/*
    * 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.updater;
  
  import javax.inject.Inject;
  import javax.inject.Named;
  import javax.inject.Singleton;
  
  import java.io.BufferedInputStream;
  import java.io.BufferedOutputStream;
  import java.io.BufferedReader;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.io.OutputStream;
  import java.io.OutputStreamWriter;
  import java.io.Writer;
  import java.nio.charset.StandardCharsets;
  import java.nio.file.Files;
  import java.text.ParseException;
  import java.text.SimpleDateFormat;
  import java.util.ArrayList;
  import java.util.Date;
  import java.util.List;
  import java.util.Properties;
  import java.util.Set;
  import java.util.TimeZone;
  
  import org.apache.lucene.document.Document;
  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.StoredFields;
  import org.apache.lucene.store.Directory;
  import org.apache.lucene.util.Bits;
  import org.apache.maven.index.context.DocumentFilter;
  import org.apache.maven.index.context.IndexUtils;
  import org.apache.maven.index.context.IndexingContext;
  import org.apache.maven.index.context.NexusAnalyzer;
  import org.apache.maven.index.context.NexusIndexWriter;
  import org.apache.maven.index.fs.Lock;
  import org.apache.maven.index.fs.Locker;
  import org.apache.maven.index.incremental.IncrementalHandler;
  import org.apache.maven.index.updater.IndexDataReader.IndexDataReadResult;
  import org.codehaus.plexus.util.FileUtils;
  import org.codehaus.plexus.util.io.RawInputStreamFacade;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A default index updater implementation
   *
   * @author Jason van Zyl
   * @author Eugene Kuleshov
   */
  @Singleton
  @Named
  public class DefaultIndexUpdater implements IndexUpdater {
  
      private final Logger logger = LoggerFactory.getLogger(getClass());
  
      protected Logger getLogger() {
          return logger;
      }
  
      private final IncrementalHandler incrementalHandler;
  
      private final List<IndexUpdateSideEffect> sideEffects;
  
      @Inject
      public DefaultIndexUpdater(
              final IncrementalHandler incrementalHandler, final List<IndexUpdateSideEffect> sideEffects) {
          this.incrementalHandler = incrementalHandler;
          this.sideEffects = sideEffects;
      }
  
      public IndexUpdateResult fetchAndUpdateIndex(final IndexUpdateRequest updateRequest) throws IOException {
         IndexUpdateResult result = new IndexUpdateResult();
 
         IndexingContext context = updateRequest.getIndexingContext();
 
         ResourceFetcher fetcher = null;
 
         if (!updateRequest.isOffline()) {
             fetcher = updateRequest.getResourceFetcher();
 
             // If no resource fetcher passed in, use the wagon fetcher by default
             // and put back in request for future use
             if (fetcher == null) {
                 throw new IOException("Update of the index without provided ResourceFetcher is impossible.");
             }
 
             fetcher.connect(context.getId(), context.getIndexUpdateUrl());
         }
 
         File cacheDir = updateRequest.getLocalIndexCacheDir();
         Locker locker = updateRequest.getLocker();
         Lock lock = locker != null && cacheDir != null ? locker.lock(cacheDir) : null;
         try {
             if (cacheDir != null) {
                 LocalCacheIndexAdaptor cache = new LocalCacheIndexAdaptor(cacheDir, result);
 
                 if (!updateRequest.isOffline()) {
                     cacheDir.mkdirs();
 
                     try {
                         if (fetchAndUpdateIndex(updateRequest, fetcher, cache).isSuccessful()) {
                             cache.commit();
                         }
                     } finally {
                         fetcher.disconnect();
                     }
                 }
 
                 fetcher = cache.getFetcher();
             } else if (updateRequest.isOffline()) {
                 throw new IllegalArgumentException("LocalIndexCacheDir can not be null in offline mode");
             }
 
             try {
                 if (!updateRequest.isCacheOnly()) {
                     LuceneIndexAdaptor target = new LuceneIndexAdaptor(updateRequest);
                     result = fetchAndUpdateIndex(updateRequest, fetcher, target);
 
                     if (result.isSuccessful()) {
                         target.commit();
                     }
                 }
             } finally {
                 fetcher.disconnect();
             }
         } finally {
             if (lock != null) {
                 lock.release();
             }
         }
 
         return result;
     }
 
     private Date loadIndexDirectory(
             final IndexUpdateRequest updateRequest,
             final ResourceFetcher fetcher,
             final boolean merge,
             final String remoteIndexFile)
             throws IOException {
         File indexDir;
         if (updateRequest.getIndexTempDir() != null) {
             updateRequest.getIndexTempDir().mkdirs();
             indexDir = Files.createTempDirectory(updateRequest.getIndexTempDir().toPath(), remoteIndexFile + ".dir")
                     .toFile();
         } else {
             indexDir = Files.createTempDirectory(remoteIndexFile + ".dir").toFile();
         }
         try (BufferedInputStream is = new BufferedInputStream(fetcher.retrieve(remoteIndexFile)); //
                 Directory directory = updateRequest.getFSDirectoryFactory().open(indexDir)) {
             Date timestamp;
 
             Set<String> rootGroups;
             Set<String> allGroups;
             if (remoteIndexFile.endsWith(".gz")) {
                 IndexDataReadResult result =
                         unpackIndexData(is, updateRequest, directory, updateRequest.getIndexingContext());
                 timestamp = result.getTimestamp();
                 rootGroups = result.getRootGroups();
                 allGroups = result.getAllGroups();
             } else {
                 // legacy transfer format
                 throw new IllegalArgumentException(
                         "The legacy format is no longer supported " + "by this version of maven-indexer.");
             }
 
             if (updateRequest.getDocumentFilter() != null) {
                 filterDirectory(directory, updateRequest.getDocumentFilter());
             }
 
             if (merge) {
                 updateRequest.getIndexingContext().merge(directory, null, allGroups, rootGroups);
             } else {
                 updateRequest.getIndexingContext().replace(directory, allGroups, rootGroups);
             }
             if (sideEffects != null && sideEffects.size() > 0) {
                 getLogger().info(IndexUpdateSideEffect.class.getName() + " extensions found: " + sideEffects.size());
                 for (IndexUpdateSideEffect sideeffect : sideEffects) {
                     sideeffect.updateIndex(directory, updateRequest.getIndexingContext(), merge);
                 }
             }
 
             return timestamp;
         } finally {
             try {
                 FileUtils.deleteDirectory(indexDir);
             } catch (IOException ex) {
                 // ignore
             }
         }
     }
 
     @SuppressWarnings("UnusedLocalVariable")
     private static void filterDirectory(final Directory directory, final DocumentFilter filter) throws IOException {
         IndexReader r = null;
         IndexWriter w = null;
         try {
             r = DirectoryReader.open(directory);
             w = new NexusIndexWriter(directory, new IndexWriterConfig(new NexusAnalyzer()));
 
             Bits liveDocs = MultiBits.getLiveDocs(r);
 
             int numDocs = r.maxDoc();
             StoredFields storedFields = r.storedFields();
 
             for (int i = 0; i < numDocs; i++) {
                 if (liveDocs != null && !liveDocs.get(i)) {
                     continue;
                 }
 
                 Document d = storedFields.document(i);
 
                 if (!filter.accept(d)) {
                     boolean success = w.tryDeleteDocument(r, i) != -1;
                     // FIXME handle deletion failure
                 }
             }
             w.commit();
         } finally {
             IndexUtils.close(r);
             IndexUtils.close(w);
         }
 
         w = null;
         try {
             // analyzer is unimportant, since we are not adding/searching to/on index, only reading/deleting
             w = new NexusIndexWriter(directory, new IndexWriterConfig(new NexusAnalyzer()));
 
             w.commit();
         } finally {
             IndexUtils.close(w);
         }
     }
 
     private Properties loadIndexProperties(final File indexDirectoryFile, final String remoteIndexPropertiesName) {
         File indexProperties = new File(indexDirectoryFile, remoteIndexPropertiesName);
 
         try (FileInputStream fis = new FileInputStream(indexProperties)) {
             Properties properties = new Properties();
 
             properties.load(fis);
 
             return properties;
         } catch (IOException e) {
             getLogger().debug("Unable to read remote properties stored locally", e);
         }
         return null;
     }
 
     private void storeIndexProperties(final File dir, final String indexPropertiesName, final Properties properties)
             throws IOException {
         File file = new File(dir, indexPropertiesName);
 
         if (properties != null) {
             try (OutputStream os = new BufferedOutputStream(new FileOutputStream(file))) {
                 properties.store(os, null);
             }
         } else {
             file.delete();
         }
     }
 
     private Properties downloadIndexProperties(final ResourceFetcher fetcher) throws IOException {
         try (InputStream fis = fetcher.retrieve(IndexingContext.INDEX_REMOTE_PROPERTIES_FILE)) {
             Properties properties = new Properties();
 
             properties.load(fis);
 
             return properties;
         }
     }
 
     public Date getTimestamp(final Properties properties, final String key) {
         String indexTimestamp = properties.getProperty(key);
 
         if (indexTimestamp != null) {
             try {
                 SimpleDateFormat df = new SimpleDateFormat(IndexingContext.INDEX_TIME_FORMAT);
                 df.setTimeZone(TimeZone.getTimeZone("GMT"));
                 return df.parse(indexTimestamp);
             } catch (ParseException ex) {
             }
         }
         return null;
     }
 
     /**
      * @param is an input stream to unpack index data from
      * @param threads thread count to use
      * @param d
      * @param context
      */
     public static IndexDataReadResult unpackIndexData(
             final InputStream is, final int threads, final Directory d, final IndexingContext context)
             throws IOException {
         return unpackIndexData(d, new IndexDataReader(is, threads), context);
     }
 
     /**
      * @param is an input stream to unpack index data from
      * @param request IndexUpdateRequest for configuration
      * @param d
      * @param context
      */
     public static IndexDataReadResult unpackIndexData(
             final InputStream is, final IndexUpdateRequest request, final Directory d, final IndexingContext context)
             throws IOException {
         return unpackIndexData(d, new IndexDataReader(is, request), context);
     }
 
     private static IndexDataReadResult unpackIndexData(
             final Directory d, IndexDataReader dr, final IndexingContext context) throws IOException {
         IndexWriterConfig config = new IndexWriterConfig(new NexusAnalyzer());
         config.setUseCompoundFile(false);
         try (NexusIndexWriter w = new NexusIndexWriter(d, config)) {
             return dr.readIndex(w, context);
         }
     }
 
     /**
      * Filesystem-based ResourceFetcher implementation
      */
     public static class FileFetcher implements ResourceFetcher {
         private final File basedir;
 
         public FileFetcher(File basedir) {
             this.basedir = basedir;
         }
 
         public void connect(String id, String url) throws IOException {
             // don't need to do anything
         }
 
         public void disconnect() throws IOException {
             // don't need to do anything
         }
 
         public void retrieve(String name, File targetFile) throws IOException, FileNotFoundException {
             FileUtils.copyFile(getFile(name), targetFile);
         }
 
         public InputStream retrieve(String name) throws IOException, FileNotFoundException {
             return new FileInputStream(getFile(name));
         }
 
         private File getFile(String name) {
             return new File(basedir, name);
         }
     }
 
     private abstract class IndexAdaptor {
         protected final File dir;
 
         protected Properties properties;
 
         protected IndexAdaptor(File dir) {
             this.dir = dir;
         }
 
         public abstract Properties getProperties();
 
         public abstract void storeProperties() throws IOException;
 
         public abstract void addIndexChunk(ResourceFetcher source, String filename) throws IOException;
 
         public abstract Date setIndexFile(ResourceFetcher source, String string) throws IOException;
 
         public Properties setProperties(ResourceFetcher source) throws IOException {
             this.properties = downloadIndexProperties(source);
             return properties;
         }
 
         public abstract Date getTimestamp();
 
         public void commit() throws IOException {
             storeProperties();
         }
     }
 
     private class LuceneIndexAdaptor extends IndexAdaptor {
         private final IndexUpdateRequest updateRequest;
 
         LuceneIndexAdaptor(IndexUpdateRequest updateRequest) {
             super(updateRequest.getIndexingContext().getIndexDirectoryFile());
             this.updateRequest = updateRequest;
         }
 
         public Properties getProperties() {
             if (properties == null) {
                 properties = loadIndexProperties(dir, IndexingContext.INDEX_UPDATER_PROPERTIES_FILE);
             }
             return properties;
         }
 
         public void storeProperties() throws IOException {
             storeIndexProperties(dir, IndexingContext.INDEX_UPDATER_PROPERTIES_FILE, properties);
         }
 
         public Date getTimestamp() {
             return updateRequest.getIndexingContext().getTimestamp();
         }
 
         public void addIndexChunk(ResourceFetcher source, String filename) throws IOException {
             loadIndexDirectory(updateRequest, source, true, filename);
         }
 
         public Date setIndexFile(ResourceFetcher source, String filename) throws IOException {
             return loadIndexDirectory(updateRequest, source, false, filename);
         }
 
         public void commit() throws IOException {
             super.commit();
 
             updateRequest.getIndexingContext().commit();
         }
     }
 
     private class LocalCacheIndexAdaptor extends IndexAdaptor {
         private static final String CHUNKS_FILENAME = "chunks.lst";
 
         private final IndexUpdateResult result;
 
         private final ArrayList<String> newChunks = new ArrayList<>();
 
         LocalCacheIndexAdaptor(File dir, IndexUpdateResult result) {
             super(dir);
             this.result = result;
         }
 
         public Properties getProperties() {
             if (properties == null) {
                 properties = loadIndexProperties(dir, IndexingContext.INDEX_REMOTE_PROPERTIES_FILE);
             }
             return properties;
         }
 
         public void storeProperties() throws IOException {
             storeIndexProperties(dir, IndexingContext.INDEX_REMOTE_PROPERTIES_FILE, properties);
         }
 
         public Date getTimestamp() {
             Properties properties = getProperties();
             if (properties == null) {
                 return null;
             }
 
             Date timestamp = DefaultIndexUpdater.this.getTimestamp(properties, IndexingContext.INDEX_TIMESTAMP);
 
             if (timestamp == null) {
                 timestamp = DefaultIndexUpdater.this.getTimestamp(properties, IndexingContext.INDEX_LEGACY_TIMESTAMP);
             }
 
             return timestamp;
         }
 
         public void addIndexChunk(ResourceFetcher source, String filename) throws IOException {
             File chunk = new File(dir, filename);
             FileUtils.copyStreamToFile(new RawInputStreamFacade(source.retrieve(filename)), chunk);
             newChunks.add(filename);
         }
 
         public Date setIndexFile(ResourceFetcher source, String filename) throws IOException {
             cleanCacheDirectory(dir);
 
             result.setFullUpdate(true);
 
             File target = new File(dir, filename);
             FileUtils.copyStreamToFile(new RawInputStreamFacade(source.retrieve(filename)), target);
 
             return null;
         }
 
         @Override
         public void commit() throws IOException {
             File chunksFile = new File(dir, CHUNKS_FILENAME);
             try (BufferedOutputStream os = new BufferedOutputStream(new FileOutputStream(chunksFile, true)); //
                     Writer w = new OutputStreamWriter(os, StandardCharsets.UTF_8)) {
                 for (String filename : newChunks) {
                     w.write(filename + "\n");
                 }
                 w.flush();
             }
             super.commit();
         }
 
         public List<String> getChunks() throws IOException {
             ArrayList<String> chunks = new ArrayList<>();
 
             File chunksFile = new File(dir, CHUNKS_FILENAME);
             try (BufferedReader r = new BufferedReader(
                     new InputStreamReader(new FileInputStream(chunksFile), StandardCharsets.UTF_8))) {
                 String str;
                 while ((str = r.readLine()) != null) {
                     chunks.add(str);
                 }
             }
             return chunks;
         }
 
         public ResourceFetcher getFetcher() {
             return new LocalIndexCacheFetcher(dir) {
                 @Override
                 public List<String> getChunks() throws IOException {
                     return LocalCacheIndexAdaptor.this.getChunks();
                 }
             };
         }
     }
 
     abstract static class LocalIndexCacheFetcher extends FileFetcher {
         LocalIndexCacheFetcher(File basedir) {
             super(basedir);
         }
 
         public abstract List<String> getChunks() throws IOException;
     }
 
     private IndexUpdateResult fetchAndUpdateIndex(
             final IndexUpdateRequest updateRequest, ResourceFetcher source, IndexAdaptor target) throws IOException {
         IndexUpdateResult result = new IndexUpdateResult();
 
         if (!updateRequest.isForceFullUpdate()) {
             Properties localProperties = target.getProperties();
             Date localTimestamp = null;
 
             if (localProperties != null) {
                 localTimestamp = getTimestamp(localProperties, IndexingContext.INDEX_TIMESTAMP);
             }
 
             // this will download and store properties in the target, so next run
             // target.getProperties() will retrieve it
             Properties remoteProperties = target.setProperties(source);
 
             Date updateTimestamp = getTimestamp(remoteProperties, IndexingContext.INDEX_TIMESTAMP);
 
             // If new timestamp is missing, dont bother checking incremental, we have an old file
             if (updateTimestamp != null) {
                 List<String> filenames = incrementalHandler.loadRemoteIncrementalUpdates(
                         updateRequest, localProperties, remoteProperties);
 
                 // if we have some incremental files, merge them in
                 if (filenames != null) {
                     for (String filename : filenames) {
                         target.addIndexChunk(source, filename);
                     }
 
                     result.setTimestamp(updateTimestamp);
                     result.setSuccessful(true);
                     return result;
                 }
             } else {
                 updateTimestamp = getTimestamp(remoteProperties, IndexingContext.INDEX_LEGACY_TIMESTAMP);
             }
 
             // fallback to timestamp comparison, but try with one coming from local properties, and if not possible (is
             // null)
             // fallback to context timestamp
             if (localTimestamp != null) {
                 // if we have localTimestamp
                 // if incremental can't be done for whatever reason, simply use old logic of
                 // checking the timestamp, if the same, nothing to do
                 if (updateTimestamp != null && localTimestamp != null && !updateTimestamp.after(localTimestamp)) {
                     // Index is up to date
                     result.setSuccessful(true);
                     return result;
                 }
             }
         } else {
             // create index properties during forced full index download
             target.setProperties(source);
         }
 
         if (!updateRequest.isIncrementalOnly()) {
             Date timestamp;
             try {
                 timestamp = target.setIndexFile(source, IndexingContext.INDEX_FILE_PREFIX + ".gz");
                 if (source instanceof LocalIndexCacheFetcher) {
                     // local cache has inverse organization compared to remote indexes,
                     // i.e. initial index file and delta chunks to apply on top of it
                     for (String filename : ((LocalIndexCacheFetcher) source).getChunks()) {
                         target.addIndexChunk(source, filename);
                     }
                 }
             } catch (IOException ex) {
                 // try to look for legacy index transfer format
                 try {
                     timestamp = target.setIndexFile(source, IndexingContext.INDEX_FILE_PREFIX + ".zip");
                 } catch (IOException ex2) {
                     getLogger().error("Fallback to *.zip also failed: " + ex2); // do not bother with stack trace
 
                     throw ex; // original exception more likely to be interesting
                 }
             }
 
             result.setTimestamp(timestamp);
             result.setSuccessful(true);
             result.setFullUpdate(true);
         }
 
         return result;
     }
 
     /**
      * Cleans specified cache directory. If present, Locker.LOCK_FILE will not be deleted.
      */
     protected void cleanCacheDirectory(File dir) throws IOException {
         File[] members = dir.listFiles();
         if (members == null) {
             return;
         }
 
         for (File member : members) {
             if (!Locker.LOCK_FILE.equals(member.getName())) {
                 FileUtils.forceDelete(member);
             }
         }
     }
 }