/*
 *  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;

/** Can be used to indicate whether we know the attribute set exactly,
 *  or only know that it is a subset/superset of a given set. 
 *  
 *  @author Simon Fischer
 *  */
public enum SetRelation {
	UNKNOWN("unkown"),
	SUPERSET("\u2287"),
	SUBSET("\u2286"),
	EQUAL("=");

	private String description;

	private SetRelation(String description) {
		this.description = description;
	}

	public SetRelation merge(SetRelation relation) {
		switch (relation) {
		case EQUAL:
			return this;
		case SUBSET:
			switch (this) {
			case SUBSET:
			case EQUAL:
				return SUBSET;
			case SUPERSET:
			case UNKNOWN:
				return UNKNOWN;
			}
		case SUPERSET:
			switch (this) {
			case SUPERSET:
			case EQUAL:
				return SUPERSET;
			case SUBSET:
			case UNKNOWN:
				return UNKNOWN;
			}
		case UNKNOWN:
		default:
			return UNKNOWN;
		}			
	}

	@Override
	public String toString() {
		return description;
	}
}