/**
    *
    * 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.master.handler;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.Set;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.Server;
  import org.apache.hadoop.hbase.executor.EventType;
  import org.apache.hadoop.hbase.master.HMaster;
  import org.apache.hadoop.hbase.master.MasterCoprocessorHost;
  import org.apache.hadoop.hbase.master.MasterFileSystem;
  import org.apache.hadoop.hbase.master.MasterServices;
  import org.apache.hadoop.hbase.util.Bytes;
  
  @InterfaceAudience.Private
  public class ModifyTableHandler extends TableEventHandler {
    private static final Log LOG = LogFactory.getLog(ModifyTableHandler.class);
  
    private final HTableDescriptor htd;
  
    public ModifyTableHandler(final byte [] tableName,
        final HTableDescriptor htd, final Server server,
        final MasterServices masterServices) {
      super(EventType.C_M_MODIFY_TABLE, tableName, server, masterServices);
      // This is the new schema we are going to write out as this modification.
      this.htd = htd;
    }
  
    @Override
    protected void prepareWithTableLock() throws IOException {
      super.prepareWithTableLock();
      // Check table exists.
      getTableDescriptor();
    }
  
    @Override
    protected void handleTableOperation(List<HRegionInfo> hris)
    throws IOException {
      MasterCoprocessorHost cpHost = ((HMaster) this.server).getCoprocessorHost();
      if (cpHost != null) {
        cpHost.preModifyTableHandler(this.tableName, this.htd);
      }
      // Update descriptor
      HTableDescriptor oldHtd = getTableDescriptor();
      this.masterServices.getTableDescriptors().add(this.htd);
      deleteFamilyFromFS(hris, oldHtd.getFamiliesKeys());
      if (cpHost != null) {
        cpHost.postModifyTableHandler(this.tableName, this.htd);
      }
    }
  
    /**
     * Removes from hdfs the families that are not longer present in the new table descriptor.
     */
    private void deleteFamilyFromFS(final List<HRegionInfo> hris, final Set<byte[]> oldFamilies) {
      try {
        Set<byte[]> newFamilies = this.htd.getFamiliesKeys();
        MasterFileSystem mfs = this.masterServices.getMasterFileSystem();
        for (byte[] familyName: oldFamilies) {
          if (!newFamilies.contains(familyName)) {
            LOG.debug("Removing family=" + Bytes.toString(familyName) +
                      " from table=" + this.tableName);
            for (HRegionInfo hri: hris) {
              // Delete the family directory in FS for all the regions one by one
              mfs.deleteFamilyFromFS(hri, familyName);
            }
          }
        }
      } catch (IOException e) {
        LOG.warn("Unable to remove on-disk directories for the removed families", e);
      }
    }
  
    @Override
    public String toString() {
      String name = "UnknownServerName";
     if(server != null && server.getServerName() != null) {
       name = server.getServerName().toString();
     }
     return getClass().getSimpleName() + "-" + name + "-" + getSeqid() + "-" +
       tableNameStr;
   }
 }