001    /* 
002        Licensed to the Apache Software Foundation (ASF) under one
003        or more contributor license agreements.  See the NOTICE file
004        distributed with this work for additional information
005        regarding copyright ownership.  The ASF licenses this file
006        to you under the Apache License, Version 2.0 (the
007        "License"); you may not use this file except in compliance
008        with the License.  You may obtain a copy of the License at
009    
010           http://www.apache.org/licenses/LICENSE-2.0
011    
012        Unless required by applicable law or agreed to in writing,
013        software distributed under the License is distributed on an
014        "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015        KIND, either express or implied.  See the License for the
016        specific language governing permissions and limitations
017        under the License.  
018     */
019    package org.apache.wiki.diff;
020    
021    import java.io.IOException;
022    import java.util.Properties;
023    
024    import org.apache.wiki.WikiContext;
025    import org.apache.wiki.WikiEngine;
026    import org.apache.wiki.WikiProvider;
027    import org.apache.wiki.api.exceptions.NoRequiredPropertyException;
028    
029    /**
030     *  Provides an SPI for creating a diff between two page versions.
031     */
032    public interface DiffProvider extends WikiProvider
033    {
034        /**
035         * The return string is to be XHTML compliant ready to display html.  No further
036         * processing of this text will be done by the wiki engine.
037         * 
038         * @return An XHTML diff.
039         * @param context The Wiki Context
040         * @param oldWikiText the old text
041         * @param newWikiText the new text
042         */
043        String makeDiffHtml(WikiContext context, String oldWikiText, String newWikiText);
044        
045        /**
046         *  If there is no diff provider set, this provider will work instead.
047         */
048        class NullDiffProvider implements DiffProvider
049        {
050            /**
051             *  {@inheritDoc}
052             */
053            public String makeDiffHtml(WikiContext ctx, String oldWikiText, String newWikiText)
054            {
055                return "You are using the NullDiffProvider, check your properties file.";
056            }
057    
058            /**
059             *  {@inheritDoc}
060             */
061            public void initialize(WikiEngine engine, Properties properties) 
062                throws NoRequiredPropertyException, IOException
063            {
064            }
065    
066            /**
067             *  {@inheritDoc}
068             */
069            public String getProviderInfo()
070            {
071                return "NullDiffProvider";
072            }
073        }
074        
075    }