library/src/main/java/com/datatorrent/lib/algo/FilterKeysHashMap.java

/*
 * Copyright (c) 2013 DataTorrent, Inc. ALL Rights Reserved.
 *
 * Licensed 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 com.datatorrent.lib.algo;

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

import javax.validation.constraints.NotNull;

import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.annotation.OperatorAnnotation;
import com.datatorrent.api.annotation.Stateless;

import com.datatorrent.lib.util.BaseKeyOperator;


/**
 * This operator filters the incoming stream of key value pairs based on the keys specified by property "keys".
 * <p>
 * Filters the incoming stream based of keys specified by property "keys". If
 * property "inverse" is set to "true", then all keys except those specified by "keys" are emitted
 * </p>
 * <p>
 * Operator assumes that the key, val pairs are immutable objects. If this operator has to be used for mutable objects,
 * override "cloneKey()" to make copy of K, and "cloneValue()" to make copy of V.<br>
 * This is a pass through node.<br>
 * <br>
 * <b>StateFull : No, </b> tuple are processed in current window. <br>
 * <b>Partitions : Yes, </b> no dependency among input tuples. <br>
 * <br>
 * <b>Ports</b>:<br>
 * <b>data</b>: Expects Map&lt;K, HashMap&lt;K,V&gt;&gt. Filters are applied only on keys of second hash map.<br>
 * <b>filter</b>: Emits HashMap&lt;K, HashMap&lt;K,V&gt;&gt.<br>
 * <br>
 * <b>Properties</b>:<br>
 * <b>keys</b>: The keys to pass through, rest are filtered/dropped. A comma separated list of keys.<br>
 * <br>
 * </p>
 *
 * @displayName Filter Keyval Pairs By Key HashMap
 * @category Algorithmic
 * @tags filter, key value
 *
 * @since 0.3.2
 */
@Stateless
@OperatorAnnotation(partitionable = true)
public class FilterKeysHashMap<K, V> extends BaseKeyOperator<K>
{
  /**
   * Filter keys map.
   */
  @NotNull()
  HashMap<K, V> keys = new HashMap<K, V>();

  /**
   * Emits key not in filter map.
   */
  boolean inverse = false;

  /**
   * The input port on which key value pairs are received.
   */
  public final transient DefaultInputPort<Map<K, HashMap<K, V>>> data = new DefaultInputPort<Map<K, HashMap<K, V>>>()
  {
    /**
     * Processes incoming tuples one key,val at a time. Emits if at least one key makes the cut.
     * By setting inverse as true, match is changed to un-matched.
     */
    @Override
    public void process(Map<K, HashMap<K, V>> tuple)
    {
      HashMap<K, HashMap<K, V>> dtuple = null;
      for (Map.Entry<K, HashMap<K, V>> e: tuple.entrySet()) {
        HashMap<K, V> dtuple2 = null;
        for (Map.Entry<K, V> e2: e.getValue().entrySet()) {
          boolean contains = keys.containsKey(e2.getKey());
          if ((contains && !inverse) || (!contains && inverse)) {
            if (dtuple2 == null) {
              dtuple2 = new HashMap<K, V>(4); // usually the filter keys are very few, so 4 is just fine
            }
            dtuple2.put(cloneKey(e2.getKey()), cloneValue(e2.getValue()));
          }
        }
        if (dtuple == null && dtuple2 != null){
          dtuple = new HashMap<K, HashMap<K, V>>();
        }
        if (dtuple != null && dtuple2 != null){
          dtuple.put(cloneKey(e.getKey()), dtuple2);
        }
      }
      if (dtuple != null) {
        filter.emit(dtuple);
      }
    }
  };

  /**
   * The output port on which filtered key value pairs are emitted.
   */
  public final transient DefaultOutputPort<HashMap<K, HashMap<K, V>>> filter = new DefaultOutputPort<HashMap<K, HashMap<K, V>>>();

  /**
   * getter function for parameter inverse
   *
   * @return inverse
   */
  public boolean getInverse()
  {
    return inverse;
  }

  /**
   * True means match; False means unmatched
   *
   * @param val
   */
  public void setInverse(boolean val)
  {
    inverse = val;
  }

  /**
   * Adds a key to the filter list
   *
   * @param str
   */
  public void setKey(K str)
  {
    keys.put(str, null);
  }

  /**
   * Adds the list of keys to the filter list
   *
   * @param list
   */
  public void setKeys(K[] list)
  {
    if (list != null) {
      for (K e: list) {
        keys.put(e, null);
      }
    }
  }

  /*
   * Clears the filter list
   */
  public void clearKeys()
  {
    keys.clear();
  }

  /**
   * Clones V object. By default assumes immutable object (i.e. a copy is not made). If object is mutable, override this method
   *
   * @param v value to be cloned
   * @return returns v as is (assumes immutable object)
   */
  public V cloneValue(V v)
  {
    return v;
  }
}