/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2014 by RapidMiner and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapidminer.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package com.rapidminer.tools.math.similarity;

import com.rapidminer.example.ExampleSet;
import com.rapidminer.operator.Operator;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.parameter.UndefinedParameterError;
import com.rapidminer.tools.Observable;
import com.rapidminer.tools.Observer;

/** This helper class installs and uninstalls additional ports at operators
 *  that operate on distance measures. It registers itself as an observer
 *  of the operator's parameters and instantiates a new {@link DistanceMeasure}
 *  whenever one of the parameters {@link DistanceMeasures#PARAMETER_MEASURE_TYPES},
 *	{@link DistanceMeasures#PARAMETER_MIXED_MEASURE},
 *	{@link DistanceMeasures#PARAMETER_NUMERICAL_MEASURE},
 *	{@link DistanceMeasures#PARAMETER_NOMINAL_MEASURE}, or
 *	{@link DistanceMeasures#PARAMETER_DIVERGENCE} changes. 
 *  If the chosen {@link DistanceMeasure} overrides 
 *  {@link DistanceMeasure#installAdditionalPorts(com.rapidminer.operator.ports.InputPorts, com.rapidminer.parameter.ParameterHandler)} 
 *  this may install new ports at the operator.
 *  
 *  In its {@link Operator#doWork()} method, the operator may call 
 *  {@link #getInitializedMeasure(ExampleSet)} in order to initialize the distance measure
 *  and obtain it. Call this method only once.
 *   
 * @author Simon Fischer
 *
 */
public class DistanceMeasureHelper {

	private Operator operator;
	private DistanceMeasure measure;

	public DistanceMeasureHelper(Operator operator) {
		this.operator = operator;
		operator.getParameters().addObserver(new Observer<String>() {
			@Override
			public void update(Observable<String> observable, String arg) {
				if (DistanceMeasures.PARAMETER_MEASURE_TYPES.equals(arg) ||
						DistanceMeasures.PARAMETER_MIXED_MEASURE.equals(arg) ||
						DistanceMeasures.PARAMETER_NUMERICAL_MEASURE.equals(arg) ||
						DistanceMeasures.PARAMETER_NOMINAL_MEASURE.equals(arg) ||
						DistanceMeasures.PARAMETER_DIVERGENCE.equals(arg)) {
					updateMeasure();
				}
			}
		}, false);
		updateMeasure();
	}

	private void updateMeasure() {
		if (measure != null) {
			measure.uninstallAdditionalPorts(operator.getInputPorts());
		}
		try {
			measure = DistanceMeasures.createMeasure(operator);
		} catch (UndefinedParameterError e) {
			operator.getLogger().warning("While updating distance measure: " + e.toString());
		} catch (OperatorException e) {
			operator.getLogger().warning("While updating distance measure: " + e.toString());
		}
		if (measure != null) {
			measure.installAdditionalPorts(operator.getInputPorts(), operator);
		}
	}

	public DistanceMeasure getInitializedMeasure(ExampleSet exampleSet) throws OperatorException {
		measure.init(exampleSet, operator);
		return measure;
	}

	public int getSelectedMeasureType() throws UndefinedParameterError {
		return DistanceMeasures.getSelectedMeasureType(operator);
	}
}