryId;
 
     private File repository;
 
     private String repositoryUrl;
 
     private String indexUpdateUrl;
 
     private NexusIndexWriter indexWriter;
 
     private SearcherManager searcherManager;
 
     private Date timestamp;
 
     private List<? extends IndexCreator> indexCreators;
 
     /**
      * Currently nexus-indexer knows only M2 reposes
      * <p>
      * XXX move this into a concrete Scanner implementation
      */
     private GavCalculator gavCalculator;
 
     private DefaultIndexingContext( String id,
                                     String repositoryId,
                                     File repository, //
                                     String repositoryUrl, String indexUpdateUrl,
                                     List<? extends IndexCreator> indexCreators, Directory indexDirectory,
                                     TrackingLockFactory lockFactory,
                                     boolean reclaimIndex,
                                     File indexDirectoryFile )
         throws ExistingLuceneIndexMismatchException, IOException
     {
 
         this.id = id;
 
         this.searchable = true;
 
         this.repositoryId = repositoryId;
 
         this.repository = repository;
 
         this.repositoryUrl = repositoryUrl;
 
         this.indexUpdateUrl = indexUpdateUrl;
 
         this.indexWriter = null;
 
         this.searcherManager = null;
 
         this.indexCreators = indexCreators;
 
         this.indexDirectory = indexDirectory;
 
         this.lockFactory = lockFactory;
 
         // eh?
         // Guice does NOT initialize these, and we have to do manually?
         // While in Plexus, all is well, but when in guice-shim,
         // these objects are still LazyHintedBeans or what not and IndexerFields are NOT registered!
         for ( IndexCreator indexCreator : indexCreators )
         {
             indexCreator.getIndexerFields();
         }
 
         this.gavCalculator = new M2GavCalculator();
 
         prepareIndex( reclaimIndex );
 
         setIndexDirectoryFile( indexDirectoryFile );
     }
 
     private DefaultIndexingContext( String id, String repositoryId, File repository, File indexDirectoryFile,
                                    TrackingLockFactory lockFactory, String repositoryUrl, String indexUpdateUrl,
                                    List<? extends IndexCreator> indexCreators, boolean reclaimIndex )
         throws IOException, ExistingLuceneIndexMismatchException
     {
         this( id, repositoryId, repository, repositoryUrl, indexUpdateUrl, indexCreators,
             FSDirectory.open( indexDirectoryFile.toPath(), lockFactory ), lockFactory, reclaimIndex,
                 indexDirectoryFile );
     }
 
     public DefaultIndexingContext( String id, String repositoryId, File repository, File indexDirectoryFile,
                                    String repositoryUrl, String indexUpdateUrl,
                                    List<? extends IndexCreator> indexCreators, boolean reclaimIndex )
         throws IOException, ExistingLuceneIndexMismatchException
     {
         this( id, repositoryId, repository, indexDirectoryFile, new TrackingLockFactory( FSLockFactory.getDefault() ),
               repositoryUrl, indexUpdateUrl, indexCreators, reclaimIndex );
     }
 
     @Deprecated
     public DefaultIndexingContext( String id, String repositoryId, File repository, Directory indexDirectory,
                                    String repositoryUrl, String indexUpdateUrl,
                                    List<? extends IndexCreator> indexCreators, boolean reclaimIndex )
         throws IOException, ExistingLuceneIndexMismatchException
     {
         this( id, repositoryId, repository, repositoryUrl, indexUpdateUrl, indexCreators, indexDirectory, null,
               reclaimIndex, indexDirectory instanceof FSDirectory
                         ? ( (FSDirectory) indexDirectory ).getDirectory().toFile() : null
         ); // Lock factory already installed - pass null
     }
 
     public Directory getIndexDirectory()
     {
         return indexDirectory;
     }
     
     /**
      * Sets index location. As usually index is persistent (is on disk), this will point to that value, but in
      * some circumstances (ie, using RAMDisk for index), this will point to an existing tmp directory.
      */
     protected void setIndexDirectoryFile( File dir )
         throws IOException
     {
         if ( dir == null )
         {
             // best effort, to have a directory through the life of a ctx
             this.indexDirectoryFile = Files.createTempDirectory( "mindexer-ctx" + id ).toFile();
             this.indexDirectoryFile.deleteOnExit();
         }
         else
         {
             this.indexDirectoryFile = dir;
         }
     }
 
     public File getIndexDirectoryFile()
     {
         return indexDirectoryFile;
     }
 
     private void prepareIndex( boolean reclaimIndex )
         throws IOException, ExistingLuceneIndexMismatchException
     {
         if ( DirectoryReader.indexExists( indexDirectory ) )
         {
             try
             {
                 // unlock the dir forcibly
                 try
                 {
                     indexDirectory.obtainLock( IndexWriter.WRITE_LOCK_NAME ).close();
                 }
                 catch ( LockObtainFailedException failed )
                 {
                     unlockForcibly( lockFactory, indexDirectory );
                 }
 
                 openAndWarmup();
 
                 checkAndUpdateIndexDescriptor( reclaimIndex );
             }
             catch ( IOException e )
             {
                 if ( reclaimIndex )
                 {
                     prepareCleanIndex( true );
                 }
                 else
                 {
                     throw e;
                 }
             }
         }
         else
         {
             prepareCleanIndex( false );
         }
 
         timestamp = IndexUtils.getTimestamp( indexDirectory );
     }
 
     private void prepareCleanIndex( boolean deleteExisting )
         throws IOException
     {
         if ( deleteExisting )
         {
             closeReaders();
 
             // unlock the dir forcibly
             try
             {
                 indexDirectory.obtainLock( IndexWriter.WRITE_LOCK_NAME ).close();
             }
             catch ( LockObtainFailedException failed )
             {
                 unlockForcibly( lockFactory, indexDirectory );
             }
 
             deleteIndexFiles( true );
         }
 
         openAndWarmup();
 
         if ( StringUtils.isEmpty( getRepositoryId() ) )
         {
             throw new IllegalArgumentException( "The repositoryId cannot be null when creating new repository!" );
         }
 
         storeDescriptor();
     }
 
     private void checkAndUpdateIndexDescriptor( boolean reclaimIndex )
         throws IOException, ExistingLuceneIndexMismatchException
     {
         if ( reclaimIndex )
         {
             // forcefully "reclaiming" the ownership of the index as ours
             storeDescriptor();
             return;
         }
 
         // check for descriptor if this is not a "virgin" index
         if ( getSize() > 0 )
         {
             final TopScoreDocCollector collector = TopScoreDocCollector.create( 1, Integer.MAX_VALUE );
             final IndexSearcher indexSearcher = acquireIndexSearcher();
             try
             {
                 indexSearcher.search( new TermQuery( DESCRIPTOR_TERM ), collector );
 
                 if ( collector.getTotalHits() == 0 )
                 {
                     throw new ExistingLuceneIndexMismatchException(
                         "The existing index has no NexusIndexer descriptor" );
                 }
 
                 if ( collector.getTotalHits() > 1 )
                 {
                     // eh? this is buggy index it seems, just iron it out then
                     storeDescriptor();
                 }
                 else
                 {
                     // good, we have one descriptor as should
                     Document descriptor = indexSearcher.doc( collector.topDocs().scoreDocs[0].doc );
                     String[] h = StringUtils.split( descriptor.get( FLD_IDXINFO ), ArtifactInfo.FS );
                     // String version = h[0];
                     String repoId = h[1];
 
                     // // compare version
                     // if ( !VERSION.equals( version ) )
                     // {
                     // throw new UnsupportedExistingLuceneIndexException(
                     // "The existing index has version [" + version + "] and not [" + VERSION + "] version!" );
                     // }
 
                     if ( getRepositoryId() == null )
                     {
                         repositoryId = repoId;
                     }
                     else if ( !getRepositoryId().equals( repoId ) )
                     {
                         throw new ExistingLuceneIndexMismatchException( "The existing index is for repository " //
                             + "[" + repoId + "] and not for repository [" + getRepositoryId() + "]" );
                     }
                 }
             }
             finally
             {
                 releaseIndexSearcher( indexSearcher );
             }
         }
     }
 
     private void storeDescriptor()
         throws IOException
     {
         Document hdr = new Document();
 
         hdr.add( new Field( FLD_DESCRIPTOR, FLD_DESCRIPTOR_CONTENTS, IndexerField.KEYWORD_STORED ) );
 
         hdr.add( new StoredField( FLD_IDXINFO, VERSION + ArtifactInfo.FS + getRepositoryId() ) );
 
         IndexWriter w = getIndexWriter();
 
         w.updateDocument( DESCRIPTOR_TERM, hdr );
 
         w.commit();
     }
 
     private void deleteIndexFiles( boolean full )
         throws IOException
     {
         if ( indexDirectory != null )
         {
             String[] names = indexDirectory.listAll();
 
             if ( names != null )
             {
 
                 for ( String name : names )
                 {
                     if ( !( name.equals( INDEX_PACKER_PROPERTIES_FILE )
                         || name.equals( INDEX_UPDATER_PROPERTIES_FILE ) ) )
                     {
                         indexDirectory.deleteFile( name );
                     }
                 }
             }
 
             if ( full )
             {
                 try
                 {
                     indexDirectory.deleteFile( INDEX_PACKER_PROPERTIES_FILE );
                 }
                 catch ( IOException ioe )
                 {
                     //Does not exist
                 }
 
                 try
                 {
                     indexDirectory.deleteFile( INDEX_UPDATER_PROPERTIES_FILE );
                 }
                 catch ( IOException ioe )
                 {
                     //Does not exist
                 }
             }
 
             IndexUtils.deleteTimestamp( indexDirectory );
         }
     }
 
     // ==
 
     public boolean isSearchable()
     {
         return searchable;
     }
 
     public void setSearchable( boolean searchable )
     {
         this.searchable = searchable;
     }
 
     public String getId()
     {
         return id;
     }
 
     public void updateTimestamp()
         throws IOException
     {
         updateTimestamp( false );
     }
 
     public void updateTimestamp( boolean save )
         throws IOException
     {
         updateTimestamp( save, new Date() );
     }
 
     public void updateTimestamp( boolean save, Date timestamp )
         throws IOException
     {
         this.timestamp = timestamp;
 
         if ( save )
         {
             IndexUtils.updateTimestamp( indexDirectory, getTimestamp() );
         }
     }
 
     public Date getTimestamp()
     {
         return timestamp;
     }
 
     public int getSize()
         throws IOException
     {
         final IndexSearcher is = acquireIndexSearcher();
         try
         {
             return is.getIndexReader().numDocs();
         }
         finally
         {
             releaseIndexSearcher( is );
         }
     }
 
     public String getRepositoryId()
     {
         return repositoryId;
     }
 
     public File getRepository()
     {
         return repository;
     }
 
     public String getRepositoryUrl()
     {
         return repositoryUrl;
     }
 
     public String getIndexUpdateUrl()
     {
         if ( repositoryUrl != null )
         {
             if ( indexUpdateUrl == null || indexUpdateUrl.trim().length() == 0 )
             {
                 return repositoryUrl + ( repositoryUrl.endsWith( "/" ) ? "" : "/" ) + INDEX_DIRECTORY;
             }
         }
         return indexUpdateUrl;
     }
 
     public Analyzer getAnalyzer()
     {
         return new NexusAnalyzer();
     }
 
     protected void openAndWarmup()
         throws IOException
     {
         // IndexWriter (close)
         if ( indexWriter != null )
         {
             indexWriter.close();
 
             indexWriter = null;
         }
         if ( searcherManager != null )
         {
             searcherManager.close();
 
             searcherManager = null;
         }
 
         this.indexWriter = new NexusIndexWriter( getIndexDirectory(), getWriterConfig() );
         this.indexWriter.commit(); // LUCENE-2386
         this.searcherManager = new SearcherManager( indexWriter, false, false, new NexusIndexSearcherFactory( this ) );
     }
 
     /**
      * Returns new IndexWriterConfig instance
      * 
      * @since 5.1
      */
     protected IndexWriterConfig getWriterConfig()
     {
         return NexusIndexWriter.defaultConfig();
     }
 
     public IndexWriter getIndexWriter()
         throws IOException
     {
         return indexWriter;
     }
 
     public IndexSearcher acquireIndexSearcher()
         throws IOException
     {
         // TODO: move this to separate thread to not penalty next incoming searcher
         searcherManager.maybeRefresh();
         return searcherManager.acquire();
     }
 
     public void releaseIndexSearcher( final IndexSearcher is )
         throws IOException
     {
         if ( is == null )
         {
             return;
         }
         searcherManager.release( is );
     }
 
     public void commit()
         throws IOException
     {
         getIndexWriter().commit();
     }
 
     public void rollback()
         throws IOException
     {
         getIndexWriter().rollback();
     }
 
     public synchronized void optimize()
         throws CorruptIndexException, IOException
     {
         commit();
     }
 
     public synchronized void close( boolean deleteFiles )
         throws IOException
     {
         if ( indexDirectory != null )
         {
             IndexUtils.updateTimestamp( indexDirectory, getTimestamp() );
             closeReaders();
             if ( deleteFiles )
             {
                 deleteIndexFiles( true );
             }
             indexDirectory.close();
         }
         indexDirectory = null;
     }
 
     public synchronized void purge()
         throws IOException
     {
         closeReaders();
         deleteIndexFiles( true );
         try
         {
             prepareIndex( true );
         }
         catch ( ExistingLuceneIndexMismatchException e )
         {
             // just deleted it
         }
         rebuildGroups();
         updateTimestamp( true, null );
     }
 
     public synchronized void replace( Directory directory )
         throws IOException
     {
         replace( directory, null, null );
     }
 
     public synchronized void replace( Directory directory, Set<String> allGroups, Set<String> rootGroups )
         throws IOException
     {
         final Date ts = IndexUtils.getTimestamp( directory );
         closeReaders();
         deleteIndexFiles( false );
         IndexUtils.copyDirectory( directory, indexDirectory );
         openAndWarmup();
         // reclaim the index as mine
         storeDescriptor();
         if ( allGroups == null && rootGroups == null )
         {
             rebuildGroups();
         }
         else
         {
             if ( allGroups != null )
             {
                 setAllGroups( allGroups );
             }
             if ( rootGroups != null )
             {
                 setRootGroups( rootGroups );
             }
         }
         updateTimestamp( true, ts );
         optimize();
     }
 
     public synchronized void merge( Directory directory )
         throws IOException
     {
         merge( directory, null );
     }
 
     public synchronized void merge( Directory directory, DocumentFilter filter )
         throws IOException
     {
         final IndexSearcher s = acquireIndexSearcher();
         try
         {
             final IndexWriter w = getIndexWriter();
             try ( IndexReader directoryReader = DirectoryReader.open( directory ) )
             {
                 TopScoreDocCollector collector;
                 int numDocs = directoryReader.maxDoc();
 
                 Bits liveDocs = MultiBits.getLiveDocs( directoryReader );
                 for ( int i = 0; i < numDocs; i++ )
                 {
                     if ( liveDocs != null && !liveDocs.get( i ) )
                     {
                         continue;
                     }
 
                     Document d = directoryReader.document( i );
                     if ( filter != null && !filter.accept( d ) )
                     {
                         continue;
                     }
 
                     String uinfo = d.get( ArtifactInfo.UINFO );
                     if ( uinfo != null )
                     {
                         collector = TopScoreDocCollector.create( 1, Integer.MAX_VALUE );
                         s.search( new TermQuery( new Term( ArtifactInfo.UINFO, uinfo ) ), collector );
                         if ( collector.getTotalHits() == 0 )
                         {
                             w.addDocument( IndexUtils.updateDocument( d, this, false ) );
                         }
                     }
                     else
                     {
                         String deleted = d.get( ArtifactInfo.DELETED );
 
                         if ( deleted != null )
                         {
                             // Deleting the document loses history that it was delete,
                             // so incrementals wont work. Therefore, put the delete
                             // document in as well
                             w.deleteDocuments( new Term( ArtifactInfo.UINFO, deleted ) );
                             w.addDocument( d );
                         }
                     }
                 }
 
             }
             finally
             {
                 commit();
             }
 
             rebuildGroups();
             Date mergedTimestamp = IndexUtils.getTimestamp( directory );
 
             if ( getTimestamp() != null && mergedTimestamp != null && mergedTimestamp.after( getTimestamp() ) )
             {
                 // we have both, keep the newest
                 updateTimestamp( true, mergedTimestamp );
             }
             else
             {
                 updateTimestamp( true );
             }
             optimize();
         }
         finally
         {
             releaseIndexSearcher( s );
         }
     }
 
     private void closeReaders()
         throws CorruptIndexException, IOException
     {
         if ( searcherManager != null )
         {
             searcherManager.close();
             searcherManager = null;
         }
         if ( indexWriter != null )
         {
             indexWriter.close();
             indexWriter = null;
         }
     }
 
     public GavCalculator getGavCalculator()
     {
         return gavCalculator;
     }
 
     public List<IndexCreator> getIndexCreators()
     {
         return Collections.unmodifiableList( indexCreators );
     }
 
     // groups
 
     public synchronized void rebuildGroups()
         throws IOException
     {
         final IndexSearcher is = acquireIndexSearcher();
         try
         {
             final IndexReader r = is.getIndexReader();
 
             Set<String> rootGroups = new LinkedHashSet<>();
             Set<String> allGroups = new LinkedHashSet<>();
 
             int numDocs = r.maxDoc();
             Bits liveDocs = MultiBits.getLiveDocs( r );
 
             for ( int i = 0; i < numDocs; i++ )
             {
                 if ( liveDocs != null && !liveDocs.get( i ) )
                 {
                     continue;
                 }
 
                 Document d = r.document( i );
 
                 String uinfo = d.get( ArtifactInfo.UINFO );
 
                 if ( uinfo != null )
                 {
                     ArtifactInfo info = IndexUtils.constructArtifactInfo( d, this );
                     rootGroups.add( info.getRootGroup() );
                     allGroups.add( info.getGroupId() );
                 }
             }
 
             setRootGroups( rootGroups );
             setAllGroups( allGroups );
 
             optimize();
         }
         finally
         {
             releaseIndexSearcher( is );
         }
     }
 
     public Set<String> getAllGroups()
         throws IOException
     {
         return getGroups( ArtifactInfo.ALL_GROUPS, ArtifactInfo.ALL_GROUPS_VALUE, ArtifactInfo.ALL_GROUPS_LIST );
     }
 
     public synchronized void setAllGroups( Collection<String> groups )
         throws IOException
     {
         setGroups( groups, ArtifactInfo.ALL_GROUPS, ArtifactInfo.ALL_GROUPS_VALUE, ArtifactInfo.ALL_GROUPS_LIST );
         commit();
     }
 
     public Set<String> getRootGroups()
         throws IOException
     {
         return getGroups( ArtifactInfo.ROOT_GROUPS, ArtifactInfo.ROOT_GROUPS_VALUE, ArtifactInfo.ROOT_GROUPS_LIST );
     }
 
     public synchronized void setRootGroups( Collection<String> groups )
         throws IOException
     {
         setGroups( groups, ArtifactInfo.ROOT_GROUPS, ArtifactInfo.ROOT_GROUPS_VALUE, ArtifactInfo.ROOT_GROUPS_LIST );
         commit();
     }
 
     protected Set<String> getGroups( String field, String filedValue, String listField )
         throws IOException, CorruptIndexException
     {
         final TopScoreDocCollector collector = TopScoreDocCollector.create( 1, Integer.MAX_VALUE );
         final IndexSearcher indexSearcher = acquireIndexSearcher();
         try
         {
             indexSearcher.search( new TermQuery( new Term( field, filedValue ) ), collector );
             TopDocs topDocs = collector.topDocs();
             // In Lucene 7 topDocs.totalHits is now a long, but we can safely cast this to an int because
             // indexes are still bound to at most 2 billion (Integer.MAX_VALUE) documents
             Set<String> groups = new LinkedHashSet<String>( (int) Math.max( 10L, topDocs.totalHits.value ) );
             if ( topDocs.totalHits.value > 0 )
             {
                 Document doc = indexSearcher.doc( topDocs.scoreDocs[0].doc );
                 String groupList = doc.get( listField );
                 if ( groupList != null )
                 {
                     groups.addAll( Arrays.asList( groupList.split( "\\|" ) ) );
                 }
             }
             return groups;
         }
         finally
         {
             releaseIndexSearcher( indexSearcher );
         }
     }
 
     protected void setGroups( Collection<String> groups, String groupField, String groupFieldValue,
                               String groupListField )
         throws IOException, CorruptIndexException
     {
         final IndexWriter w = getIndexWriter();
         w.updateDocument( new Term( groupField, groupFieldValue ),
             createGroupsDocument( groups, groupField, groupFieldValue, groupListField ) );
     }
 
     protected Document createGroupsDocument( Collection<String> groups, String field, String fieldValue,
                                              String listField )
     {
         final Document groupDoc = new Document();
         groupDoc.add( new Field( field, fieldValue, IndexerField.KEYWORD_STORED ) );
         groupDoc.add( new StoredField( listField, ArtifactInfo.lst2str( groups ) ) );
         return groupDoc;
     }
 
     @Override
     public String toString()
     {
         return id + " : " + timestamp;
     }
 
     private static void unlockForcibly( final TrackingLockFactory lockFactory, final Directory dir )
         throws IOException
     {
         //Warning: Not doable in lucene >= 5.3 consider to remove it as IndexWriter.unlock
         //was always strongly non recommended by Lucene.
         //For now try to do the best to simulate the IndexWriter.unlock at least on FSDirectory
         //using FSLockFactory, the RAMDirectory uses SingleInstanceLockFactory.
         //custom lock factory?
         if ( lockFactory != null )
         {
             final Set<? extends Lock> emittedLocks = lockFactory.getEmittedLocks( IndexWriter.WRITE_LOCK_NAME );
             for ( Lock emittedLock : emittedLocks )
             {
                 emittedLock.close();
             }
         }
         if ( dir instanceof FSDirectory )
         {
             final FSDirectory fsdir = (FSDirectory) dir;
             final Path dirPath = fsdir.getDirectory();
             if ( Files.isDirectory( dirPath ) )
             {
                 Path lockPath = dirPath.resolve( IndexWriter.WRITE_LOCK_NAME );
                 try
                 {
                     lockPath = lockPath.toRealPath();
                 }
                 catch ( IOException ioe )
                 {
                     // Not locked
                     return;
                 }
                 try ( FileChannel fc = FileChannel.open( lockPath, StandardOpenOption.CREATE,
                         StandardOpenOption.WRITE ) )
                 {
                     final FileLock lck = fc.tryLock();
                     if ( lck == null )
                     {
                         // Still active
                         throw new LockObtainFailedException( "Lock held by another process: " + lockPath );
                     }
                     else
                     {
                         // Not held fine to release
                         lck.close();
                     }
                 }
                 Files.delete( lockPath );
             }
         }
     }
 }