/* Copyright (C) 2010  Egon Willighagen <egonw@users.sf.net>
 *
 * Contact: cdk-devel@lists.sourceforge.net
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1
 * of the License, or (at your option) any later version.
 * All we ask is that proper credit is given for our work, which includes
 * - but is not limited to - adding the above copyright notice to the beginning
 * of your source code files, and to any copyright notice that you may distribute
 * with programs based on this work.
 *
 * 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 */
package org.openscience.cdk.geometry.cip.rules;

import org.openscience.cdk.geometry.cip.ILigand;
import org.openscience.cdk.interfaces.IElement;

/**
 * Compares to {@link ILigand}s based on CIP sequences sub rules. The used CIP sub rules are:
 * <ol>
 *   <li>{@link MassNumberRule}</li>
 *   <li>{@link AtomicNumberRule}</li>
 * </ol>
 *
 * @cdk.module cip
 * @cdk.githash
 */
class CombinedAtomicMassNumberRule implements ISequenceSubRule<ILigand> {

    final MassNumberRule   massNumberRule   = new MassNumberRule();
    final AtomicNumberRule atomicNumberRule = new AtomicNumberRule();

    /** {@inheritDoc} */
    @Override
    public int compare(ILigand ligand1, ILigand ligand2) {
        int atomicNumberComp = atomicNumberRule.compare(ligand1, ligand2);
        if (atomicNumberComp != 0) return atomicNumberComp;

        int massNumberComp = massNumberRule.compare(ligand1, ligand2);
        if (massNumberComp != 0) return massNumberComp;

        if (ligand1.getLigandAtom().getAtomicNumber() == IElement.H) {
            // both atoms are hydrogens
            return 0;
        }

        return massNumberComp;
    }

}
