/*
    * 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.chukwa.datacollection.agent;
  
  import java.util.Collections;
  import java.util.Map;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.chukwa.datacollection.adaptor.Adaptor;
  import org.apache.hadoop.chukwa.datacollection.adaptor.AdaptorShutdownPolicy;
  
  /**
   * The interface to the agent that is exposed to adaptors.
   *
   */
  public interface AdaptorManager {
    
  
    Configuration getConfiguration();
    int adaptorCount();
    @Deprecated
    long stopAdaptor(String id, boolean gracefully);
    
  
    long stopAdaptor(String id, AdaptorShutdownPolicy mode);
    Adaptor getAdaptor(String id);
    String processAddCommand(String cmd);
    Map<String, String> getAdaptorList();
    
    /**
     * Called to update the Agent status table.
     * 
     * Most adaptors should not call this. It is designed for adaptors that do
     * some sort of local operation that needs checkpointing, but that doesn't
     * emit chunks.  For instance, DirTailingAdaptor uses it to track sweeps. 
     *  
     * @param src the adaptor in question
     * @param uuid the number to record as checkpoint.  Must be monotonically increasing.
     * @return the adaptor ID of the associated adaptor, or null if not running.
     */
    public String reportCommit(Adaptor src, long uuid);
  
    static AdaptorManager NULL = new AdaptorManager() {
  
      @Override
      public int adaptorCount() {
        return 0;
      }
  
      @Override
      public Adaptor getAdaptor(String id) {
        return null;
      }
  
      @Override
      public Map<String, String> getAdaptorList() {
        return Collections.emptyMap();
      }
  
      @Override
      public Configuration getConfiguration() {
        return new Configuration();
      }
  
      @Override
      public String processAddCommand(String cmd) {
        return "";
      }
  
      public long stopAdaptor(String id, boolean gracefully) {
        return 0;
      }
  
      @Override
      public long stopAdaptor(String id, AdaptorShutdownPolicy mode) {
        return 0;
      }
      
      @Override
      public String reportCommit(Adaptor a, long l) {
        return null;
      }
    };
    
  }