/*
    *
    * 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.zookeeper;
  
  import java.util.UUID;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.Abortable;
  import org.apache.hadoop.hbase.ClusterId;
  import org.apache.hadoop.hbase.exceptions.DeserializationException;
  import org.apache.zookeeper.KeeperException;
  
  /**
   * Publishes and synchronizes a unique identifier specific to a given HBase
   * cluster.  The stored identifier is read from the file system by the active
   * master on startup, and is subsequently available to all watchers (including
   * clients).
   */
  @InterfaceAudience.Private
  public class ZKClusterId {
    private ZooKeeperWatcher watcher;
    private Abortable abortable;
    private String id;
  
    public ZKClusterId(ZooKeeperWatcher watcher, Abortable abortable) {
      this.watcher = watcher;
      this.abortable = abortable;
    }
  
    public boolean hasId() {
      return getId() != null;
    }
  
    public String getId() {
      try {
        if (id == null) {
          id = readClusterIdZNode(watcher);
        }
      } catch (KeeperException ke) {
        abortable.abort("Unexpected exception from ZooKeeper reading cluster ID",
            ke);
      }
      return id;
    }
  
    public static String readClusterIdZNode(ZooKeeperWatcher watcher)
    throws KeeperException {
      if (ZKUtil.checkExists(watcher, watcher.clusterIdZNode) != -1) {
        byte [] data;
        try {
          data = ZKUtil.getData(watcher, watcher.clusterIdZNode);
        } catch (InterruptedException e) {
          Thread.currentThread().interrupt();
          return null;
        }
        if (data != null) {
          try {
            return ClusterId.parseFrom(data).toString();
          } catch (DeserializationException e) {
            throw ZKUtil.convert(e);
          }
        }
      }
      return null;
    }
  
    public static void setClusterId(ZooKeeperWatcher watcher, ClusterId id)
        throws KeeperException {
      ZKUtil.createSetData(watcher, watcher.clusterIdZNode, id.toByteArray());
    }
  
    /**
     * Get the UUID for the provided ZK watcher. Doesn't handle any ZK exceptions
     * @param zkw watcher connected to an ensemble
     * @return the UUID read from zookeeper
     * @throws KeeperException
     */
    public static UUID getUUIDForCluster(ZooKeeperWatcher zkw) throws KeeperException {
      String uuid = readClusterIdZNode(zkw);
      return uuid == null ? null : UUID.fromString(uuid);
    }
  }