/*
 * This file is part of the DiffX library.
 *
 * For licensing information please see the file license.txt included in the release.
 * A copy of this licence can also be found at
 *   http://www.opensource.org/licenses/artistic-license-2.0.php
 */
package com.topologi.diffx.load;

import java.util.Comparator;

import com.topologi.diffx.event.AttributeEvent;
import com.topologi.diffx.event.impl.AttributeEventImpl;
import com.topologi.diffx.event.impl.AttributeEventNSImpl;

/**
 * A comparator in order to put attributes in the correct order, that is in the alphabetical order
 * of the attribute name and namespace URI.
 *
 * @author Christophe Lauret
 * @version 10 May 2010
 */
final class AttributeComparator implements Comparator<AttributeEvent> {

  /**
   * Compares two objects if they are attributes.
   *
   * {@inheritDoc}
   */
  @Override
  public int compare(AttributeEvent o1, AttributeEvent o2) throws ClassCastException {
    if (o1 instanceof AttributeEventImpl && o2 instanceof AttributeEventImpl)
      return compare((AttributeEventImpl)o1, (AttributeEventImpl)o2);
    else if (o1 instanceof AttributeEventNSImpl && o2 instanceof AttributeEventNSImpl)
      return compare((AttributeEventNSImpl)o1, (AttributeEventNSImpl)o2);
    else
      return 0;
  }

  /**
   * Compares two attribute events using their name.
   *
   * @param att1 The first attribute to be compared.
   * @param att2 The second attribute to be compared.
   *
   * @return a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater
   *         than the second.
   */
  public int compare(AttributeEventImpl att1, AttributeEventImpl att2) {
    return att1.getName().compareTo(att2.getName());
  }

  /**
   * Compares two simple attribute events using their name and namespace URI.
   *
   * @param att1 The first attribute to be compared.
   * @param att2 The second attribute to be compared.
   *
   * @return a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater
   *         than the second.
   */
  public int compare(AttributeEventNSImpl att1, AttributeEventNSImpl att2) {
    return toCName(att1).compareTo(toCName(att2));
  }

  /**
   * Returns a comparable name from the given attribute's namespace URI and name.
   *
   * @param att The attribute.
   * @return The comparable name.
   */
  private static String toCName(AttributeEventNSImpl att) {
    return att.getURI() != null? att.getURI() + ':' + att.getName() : att.getName();
  }

}