/*
 *  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.filter.attributes;

import java.util.List;

import com.rapidminer.example.Attribute;
import com.rapidminer.example.Example;
import com.rapidminer.example.set.ConditionCreationException;
import com.rapidminer.operator.UserError;
import com.rapidminer.operator.ports.InputPort;
import com.rapidminer.operator.ports.metadata.AttributeMetaData;
import com.rapidminer.operator.ports.metadata.MetaDataInfo;
import com.rapidminer.parameter.ParameterHandler;
import com.rapidminer.parameter.ParameterType;

/**
 * This interface must be implemented by classes implementing an AttributeFilterCondition for
 * the AttributeFilter operator.
 * 
 * @author Sebastian Land, Ingo Mierswa
 */
public interface AttributeFilterCondition {

	public static enum ScanResult {
		REMOVE,
		KEEP,
		UNCHECKED;

		public ScanResult invert(boolean invert) {
			switch (this) {
			case KEEP:
				return (invert) ? REMOVE: KEEP;
			case REMOVE:
				return (invert) ? KEEP: REMOVE;
			default:
				return UNCHECKED;
			}
		}
	};



	/** Initializes the condition before checking anything. If checking depends on parameters,
	 * their values might be retrieved in this method. 
	 * @throws UserError 
	 * @throws ConditionCreationException TODO*/
	public void init(ParameterHandler operator) throws UserError, ConditionCreationException;



	/**
	 * This method tries to check if the given attribute is contained, removed from the resulting operation
	 * or if the result is unpredictable.
	 * @param attribute the meta data of the attribute
	 * @param parameterHandler to get the value of the defined parameters
	 * @return
	 * @throws ConditionCreationException 
	 */
	public MetaDataInfo isFilteredOutMetaData(AttributeMetaData attribute, ParameterHandler parameterHandler) throws ConditionCreationException;

	/** Indicates if this filter needs a data scan, i.e. an invocation of the check method for each example. */
	public boolean isNeedingScan();

	/**
	 * Indicates that this filter needs a full data scan and can evaluate its condition only after the full
	 * scan has been performed. If this method returns true, isNeedingScan must have returned true either. 
	 */
	public boolean isNeedingFullScan();



	/**
	 * This method initializes this condition and resets all counters.
	 * It returns REMOVE, if the attribute can be removed without checking examples.
	 * If it has been removed, no checking during examples will occur.
	 * If it returns UNCHECKED, this Attribute Filter needs a full check and hence the attribute
	 * cannot be deleted or kept.
	 * Distinguishing this is important, because of the inverting, which otherwise might remove attributes
	 * although they only have been kept for later checking.
	 * @param attribute this is the attribute, the filter will have to check for.
	 * @throws ConditionCreationException 
	 */
	public ScanResult beforeScanCheck(Attribute attribute) throws UserError;

	/**
	 * This method checks the given example. During this method the filter might check data to 
	 * decide if attribute should be filtered out. If the condition needs a full scan before it can
	 * decide, this result is ignored.
	 */
	public ScanResult check(Attribute attribute, Example example);


	/**
	 * This method has to be invoked after a full scan has been performed if the isNeedingFullScan method
	 * returns true. 
	 * @return This method has to be restricted to return KEEP or REMOVED, but not unchecked
	 */
	public ScanResult checkAfterFullScan();



	/**
	 * This method is used to get parameters needed by this AttributeFilter
	 * @param handler the parameter handler for defining dependencies
	 */
	public List<ParameterType> getParameterTypes(ParameterHandler operator, InputPort inPort, int...valueTypes);

}