001/*
002 * This library is part of OpenCms -
003 * the Open Source Content Management System
004 *
005 * Copyright (c) Alkacon Software GmbH & Co. KG (http://www.alkacon.com)
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 *
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 * Lesser General Public License for more details.
016 *
017 * For further information about Alkacon Software, please see the
018 * company website: http://www.alkacon.com
019 *
020 * For further information about OpenCms, please see the
021 * project website: http://www.opencms.org
022 *
023 * You should have received a copy of the GNU Lesser General Public
024 * License along with this library; if not, write to the Free Software
025 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
026 */
027
028package org.opencms.ui.dialogs.history.diff;
029
030import org.opencms.file.CmsObject;
031import org.opencms.gwt.shared.CmsHistoryResourceBean;
032import org.opencms.main.CmsException;
033
034import com.google.common.base.Optional;
035import com.vaadin.ui.Component;
036
037/**
038 * Interface for classes which display a comparison widget in the comparison view of the history dialog.
039 */
040public interface I_CmsDiffProvider {
041
042    /**
043     * Optionally returns a comparison component to display for the given resource versions.<p>
044     *
045     * If no value is returned, then no widget is displayed.
046     *
047     * @param cms the CMS context
048     * @param v1 bean representing the first version
049     * @param v2 bean representing the second version
050     *
051     * @return the optional component to display
052     *
053     * @throws CmsException if something goes wrong
054     */
055    Optional<Component> diff(CmsObject cms, CmsHistoryResourceBean v1, CmsHistoryResourceBean v2) throws CmsException;
056
057}