/**
    *
    * 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 org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.CoordinatedStateException;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.Server;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.MetaTableAccessor;
  import org.apache.hadoop.hbase.master.AssignmentManager;
  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.protobuf.generated.ZooKeeperProtos;
  import org.apache.hadoop.hbase.util.FSTableDescriptors;
  import org.apache.hadoop.hbase.util.FSUtils;
  import org.apache.hadoop.hbase.util.ModifyRegionUtils;
  
  /**
   * Truncate the table by removing META and the HDFS files and recreating it.
   * If the 'preserveSplits' option is set to true, the region splits are preserved on recreate.
   *
   * If the operation fails in the middle it may require hbck to fix the system state.
   */
  @InterfaceAudience.Private
  public class TruncateTableHandler extends DeleteTableHandler {
    private static final Log LOG = LogFactory.getLog(TruncateTableHandler.class);
  
    private final boolean preserveSplits;
  
    public TruncateTableHandler(final TableName tableName, final Server server,
        final MasterServices masterServices, boolean preserveSplits) {
      super(tableName, server, masterServices);
      this.preserveSplits = preserveSplits;
    }
  
    @Override
    protected void handleTableOperation(List<HRegionInfo> regions)
        throws IOException, CoordinatedStateException {
      MasterCoprocessorHost cpHost = ((HMaster) this.server).getMasterCoprocessorHost();
      if (cpHost != null) {
        cpHost.preTruncateTableHandler(this.tableName);
      }
  
      // 1. Wait because of region in transition
      waitRegionInTransition(regions);
  
      // 2. Remove table from hbase:meta and HDFS
      removeTableData(regions);
  
      // -----------------------------------------------------------------------
      // PONR: At this point the table is deleted.
      //       If the recreate fails, the user can only re-create the table.
      // -----------------------------------------------------------------------
  
      // 3. Recreate the regions
      recreateTable(regions);
  
      if (cpHost != null) {
        cpHost.postTruncateTableHandler(this.tableName);
      }
    }
  
    private void recreateTable(final List<HRegionInfo> regions) throws IOException {
      MasterFileSystem mfs = this.masterServices.getMasterFileSystem();
      Path tempdir = mfs.getTempDir();
      FileSystem fs = mfs.getFileSystem();
  
      AssignmentManager assignmentManager = this.masterServices.getAssignmentManager();
  
      // 1. Set table znode
      CreateTableHandler.checkAndSetEnablingTable(assignmentManager, tableName, false);
      try {
        // 1. Create Table Descriptor
       Path tempTableDir = FSUtils.getTableDir(tempdir, this.tableName);
       new FSTableDescriptors(server.getConfiguration())
         .createTableDescriptorForTableDirectory(tempTableDir, this.hTableDescriptor, false);
       Path tableDir = FSUtils.getTableDir(mfs.getRootDir(), this.tableName);
 
       HRegionInfo[] newRegions;
       if (this.preserveSplits) {
         newRegions = recreateRegionInfo(regions);
         LOG.info("Truncate will preserve " + newRegions.length + " regions");
       } else {
         newRegions = new HRegionInfo[1];
         newRegions[0] = new HRegionInfo(this.tableName, null, null);
         LOG.info("Truncate will not preserve the regions");
       }
 
       // 2. Create Regions
       List<HRegionInfo> regionInfos = ModifyRegionUtils.createRegions(
         masterServices.getConfiguration(), tempdir,
         this.hTableDescriptor, newRegions, null);
 
       // 3. Move Table temp directory to the hbase root location
       if (!fs.rename(tempTableDir, tableDir)) {
         throw new IOException("Unable to move table from temp=" + tempTableDir +
           " to hbase root=" + tableDir);
       }
 
       // 4. Add regions to META
       MetaTableAccessor.addRegionsToMeta(masterServices.getConnection(),
         regionInfos, hTableDescriptor.getRegionReplication());
 
       // 5. Trigger immediate assignment of the regions in round-robin fashion
       ModifyRegionUtils.assignRegions(assignmentManager, regionInfos);
 
       // 6. Set table enabled flag up in zk.
       try {
         assignmentManager.getTableStateManager().setTableState(tableName,
           ZooKeeperProtos.Table.State.ENABLED);
       } catch (CoordinatedStateException e) {
         throw new IOException("Unable to ensure that " + tableName + " will be" +
           " enabled because of a ZooKeeper issue", e);
       }
     } catch (IOException e) {
       CreateTableHandler.removeEnablingTable(assignmentManager, tableName);
       throw e;
     }
   }
 
   private static HRegionInfo[] recreateRegionInfo(final List<HRegionInfo> regions) {
     HRegionInfo[] newRegions = new HRegionInfo[regions.size()];
     int index = 0;
     for (HRegionInfo hri: regions) {
       newRegions[index++] = new HRegionInfo(hri.getTable(), hri.getStartKey(), hri.getEndKey());
     }
     return newRegions;
   }
 }