/*
 *  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.operator.ports.metadata;

import java.util.Collection;

import com.rapidminer.operator.ports.InputPort;
import com.rapidminer.operator.ports.OutputPort;

/** Delivers meta data received in the first input that is not null to the output port. 
 *  TODO: Make intersection of meta data. This is all we can guarantee. 
 *  
 * @author Simon Fischer
 */
public class ManyToOnePassThroughRule implements MDTransformationRule {

	private OutputPort outputPort;
	private Collection<InputPort> inputPorts;
	
	public ManyToOnePassThroughRule(Collection<InputPort> inputPorts, OutputPort outputPort) {	
		this.inputPorts = inputPorts;
		this.outputPort = outputPort;
	}

	@Override
	public void transformMD() {		
		for (InputPort inputPort : inputPorts) {
			MetaData metaData = inputPort.getMetaData();
			if (metaData != null) {
				metaData = metaData.clone();
				metaData.addToHistory(outputPort);
				outputPort.deliverMD(modifyMetaData(metaData));
				return;
			}
		}
		outputPort.deliverMD(null);		
	}
	
	/** Modifies the standard meta data before it is passed to the output. Can be used
	 *  if the transformation depends on parameters etc. The default implementation
	 *  just returns the original. Subclasses may safely modify the meta data, since
	 *  a copy is used for this method. */
	public MetaData modifyMetaData(MetaData unmodifiedMetaData) {
		return unmodifiedMetaData;
	}
}