/*
    * 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.hadoop.hbase.io.encoding;
  
  import java.io.ByteArrayInputStream;
  import java.io.ByteArrayOutputStream;
  import java.io.DataInputStream;
  import java.io.DataOutputStream;
  import java.io.IOException;
  import java.io.OutputStream;
  import java.nio.ByteBuffer;
  import java.util.Iterator;
  
  import org.apache.commons.lang.NotImplementedException;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.io.compress.Compression.Algorithm;
  import org.apache.hadoop.hbase.io.hfile.HFileContext;
  import org.apache.hadoop.hbase.util.ByteBufferUtils;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.io.IOUtils;
  import org.apache.hadoop.io.compress.Compressor;
  
  import com.google.common.annotations.VisibleForTesting;
  import com.google.common.base.Preconditions;
  
  /**
   * Encapsulates a data block compressed using a particular encoding algorithm.
   * Useful for testing and benchmarking.
   * This is used only in testing.
   */
  @InterfaceAudience.Private
  @VisibleForTesting
  public class EncodedDataBlock {
    private byte[] rawKVs;
    private ByteBuffer rawBuffer;
    private DataBlockEncoder dataBlockEncoder;
  
    private byte[] cachedEncodedData;
  
    private final HFileBlockEncodingContext encodingCtx;
    private HFileContext meta;
  
    /**
     * Create a buffer which will be encoded using dataBlockEncoder.
     * @param dataBlockEncoder Algorithm used for compression.
     * @param encoding encoding type used
     * @param rawKVs
     * @param meta
     */
    public EncodedDataBlock(DataBlockEncoder dataBlockEncoder, DataBlockEncoding encoding,
        byte[] rawKVs, HFileContext meta) {
      Preconditions.checkNotNull(encoding,
          "Cannot create encoded data block with null encoder");
      this.dataBlockEncoder = dataBlockEncoder;
      encodingCtx = dataBlockEncoder.newDataBlockEncodingContext(encoding,
          HConstants.HFILEBLOCK_DUMMY_HEADER, meta);
      this.rawKVs = rawKVs;
      this.meta = meta;
    }
  
    /**
     * Provides access to compressed value.
     * @param headerSize header size of the block.
     * @return Forwards sequential iterator.
     */
    public Iterator<Cell> getIterator(int headerSize) {
      final int rawSize = rawKVs.length;
      byte[] encodedDataWithHeader = getEncodedData();
      int bytesToSkip = headerSize + Bytes.SIZEOF_SHORT;
      ByteArrayInputStream bais = new ByteArrayInputStream(encodedDataWithHeader,
          bytesToSkip, encodedDataWithHeader.length - bytesToSkip);
      final DataInputStream dis = new DataInputStream(bais);
  
      return new Iterator<Cell>() {
        private ByteBuffer decompressedData = null;
  
        @Override
        public boolean hasNext() {
          if (decompressedData == null) {
            return rawSize > 0;
          }
          return decompressedData.hasRemaining();
       }
 
       @Override
       public Cell next() {
         if (decompressedData == null) {
           try {
             decompressedData = dataBlockEncoder.decodeKeyValues(dis, dataBlockEncoder
                 .newDataBlockDecodingContext(meta));
           } catch (IOException e) {
             throw new RuntimeException("Problem with data block encoder, " +
                 "most likely it requested more bytes than are available.", e);
           }
           decompressedData.rewind();
         }
         int offset = decompressedData.position();
         int klen = decompressedData.getInt();
         int vlen = decompressedData.getInt();
         int tagsLen = 0;
         ByteBufferUtils.skip(decompressedData, klen + vlen);
         // Read the tag length in case when steam contain tags
         if (meta.isIncludesTags()) {
           tagsLen = ((decompressedData.get() & 0xff) << 8) ^ (decompressedData.get() & 0xff);
           ByteBufferUtils.skip(decompressedData, tagsLen);
         }
         KeyValue kv = new KeyValue(decompressedData.array(), offset,
             (int) KeyValue.getKeyValueDataStructureSize(klen, vlen, tagsLen));
         if (meta.isIncludesMvcc()) {
           long mvccVersion = ByteBufferUtils.readVLong(decompressedData);
           kv.setSequenceId(mvccVersion);
         }
         return kv;
       }
 
       @Override
       public void remove() {
         throw new NotImplementedException("remove() is not supported!");
       }
 
       @Override
       public String toString() {
         return "Iterator of: " + dataBlockEncoder.getClass().getName();
       }
 
     };
   }
 
   /**
    * Find the size of minimal buffer that could store compressed data.
    * @return Size in bytes of compressed data.
    */
   public int getSize() {
     return getEncodedData().length;
   }
 
   /**
    * Find the size of compressed data assuming that buffer will be compressed
    * using given algorithm.
    * @param algo compression algorithm
    * @param compressor compressor already requested from codec
    * @param inputBuffer Array to be compressed.
    * @param offset Offset to beginning of the data.
    * @param length Length to be compressed.
    * @return Size of compressed data in bytes.
    * @throws IOException
    */
   public static int getCompressedSize(Algorithm algo, Compressor compressor,
       byte[] inputBuffer, int offset, int length) throws IOException {
     DataOutputStream compressedStream = new DataOutputStream(
         new IOUtils.NullOutputStream());
     if (compressor != null) {
       compressor.reset();
     }
     OutputStream compressingStream = null;
 
     try {
       compressingStream = algo.createCompressionStream(
           compressedStream, compressor, 0);
 
       compressingStream.write(inputBuffer, offset, length);
       compressingStream.flush();
 
       return compressedStream.size();
     } finally {
       if (compressingStream != null) compressingStream.close();
     }
   }
 
   /**
    * Estimate size after second stage of compression (e.g. LZO).
    * @param comprAlgo compression algorithm to be used for compression
    * @param compressor compressor corresponding to the given compression
    *          algorithm
    * @return Size after second stage of compression.
    */
   public int getEncodedCompressedSize(Algorithm comprAlgo,
       Compressor compressor) throws IOException {
     byte[] compressedBytes = getEncodedData();
     return getCompressedSize(comprAlgo, compressor, compressedBytes, 0,
         compressedBytes.length);
   }
 
   /** @return encoded data with header */
   private byte[] getEncodedData() {
     if (cachedEncodedData != null) {
       return cachedEncodedData;
     }
     cachedEncodedData = encodeData();
     return cachedEncodedData;
   }
 
   private ByteBuffer getUncompressedBuffer() {
     if (rawBuffer == null || rawBuffer.limit() < rawKVs.length) {
       rawBuffer = ByteBuffer.wrap(rawKVs);
     }
     return rawBuffer;
   }
 
   /**
    * Do the encoding, but do not cache the encoded data.
    * @return encoded data block with header and checksum
    */
   public byte[] encodeData() {
     ByteArrayOutputStream baos = new ByteArrayOutputStream();
     try {
       baos.write(HConstants.HFILEBLOCK_DUMMY_HEADER);
       DataOutputStream out = new DataOutputStream(baos);
       this.dataBlockEncoder.startBlockEncoding(encodingCtx, out);
       ByteBuffer in = getUncompressedBuffer();
       in.rewind();
       int klength, vlength;
       int tagsLength = 0;
       long memstoreTS = 0L;
       KeyValue kv = null;
       while (in.hasRemaining()) {
         int kvOffset = in.position();
         klength = in.getInt();
         vlength = in.getInt();
         ByteBufferUtils.skip(in, klength + vlength);
         if (this.meta.isIncludesTags()) {
           tagsLength = ((in.get() & 0xff) << 8) ^ (in.get() & 0xff);
           ByteBufferUtils.skip(in, tagsLength);
         }
         if (this.meta.isIncludesMvcc()) {
           memstoreTS = ByteBufferUtils.readVLong(in);
         }
         kv = new KeyValue(in.array(), kvOffset, (int) KeyValue.getKeyValueDataStructureSize(
             klength, vlength, tagsLength));
         kv.setSequenceId(memstoreTS);
         this.dataBlockEncoder.encode(kv, encodingCtx, out);
       }
       BufferGrabbingByteArrayOutputStream stream = new BufferGrabbingByteArrayOutputStream();
       baos.writeTo(stream);
       this.dataBlockEncoder.endBlockEncoding(encodingCtx, out, stream.buf);
     } catch (IOException e) {
       throw new RuntimeException(String.format(
           "Bug in encoding part of algorithm %s. " +
           "Probably it requested more bytes than are available.",
           toString()), e);
     }
     return baos.toByteArray();
   }
 
   private static class BufferGrabbingByteArrayOutputStream extends ByteArrayOutputStream {
     private byte[] buf;
 
     @Override
     public void write(byte[] b, int off, int len) {
       this.buf = b;
     }
   }
 
   @Override
   public String toString() {
     return dataBlockEncoder.toString();
   }
 }