content: /**
   * Copyright The Apache Software Foundation
   *
   * 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 com.alibaba.wasp.zookeeper;
  
  import com.alibaba.wasp.protobuf.generated.ZooKeeperProtos;
  import com.google.protobuf.InvalidProtocolBufferException;
  import org.apache.zookeeper.KeeperException;
  
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  
  /**
   * Non-instantiable class that provides helper functions for clients other than
   * {@link org.apache.hadoop.hbase.master.AssignmentManager} for reading the state of a table in ZK.
   *
   * <p>
   * Does not cache state like {@link ZKTable}, actually reads from ZK each call.
   */
  public class ZKTableReadOnly {
  
    private ZKTableReadOnly() {
    }
  
    /**
     * Go to zookeeper and see if state of table is {@link org.apache.hadoop.hbase.zookeeper.ZKTable.TableState#DISABLED}.
     * This method does not use cache as {@link #isDisabledTable(String)} does.
     * This method is for clients other than {@link org.apache.hadoop.hbase.master.AssignmentManager}
     *
     * @param zkw
     * @param tableName
     * @return True if table is enabled.
     * @throws org.apache.zookeeper.KeeperException
     */
    public static boolean isDisabledTable(final ZooKeeperWatcher zkw,
        final String tableName) throws KeeperException {
      ZooKeeperProtos.Table.State state = getTableState(zkw, tableName);
      return isTableState(ZooKeeperProtos.Table.State.DISABLED, state);
    }
  
    /**
     * Go to zookeeper and see if state of table is {@link org.apache.hadoop.hbase.zookeeper.ZKTable.TableState#ENABLED}.
     * This method does not use cache as {@link #isEnabledTable(String)} does.
     * This method is for clients other than {@link org.apache.hadoop.hbase.master.AssignmentManager}
     *
     * @param zkw
     * @param tableName
     * @return True if table is enabled.
     * @throws org.apache.zookeeper.KeeperException
     */
    public static boolean isEnabledTable(final ZooKeeperWatcher zkw,
        final String tableName) throws KeeperException {
      return getTableState(zkw, tableName) == ZooKeeperProtos.Table.State.ENABLED;
    }
  
    /**
     * Go to zookeeper and see if state of table is {@link org.apache.hadoop.hbase.zookeeper.ZKTable.TableState#DISABLING}
     * of {@link org.apache.hadoop.hbase.zookeeper.ZKTable.TableState#DISABLED}. This method does not use cache as
     * {@link #isEnabledTable(String)} does. This method is for clients other than
     * {@link org.apache.hadoop.hbase.master.AssignmentManager}.
     *
     * @param zkw
     * @param tableName
     * @return True if table is enabled.
     * @throws org.apache.zookeeper.KeeperException
     */
    public static boolean isDisablingOrDisabledTable(final ZooKeeperWatcher zkw,
        final String tableName) throws KeeperException {
      ZooKeeperProtos.Table.State state = getTableState(zkw, tableName);
      return isTableState(ZooKeeperProtos.Table.State.DISABLING, state)
          || isTableState(ZooKeeperProtos.Table.State.DISABLED, state);
    }
  
    /**
     * Gets a list of all the tables set as disabled in zookeeper.
     *
     * @return Set of disabled tables, empty Set if none
     * @throws org.apache.zookeeper.KeeperException
     */
    public static Set<String> getDisabledTables(ZooKeeperWatcher zkw)
        throws KeeperException {
      Set<String> disabledTables = new HashSet<String>();
      List<String> children = ZKUtil.listChildrenNoWatch(zkw, zkw.tableZNode);
      for (String child : children) {
        ZooKeeperProtos.Table.State state = getTableState(zkw, child);
        if (state == ZooKeeperProtos.Table.State.DISABLED)
          disabledTables.add(child);
      }
      return disabledTables;
    }
  
    /**
     * Gets a list of all the tables set as disabled in zookeeper.
     *
     * @return Set of disabled tables, empty Set if none
     * @throws org.apache.zookeeper.KeeperException
     */
    public static Set<String> getDisabledOrDisablingTables(ZooKeeperWatcher zkw)
        throws KeeperException {
      Set<String> disabledTables = new HashSet<String>();
      List<String> children = ZKUtil.listChildrenNoWatch(zkw, zkw.tableZNode);
      for (String child : children) {
        ZooKeeperProtos.Table.State state = getTableState(zkw, child);
        if (state == ZooKeeperProtos.Table.State.DISABLED
            || state == ZooKeeperProtos.Table.State.DISABLING)
          disabledTables.add(child);
      }
      return disabledTables;
    }
  
    static boolean isTableState(final ZooKeeperProtos.Table.State expectedState,
        final ZooKeeperProtos.Table.State currentState) {
      return currentState != null && currentState.equals(expectedState);
    }
  
    /**
     * @param zkw
     * @param child
     * @return Null or {@link org.apache.hadoop.hbase.zookeeper.ZKTable.TableState} found in znode.
     * @throws org.apache.zookeeper.KeeperException
     */
    static ZooKeeperProtos.Table.State getTableState(final ZooKeeperWatcher zkw,
        final String child) throws KeeperException {
      String znode = ZKUtil.joinZNode(zkw.tableZNode, child);
      byte[] data = ZKUtil.getData(zkw, znode);
      if (data == null || data.length <= 0)
        return null;
      try {
        ZooKeeperProtos.Table.Builder builder = ZooKeeperProtos.Table
            .newBuilder();
        ZooKeeperProtos.Table t = builder.mergeFrom(data, 0, data.length).build();
        return t.getState();
      } catch (InvalidProtocolBufferException e) {
        KeeperException ke = new KeeperException.DataInconsistencyException();
        ke.initCause(e);
        throw ke;
      }
    }
  }
  