/**
    *
    * 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.DataInput;
  import java.io.DataOutput;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.NavigableMap;
  import java.util.TreeMap;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.CellUtil;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.KeyValueUtil;
  import org.apache.hadoop.hbase.codec.Codec;
  import org.apache.hadoop.hbase.io.HeapSize;
  import org.apache.hadoop.hbase.protobuf.generated.WALProtos;
  import org.apache.hadoop.hbase.protobuf.generated.WALProtos.CompactionDescriptor;
  import org.apache.hadoop.hbase.protobuf.generated.WALProtos.FlushDescriptor;
  import org.apache.hadoop.hbase.protobuf.generated.WALProtos.RegionEventDescriptor;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.util.ClassSize;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.io.Writable;
  
  import com.google.common.annotations.VisibleForTesting;
  
  
  /**
   * WALEdit: Used in HBase's transaction log (WAL) to represent
   * the collection of edits (KeyValue objects) corresponding to a
   * single transaction. The class implements "Writable" interface
   * for serializing/deserializing a set of KeyValue items.
   *
   * Previously, if a transaction contains 3 edits to c1, c2, c3 for a row R,
   * the WAL would have three log entries as follows:
   *
   *    <logseq1-for-edit1>:<KeyValue-for-edit-c1>
   *    <logseq2-for-edit2>:<KeyValue-for-edit-c2>
   *    <logseq3-for-edit3>:<KeyValue-for-edit-c3>
   *
   * This presents problems because row level atomicity of transactions
   * was not guaranteed. If we crash after few of the above appends make
   * it, then recovery will restore a partial transaction.
   *
   * In the new world, all the edits for a given transaction are written
   * out as a single record, for example:
   *
   *   <logseq#-for-entire-txn>:<WALEdit-for-entire-txn>
   *
   * where, the WALEdit is serialized as:
   *   <-1, # of edits, <KeyValue>, <KeyValue>, ... >
   * For example:
   *   <-1, 3, <Keyvalue-for-edit-c1>, <KeyValue-for-edit-c2>, <KeyValue-for-edit-c3>>
   *
   * The -1 marker is just a special way of being backward compatible with
   * an old WAL which would have contained a single <KeyValue>.
   *
   * The deserializer for WALEdit backward compatibly detects if the record
   * is an old style KeyValue or the new style WALEdit.
   *
   */
  @InterfaceAudience.LimitedPrivate({ HBaseInterfaceAudience.REPLICATION,
      HBaseInterfaceAudience.COPROC })
  public class WALEdit implements Writable, HeapSize {
    public static final Log LOG = LogFactory.getLog(WALEdit.class);
  
    // TODO: Get rid of this; see HBASE-8457
    public static final byte [] METAFAMILY = Bytes.toBytes("METAFAMILY");
    static final byte [] METAROW = Bytes.toBytes("METAROW");
    static final byte[] COMPACTION = Bytes.toBytes("HBASE::COMPACTION");
    static final byte [] FLUSH = Bytes.toBytes("HBASE::FLUSH");
    static final byte [] REGION_EVENT = Bytes.toBytes("HBASE::REGION_EVENT");
    @VisibleForTesting
    public static final byte [] BULK_LOAD = Bytes.toBytes("HBASE::BULK_LOAD");
  
    private final int VERSION_2 = -1;
   private final boolean isReplay;
 
   private final ArrayList<Cell> cells = new ArrayList<Cell>(1);
 
   public static final WALEdit EMPTY_WALEDIT = new WALEdit();
 
   // Only here for legacy writable deserialization
   @Deprecated
   private NavigableMap<byte[], Integer> scopes;
 
   private CompressionContext compressionContext;
 
   public WALEdit() {
     this(false);
   }
 
   public WALEdit(boolean isReplay) {
     this.isReplay = isReplay;
   }
 
   /**
    * @param f
    * @return True is <code>f</code> is {@link #METAFAMILY}
    */
   public static boolean isMetaEditFamily(final byte [] f) {
     return Bytes.equals(METAFAMILY, f);
   }
 
   public static boolean isMetaEditFamily(Cell cell) {
     return CellUtil.matchingFamily(cell, METAFAMILY);
   }
 
   public boolean isMetaEdit() {
     for (Cell cell: cells) {
       if (!isMetaEditFamily(cell)) {
         return false;
       }
     }
     return true;
   }
 
   /**
    * @return True when current WALEdit is created by log replay. Replication skips WALEdits from
    *         replay.
    */
   public boolean isReplay() {
     return this.isReplay;
   }
 
   public void setCompressionContext(final CompressionContext compressionContext) {
     this.compressionContext = compressionContext;
   }
 
   public WALEdit add(Cell cell) {
     this.cells.add(cell);
     return this;
   }
 
   public boolean isEmpty() {
     return cells.isEmpty();
   }
 
   public int size() {
     return cells.size();
   }
 
   public ArrayList<Cell> getCells() {
     return cells;
   }
 
   public NavigableMap<byte[], Integer> getAndRemoveScopes() {
     NavigableMap<byte[], Integer> result = scopes;
     scopes = null;
     return result;
   }
 
   @Override
   public void readFields(DataInput in) throws IOException {
     cells.clear();
     if (scopes != null) {
       scopes.clear();
     }
     int versionOrLength = in.readInt();
     // TODO: Change version when we protobuf.  Also, change way we serialize KV!  Pb it too.
     if (versionOrLength == VERSION_2) {
       // this is new style WAL entry containing multiple KeyValues.
       int numEdits = in.readInt();
       for (int idx = 0; idx < numEdits; idx++) {
         if (compressionContext != null) {
           this.add(KeyValueCompression.readKV(in, compressionContext));
         } else {
           this.add(KeyValue.create(in));
         }
       }
       int numFamilies = in.readInt();
       if (numFamilies > 0) {
         if (scopes == null) {
           scopes = new TreeMap<byte[], Integer>(Bytes.BYTES_COMPARATOR);
         }
         for (int i = 0; i < numFamilies; i++) {
           byte[] fam = Bytes.readByteArray(in);
           int scope = in.readInt();
           scopes.put(fam, scope);
         }
       }
     } else {
       // this is an old style WAL entry. The int that we just
       // read is actually the length of a single KeyValue
       this.add(KeyValue.create(versionOrLength, in));
     }
   }
 
   @Override
   public void write(DataOutput out) throws IOException {
     LOG.warn("WALEdit is being serialized to writable - only expected in test code");
     out.writeInt(VERSION_2);
     out.writeInt(cells.size());
     // We interleave the two lists for code simplicity
     for (Cell cell : cells) {
       // This is not used in any of the core code flows so it is just fine to convert to KV
       KeyValue kv = KeyValueUtil.ensureKeyValue(cell);
       if (compressionContext != null) {
         KeyValueCompression.writeKV(out, kv, compressionContext);
       } else{
         KeyValue.write(kv, out);
       }
     }
     if (scopes == null) {
       out.writeInt(0);
     } else {
       out.writeInt(scopes.size());
       for (byte[] key : scopes.keySet()) {
         Bytes.writeByteArray(out, key);
         out.writeInt(scopes.get(key));
       }
     }
   }
 
   /**
    * Reads WALEdit from cells.
    * @param cellDecoder Cell decoder.
    * @param expectedCount Expected cell count.
    * @return Number of KVs read.
    */
   public int readFromCells(Codec.Decoder cellDecoder, int expectedCount) throws IOException {
     cells.clear();
     cells.ensureCapacity(expectedCount);
     while (cells.size() < expectedCount && cellDecoder.advance()) {
       cells.add(cellDecoder.current());
     }
     return cells.size();
   }
 
   @Override
   public long heapSize() {
     long ret = ClassSize.ARRAYLIST;
     for (Cell cell : cells) {
       ret += CellUtil.estimatedHeapSizeOf(cell);
     }
     if (scopes != null) {
       ret += ClassSize.TREEMAP;
       ret += ClassSize.align(scopes.size() * ClassSize.MAP_ENTRY);
       // TODO this isn't quite right, need help here
     }
     return ret;
   }
 
   @Override
   public String toString() {
     StringBuilder sb = new StringBuilder();
 
     sb.append("[#edits: " + cells.size() + " = <");
     for (Cell cell : cells) {
       sb.append(cell);
       sb.append("; ");
     }
     if (scopes != null) {
       sb.append(" scopes: " + scopes.toString());
     }
     sb.append(">]");
     return sb.toString();
   }
 
   public static WALEdit createFlushWALEdit(HRegionInfo hri, FlushDescriptor f) {
     KeyValue kv = new KeyValue(getRowForRegion(hri), METAFAMILY, FLUSH,
       EnvironmentEdgeManager.currentTime(), f.toByteArray());
     return new WALEdit().add(kv);
   }
 
   public static FlushDescriptor getFlushDescriptor(Cell cell) throws IOException {
     if (CellUtil.matchingColumn(cell, METAFAMILY, FLUSH)) {
       return FlushDescriptor.parseFrom(cell.getValue());
     }
     return null;
   }
 
   public static WALEdit createRegionEventWALEdit(HRegionInfo hri,
       RegionEventDescriptor regionEventDesc) {
     KeyValue kv = new KeyValue(getRowForRegion(hri), METAFAMILY, REGION_EVENT,
       EnvironmentEdgeManager.currentTime(), regionEventDesc.toByteArray());
     return new WALEdit().add(kv);
   }
 
   public static RegionEventDescriptor getRegionEventDescriptor(Cell cell) throws IOException {
     if (CellUtil.matchingColumn(cell, METAFAMILY, REGION_EVENT)) {
       return RegionEventDescriptor.parseFrom(cell.getValue());
     }
     return null;
   }
 
   /**
    * Create a compaction WALEdit
    * @param c
    * @return A WALEdit that has <code>c</code> serialized as its value
    */
   public static WALEdit createCompaction(final HRegionInfo hri, final CompactionDescriptor c) {
     byte [] pbbytes = c.toByteArray();
     KeyValue kv = new KeyValue(getRowForRegion(hri), METAFAMILY, COMPACTION,
       EnvironmentEdgeManager.currentTime(), pbbytes);
     return new WALEdit().add(kv); //replication scope null so that this won't be replicated
   }
 
   private static byte[] getRowForRegion(HRegionInfo hri) {
     byte[] startKey = hri.getStartKey();
     if (startKey.length == 0) {
       // empty row key is not allowed in mutations because it is both the start key and the end key
       // we return the smallest byte[] that is bigger (in lex comparison) than byte[0].
       return new byte[] {0};
     }
     return startKey;
   }
 
   /**
    * Deserialized and returns a CompactionDescriptor is the KeyValue contains one.
    * @param kv the key value
    * @return deserialized CompactionDescriptor or null.
    */
   public static CompactionDescriptor getCompaction(Cell kv) throws IOException {
     if (CellUtil.matchingColumn(kv, METAFAMILY, COMPACTION)) {
       return CompactionDescriptor.parseFrom(kv.getValue());
     }
     return null;
   }
 
   /**
    * Create a bulk loader WALEdit
    *
    * @param hri                The HRegionInfo for the region in which we are bulk loading
    * @param bulkLoadDescriptor The descriptor for the Bulk Loader
    * @return The WALEdit for the BulkLoad
    */
   public static WALEdit createBulkLoadEvent(HRegionInfo hri,
                                             WALProtos.BulkLoadDescriptor bulkLoadDescriptor) {
     KeyValue kv = new KeyValue(getRowForRegion(hri),
         METAFAMILY,
         BULK_LOAD,
         EnvironmentEdgeManager.currentTime(),
         bulkLoadDescriptor.toByteArray());
     return new WALEdit().add(kv);
   }
 
   /**
    * Deserialized and returns a BulkLoadDescriptor from the passed in Cell
    * @param cell the key value
    * @return deserialized BulkLoadDescriptor or null.
    */
   public static WALProtos.BulkLoadDescriptor getBulkLoadDescriptor(Cell cell) throws IOException {
     if (CellUtil.matchingColumn(cell, METAFAMILY, BULK_LOAD)) {
       return WALProtos.BulkLoadDescriptor.parseFrom(cell.getValue());
     }
     return null;
   }
 }