/*
 *  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.ports.metadata;

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

/** Assigns meta data received from an input port to an output port. Useful e.g. for preprocessing operators. 
 *  If meta data changes dynamically, can be modified by overriding {@link #modifyMetaData(MetaData)}. 
 *  
 *  @author Simon Fischer
 *  */
public class PassThroughRule implements MDTransformationRule {

	private final OutputPort outputPort;

	private final InputPort inputPort;
	private final boolean optional;

	public PassThroughRule(InputPort inputPort, OutputPort outputPort, boolean mandatory) {
		super();
		this.outputPort = outputPort;
		this.inputPort = inputPort;
		this.optional = !mandatory;		
	}

	@Override
	public void transformMD() {		
		MetaData modified = inputPort.getMetaData();		
		if (modified == null) {
			if (!optional) {			
				inputPort.addError(new InputMissingMetaDataError(inputPort, null, null));
			}			
			outputPort.deliverMD(null);
		} else {
			modified = modified.clone();
			modified.addToHistory(outputPort);
			outputPort.deliverMD(modifyMetaData(modified));
		}
	}

	/** Modifies the received 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;
	}

	public OutputPort getOutputPort() {
		return this.outputPort;
	}

	public InputPort getInputPort() {
		return this.inputPort;
	}

	public boolean isOptional() {
		return this.optional;
	}

}