/*******************************************************************************
 * Copyright (c) 2000, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.viewers;

import java.util.EventObject;

/**
 * Event object describing a label provider state change.
 *
 * @see ILabelProviderListener
 */
public class LabelProviderChangedEvent extends EventObject {

	/**
	 * Generated serial version UID for this class.
	 * @since 3.1
	 */
	private static final long serialVersionUID = 3258410612479309878L;

	/**
	 * The elements whose labels need to be updated or <code>null</code>.
	 */
	private Object[] elements;

	/**
	 * Creates a new event for the given source, indicating that all labels
	 * provided by the source are no longer valid and should be updated.
	 *
	 * @param source the label provider
	 */
	public LabelProviderChangedEvent(IBaseLabelProvider source) {
		super(source);
	}

	/**
	 * Creates a new event for the given source, indicating that the label
	 * provided by the source for the given elements is no longer valid and should be updated.
	 *
	 * @param source the label provider
	 * @param elements the element whose labels have changed
	 */
	public LabelProviderChangedEvent(IBaseLabelProvider source,
			Object[] elements) {
		super(source);
		this.elements = elements;
	}

	/**
	 * Creates a new event for the given source, indicating that the label
	 * provided by the source for the given element is no longer valid and should be updated.
	 *
	 * @param source the label provider
	 * @param element the element whose label needs to be updated
	 */
	public LabelProviderChangedEvent(IBaseLabelProvider source, Object element) {
		super(source);
		this.elements = new Object[1];
		this.elements[0] = element;
	}

	/**
	 * Returns the first element whose label needs to be updated,
	 * or <code>null</code> if all labels need to be updated.
	 *
	 * @return the element whose label needs to be updated or <code>null</code>
	 */
	public Object getElement() {
		if (this.elements == null || this.elements.length == 0) {
			return null;
		}
		return this.elements[0];
	}

	/**
	 * Returns the elements whose labels need to be updated,
	 * or <code>null</code> if all labels need to be updated.
	 *
	 * @return the element whose labels need to be updated or <code>null</code>
	 */
	public Object[] getElements() {
		if (this.elements == null) {
			return null;
		}
		return this.elements;
	}
}
