//  OverallConstraintViolationComparator.java
//
//  Author:
//       Antonio J. Nebro <antonio@lcc.uma.es>
//       Juan J. Durillo <durillo@lcc.uma.es>
//
//  Copyright (c) 2011 Antonio J. Nebro, Juan J. Durillo
//
//  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 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 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, see <http://www.gnu.org/licenses/>.

package jmetal.util.comparators;

import jmetal.core.Solution;

/**
 * This class implements a <code>Comparator</code> (a method for comparing
 * <code>Solution</code> objects) based on the overall constraint violation of
 * the solucions, as in NSGA-II.
 */
public class OverallConstraintViolationComparator 
  implements IConstraintViolationComparator {
   
 /** 
  * Compares two solutions.
  * @param o1 Object representing the first <code>Solution</code>.
  * @param o2 Object representing the second <code>Solution</code>.
  * @return -1, or 0, or 1 if o1 is less than, equal, or greater than o2,
  * respectively.
  */
  public int compare(Object o1, Object o2) {    
    double overall1, overall2;
    overall1 = ((Solution)o1).getOverallConstraintViolation();
    overall2 = ((Solution)o2).getOverallConstraintViolation();
        
    if ((overall1 < 0) && (overall2 < 0)) {
      if (overall1 > overall2){
        return -1;
      } else if (overall2 > overall1){
        return 1;
      } else {
        return 0;
      }
    } else if ((overall1 == 0) && (overall2 < 0)) {
      return -1;
    } else if ((overall1 < 0) && (overall2 == 0)) {        
      return 1;
    } else {
      return 0;        
    }
  } // compare    
  
  /**
   * Returns true if solutions s1 and/or s2 have an overall constraint
   * violation < 0
   */
  public boolean needToCompare(Solution s1, Solution s2) {
    boolean needToCompare ;
    needToCompare = (s1.getOverallConstraintViolation() < 0) ||
            (s2.getOverallConstraintViolation() < 0);
    
    return needToCompare ;
  }
} // OverallConstraintViolationComparator