content: /**
   * 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.storm.starter.bolt;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.storm.starter.tools.Rankings;
  
  import backtype.storm.Config;
  import backtype.storm.topology.BasicOutputCollector;
  import backtype.storm.topology.OutputFieldsDeclarer;
  import backtype.storm.topology.base.BaseBasicBolt;
  import backtype.storm.tuple.Fields;
  import backtype.storm.tuple.Tuple;
  import backtype.storm.tuple.Values;
  import backtype.storm.utils.TupleUtils;
  import org.slf4j.Logger;
  
  /**
   * This abstract bolt provides the basic behavior of bolts that rank objects
   * according to their count.
   * <p/>
   * It uses a template method design pattern for
   * {@link AbstractRankerBolt#execute(Tuple, BasicOutputCollector)} to allow
   * actual bolt implementations to specify how incoming tuples are processed,
   * i.e. how the objects embedded within those tuples are retrieved and counted.
   */
  public abstract class AbstractRankerBolt extends BaseBasicBolt {
      
      private static final long serialVersionUID                  = 4931640198501530202L;
      private static final int  DEFAULT_EMIT_FREQUENCY_IN_SECONDS = 2;
      private static final int  DEFAULT_COUNT                     = 10;
      
      private final int      emitFrequencyInSeconds;
      private final int      count;
      private final Rankings rankings;
      
      public AbstractRankerBolt() {
          this(DEFAULT_COUNT, DEFAULT_EMIT_FREQUENCY_IN_SECONDS);
      }
      
      public AbstractRankerBolt(int topN) {
          this(topN, DEFAULT_EMIT_FREQUENCY_IN_SECONDS);
      }
      
      public AbstractRankerBolt(int topN, int emitFrequencyInSeconds) {
          if (topN < 1) {
              throw new IllegalArgumentException("topN must be >= 1 (you requested " + topN + ")");
          }
          if (emitFrequencyInSeconds < 1) {
              throw new IllegalArgumentException(
                      "The emit frequency must be >= 1 seconds (you requested " + emitFrequencyInSeconds + " seconds)");
          }
          count = topN;
          this.emitFrequencyInSeconds = emitFrequencyInSeconds;
          rankings = new Rankings(count);
      }
      
      protected Rankings getRankings() {
          return rankings;
      }
      
      /**
       * This method functions as a template method (design pattern).
       */
      @Override
      public final void execute(Tuple tuple, BasicOutputCollector collector) {
          if (TupleUtils.isTick(tuple)) {
              getLogger().debug("Received tick tuple, triggering emit of current rankings");
              emitRankings(collector);
          } else {
              updateRankingsWithTuple(tuple);
          }
      }
      
      abstract void updateRankingsWithTuple(Tuple tuple);
      
      private void emitRankings(BasicOutputCollector collector) {
          collector.emit(new Values(rankings.copy()));
          getLogger().debug("Rankings: " + rankings);
      }
      
      @Override
      public void declareOutputFields(OutputFieldsDeclarer declarer) {
          declarer.declare(new Fields("rankings"));
      }
      
      @Override
      public Map<String, Object> getComponentConfiguration() {
          Map<String, Object> conf = new HashMap<String, Object>();
          conf.put(Config.TOPOLOGY_TICK_TUPLE_FREQ_SECS, emitFrequencyInSeconds);
          return conf;
      }
      
      abstract Logger getLogger();
  }
  