/*
    * 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.nio.ByteBuffer;
  
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.HConstants;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.KeyValue.KVComparator;
  import org.apache.hadoop.hbase.NoTagsKeyValue;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.io.encoding.AbstractDataBlockEncoder.AbstractEncodedSeeker;
  import org.apache.hadoop.hbase.util.ByteBufferUtils;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.SimpleMutableByteRange;
  import org.apache.hadoop.io.WritableUtils;
  
  @InterfaceAudience.Private
  public class RowIndexSeekerV1 extends AbstractEncodedSeeker {
  
    private ByteBuffer currentBuffer;
    private SeekerState current = new SeekerState(); // always valid
    private SeekerState previous = new SeekerState(); // may not be valid
  
    private int rowNumber;
    private ByteBuffer rowOffsets = null;
  
    public RowIndexSeekerV1(KVComparator comparator,
        HFileBlockDecodingContext decodingCtx) {
      super(comparator, decodingCtx);
    }
  
    @Override
    public void setCurrentBuffer(ByteBuffer buffer) {
      int onDiskSize = Bytes.toIntUnsafe(buffer.array(), buffer.arrayOffset()
          + buffer.limit() - Bytes.SIZEOF_INT);
      // int onDiskSize = buffer.getInt(buffer.limit() - Bytes.SIZEOF_INT);
  
      // Data part
      ByteBuffer dup = buffer.duplicate();
      dup.position(buffer.position());
      dup.limit(buffer.position() + onDiskSize);
      currentBuffer = dup.slice();
      current.currentBuffer = currentBuffer;
      ByteBufferUtils.skip(buffer, onDiskSize);
  
      // Row offset
      rowNumber = buffer.getInt();
      // equals Bytes.SIZEOF_INT * rowNumber
      int totalRowOffsetsLength = rowNumber << 2;
      ByteBuffer rowDup = buffer.duplicate();
      rowDup.position(buffer.position());
      rowDup.limit(buffer.position() + totalRowOffsetsLength);
      rowOffsets = rowDup.slice();
  
      decodeFirst();
    }
  
    @Override
    public ByteBuffer getKeyDeepCopy() {
      ByteBuffer keyBuffer = ByteBuffer.allocate(current.keyLength);
      keyBuffer.put(current.keyBuffer.getBytes(), current.keyBuffer.getOffset(),
          current.keyLength);
      keyBuffer.rewind();
      return keyBuffer;
    }
  
    @Override
    public ByteBuffer getValueShallowCopy() {
      ByteBuffer dup = currentBuffer.duplicate();
      dup.position(current.valueOffset);
      dup.limit(current.valueOffset + current.valueLength);
      return dup.slice();
    }
  
    ByteBuffer getKeyValueBuffer() {
      ByteBuffer kvBuffer = createKVBuffer();
      kvBuffer.putInt(current.keyLength);
      kvBuffer.putInt(current.valueLength);
      kvBuffer.put(current.keyBuffer.getBytes(), current.keyBuffer.getOffset(),
          current.keyLength);
      ByteBufferUtils.copyFromBufferToBuffer(kvBuffer, currentBuffer,
          current.valueOffset, current.valueLength);
     if (current.tagsLength > 0) {
       // Put short as unsigned
       kvBuffer.put((byte) (current.tagsLength >> 8 & 0xff));
       kvBuffer.put((byte) (current.tagsLength & 0xff));
       if (current.tagsOffset != -1) {
         ByteBufferUtils.copyFromBufferToBuffer(kvBuffer, currentBuffer,
             current.tagsOffset, current.tagsLength);
       }
     }
     if (includesMvcc()) {
       ByteBufferUtils.writeVLong(kvBuffer, current.getSequenceId());
     }
     kvBuffer.rewind();
     return kvBuffer;
   }
 
   protected ByteBuffer createKVBuffer() {
     int kvBufSize = (int) KeyValue.getKeyValueDataStructureSize(
         current.keyLength, current.valueLength, current.tagsLength);
     if (includesMvcc()) {
       kvBufSize += WritableUtils.getVIntSize(current.getSequenceId());
     }
     ByteBuffer kvBuffer = ByteBuffer.allocate(kvBufSize);
     return kvBuffer;
   }
 
   @Override
   public Cell getKeyValue() {
     return current.toCell();
   }
 
   @Override
   public void rewind() {
     currentBuffer.rewind();
     decodeFirst();
   }
 
   @Override
   public boolean next() {
     if (!currentBuffer.hasRemaining()) {
       return false;
     }
     decodeNext();
     previous.invalidate();
     return true;
   }
 
   @Override
   public int seekToKeyInBlock(byte[] key, int offset, int length,
       boolean seekBefore) {
     return seekToKeyInBlock(new KeyValue.KeyOnlyKeyValue(key, offset, length),
         seekBefore);
   }
 
   private int binarySearch(Cell seekCell, boolean seekBefore) {
     int low = 0;
     int high = rowNumber - 1;
     int mid = (low + high) >>> 1;
     int comp = 0;
     SimpleMutableByteRange row = new SimpleMutableByteRange();
     while (low <= high) {
       mid = (low + high) >>> 1;
       getRow(mid, row);
       comp = comparator.compareRows(row.getBytes(), row.getOffset(),
           row.getLength(), seekCell.getRowArray(), seekCell.getRowOffset(),
           seekCell.getRowLength());
       if (comp < 0) {
         low = mid + 1;
       } else if (comp > 0) {
         high = mid - 1;
       } else {
         // key found
         if (seekBefore) {
           return mid - 1;
         } else {
           return mid;
         }
       }
     }
     // key not found.
     if (comp > 0) {
       return mid - 1;
     } else {
       return mid;
     }
   }
 
   private void getRow(int index, SimpleMutableByteRange row) {
     int offset = Bytes.toIntUnsafe(rowOffsets.array(), rowOffsets.arrayOffset()
         + (index << 2)); // index * Bytes.SIZEOF_INT
     int position = currentBuffer.arrayOffset() + offset + Bytes.SIZEOF_LONG;
     short rowLen = Bytes.toShortUnsafe(currentBuffer.array(), position);
     row.set(currentBuffer.array(), position + Bytes.SIZEOF_SHORT, rowLen);
   }
 
   @Override
   public int seekToKeyInBlock(Cell seekCell, boolean seekBefore) {
     previous.invalidate();
     int index = binarySearch(seekCell, seekBefore);
     if (index < 0) {
       return HConstants.INDEX_KEY_MAGIC; // using optimized index key
     } else {
       int offset = Bytes.toIntUnsafe(rowOffsets.array(),
           rowOffsets.arrayOffset() + (index << 2));
       if (offset != 0) {
         decodeAtPosition(offset);
       }
     }
     do {
       int comp;
       comp = comparator.compareOnlyKeyPortion(seekCell, current.currentKey);
       if (comp == 0) { // exact match
         if (seekBefore) {
           if (!previous.isValid()) {
             // The caller (seekBefore) has to ensure that we are not at the
             // first key in the block.
             throw new IllegalStateException("Cannot seekBefore if "
                 + "positioned at the first key in the block: key="
                 + Bytes.toStringBinary(seekCell.getRowArray()));
           }
           moveToPrevious();
           return 1;
         }
         return 0;
       }
 
       if (comp < 0) { // already too large, check previous
         if (previous.isValid()) {
           moveToPrevious();
         } else {
           return HConstants.INDEX_KEY_MAGIC; // using optimized index key
         }
         return 1;
       }
 
       // move to next, if more data is available
       if (currentBuffer.hasRemaining()) {
         previous.copyFromNext(current);
         decodeNext();
       } else {
         break;
       }
     } while (true);
 
     // we hit the end of the block, not an exact match
     return 1;
   }
 
   private void moveToPrevious() {
     if (!previous.isValid()) {
       throw new IllegalStateException(
           "Can move back only once and not in first key in the block.");
     }
 
     SeekerState tmp = previous;
     previous = current;
     current = tmp;
 
     // move after last key value
     currentBuffer.position(current.nextKvOffset);
     previous.invalidate();
   }
 
   @Override
   public int compareKey(KVComparator comparator, byte[] key, int offset,
       int length) {
     return comparator.compareFlatKey(key, offset, length,
         current.keyBuffer.getBytes(), current.keyBuffer.getOffset(),
         current.keyBuffer.getLength());
   }
 
   @Override
   public int compareKey(KVComparator comparator, Cell key) {
     return comparator.compareOnlyKeyPortion(key, new KeyValue.KeyOnlyKeyValue(
         current.keyBuffer.getBytes(), current.keyBuffer.getOffset(),
         current.keyBuffer.getLength()));
   }
 
   protected void decodeFirst() {
     decodeNext();
     previous.invalidate();
   }
 
   protected void decodeAtPosition(int position) {
     currentBuffer.position(position);
     decodeNext();
     previous.invalidate();
   }
 
   protected void decodeNext() {
     current.startOffset = currentBuffer.position();
     int p = currentBuffer.position() + currentBuffer.arrayOffset();
     long ll = Bytes.toLong(currentBuffer.array(), p);
     // Read top half as an int of key length and bottom int as value length
     current.keyLength = (int) (ll >> Integer.SIZE);
     current.valueLength = (int) (Bytes.MASK_FOR_LOWER_INT_IN_LONG ^ ll);
     ByteBufferUtils.skip(currentBuffer, Bytes.SIZEOF_LONG);
     // key part
     current.keyBuffer.set(currentBuffer.array(), currentBuffer.arrayOffset()
         + currentBuffer.position(), current.keyLength);
     ByteBufferUtils.skip(currentBuffer, current.keyLength);
     // value part
     current.valueOffset = currentBuffer.position();
     ByteBufferUtils.skip(currentBuffer, current.valueLength);
     if (includesTags()) {
       decodeTags();
     }
     if (includesMvcc()) {
       current.memstoreTS = ByteBufferUtils.readVLong(currentBuffer);
     } else {
       current.memstoreTS = 0;
     }
     current.nextKvOffset = currentBuffer.position();
     current.setKey(current.keyBuffer.getBytes(), current.keyBuffer.getOffset(),
         current.keyBuffer.getLength());
   }
 
   protected void decodeTags() {
     current.tagsLength = currentBuffer.getShort();
     current.tagsOffset = currentBuffer.position();
     ByteBufferUtils.skip(currentBuffer, current.tagsLength);
   }
 
   protected class SeekerState {
     /**
      * The size of a (key length, value length) tuple that prefixes each entry
      * in a data block.
      */
     public final static int KEY_VALUE_LEN_SIZE = 2 * Bytes.SIZEOF_INT;
 
     protected ByteBuffer currentBuffer;
     protected int startOffset = -1;
     protected int valueOffset = -1;
     protected int keyLength;
     protected int valueLength;
     protected int tagsLength = 0;
     protected int tagsOffset = -1;
 
     protected SimpleMutableByteRange keyBuffer = new SimpleMutableByteRange();
     protected long memstoreTS;
     protected int nextKvOffset;
     protected KeyValue.KeyOnlyKeyValue currentKey = new KeyValue.KeyOnlyKeyValue();
 
     protected boolean isValid() {
       return valueOffset != -1;
     }
 
     protected void invalidate() {
       valueOffset = -1;
       currentKey = new KeyValue.KeyOnlyKeyValue();
       currentBuffer = null;
     }
 
     protected void setKey(byte[] key, int offset, int length) {
       currentKey.setKey(key, offset, length);
     }
 
     protected long getSequenceId() {
       return memstoreTS;
     }
 
     /**
      * Copy the state from the next one into this instance (the previous state
      * placeholder). Used to save the previous state when we are advancing the
      * seeker to the next key/value.
      */
     protected void copyFromNext(SeekerState nextState) {
       keyBuffer.set(nextState.keyBuffer.getBytes(),
           nextState.keyBuffer.getOffset(), nextState.keyBuffer.getLength());
       currentKey.setKey(nextState.keyBuffer.getBytes(),
           nextState.keyBuffer.getOffset(), nextState.keyBuffer.getLength());
 
       startOffset = nextState.startOffset;
       valueOffset = nextState.valueOffset;
       keyLength = nextState.keyLength;
       valueLength = nextState.valueLength;
       nextKvOffset = nextState.nextKvOffset;
       memstoreTS = nextState.memstoreTS;
       currentBuffer = nextState.currentBuffer;
       tagsOffset = nextState.tagsOffset;
       tagsLength = nextState.tagsLength;
     }
 
     @Override
     public String toString() {
       return CellUtil.getCellKeyAsString(toCell());
     }
 
     protected int getCellBufSize() {
       int kvBufSize = KEY_VALUE_LEN_SIZE + keyLength + valueLength;
       if (includesTags()) {
         kvBufSize += Bytes.SIZEOF_SHORT + tagsLength;
       }
       return kvBufSize;
     }
 
     protected Cell formNoTagsKeyValue() {
       NoTagsKeyValue ret = new NoTagsKeyValue(currentBuffer.array(),
           currentBuffer.arrayOffset() + startOffset, getCellBufSize());
       if (includesMvcc()) {
         ret.setSequenceId(memstoreTS);
       }
       return ret;
     }
 
     public Cell toCell() {
       if (tagsOffset > 0) {
         KeyValue ret = new KeyValue(currentBuffer.array(),
             currentBuffer.arrayOffset() + startOffset, getCellBufSize());
         if (includesMvcc()) {
           ret.setSequenceId(memstoreTS);
         }
         return ret;
       } else {
         return formNoTagsKeyValue();
       }
     }
   }
 
 }