/*
 *                    BioJava development code
 *
 * This code may be freely distributed and modified under the
 * terms of the GNU Lesser General Public Licence.  This should
 * be distributed with the code.  If you do not have a copy,
 * see:
 *
 *      http://www.gnu.org/copyleft/lesser.html
 *
 * Copyright for this code is held jointly by the individual
 * authors.  These should be listed in @author doc comments.
 *
 * For more information on the BioJava project and its aims,
 * or to join the biojava-l mailing list, visit the home page
 * at:
 *
 *      http://www.biojava.org/
 *
 */

package org.biojava.bio.seq;

/**
 * Accept features which are top-level sequence features.  This is implemented
 * by the logic that the <code>parent</code> property of top-level features
 * will implement the <code>Sequence</code> interface.
 *
 * @author Thomas Down
 * @since 1.3
 */

final class IsTopLevel implements OptimizableFilter {
  public boolean accept(Feature f) {
    return f.getParent() instanceof Sequence;
  }
  
  public int hashCode() {
    return 42;
  }
  
  /**
  * All instances are equal (this should really be a singleton, but
  * that doesn't quite fit current </code>FeatureFilter</code>
  * patterns.
  */
  
  public boolean equals(Object o) {
    return (o instanceof IsTopLevel);
  }
  
  public boolean isProperSubset(FeatureFilter ff) {
    return (ff instanceof IsTopLevel) || (ff instanceof AcceptAllFilter);
  }
  
  public boolean isDisjoint(FeatureFilter ff) {
    return (ff instanceof ByParent) || (ff instanceof ByAncestor);
  }
}