/*
 *  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.io;

import java.util.LinkedList;
import java.util.List;

import com.rapidminer.operator.IOObject;
import com.rapidminer.operator.Operator;
import com.rapidminer.operator.OperatorDescription;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.operator.ports.InputPort;
import com.rapidminer.operator.ports.OutputPort;
import com.rapidminer.operator.ports.metadata.MetaData;
import com.rapidminer.operator.ports.metadata.PassThroughRule;
import com.rapidminer.operator.ports.metadata.SimplePrecondition;
import com.rapidminer.parameter.ParameterType;
import com.rapidminer.tools.io.Encoding;

/** 
 * Superclass of all operators that take a single object as input, save it to disk
 * and return the same object as output.
 * This class is mainly a tribute to the e-LICO DMO.
 *  
 *  It defines precondition and a pass through rule for its output port.
 * 
 * @author Simon Fischer 
 */
public abstract class AbstractWriter<T extends IOObject> extends Operator {

	private InputPort inputPort = getInputPorts().createPort("input");
	private OutputPort outputPort = getOutputPorts().createPort("through");

	public AbstractWriter(OperatorDescription description, Class<T> savedClass) {
		super(description);		
		inputPort.addPrecondition(new SimplePrecondition(inputPort, new MetaData(savedClass)));
		getTransformer().addRule(new PassThroughRule(inputPort, outputPort, false));		
	}

	/** Creates (or reads) the ExampleSet that will be returned by {@link #apply()}. 
	 * @return  the written IOObject itself*/
	public abstract T write(T ioobject) throws OperatorException;

	@Override
	public final void doWork() throws OperatorException {
		T ioobject = inputPort.<T>getData();
		ioobject = write(ioobject);
		outputPort.deliver(ioobject);		
	}	

	protected boolean supportsEncoding() {
		return false;
	}

	@Override
	public List<ParameterType> getParameterTypes() {
		List<ParameterType> types = new LinkedList<ParameterType>();
		types.addAll(super.getParameterTypes());
		if (supportsEncoding())
			types.addAll(Encoding.getParameterTypes(this));
		return types;
	}
}