001/*
002 * Copyright 2025 The Apache Software Foundation.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package org.apache.wiki.diff;
017
018import com.github.difflib.DiffUtils;
019import com.github.difflib.patch.AbstractDelta;
020import com.github.difflib.patch.Patch;
021import java.io.IOException;
022import java.util.List;
023import java.util.Properties;
024import org.apache.wiki.api.core.Context;
025import org.apache.wiki.api.core.Engine;
026import org.apache.wiki.api.exceptions.NoRequiredPropertyException;
027
028/**
029 * SVN/Git style diff provider. Uses the DiffLib, ASF 2.0 licensed.
030 *
031 * @since 3.0.0
032 */
033public class SvnStyleDiffProvider implements DiffProvider {
034
035    public static final String CSS_DIFF_ADDED = "<tr class=\"diffadd\"><td>";
036    public static final String CSS_DIFF_REMOVED = "<tr class=\"diffrem\"><td>";
037    public static final String CSS_DIFF_UNCHANGED = "<tr class=\"diff\"><td>";
038    public static final String CSS_DIFF_CLOSE = "</td></tr>\n";
039    public static final String CELL_CHANGE = "</td><td>";
040
041    @Override
042    public String makeDiffHtml(Context context, String originalText, String modifiedText) {
043
044        List<String> original = originalText.lines().toList();
045        List<String> modified = modifiedText.lines().toList();
046        StringBuilder ret = new StringBuilder();
047        ret.append("<table class=\"diff\" border=\"0\" cellspacing=\"0\" cellpadding=\"0\">\n");
048
049        Patch<String> patch = DiffUtils.diff(original, modified);
050        int lineNumber = 1;
051        int currentOriginalLine = 0;
052        int currentModifiedLine = 0;
053
054        for (AbstractDelta<String> delta : patch.getDeltas()) {
055            int originalPosition = delta.getSource().getPosition();
056            int modifiedPosition = delta.getTarget().getPosition();
057
058            // Output unchanged lines before the delta
059            while (currentOriginalLine < originalPosition && currentModifiedLine < modifiedPosition) {
060                ret.append(CSS_DIFF_UNCHANGED);
061                ret.append(lineNumber).append(CELL_CHANGE);
062                ret.append(original.get(currentOriginalLine));
063                ret.append(CSS_DIFF_CLOSE);
064                //System.out.println("  " + lineNumber + " " + original.get(currentOriginalLine));
065                lineNumber++;
066                currentOriginalLine++;
067                currentModifiedLine++;
068            }
069
070            List<String> originalLines = delta.getSource().getLines();
071            List<String> revisedLines = delta.getTarget().getLines();
072
073            for (String line : originalLines) {
074                ret.append(CSS_DIFF_REMOVED);
075                ret.append(lineNumber).append(CELL_CHANGE);
076                ret.append(line);
077                ret.append(CSS_DIFF_CLOSE);
078                //System.out.println("- " + lineNumber + " " + line);
079                lineNumber++;
080                currentOriginalLine++;
081            }
082
083            for (String line : revisedLines) {
084                ret.append(CSS_DIFF_ADDED);
085                ret.append(lineNumber).append(CELL_CHANGE);
086                ret.append(line);
087                ret.append(CSS_DIFF_CLOSE);
088                //System.out.println("+ " + lineNumber + " " + line);
089                lineNumber++;
090                currentModifiedLine++;
091            }
092        }
093
094        // Output any remaining unchanged lines at the end
095        while (currentOriginalLine < original.size() && currentModifiedLine < modified.size()) {
096            ret.append(CSS_DIFF_UNCHANGED);
097            ret.append(lineNumber).append(CELL_CHANGE);
098            ret.append(original.get(currentOriginalLine));
099            ret.append(CSS_DIFF_CLOSE);
100
101            //System.out.println("  " + lineNumber + " " + original.get(currentOriginalLine));
102            lineNumber++;
103            currentOriginalLine++;
104            currentModifiedLine++;
105        }
106        ret.append("</table>\n");
107        return ret.toString();
108    }
109
110    @Override
111    public void initialize(Engine engine, Properties properties) throws NoRequiredPropertyException, IOException {
112    }
113
114    @Override
115    public String getProviderInfo() {
116        return "SvnStyleDiffProvider";
117    }
118
119}