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/**
 * 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 com.datatorrent.lib.algo;

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

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

import com.datatorrent.lib.util.BaseKeyValueOperator;
import com.datatorrent.lib.util.UnifierHashMap;

/**
 * This operator computes and emits distinct key,val pairs (i.e drops duplicates).
 * 
 * Computes and emits distinct key,val pairs (i.e drops duplicates)
 * 
 * 
 * This is a pass through operator

 * 

 * This module is same as a "FirstOf" metric on any key,val pair. At end of window all data is flushed.

 * 

 * StateFull : Yes,  tuple are compare across application window(s). 

 * Partitions : Yes,  distinct output is unified by unifier hash map operator. 

 * 

 * Ports:

 * data: Input data port expects Map<K,V>

 * distinct: Output data port, emits HashMap<K,V>(1)

 * 

 * 
 *
 * @displayName Distinct Key Value Merge
 * @category Stream Manipulators
 * @tags filter, unique, key value
 *
 * @since 0.3.2
 */

@OperatorAnnotation(partitionable = true)
public class DistinctMap extends BaseKeyValueOperator
{
  /**
   * The input port on which key value pairs are received.
   */
  public final transient DefaultInputPort> data = new DefaultInputPort>()
  {
    /**
     * Process HashMap tuple on input port data, and emits if match not found. Updates the cache
     * with new key,val pair
     */
    @Override
    public void process(Map tuple)
    {
      for (Map.Entry e: tuple.entrySet()) {
        HashMap vals = mapkeyval.get(e.getKey());
        if ((vals == null) || !vals.containsKey(e.getValue())) {
          HashMap otuple = new HashMap(1);
          otuple.put(cloneKey(e.getKey()), cloneValue(e.getValue()));
          distinct.emit(otuple);
          if (vals == null) {
            vals = new HashMap();
            mapkeyval.put(cloneKey(e.getKey()), vals);
          }
          vals.put(cloneValue(e.getValue()), null);
        }
      }
    }
  };

  /**
   * The output port on which distinct key value pairs are emitted.
   */
  public final transient DefaultOutputPort> distinct = new DefaultOutputPort>()
  {
    @Override
    public Unifier> getUnifier()
    {
      return new UnifierHashMap();
    }
  };


  protected HashMap> mapkeyval = new HashMap>();

  /**
   * Clears the cache/hash
   */
  @Override
  public void endWindow()
  {
    mapkeyval.clear();
  }
}