/*
    * 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 java.io.BufferedInputStream;
  import java.io.DataInput;
  import java.io.DataInputStream;
  import java.io.EOFException;
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.UTFDataFormatException;
  import java.nio.file.Files;
  import java.time.Duration;
  import java.time.Instant;
  import java.util.ArrayList;
  import java.util.Date;
  import java.util.HashSet;
  import java.util.Set;
  import java.util.concurrent.ArrayBlockingQueue;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.TimeUnit;
  import java.util.zip.GZIPInputStream;
  
  import org.apache.lucene.document.Document;
  import org.apache.lucene.document.Field;
  import org.apache.lucene.document.FieldType;
  import org.apache.lucene.index.IndexOptions;
  import org.apache.lucene.index.IndexWriter;
  import org.apache.lucene.index.IndexWriterConfig;
  import org.apache.lucene.store.Directory;
  import org.apache.lucene.store.FSDirectory;
  import org.apache.maven.index.ArtifactInfo;
  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.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * An index data reader used to parse transfer index format.
   *
   * @author Eugene Kuleshov
   */
  public class IndexDataReader {
      private static final Logger LOGGER = LoggerFactory.getLogger(IndexDataReader.class);
  
      private final DataInputStream dis;
  
      private final int threads;
  
      public IndexDataReader(final InputStream is) throws IOException {
          this(is, 1);
      }
  
      public IndexDataReader(final InputStream is, final int threads) throws IOException {
          if (threads < 1) {
              throw new IllegalArgumentException("Reader threads must be greater than zero: " + threads);
          }
          this.threads = threads;
          // MINDEXER-13
          // LightweightHttpWagon may have performed automatic decompression
          // Handle it transparently
          is.mark(2);
          InputStream data;
          if (is.read() == 0x1f && is.read() == 0x8b) // GZIPInputStream.GZIP_MAGIC
          {
              is.reset();
              data = new BufferedInputStream(new GZIPInputStream(is, 1024 * 8), 1024 * 8);
          } else {
              is.reset();
              data = new BufferedInputStream(is, 1024 * 8);
          }
  
          this.dis = new DataInputStream(data);
      }
  
      public IndexDataReadResult readIndex(IndexWriter w, IndexingContext context) throws IOException {
          if (threads == 1) {
              return readIndexST(w, context);
         } else {
             return readIndexMT(w, context);
         }
     }
 
     private IndexDataReadResult readIndexST(IndexWriter w, IndexingContext context) throws IOException {
         LOGGER.debug("Reading ST index...");
         Instant start = Instant.now();
         long timestamp = readHeader();
 
         Date date = null;
 
         if (timestamp != -1) {
             date = new Date(timestamp);
 
             IndexUtils.updateTimestamp(w.getDirectory(), date);
         }
 
         int n = 0;
 
         Document doc;
         Set<String> rootGroups = new HashSet<>();
         Set<String> allGroups = new HashSet<>();
 
         while ((doc = readDocument()) != null) {
             addToIndex(doc, context, w, rootGroups, allGroups);
             n++;
         }
 
         w.commit();
 
         IndexDataReadResult result = new IndexDataReadResult();
         result.setDocumentCount(n);
         result.setTimestamp(date);
         result.setRootGroups(rootGroups);
         result.setAllGroups(allGroups);
 
         LOGGER.debug(
                 "Reading ST index done in {} sec",
                 Duration.between(start, Instant.now()).getSeconds());
         return result;
     }
 
     private IndexDataReadResult readIndexMT(IndexWriter w, IndexingContext context) throws IOException {
         LOGGER.debug("Reading MT index...");
         Instant start = Instant.now();
         long timestamp = readHeader();
 
         int n = 0;
 
         final Document theEnd = new Document();
 
         Set<String> rootGroups = ConcurrentHashMap.newKeySet();
         Set<String> allGroups = ConcurrentHashMap.newKeySet();
         ArrayBlockingQueue<Document> queue = new ArrayBlockingQueue<>(10000);
 
         ExecutorService executorService = Executors.newFixedThreadPool(threads);
         ArrayList<Exception> errors = new ArrayList<>();
         ArrayList<FSDirectory> siloDirectories = new ArrayList<>(threads);
         ArrayList<IndexWriter> siloWriters = new ArrayList<>(threads);
         LOGGER.debug("Creating {} silo writer threads...", threads);
         for (int i = 0; i < threads; i++) {
             final int silo = i;
             FSDirectory siloDirectory = tempDirectory("silo" + i);
             siloDirectories.add(siloDirectory);
             siloWriters.add(tempWriter(siloDirectory));
             executorService.execute(() -> {
                 LOGGER.debug("Starting thread {}", Thread.currentThread().getName());
                 try {
                     while (true) {
                         try {
                             Document doc = queue.take();
                             if (doc == theEnd) {
                                 break;
                             }
                             addToIndex(doc, context, siloWriters.get(silo), rootGroups, allGroups);
                         } catch (InterruptedException | IOException e) {
                             errors.add(e);
                             break;
                         }
                     }
                 } finally {
                     LOGGER.debug("Done thread {}", Thread.currentThread().getName());
                 }
             });
         }
 
         LOGGER.debug("Loading up documents into silos");
         try {
             Document doc;
             while ((doc = readDocument()) != null) {
                 queue.put(doc);
                 n++;
             }
             LOGGER.debug("Signalling END");
             for (int i = 0; i < threads; i++) {
                 queue.put(theEnd);
             }
 
             LOGGER.debug("Shutting down threads");
             executorService.shutdown();
             executorService.awaitTermination(5L, TimeUnit.MINUTES);
         } catch (InterruptedException e) {
             throw new IOException("Interrupted", e);
         }
 
         if (!errors.isEmpty()) {
             IOException exception = new IOException("Error during load of index");
             errors.forEach(exception::addSuppressed);
             throw exception;
         }
 
         LOGGER.debug("Silos loaded...");
         Date date = null;
         if (timestamp != -1) {
             date = new Date(timestamp);
             IndexUtils.updateTimestamp(w.getDirectory(), date);
         }
 
         LOGGER.debug("Closing silo writers...");
         for (IndexWriter siloWriter : siloWriters) {
             siloWriter.commit();
             siloWriter.close();
         }
 
         LOGGER.debug("Merging silo directories...");
         w.addIndexes(siloDirectories.toArray(new Directory[0]));
 
         LOGGER.debug("Cleanup of silo directories...");
         for (FSDirectory siloDirectory : siloDirectories) {
             File dir = siloDirectory.getDirectory().toFile();
             siloDirectory.close();
             IndexUtils.delete(dir);
         }
 
         LOGGER.debug("Finalizing...");
         w.commit();
 
         IndexDataReadResult result = new IndexDataReadResult();
         result.setDocumentCount(n);
         result.setTimestamp(date);
         result.setRootGroups(rootGroups);
         result.setAllGroups(allGroups);
 
         LOGGER.debug(
                 "Reading MT index done in {} sec",
                 Duration.between(start, Instant.now()).getSeconds());
         return result;
     }
 
     private FSDirectory tempDirectory(final String name) throws IOException {
         return FSDirectory.open(Files.createTempDirectory(name + ".dir"));
     }
 
     private IndexWriter tempWriter(final FSDirectory directory) throws IOException {
         IndexWriterConfig config = new IndexWriterConfig(new NexusAnalyzer());
         config.setUseCompoundFile(false);
         return new NexusIndexWriter(directory, config);
     }
 
     private void addToIndex(
             final Document doc,
             final IndexingContext context,
             final IndexWriter indexWriter,
             final Set<String> rootGroups,
             final Set<String> allGroups)
             throws IOException {
         ArtifactInfo ai = IndexUtils.constructArtifactInfo(doc, context);
         if (ai != null) {
             indexWriter.addDocument(IndexUtils.updateDocument(doc, context, false, ai));
 
             rootGroups.add(ai.getRootGroup());
             allGroups.add(ai.getGroupId());
         } else {
             // these two fields are automatically handled in code above
             if (doc.getField(ArtifactInfo.ALL_GROUPS) == null && doc.getField(ArtifactInfo.ROOT_GROUPS) == null) {
                 indexWriter.addDocument(doc);
             }
         }
     }
 
     public long readHeader() throws IOException {
         final byte hdrbyte = (byte) ((IndexDataWriter.VERSION << 24) >> 24);
 
         if (hdrbyte != dis.readByte()) {
             // data format version mismatch
             throw new IOException("Provided input contains unexpected data (0x01 expected as 1st byte)!");
         }
 
         return dis.readLong();
     }
 
     public Document readDocument() throws IOException {
         int fieldCount;
         try {
             fieldCount = dis.readInt();
         } catch (EOFException ex) {
             return null; // no more documents
         }
 
         Document doc = new Document();
 
         for (int i = 0; i < fieldCount; i++) {
             doc.add(readField());
         }
 
         // Fix up UINFO field wrt MINDEXER-41
         final Field uinfoField = (Field) doc.getField(ArtifactInfo.UINFO);
         final String info = doc.get(ArtifactInfo.INFO);
         if (uinfoField != null && info != null && !info.isEmpty()) {
             final String[] splitInfo = ArtifactInfo.FS_PATTERN.split(info);
             if (splitInfo.length > 6) {
                 final String extension = splitInfo[6];
                 final String uinfoString = uinfoField.stringValue();
                 if (uinfoString.endsWith(ArtifactInfo.FS + ArtifactInfo.NA)) {
                     uinfoField.setStringValue(uinfoString + ArtifactInfo.FS + ArtifactInfo.nvl(extension));
                 }
             }
         }
 
         return doc;
     }
 
     private Field readField() throws IOException {
         int flags = dis.read();
 
         FieldType fieldType = new FieldType();
         if ((flags & IndexDataWriter.F_INDEXED) > 0) {
             boolean tokenized = (flags & IndexDataWriter.F_TOKENIZED) > 0;
             fieldType.setTokenized(tokenized);
         }
         fieldType.setIndexOptions(IndexOptions.DOCS_AND_FREQS_AND_POSITIONS);
         fieldType.setStored((flags & IndexDataWriter.F_STORED) > 0);
 
         String name = dis.readUTF();
         String value = readUTF(dis);
 
         return new Field(name, value, fieldType);
     }
 
     private static String readUTF(DataInput in) throws IOException {
         int utflen = in.readInt();
 
         byte[] bytearr;
         char[] chararr;
 
         try {
             bytearr = new byte[utflen];
             chararr = new char[utflen];
         } catch (OutOfMemoryError e) {
             throw new IOException(
                     "Index data content is inappropriate (is junk?), leads to OutOfMemoryError!"
                             + " See MINDEXER-28 for more information!",
                     e);
         }
 
         int c, char2, char3;
         int count = 0;
         int chararrCount = 0;
 
         in.readFully(bytearr, 0, utflen);
 
         while (count < utflen) {
             c = bytearr[count] & 0xff;
             if (c > 127) {
                 break;
             }
             count++;
             chararr[chararrCount++] = (char) c;
         }
 
         while (count < utflen) {
             c = bytearr[count] & 0xff;
             switch (c >> 4) {
                 case 0:
                 case 1:
                 case 2:
                 case 3:
                 case 4:
                 case 5:
                 case 6:
                 case 7:
                     /* 0xxxxxxx */
                     count++;
                     chararr[chararrCount++] = (char) c;
                     break;
 
                 case 12:
                 case 13:
                     /* 110x xxxx 10xx xxxx */
                     count += 2;
                     if (count > utflen) {
                         throw new UTFDataFormatException("malformed input: partial character at end");
                     }
                     char2 = bytearr[count - 1];
                     if ((char2 & 0xC0) != 0x80) {
                         throw new UTFDataFormatException("malformed input around byte " + count);
                     }
                     chararr[chararrCount++] = (char) (((c & 0x1F) << 6) | (char2 & 0x3F));
                     break;
 
                 case 14:
                     /* 1110 xxxx 10xx xxxx 10xx xxxx */
                     count += 3;
                     if (count > utflen) {
                         throw new UTFDataFormatException("malformed input: partial character at end");
                     }
                     char2 = bytearr[count - 2];
                     char3 = bytearr[count - 1];
                     if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80)) {
                         throw new UTFDataFormatException("malformed input around byte " + (count - 1));
                     }
                     chararr[chararrCount++] = (char) (((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F)));
                     break;
 
                 default:
                     /* 10xx xxxx, 1111 xxxx */
                     throw new UTFDataFormatException("malformed input around byte " + count);
             }
         }
 
         // The number of chars produced may be less than utflen
         return new String(chararr, 0, chararrCount);
     }
 
     /**
      * An index data read result holder
      */
     public static class IndexDataReadResult {
         private Date timestamp;
 
         private int documentCount;
 
         private Set<String> rootGroups;
 
         private Set<String> allGroups;
 
         public void setDocumentCount(int documentCount) {
             this.documentCount = documentCount;
         }
 
         public int getDocumentCount() {
             return documentCount;
         }
 
         public void setTimestamp(Date timestamp) {
             this.timestamp = timestamp;
         }
 
         public Date getTimestamp() {
             return timestamp;
         }
 
         public void setRootGroups(Set<String> rootGroups) {
             this.rootGroups = rootGroups;
         }
 
         public Set<String> getRootGroups() {
             return rootGroups;
         }
 
         public void setAllGroups(Set<String> allGroups) {
             this.allGroups = allGroups;
         }
 
         public Set<String> getAllGroups() {
             return allGroups;
         }
     }
 
     /**
      * Reads index content by using a visitor. <br>
      * The visitor is called for each read documents after it has been populated with Lucene fields.
      *
      * @param visitor an index data visitor
      * @param context indexing context
      * @return statistics about read data
      * @throws IOException in case of an IO exception during index file access
      */
     public IndexDataReadResult readIndex(final IndexDataReadVisitor visitor, final IndexingContext context)
             throws IOException {
         dis.readByte(); // data format version
 
         long timestamp = dis.readLong();
 
         Date date = null;
 
         if (timestamp != -1) {
             date = new Date(timestamp);
         }
 
         int n = 0;
 
         Document doc;
         while ((doc = readDocument()) != null) {
             visitor.visitDocument(IndexUtils.updateDocument(doc, context, false));
 
             n++;
         }
 
         IndexDataReadResult result = new IndexDataReadResult();
         result.setDocumentCount(n);
         result.setTimestamp(date);
         return result;
     }
 
     /**
      * Visitor of indexed Lucene documents.
      */
     public interface IndexDataReadVisitor {
 
         /**
          * Called on each read document. The document is already populated with fields.
          *
          * @param document read document
          */
         void visitDocument(Document document);
     }
 }