/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2008 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.filter;

import java.util.Iterator;
import java.util.List;

import com.rapidminer.example.AttributeRole;
import com.rapidminer.example.ExampleSet;
import com.rapidminer.operator.IOObject;
import com.rapidminer.operator.Operator;
import com.rapidminer.operator.OperatorDescription;
import com.rapidminer.operator.OperatorException;
import com.rapidminer.parameter.ParameterType;
import com.rapidminer.parameter.ParameterTypeBoolean;


/**
 * This is an abstract superclass for feature filters. These operators take an
 * <code>ExampleSet</code> as input and switch off all features that fulfill a
 * condition. Subclasses must implement the condition in the method
 * <code>switchOffFeature()</code>, which returns a boolean.
 * 
 * @author Ingo Mierswa
 * @version $Id: FeatureFilter.java,v 1.6 2008/07/07 07:06:40 ingomierswa Exp $
 */
public abstract class FeatureFilter extends Operator {


	/** The parameter name for "Filter also special attributes (label, id...)" */
	public static final String PARAMETER_FILTER_SPECIAL_FEATURES = "filter_special_features";
	private static final Class[] INPUT_CLASSES = { ExampleSet.class };

	private static final Class[] OUTPUT_CLASSES = { ExampleSet.class };

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

	/**
	 * Must be implemented by subclasses. When operators extending this class
	 * are applied, they loop through the set of features and switch off all
	 * features for which this method returns TRUE, while keeping the status of
	 * the other features.
	 * 
	 * @param theFeature
	 *            Feature to check.
	 * @return TRUE if this feature should <b>not</b> be active in the output
	 *         example set of this operator. FALSE otherwise.
	 */
	public abstract boolean switchOffFeature(AttributeRole theFeature) throws OperatorException;

	/**
	 * Applies filtering of features by looping through all features and
	 * checking <code>switchOffFeature()</code>. If TRUE is returned, the
	 * feature is switched off, ie it won't be used by the following operators
	 * in the chain. If FALSE is returned by <code>switchOffFeature()</code>,
	 * the feature will keep its previous status.
	 * 
	 * @return An array of IOObjects, with the output example set as the only
	 *         member.
	 */
	public IOObject[] apply() throws OperatorException {
		ExampleSet eSet = getInput(ExampleSet.class);
		log(eSet.getAttributes().size() + " features before filtering.");

		Iterator<AttributeRole> i = eSet.getAttributes().allAttributeRoles();
        boolean filterSpecial = getParameterAsBoolean(PARAMETER_FILTER_SPECIAL_FEATURES);
		while (i.hasNext()) {
			AttributeRole role = i.next();
			if ((role.isSpecial()) && (!filterSpecial))
				continue;
			if (switchOffFeature(role)) {
				i.remove();
			}
			checkForStop();
		}

		log(eSet.getAttributes().size() + " features left after filtering.");
		return new IOObject[] { eSet };
	}

	public Class<?>[] getInputClasses() {
		return INPUT_CLASSES;
	}

	public Class<?>[] getOutputClasses() {
		return OUTPUT_CLASSES;
	}
    
    public List<ParameterType> getParameterTypes() {
        List<ParameterType> types = super.getParameterTypes();
        types.add(new ParameterTypeBoolean(PARAMETER_FILTER_SPECIAL_FEATURES, "Filter also special attributes (label, id...)", false));
        return types;
    }
}