library/src/main/java/com/datatorrent/lib/math/ChangeKeyVal.java

/*
 * Copyright (c) 2013 Malhar 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.math;

import java.util.HashMap;

import org.apache.commons.lang.mutable.MutableDouble;

import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.annotation.InputPortFieldAnnotation;
import com.datatorrent.api.annotation.OutputPortFieldAnnotation;
import com.datatorrent.lib.util.BaseNumberKeyValueOperator;
import com.datatorrent.lib.util.KeyValPair;

/**
 * <p>
 * Operator takes input from two ports data port and base value. Operator stores kay/value pair arriving at input
 * port in  base map across the windows. For key/value pair arriving at data port are compared with stored value if
 * key exists in base map. Change value/percent are emitted on separate ports.
 * <p>
 * StateFull : Yes, base map values are stored across windows. <br>
 * Partitions : No, Base value won;t be consistent across windows.
 * <br>
 * <b>Ports</b>:<br>
 * <b>data</b>: expects KeyValPair&lt;K,V extends Number&gt;<br>
 * <b>base</b>: expects KeyValPair&lt;K,V extends Number&gt;<br>
 * <b>change</b>: emits KeyValPair&lt;K,V&gt;(1)<br>
 * <b>percent</b>: emits KeyValPair&lt;K,Double&gt;(1)<br>
 * <br>
 * <br>
 * <b>Properties</b>:<br>
 * <b>inverse</b>: if set to true the key in the filter will block tuple<br>
 * <b>filterBy</b>: List of keys to filter on<br>
 *
 * @since 0.3.3
 */
public class ChangeKeyVal<K, V extends Number> extends
		BaseNumberKeyValueOperator<K, V>
{
	/**
	 * basemap is a stateful field. It is retained across windows
	 */
	private HashMap<K, MutableDouble> basemap = new HashMap<K, MutableDouble>();
	
	/**
	 * Data tuples input port.
	 */
	@InputPortFieldAnnotation(name = "data")
	public final transient DefaultInputPort<KeyValPair<K, V>> data = new DefaultInputPort<KeyValPair<K, V>>()
	{
		/**
		 * Process each key, compute change or percent, and emit it.
		 */
		@Override
		public void process(KeyValPair<K, V> tuple)
		{
			K key = tuple.getKey();
			if (!doprocessKey(key)) {
				return;
			}
			MutableDouble bval = basemap.get(key);
			if (bval != null) { // Only process keys that are in the basemap
				double cval = tuple.getValue().doubleValue() - bval.doubleValue();
				change.emit(new KeyValPair<K, V>(cloneKey(key), getValue(cval)));
				percent.emit(new KeyValPair<K, Double>(cloneKey(key), (cval / bval
						.doubleValue()) * 100));
			}
		}
	};
	
	/**
	 * Base value port, stored in base map for comparison.
	 */
	@InputPortFieldAnnotation(name = "base")
	public final transient DefaultInputPort<KeyValPair<K, V>> base = new DefaultInputPort<KeyValPair<K, V>>()
	{
		/**
		 * Process each key to store the value. If same key appears again update
		 * with latest value.
		 */
		@Override
		public void process(KeyValPair<K, V> tuple)
		{
			if (tuple.getValue().doubleValue() != 0.0) { // Avoid divide by zero, Emit
																									 // an error tuple?
				MutableDouble val = basemap.get(tuple.getKey());
				if (val == null) {
					val = new MutableDouble(0.0);
					basemap.put(cloneKey(tuple.getKey()), val);
				}
				val.setValue(tuple.getValue().doubleValue());
			}
		}
	};
	
	/**
	 * Key/Change output port. 
	 */
	@OutputPortFieldAnnotation(name = "change", optional = true)
	public final transient DefaultOutputPort<KeyValPair<K, V>> change = new DefaultOutputPort<KeyValPair<K, V>>();
	
	/**
	 * key/percent change pair output port.
	 */
	@OutputPortFieldAnnotation(name = "percent", optional = true)
	public final transient DefaultOutputPort<KeyValPair<K, Double>> percent = new DefaultOutputPort<KeyValPair<K, Double>>();
}