/**
    *
    * 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.io.IOException;
  import java.io.InterruptedIOException;
  import java.util.Arrays;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.CoordinatedStateException;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.TableStateManager;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  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;
  
  /**
   * Implementation of TableStateManager which reads, caches and sets state
   * up in ZooKeeper.  If multiple read/write clients, will make for confusion.
   * Code running on client side without consensus context should use
   * {@link ZKTableStateClientSideReader} instead.
   *
   * <p>To save on trips to the zookeeper ensemble, internally we cache table
   * state.
   */
  @InterfaceAudience.Private
  public class ZKTableStateManager implements TableStateManager {
    // A znode will exist under the table directory if it is in any of the
    // following states: {@link TableState#ENABLING} , {@link TableState#DISABLING},
    // or {@link TableState#DISABLED}.  If {@link TableState#ENABLED}, there will
    // be no entry for a table in zk.  Thats how it currently works.
  
    private static final Log LOG = LogFactory.getLog(ZKTableStateManager.class);
    private final ZooKeeperWatcher watcher;
  
    /**
     * Cache of what we found in zookeeper so we don't have to go to zk ensemble
     * for every query.  Synchronize access rather than use concurrent Map because
     * synchronization needs to span query of zk.
     */
    private final Map<TableName, ZooKeeperProtos.Table.State> cache =
      new HashMap<TableName, ZooKeeperProtos.Table.State>();
  
    public ZKTableStateManager(final ZooKeeperWatcher zkw) throws KeeperException,
        InterruptedException {
      super();
      this.watcher = zkw;
      populateTableStates();
    }
  
    /**
     * Gets a list of all the tables set as disabled in zookeeper.
     * @throws KeeperException, InterruptedException
     */
    private void populateTableStates() throws KeeperException, InterruptedException {
      synchronized (this.cache) {
        List<String> children = ZKUtil.listChildrenNoWatch(this.watcher, this.watcher.tableZNode);
        if (children == null) return;
        for (String child: children) {
          TableName tableName = TableName.valueOf(child);
          ZooKeeperProtos.Table.State state = getTableState(this.watcher, tableName);
          if (state != null) this.cache.put(tableName, state);
        }
      }
    }
  
    /**
     * Sets table state in ZK. Sets no watches.
     *
     * {@inheritDoc}
     */
    @Override
    public void setTableState(TableName tableName, ZooKeeperProtos.Table.State state)
    throws CoordinatedStateException {
      synchronized (this.cache) {
       LOG.info("Moving table " + tableName + " state from " + this.cache.get(tableName)
         + " to " + state);
       try {
         setTableStateInZK(tableName, state);
       } catch (KeeperException e) {
         throw new CoordinatedStateException(e);
       }
     }
   }
 
   /**
    * Checks and sets table state in ZK. Sets no watches.
    * {@inheritDoc}
    */
   @Override
   public boolean setTableStateIfInStates(TableName tableName,
                                          ZooKeeperProtos.Table.State newState,
                                          ZooKeeperProtos.Table.State... states)
       throws CoordinatedStateException {
     synchronized (this.cache) {
       // Transition ENABLED->DISABLING has to be performed with a hack, because
       // we treat empty state as enabled in this case because 0.92- clusters.
       if (
           (newState == ZooKeeperProtos.Table.State.DISABLING) &&
                this.cache.get(tableName) != null && !isTableState(tableName, states) ||
           (newState != ZooKeeperProtos.Table.State.DISABLING &&
                !isTableState(tableName, states) )) {
         return false;
       }
       try {
         setTableStateInZK(tableName, newState);
       } catch (KeeperException e) {
         throw new CoordinatedStateException(e);
       }
       return true;
     }
   }
 
   /**
    * Checks and sets table state in ZK. Sets no watches.
    * {@inheritDoc}
    */
   @Override
   public boolean setTableStateIfNotInStates(TableName tableName,
                                             ZooKeeperProtos.Table.State newState,
                                             ZooKeeperProtos.Table.State... states)
     throws CoordinatedStateException {
     synchronized (this.cache) {
       if (isTableState(tableName, states)) {
         // If the table is in the one of the states from the states list, the cache
         // might be out-of-date, try to find it out from the master source (zookeeper server).
         //
         // Note: this adds extra zookeeper server calls and might have performance impact.
         // However, this is not the happy path so we should not reach here often. Therefore,
         // the performance impact should be minimal to none.
         try {
           ZooKeeperProtos.Table.State curstate = getTableState(watcher, tableName);
 
           if (isTableInState(Arrays.asList(states), curstate)) {
             return false;
           }
         } catch (KeeperException e) {
           throw new CoordinatedStateException(e);
         } catch (InterruptedException e) {
           throw new CoordinatedStateException(e);
         }
       }
       try {
         setTableStateInZK(tableName, newState);
       } catch (KeeperException e) {
         throw new CoordinatedStateException(e);
       }
       return true;
     }
   }
 
   private void setTableStateInZK(final TableName tableName,
                                  final ZooKeeperProtos.Table.State state)
       throws KeeperException {
     String znode = ZKUtil.joinZNode(this.watcher.tableZNode, tableName.getNameAsString());
     if (ZKUtil.checkExists(this.watcher, znode) == -1) {
       ZKUtil.createAndFailSilent(this.watcher, znode);
     }
     synchronized (this.cache) {
       ZooKeeperProtos.Table.Builder builder = ZooKeeperProtos.Table.newBuilder();
       builder.setState(state);
       byte [] data = ProtobufUtil.prependPBMagic(builder.build().toByteArray());
       ZKUtil.setData(this.watcher, znode, data);
       this.cache.put(tableName, state);
     }
   }
 
   /**
    * Checks if table is marked in specified state in ZK (using cache only). {@inheritDoc}
    */
   @Override
   public boolean isTableState(final TableName tableName,
       final ZooKeeperProtos.Table.State... states) {
     return isTableState(tableName, false, states); // only check cache
   }
 
   /**
    * Checks if table is marked in specified state in ZK. {@inheritDoc}
    */
   @Override
   public boolean isTableState(final TableName tableName, final boolean checkSource,
       final ZooKeeperProtos.Table.State... states) {
     boolean isTableInSpecifiedState;
     synchronized (this.cache) {
       ZooKeeperProtos.Table.State currentState = this.cache.get(tableName);
       if (checkSource) {
         // The cache might be out-of-date, try to find it out from the master source (zookeeper
         // server) and update the cache.
         try {
           ZooKeeperProtos.Table.State stateInZK = getTableState(watcher, tableName);
 
           if (currentState != stateInZK) {
             if (stateInZK != null) {
               this.cache.put(tableName, stateInZK);
             } else {
               this.cache.remove(tableName);
             }
             currentState = stateInZK;
           }
         } catch (KeeperException | InterruptedException e) {
           // Contacting zookeeper failed.  Let us just trust the value in cache.
         }
       }
       return isTableInState(Arrays.asList(states), currentState);
     }
   }
 
   /**
    * Deletes the table in zookeeper. Fails silently if the table is not currently disabled in
    * zookeeper. Sets no watches. {@inheritDoc}
    */
   @Override
   public void setDeletedTable(final TableName tableName)
   throws CoordinatedStateException {
     synchronized (this.cache) {
       if (this.cache.remove(tableName) == null) {
         LOG.warn("Moving table " + tableName + " state to deleted but was already deleted");
       }
       try {
         ZKUtil.deleteNodeFailSilent(this.watcher,
           ZKUtil.joinZNode(this.watcher.tableZNode, tableName.getNameAsString()));
       } catch (KeeperException e) {
         throw new CoordinatedStateException(e);
       }
     }
   }
 
   /**
    * check if table is present.
    *
    * @param tableName table we're working on
    * @return true if the table is present
    */
   @Override
   public boolean isTablePresent(final TableName tableName) {
     synchronized (this.cache) {
       ZooKeeperProtos.Table.State state = this.cache.get(tableName);
       return !(state == null);
     }
   }
 
   /**
    * Gets a list of all the tables set as disabling in zookeeper.
    * @return Set of disabling tables, empty Set if none
    * @throws CoordinatedStateException if error happened in underlying coordination engine
    */
   @Override
   public Set<TableName> getTablesInStates(ZooKeeperProtos.Table.State... states)
     throws InterruptedIOException, CoordinatedStateException {
     try {
       return getAllTables(states);
     } catch (KeeperException e) {
       throw new CoordinatedStateException(e);
     }
   }
 
   /**
    * {@inheritDoc}
    */
   @Override
   public void checkAndRemoveTableState(TableName tableName, ZooKeeperProtos.Table.State states,
                                        boolean deletePermanentState)
       throws CoordinatedStateException {
     synchronized (this.cache) {
       if (isTableState(tableName, states)) {
         this.cache.remove(tableName);
         if (deletePermanentState) {
           try {
             ZKUtil.deleteNodeFailSilent(this.watcher,
                 ZKUtil.joinZNode(this.watcher.tableZNode, tableName.getNameAsString()));
           } catch (KeeperException e) {
             throw new CoordinatedStateException(e);
           }
         }
       }
     }
   }
 
   /**
    * Gets a list of all the tables of specified states in zookeeper.
    * @return Set of tables of specified states, empty Set if none
    * @throws KeeperException
    */
   Set<TableName> getAllTables(final ZooKeeperProtos.Table.State... states)
       throws KeeperException, InterruptedIOException {
 
     Set<TableName> allTables = new HashSet<TableName>();
     List<String> children =
       ZKUtil.listChildrenNoWatch(watcher, watcher.tableZNode);
     if(children == null) return allTables;
     for (String child: children) {
       TableName tableName = TableName.valueOf(child);
       ZooKeeperProtos.Table.State state;
       try {
         state = getTableState(watcher, tableName);
       } catch (InterruptedException e) {
         throw new InterruptedIOException();
       }
       for (ZooKeeperProtos.Table.State expectedState: states) {
         if (state == expectedState) {
           allTables.add(tableName);
           break;
         }
       }
     }
     return allTables;
   }
 
   /**
    * Gets table state from ZK.
    * @param zkw ZooKeeperWatcher instance to use
    * @param tableName table we're checking
    * @return Null or {@link ZooKeeperProtos.Table.State} found in znode.
    * @throws KeeperException
    */
   private 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);
     }
   }
 
   /**
    * @return true if current state isn't null and is contained
    * in the list of expected states.
    */
   private boolean isTableInState(final List<ZooKeeperProtos.Table.State> expectedStates,
                        final ZooKeeperProtos.Table.State currentState) {
     return currentState != null && expectedStates.contains(currentState);
   }
 }