/**
    * 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 org.apache.hadoop.hbase.zookeeper;
  
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.TableName;
  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.zookeeper.KeeperException;
  
  import java.io.IOException;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Set;
  
  /**
   * Non-instantiable class that provides helper functions to learn
   * about HBase table state for code running on client side (hence, not having
   * access to consensus context).
   *
   * Doesn't cache any table state, just goes directly to ZooKeeper.
   * TODO: decouple this class from ZooKeeper.
   */
  @InterfaceAudience.Private
  public class ZKTableStateClientSideReader {
  
    private ZKTableStateClientSideReader() {}
    
    /**
     * Go to zookeeper and see if state of table is {@code ZooKeeperProtos.Table.State#DISABLED}.
     * This method does not use cache.
     * This method is for clients other than AssignmentManager
     * @param zkw ZooKeeperWatcher instance to use
     * @param tableName table we're checking
     * @return True if table is enabled.
     * @throws KeeperException
     */
    public static boolean isDisabledTable(final ZooKeeperWatcher zkw,
        final TableName tableName)
        throws KeeperException, InterruptedException {
      ZooKeeperProtos.Table.State state = getTableState(zkw, tableName);
      return isTableState(ZooKeeperProtos.Table.State.DISABLED, state);
    }
  
    /**
     * Go to zookeeper and see if state of table is {@code ZooKeeperProtos.Table.State#ENABLED}.
     * This method does not use cache.
     * This method is for clients other than AssignmentManager
     * @param zkw ZooKeeperWatcher instance to use
     * @param tableName table we're checking
     * @return True if table is enabled.
     * @throws KeeperException
     */
    public static boolean isEnabledTable(final ZooKeeperWatcher zkw,
        final TableName tableName)
        throws KeeperException, InterruptedException {
      return getTableState(zkw, tableName) == ZooKeeperProtos.Table.State.ENABLED;
    }
  
    /**
     * Go to zookeeper and see if state of table is {@code ZooKeeperProtos.Table.State#DISABLING}
     * of {@code ZooKeeperProtos.Table.State#DISABLED}.
     * This method does not use cache.
     * This method is for clients other than AssignmentManager.
     * @param zkw ZooKeeperWatcher instance to use
     * @param tableName table we're checking
     * @return True if table is enabled.
     * @throws KeeperException
     */
    public static boolean isDisablingOrDisabledTable(final ZooKeeperWatcher zkw,
        final TableName tableName)
        throws KeeperException, InterruptedException {
      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 KeeperException
    */
   public static Set<TableName> getDisabledTables(ZooKeeperWatcher zkw)
       throws KeeperException, InterruptedException {
     Set<TableName> disabledTables = new HashSet<TableName>();
     List<String> children =
       ZKUtil.listChildrenNoWatch(zkw, zkw.tableZNode);
     for (String child: children) {
       TableName tableName =
           TableName.valueOf(child);
       ZooKeeperProtos.Table.State state = getTableState(zkw, tableName);
       if (state == ZooKeeperProtos.Table.State.DISABLED) disabledTables.add(tableName);
     }
     return disabledTables;
   }
 
   /**
    * Gets a list of all the tables set as disabled in zookeeper.
    * @return Set of disabled tables, empty Set if none
    * @throws KeeperException
    */
   public static Set<TableName> getDisabledOrDisablingTables(ZooKeeperWatcher zkw)
       throws KeeperException, InterruptedException {
     return
         getTablesInStates(
           zkw,
           ZooKeeperProtos.Table.State.DISABLED,
           ZooKeeperProtos.Table.State.DISABLING);
   }
 
   /**
    * Gets a list of all the tables set as enabling in zookeeper.
    * @param zkw ZooKeeperWatcher instance to use
    * @return Set of enabling tables, empty Set if none
    * @throws KeeperException
    * @throws InterruptedException
    */
   public static Set<TableName> getEnablingTables(ZooKeeperWatcher zkw)
       throws KeeperException, InterruptedException {
     return getTablesInStates(zkw, ZooKeeperProtos.Table.State.ENABLING);
   }
 
   /**
    * Gets a list of tables that are set as one of the passing in states in zookeeper.
    * @param zkw ZooKeeperWatcher instance to use
    * @param states the list of states that a table could be in
    * @return Set of tables in one of the states, empty Set if none
    * @throws KeeperException
    * @throws InterruptedException
    */
   private static Set<TableName> getTablesInStates(
     ZooKeeperWatcher zkw,
     ZooKeeperProtos.Table.State... states)
       throws KeeperException, InterruptedException {
     Set<TableName> tableNameSet = new HashSet<TableName>();
     List<String> children = ZKUtil.listChildrenNoWatch(zkw, zkw.tableZNode);
     TableName tableName;
     ZooKeeperProtos.Table.State tableState;
     for (String child: children) {
       tableName = TableName.valueOf(child);
       tableState = getTableState(zkw, tableName);
       for (ZooKeeperProtos.Table.State state : states) {
          if (tableState == state) {
            tableNameSet.add(tableName);
            break;
          }
       }
     }
     return tableNameSet;
   }
 
   static boolean isTableState(final ZooKeeperProtos.Table.State expectedState,
       final ZooKeeperProtos.Table.State currentState) {
     return currentState != null && currentState.equals(expectedState);
   }
 
   /**
    * @param zkw ZooKeeperWatcher instance to use
    * @param tableName table we're checking
    * @return Null or {@link ZooKeeperProtos.Table.State} found in znode.
    * @throws KeeperException
    */
   static ZooKeeperProtos.Table.State getTableState(final ZooKeeperWatcher zkw,
       final TableName tableName)
       throws KeeperException, InterruptedException {
     String znode = ZKUtil.joinZNode(zkw.tableZNode, tableName.getNameAsString());
     byte [] data = ZKUtil.getData(zkw, znode);
     if (data == null || data.length <= 0) return null;
     try {
       ProtobufUtil.expectPBMagicPrefix(data);
       ZooKeeperProtos.Table.Builder builder = ZooKeeperProtos.Table.newBuilder();
       int magicLen = ProtobufUtil.lengthOfPBMagic();
       ProtobufUtil.mergeFrom(builder, data, magicLen, data.length - magicLen);
       return builder.getState();
     } catch (IOException e) {
       KeeperException ke = new KeeperException.DataInconsistencyException();
       ke.initCause(e);
       throw ke;
     } catch (DeserializationException e) {
       throw ZKUtil.convert(e);
     }
   }
 }