/*
    * 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.
   */
  package org.apache.maven.index.context;
  
  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.Collection;
  import java.util.Collections;
  import java.util.Date;
  import java.util.HashSet;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Set;
  import java.util.concurrent.atomic.AtomicReference;
  
  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.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(), IndexerField.KEYWORD_STORED));
 
         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() {
         return allGroups.get();
     }
 
     public synchronized void setAllGroups(Collection<String> groups) {
         allGroups.set(new HashSet<>(groups));
     }
 
     public Set<String> getRootGroups() throws IOException {
         return rootGroups.get();
     }
 
     public synchronized void setRootGroups(Collection<String> groups) {
         rootGroups.set(new HashSet<>(groups));
     }
 
     private final AtomicReference<HashSet<String>> rootGroups = new AtomicReference<>(new HashSet<>());
 
     private final AtomicReference<HashSet<String>> allGroups = new AtomicReference<>(new HashSet<>());
 
     @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);
             }
         }
     }
 }