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 */
019package org.apache.wiki.diff;
020
021import org.apache.wiki.api.core.Context;
022import org.apache.wiki.api.core.Engine;
023import org.apache.wiki.api.exceptions.NoRequiredPropertyException;
024import org.apache.wiki.api.providers.WikiProvider;
025
026import java.io.IOException;
027import java.util.Properties;
028
029
030/**
031 *  Provides an SPI for creating a diff between two page versions.
032 */
033public interface DiffProvider extends WikiProvider {
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( Context 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         *  {@inheritDoc}
051         */
052        @Override
053        public String makeDiffHtml( final Context ctx, final String oldWikiText, final String newWikiText ) {
054            return "You are using the NullDiffProvider, check your properties file.";
055        }
056
057        /**
058         *  {@inheritDoc}
059         */
060        @Override
061        public void initialize( final Engine engine, final Properties properties ) throws NoRequiredPropertyException, IOException {
062        }
063
064        /**
065         *  {@inheritDoc}
066         */
067        @Override
068        public String getProviderInfo()
069        {
070            return "NullDiffProvider";
071        }
072    }
073    
074}