library/src/main/java/org/apache/apex/malhar/lib/util/AbstractBaseNUniqueOperatorMap.java

/**
 * 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.apex.malhar.lib.util;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

/**
 * This is the base implementation of an operator,
 * which orders tuples per key and emits the top N unique tuples per key at the end of the window. 
 * Subclasses should implement the methods which control the ordering and emission of tuples.
 * <p></p>
 * @displayName Abstract Base N Unique Map
 * @category Algorithmic
 * @tags rank
 * @since 0.3.2
 */
public abstract class AbstractBaseNUniqueOperatorMap<K, V> extends AbstractBaseNOperatorMap<K, V>
{
  HashMap<K, TopNUniqueSort<V>> kmap = new HashMap<K, TopNUniqueSort<V>>();

  /**
   * Override to decide the direction (ascending vs descending)
   * @return true if ascending
   */
  public abstract boolean isAscending();

  /**
   * Override to decide which port to emit to and its schema
   * @param tuple
   */
  public abstract void emit(HashMap<K, ArrayList<HashMap<V,Integer>>> tuple);

  /**
   * Inserts tuples into the queue
   *
   * @param tuple to insert in the queue
   */
  @Override
  public void processTuple(Map<K, V> tuple)
  {
    for (Map.Entry<K, V> e: tuple.entrySet()) {

      TopNUniqueSort<V> pqueue = kmap.get(e.getKey());
      if (pqueue == null) {
        pqueue = new TopNUniqueSort<V>(5, n, isAscending());
        kmap.put(cloneKey(e.getKey()), pqueue);
        pqueue.offer(cloneValue(e.getValue()));
      } else {
        pqueue.offer(cloneValue(e.getValue()));
      }
    }
  }

  /**
   * Emits the result
   */
  @SuppressWarnings("unchecked")
  @Override
  public void endWindow()
  {
    for (Map.Entry<K, TopNUniqueSort<V>> e: kmap.entrySet()) {
      HashMap<K, ArrayList<HashMap<V,Integer>>> tuple = new HashMap<K, ArrayList<HashMap<V,Integer>>>(1);
      tuple.put(e.getKey(), e.getValue().getTopN(getN()));
      emit(tuple);
    }
    kmap.clear();
  }
}