/*
    *
    * 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.replication;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.Abortable;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.client.replication.ReplicationAdmin;
  import org.apache.hadoop.hbase.exceptions.DeserializationException;
  import org.apache.hadoop.hbase.protobuf.ProtobufUtil;
  import org.apache.hadoop.hbase.protobuf.generated.ZooKeeperProtos;
  import org.apache.hadoop.hbase.util.Bytes;
  import org.apache.hadoop.hbase.zookeeper.ZKUtil;
  import org.apache.hadoop.hbase.zookeeper.ZooKeeperNodeTracker;
  import org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher;
  import org.apache.zookeeper.KeeperException;
  import org.apache.zookeeper.KeeperException.NodeExistsException;
  
  @InterfaceAudience.Private
  public class ReplicationPeerZKImpl implements ReplicationPeer, Abortable, Closeable {
    private static final Log LOG = LogFactory.getLog(ReplicationPeerZKImpl.class);
  
    private final ReplicationPeerConfig peerConfig;
    private final String id;
    private volatile PeerState peerState;
    private volatile Map<TableName, List<String>> tableCFs = new HashMap<TableName, List<String>>();
    private final Configuration conf;
  
    private PeerStateTracker peerStateTracker;
    private TableCFsTracker tableCFsTracker;
  
    /**
     * Constructor that takes all the objects required to communicate with the specified peer, except
     * for the region server addresses.
     * @param conf configuration object to this peer
     * @param id string representation of this peer's identifier
     * @param peerConfig configuration for the replication peer
     */
    public ReplicationPeerZKImpl(Configuration conf, String id, ReplicationPeerConfig peerConfig)
        throws ReplicationException {
      this.conf = conf;
      this.peerConfig = peerConfig;
      this.id = id;
    }
    
    /**
     * Constructor that takes all the objects required to communicate with the specified peer, except
     * for the region server addresses.
     * @param conf configuration object to this peer
     * @param id string representation of this peer's identifier
     * @param peerConfig configuration for the replication peer
     * @param tableCFs table-cf configuration for this peer
     */
    public ReplicationPeerZKImpl(Configuration conf, String id, ReplicationPeerConfig peerConfig,
        Map<TableName, List<String>> tableCFs) throws ReplicationException {
      this.conf = conf;
      this.peerConfig = peerConfig;
      this.id = id;
      this.tableCFs = tableCFs;
    }
  
    /**
     * start a state tracker to check whether this peer is enabled or not
     *
     * @param zookeeper zk watcher for the local cluster
     * @param peerStateNode path to zk node which stores peer state
     * @throws KeeperException
     */
    public void startStateTracker(ZooKeeperWatcher zookeeper, String peerStateNode)
        throws KeeperException {
      ensurePeerEnabled(zookeeper, peerStateNode);
      this.peerStateTracker = new PeerStateTracker(peerStateNode, zookeeper, this);
      this.peerStateTracker.start();
      try {
       this.readPeerStateZnode();
     } catch (DeserializationException e) {
       throw ZKUtil.convert(e);
     }
   }
 
   private void readPeerStateZnode() throws DeserializationException {
     this.peerState =
         isStateEnabled(this.peerStateTracker.getData(false))
           ? PeerState.ENABLED
           : PeerState.DISABLED;
   }
 
   /**
    * start a table-cfs tracker to listen the (table, cf-list) map change
    *
    * @param zookeeper zk watcher for the local cluster
    * @param tableCFsNode path to zk node which stores table-cfs
    * @throws KeeperException
    */
   public void startTableCFsTracker(ZooKeeperWatcher zookeeper, String tableCFsNode)
     throws KeeperException {
     this.tableCFsTracker = new TableCFsTracker(tableCFsNode, zookeeper,
         this);
     this.tableCFsTracker.start();
     this.readTableCFsZnode();
   }
 
   private void readTableCFsZnode() {
     String currentTableCFs = Bytes.toString(tableCFsTracker.getData(false));
     this.tableCFs = ReplicationAdmin.parseTableCFsFromConfig(currentTableCFs);
   }
 
   @Override
   public PeerState getPeerState() {
     return peerState;
   }
 
   /**
    * Get the identifier of this peer
    * @return string representation of the id (short)
    */
   @Override
   public String getId() {
     return id;
   }
 
   /**
    * Get the peer config object
    * @return the ReplicationPeerConfig for this peer
    */
   @Override
   public ReplicationPeerConfig getPeerConfig() {
     return peerConfig;
   }
 
   /**
    * Get the configuration object required to communicate with this peer
    * @return configuration object
    */
   @Override
   public Configuration getConfiguration() {
     return conf;
   }
 
   /**
    * Get replicable (table, cf-list) map of this peer
    * @return the replicable (table, cf-list) map
    */
   @Override
   public Map<TableName, List<String>> getTableCFs() {
     return this.tableCFs;
   }
 
   @Override
   public void abort(String why, Throwable e) {
     LOG.fatal("The ReplicationPeer coresponding to peer " + peerConfig
         + " was aborted for the following reason(s):" + why, e);
   }
 
   @Override
   public boolean isAborted() {
     // Currently the replication peer is never "Aborted", we just log when the
     // abort method is called.
     return false;
   }
 
   @Override
   public void close() throws IOException {
     // TODO: stop zkw?
   }
 
   /**
    * Parse the raw data from ZK to get a peer's state
    * @param bytes raw ZK data
    * @return True if the passed in <code>bytes</code> are those of a pb serialized ENABLED state.
    * @throws DeserializationException
    */
   public static boolean isStateEnabled(final byte[] bytes) throws DeserializationException {
     ZooKeeperProtos.ReplicationState.State state = parseStateFrom(bytes);
     return ZooKeeperProtos.ReplicationState.State.ENABLED == state;
   }
 
   /**
    * @param bytes Content of a state znode.
    * @return State parsed from the passed bytes.
    * @throws DeserializationException
    */
   private static ZooKeeperProtos.ReplicationState.State parseStateFrom(final byte[] bytes)
       throws DeserializationException {
     ProtobufUtil.expectPBMagicPrefix(bytes);
     int pblen = ProtobufUtil.lengthOfPBMagic();
     ZooKeeperProtos.ReplicationState.Builder builder =
         ZooKeeperProtos.ReplicationState.newBuilder();
     ZooKeeperProtos.ReplicationState state;
     try {
       ProtobufUtil.mergeFrom(builder, bytes, pblen, bytes.length - pblen);
       state = builder.build();
       return state.getState();
     } catch (IOException e) {
       throw new DeserializationException(e);
     }
   }
 
   /**
    * Utility method to ensure an ENABLED znode is in place; if not present, we create it.
    * @param zookeeper
    * @param path Path to znode to check
    * @return True if we created the znode.
    * @throws NodeExistsException
    * @throws KeeperException
    */
   private static boolean ensurePeerEnabled(final ZooKeeperWatcher zookeeper, final String path)
       throws NodeExistsException, KeeperException {
     if (ZKUtil.checkExists(zookeeper, path) == -1) {
       // There is a race b/w PeerWatcher and ReplicationZookeeper#add method to create the
       // peer-state znode. This happens while adding a peer.
       // The peer state data is set as "ENABLED" by default.
       ZKUtil.createNodeIfNotExistsAndWatch(zookeeper, path,
         ReplicationStateZKBase.ENABLED_ZNODE_BYTES);
       return true;
     }
     return false;
   }
 
   /**
    * Tracker for state of this peer
    */
   public class PeerStateTracker extends ZooKeeperNodeTracker {
 
     public PeerStateTracker(String peerStateZNode, ZooKeeperWatcher watcher,
         Abortable abortable) {
       super(watcher, peerStateZNode, abortable);
     }
 
     @Override
     public synchronized void nodeDataChanged(String path) {
       if (path.equals(node)) {
         super.nodeDataChanged(path);
         try {
           readPeerStateZnode();
         } catch (DeserializationException e) {
           LOG.warn("Failed deserializing the content of " + path, e);
         }
       }
     }
   }
 
   /**
    * Tracker for (table, cf-list) map of this peer
    */
   public class TableCFsTracker extends ZooKeeperNodeTracker {
 
     public TableCFsTracker(String tableCFsZNode, ZooKeeperWatcher watcher,
         Abortable abortable) {
       super(watcher, tableCFsZNode, abortable);
     }
     
     @Override
     public synchronized void nodeCreated(String path) {
       if (path.equals(node)) {
         super.nodeCreated(path);
         readTableCFsZnode();
       }
     }
 
     @Override
     public synchronized void nodeDataChanged(String path) {
       if (path.equals(node)) {
         super.nodeDataChanged(path);
       }
     }
   }
 }