GetDiffLines.java

/*
 * The MIT License
 *
 * Copyright 2013 Mirko Friedenhagen, Kojima Takanori.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package hudson.plugins.jobConfigHistory;

import java.util.List;

import org.apache.commons.lang.StringUtils;

import difflib.Chunk;
import difflib.Delta;
import difflib.DiffRow;
import difflib.DiffRowGenerator;
import difflib.DiffUtils;
import difflib.Patch;

/**
 * Returns side-by-side (i.e. human-readable) diff view lines.
 *
 * @author Mirko Friedenhagen
 * @author Kojima Takanori
 */
public class GetDiffLines {

	/**
	 * Lines.
	 */
	private final List<String> diffLines;
	/**
	 * View.
	 */
	private final SideBySideView view;
	/**
	 * Generator for diff rows.
	 */
	private final DiffRowGenerator dfg;

	/**
	 * Constructor.
	 *
	 * @param diffLines
	 *            to construct the {@link SideBySideView} for.
	 */
	public GetDiffLines(List<String> diffLines) {
		final DiffRowGenerator.Builder builder = new DiffRowGenerator.Builder();
		builder.columnWidth(Integer.MAX_VALUE);
		dfg = builder.build();
		this.diffLines = diffLines;
		view = new SideBySideView();
	}

	/**
	 * Returns a list of {@link SideBySideView} lines.
	 *
	 * @return list of {@link SideBySideView} lines.
	 */
	public List<SideBySideView.Line> get() {
		final Patch diff = DiffUtils.parseUnifiedDiff(diffLines);
		int previousLeftPos = 0;
		for (final Delta delta : diff.getDeltas()) {
			previousLeftPos = deltaLoop(delta, previousLeftPos);
		}
		view.clearDuplicateLines();
		return view.getLines();
	}

	/**
	 * DeltaLoop.
	 */
	static class DeltaLoop {

		/**
		 * View.
		 */
		private final SideBySideView view;
		/**
		 * Dfg.
		 */
		private final DiffRowGenerator dfg;
		/**
		 * delta.
		 */
		private final Delta delta;
		/**
		 * Current leftPos.
		 */
		private int leftPos;
		/**
		 * Current rightPos.
		 */
		private int rightPos;

		/**
		 *
		 * @param view
		 *            to extend.
		 * @param dfg
		 *            dfg
		 * @param delta
		 *            delta
		 */
		public DeltaLoop(SideBySideView view, DiffRowGenerator dfg,
				Delta delta) {
			this.view = view;
			this.dfg = dfg;
			this.delta = delta;
		}

		/**
		 * Loop through Delta.
		 *
		 * @param previousLeftPos
		 *            previous indentation
		 * @return current indentation
		 */
		int loop(int previousLeftPos) {
			final Chunk original = delta.getOriginal();
			final Chunk revised = delta.getRevised();
			@SuppressWarnings("unchecked")
			final List<DiffRow> diffRows = dfg.generateDiffRows(
					(List<String>) original.getLines(),
					(List<String>) revised.getLines());
			// Chunk#getPosition() returns 0-origin line numbers, but we need
			// 1-origin line numbers
			leftPos = original.getPosition() + 1;
			rightPos = revised.getPosition() + 1;
			if (previousLeftPos > 0 && leftPos - previousLeftPos > 1) {
				final SideBySideView.Line skippingLine = new SideBySideView.Line();
				skippingLine.setSkipping(true);
				view.addLine(skippingLine);
			}
			for (final DiffRow row : diffRows) {
				previousLeftPos = processDiffRow(row);
			}
			return previousLeftPos;
		}

		/**
		 * Processes one DiffRow.
		 *
		 * @param row
		 *            to process
		 * @return indentation
		 */
		int processDiffRow(final DiffRow row) {
			final DiffRow.Tag tag = row.getTag();
			final SideBySideView.Line line = new SideBySideView.Line();
			final SideBySideView.Line.Item left = line.getLeft();
			final SideBySideView.Line.Item right = line.getRight();
			if (tag == DiffRow.Tag.INSERT) {
				left.setCssClass("diff_original");
				right.setLineNumber(rightPos);
				right.setText(row.getNewLine());
				right.setCssClass("diff_revised");
				rightPos++;
			} else if (tag == DiffRow.Tag.CHANGE) {
				if (StringUtils.isNotEmpty(row.getOldLine())) {
					left.setLineNumber(leftPos);
					left.setText(row.getOldLine());
					leftPos++;
				}
				left.setCssClass("diff_original");
				if (StringUtils.isNotEmpty(row.getNewLine())) {
					right.setLineNumber(rightPos);
					right.setText(row.getNewLine());
					rightPos++;
				}
				right.setCssClass("diff_revised");
			} else if (tag == DiffRow.Tag.DELETE) {
				left.setLineNumber(leftPos);
				left.setText(row.getOldLine());
				left.setCssClass("diff_original");
				leftPos++;
				right.setCssClass("diff_revised");
			} else if (tag == DiffRow.Tag.EQUAL) {
				left.setLineNumber(leftPos);
				left.setText(row.getOldLine());
				leftPos++;
				right.setLineNumber(rightPos);
				right.setText(row.getNewLine());
				rightPos++;
			} else {
				throw new IllegalStateException("Unknown tag pattern: " + tag);
			}
			line.setTag(tag);
			view.addLine(line);
			return leftPos;
		}

	}

	/**
	 * Extends view with lines of a single delta.
	 *
	 * @param delta
	 *            to inspect.
	 * @param previousLeftPos
	 *            indentation.
	 *
	 * @return new previousLeftPos
	 */
	int deltaLoop(final Delta delta, int previousLeftPos) {
		return new DeltaLoop(view, dfg, delta).loop(previousLeftPos);
	}

}