/**
 * 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.hdfs.server.namenode;

/**
 * Context for an ongoing SaveNamespace operation. This class
 * allows cancellation.
 */
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.hadoop.hdfs.server.common.HdfsConstants;
import org.apache.hadoop.hdfs.server.common.Storage.StorageDirectory;
import org.apache.hadoop.hdfs.util.InjectionEvent;
import org.apache.hadoop.util.InjectionHandler;

/**
 * Context for an ongoing SaveNamespace operation. This class
 * allows cancellation, and also is responsible for accumulating
 * failed storage directories.
 */
class SaveNamespaceContext {
  private FSNamesystem sourceNamesystem;
  private long txid = HdfsConstants.INVALID_TXID;
  private List<StorageDirectory> errorSDs =
    Collections.synchronizedList(new ArrayList<StorageDirectory>());
  
  /**
   * If the operation has been canceled, set to the reason why
   * it has been canceled (eg standby moving to active)
   */
  private volatile String cancelReason = null;
  
  private int numFailures = 0;
  
  SaveNamespaceContext() {}

  FSNamesystem getSourceNamesystem() {
    return sourceNamesystem;
  }

  long getTxId() {
    return txid;
  }
  
  public void set(FSNamesystem sourceNamesystem, long txid) {
    this.sourceNamesystem = sourceNamesystem;
    this.txid = txid;
  }

  synchronized void reportErrorOnStorageDirectory(StorageDirectory sd) {
    if (sd != null)
      errorSDs.add(sd);
    numFailures++;
  }
  
  synchronized int getNumFailures() {
    return numFailures;
  }

  List<StorageDirectory> getErrorSDs() {
    return errorSDs;
  }
  
  /**
   * Requests that the current saveNamespace operation be
   * canceled if it is still running.
   */
  void cancel(String reason) {
    this.cancelReason = reason;
  }

  void checkCancelled() throws SaveNamespaceCancelledException {
    if (cancelReason != null) {
      InjectionHandler
          .processEvent(InjectionEvent.SAVE_NAMESPACE_CONTEXT_EXCEPTION);
      throw new SaveNamespaceCancelledException(
          cancelReason);
    }
  }

  boolean isCancelled() {
    return cancelReason != null;
  }
  
  public void clear() {
    this.cancelReason = null;
    this.sourceNamesystem = null;
    this.txid = HdfsConstants.INVALID_TXID;
    this.errorSDs.clear();
    this.numFailures = 0;
  }
}