/**
 * Copyright (C) 2001-2017 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.operator.preprocessing.sampling;

import com.rapidminer.operator.OperatorDescription;
import com.rapidminer.operator.ports.metadata.ExampleSetMetaData;
import com.rapidminer.operator.ports.metadata.MDInteger;
import com.rapidminer.operator.ports.metadata.MetaData;
import com.rapidminer.operator.preprocessing.AbstractDataProcessing;
import com.rapidminer.parameter.UndefinedParameterError;


/**
 * Abstract superclass of operators leaving the attribute set and data unchanged but reducing the
 * number of examples.
 * 
 * @author Simon Fischer
 */
public abstract class AbstractSamplingOperator extends AbstractDataProcessing {

	public AbstractSamplingOperator(OperatorDescription description) {
		super(description);
	}

	@Override
	protected MetaData modifyMetaData(ExampleSetMetaData metaData) {
		try {
			metaData.setNumberOfExamples(getSampledSize(metaData));
		} catch (UndefinedParameterError e) {
			metaData.setNumberOfExamples(new MDInteger());
		}
		return metaData;
	}

	/**
	 * subclasses must implement this method for exact size meta data.
	 */
	protected abstract MDInteger getSampledSize(ExampleSetMetaData emd) throws UndefinedParameterError;

	@Override
	public boolean writesIntoExistingData() {
		return false;
	}
}