/**
    *
    * 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.snapshot;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.concurrent.CancellationException;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.classification.InterfaceAudience;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  import org.apache.hadoop.hbase.HRegionInfo;
  import org.apache.hadoop.hbase.HTableDescriptor;
  import org.apache.hadoop.hbase.errorhandling.ForeignException;
  import org.apache.hadoop.hbase.errorhandling.ForeignExceptionDispatcher;
  import org.apache.hadoop.hbase.exceptions.NotAllMetaRegionsOnlineException;
  import org.apache.hadoop.hbase.exceptions.RestoreSnapshotException;
  import org.apache.hadoop.hbase.exceptions.TableExistsException;
  import org.apache.hadoop.hbase.master.MasterServices;
  import org.apache.hadoop.hbase.master.MetricsMaster;
  import org.apache.hadoop.hbase.master.SnapshotSentinel;
  import org.apache.hadoop.hbase.master.handler.CreateTableHandler;
  import org.apache.hadoop.hbase.monitoring.MonitoredTask;
  import org.apache.hadoop.hbase.monitoring.TaskMonitor;
  import org.apache.hadoop.hbase.protobuf.generated.HBaseProtos.SnapshotDescription;
  import org.apache.hadoop.hbase.snapshot.ClientSnapshotDescriptionUtils;
  import org.apache.hadoop.hbase.snapshot.RestoreSnapshotHelper;
  import org.apache.hadoop.hbase.snapshot.SnapshotDescriptionUtils;
  
  import com.google.common.base.Preconditions;
  
  /**
   * Handler to Clone a snapshot.
   *
   * <p>Uses {@link RestoreSnapshotHelper} to create a new table with the same
   * content of the specified snapshot.
   */
  @InterfaceAudience.Private
  public class CloneSnapshotHandler extends CreateTableHandler implements SnapshotSentinel {
    private static final Log LOG = LogFactory.getLog(CloneSnapshotHandler.class);
  
    private final static String NAME = "Master CloneSnapshotHandler";
  
    private final SnapshotDescription snapshot;
  
    private final ForeignExceptionDispatcher monitor;
    private final MetricsMaster metricsMaster;
    private final MonitoredTask status;
  
    private volatile boolean stopped = false;
  
    public CloneSnapshotHandler(final MasterServices masterServices,
        final SnapshotDescription snapshot, final HTableDescriptor hTableDescriptor,
        final MetricsMaster metricsMaster) {
      super(masterServices, masterServices.getMasterFileSystem(), hTableDescriptor,
        masterServices.getConfiguration(), null, masterServices);
      this.metricsMaster = metricsMaster;
  
      // Snapshot information
      this.snapshot = snapshot;
  
      // Monitor
      this.monitor = new ForeignExceptionDispatcher();
      this.status = TaskMonitor.get().createStatus("Cloning  snapshot '" + snapshot.getName() +
        "' to table " + hTableDescriptor.getNameAsString());
    }
  
    @Override
    public CloneSnapshotHandler prepare() throws NotAllMetaRegionsOnlineException,
        TableExistsException, IOException {
      return (CloneSnapshotHandler) super.prepare();
    }
  
    /**
     * Create the on-disk regions, using the tableRootDir provided by the CreateTableHandler.
     * The cloned table will be created in a temp directory, and then the CreateTableHandler
     * will be responsible to add the regions returned by this method to META and do the assignment.
     */
    @Override
    protected List<HRegionInfo> handleCreateHdfsRegions(final Path tableRootDir,
       final String tableName) throws IOException {
     status.setStatus("Creating regions for table: " + tableName);
     FileSystem fs = fileSystemManager.getFileSystem();
     Path rootDir = fileSystemManager.getRootDir();
     Path tableDir = new Path(tableRootDir, tableName);
 
     try {
       // 1. Execute the on-disk Clone
       Path snapshotDir = SnapshotDescriptionUtils.getCompletedSnapshotDir(snapshot, rootDir);
       RestoreSnapshotHelper restoreHelper = new RestoreSnapshotHelper(conf, fs,
           snapshot, snapshotDir, hTableDescriptor, tableDir, monitor, status);
       RestoreSnapshotHelper.RestoreMetaChanges metaChanges = restoreHelper.restoreHdfsRegions();
 
       // Clone operation should not have stuff to restore or remove
       Preconditions.checkArgument(!metaChanges.hasRegionsToRestore(),
           "A clone should not have regions to restore");
       Preconditions.checkArgument(!metaChanges.hasRegionsToRemove(),
           "A clone should not have regions to remove");
 
       // At this point the clone is complete. Next step is enabling the table.
       String msg = "Clone snapshot="+ snapshot.getName() +" on table=" + tableName + " completed!";
       LOG.info(msg);
       status.setStatus(msg + " Waiting for table to be enabled...");
 
       // 2. let the CreateTableHandler add the regions to meta
       return metaChanges.getRegionsToAdd();
     } catch (Exception e) {
       String msg = "clone snapshot=" + ClientSnapshotDescriptionUtils.toString(snapshot) +
         " failed because " + e.getMessage();
       LOG.error(msg, e);
       IOException rse = new RestoreSnapshotException(msg, e, snapshot);
 
       // these handlers aren't futures so we need to register the error here.
       this.monitor.receive(new ForeignException(NAME, rse));
       throw rse;
     }
   }
 
   @Override
   protected void completed(final Throwable exception) {
     this.stopped = true;
     if (exception != null) {
       status.abort("Snapshot '" + snapshot.getName() + "' clone failed because " +
           exception.getMessage());
     } else {
       status.markComplete("Snapshot '"+ snapshot.getName() +"' clone completed and table enabled!");
     }
     metricsMaster.addSnapshotClone(status.getCompletionTimestamp() - status.getStartTime());
     super.completed(exception);
   }
 
   @Override
   public boolean isFinished() {
     return this.stopped;
   }
 
   @Override
   public long getCompletionTimestamp() {
     return this.status.getCompletionTimestamp();
   }
 
   @Override
   public SnapshotDescription getSnapshot() {
     return snapshot;
   }
 
   @Override
   public void cancel(String why) {
     if (this.stopped) return;
     this.stopped = true;
     String msg = "Stopping clone snapshot=" + snapshot + " because: " + why;
     LOG.info(msg);
     status.abort(msg);
     this.monitor.receive(new ForeignException(NAME, new CancellationException(why)));
   }
 
   @Override
   public ForeignException getExceptionIfFailed() {
     return this.monitor.getException();
   }
 
   @Override
   public void rethrowExceptionIfFailed() throws ForeignException {
     monitor.rethrowException();
   }
 }