/**
    * 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.regionserver.wal;
  
  
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.Set;
  
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.regionserver.MultiVersionConcurrencyControl;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.CollectionUtils;
  
  import com.google.common.collect.Sets;
  
  import org.apache.hadoop.hbase.wal.WAL.Entry;
  import org.apache.hadoop.hbase.wal.WALKey;
  
  /**
   * A WAL Entry for {@link FSHLog} implementation.  Immutable.
   * A subclass of {@link Entry} that carries extra info across the ring buffer such as
   * region sequence id (we want to use this later, just before we write the WAL to ensure region
   * edits maintain order).  The extra info added here is not 'serialized' as part of the WALEdit
   * hence marked 'transient' to underline this fact.  It also adds mechanism so we can wait on
   * the assign of the region sequence id.  See #stampRegionSequenceId().
   */
  @InterfaceAudience.Private
  class FSWALEntry extends Entry {
    // The below data members are denoted 'transient' just to highlight these are not persisted;
    // they are only in memory and held here while passing over the ring buffer.
    private final transient long sequence;
    private final transient boolean inMemstore;
    private final transient HTableDescriptor htd;
    private final transient HRegionInfo hri;
    private final Set<byte[]> familyNames;
  
    FSWALEntry(final long sequence, final WALKey key, final WALEdit edit,
        final HTableDescriptor htd, final HRegionInfo hri, final boolean inMemstore) {
      super(key, edit);
      this.inMemstore = inMemstore;
      this.htd = htd;
      this.hri = hri;
      this.sequence = sequence;
      if (inMemstore) {
        // construct familyNames here to reduce the work of log sinker.
        ArrayList<Cell> cells = this.getEdit().getCells();
        if (CollectionUtils.isEmpty(cells)) {
          this.familyNames = Collections.<byte[]> emptySet();
        } else {
          Set<byte[]> familySet = Sets.newTreeSet(Bytes.BYTES_COMPARATOR);
          for (Cell cell : cells) {
            if (!CellUtil.matchingFamily(cell, WALEdit.METAFAMILY)) {
              familySet.add(CellUtil.cloneFamily(cell));
            }
          }
          this.familyNames = Collections.unmodifiableSet(familySet);
        }
      } else {
        this.familyNames = Collections.<byte[]> emptySet();
      }
    }
  
    public String toString() {
      return "sequence=" + this.sequence + ", " + super.toString();
    };
  
    boolean isInMemstore() {
      return this.inMemstore;
    }
  
    HTableDescriptor getHTableDescriptor() {
      return this.htd;
    }
  
    HRegionInfo getHRegionInfo() {
      return this.hri;
    }
  
   /**
    * @return The sequence on the ring buffer when this edit was added.
    */
   long getSequence() {
     return this.sequence;
   }
 
   /**
    * Here is where a WAL edit gets its sequenceid.
    * @return The sequenceid we stamped on this edit.
    * @throws IOException
    */
   long stampRegionSequenceId() throws IOException {
     long regionSequenceId = WALKey.NO_SEQUENCE_ID;
     MultiVersionConcurrencyControl mvcc = getKey().getMvcc();
     MultiVersionConcurrencyControl.WriteEntry we = null;
 
     if (mvcc != null) {
       we = mvcc.begin();
       regionSequenceId = we.getWriteNumber();
     }
 
     if (!this.getEdit().isReplay() && inMemstore) {
       for (Cell c:getEdit().getCells()) {
         CellUtil.setSequenceId(c, regionSequenceId);
       }
     }
 
     // This has to stay in this order
     WALKey key = getKey();
     key.setLogSeqNum(regionSequenceId);
     key.setWriteEntry(we);
     return regionSequenceId;
   }
 
   /**
    * @return the family names which are effected by this edit.
    */
   Set<byte[]> getFamilyNames() {
     return familyNames;
   }
 }