/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2011 by Rapid-I and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapid-i.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;
	}
}