IntersectionUtils.java

/*-
 * Copyright © 2009 Diamond Light Source Ltd.
 *
 * This file is part of GDA.
 *
 * GDA is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License version 3 as published by the Free
 * Software Foundation.
 *
 * GDA 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 General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along
 * with GDA. If not, see <http://www.gnu.org/licenses/>.
 */

package uk.ac.gda.util.list;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class IntersectionUtils {


	/**
	 * Checks if a list of two doubles (start,end) arrays intersect. Throws
	 * Exception with information about what hit what if do.
	 *
	 * @param values a list of the array {startValue, endValue, name}
	 * where startValue and endValue must be Numbers, and name will have toString() called on it
	 * when assigning the exception.
	 */
	public static void checkIntersection(final List<Object[]> values) throws IntersectionException {

		if (values.size()<2) return;

		// First order entries by start value
		Collections.sort(values, new Comparator<Object[]>() {
			@Override
			public int compare(Object[] o1, Object[] o2) {
				return Double.compare(((Number)o1[0]).doubleValue(), ((Number)o2[0]).doubleValue());
			}
		});

		for (int i = 1; i < values.size(); i++) {
			final Object[] prev = values.get(i-1);
			final Object[] val  = values.get(i);

			final Number start1    = (Number)prev[0];
			final Number end1      = (Number)prev[1];
			final Number start2    = (Number)val[0];
			final Number end2      = (Number)val[1];

			if (start1.doubleValue()>start2.doubleValue() || start1.doubleValue()>end2.doubleValue() || end1.doubleValue()>start2.doubleValue() || end1.doubleValue()>end2.doubleValue()) {
				final IntersectionException e = new IntersectionException("The indices "+(i-1)+" and "+i+" intersect!");
				e.setFirstName(prev[2].toString());
				e.setSecondName(val[2].toString());
				throw e;
			}
		}
	}
}