http://www.eclipse.org/platform: Core Compare Support (Eclipse Foundation) 
Copyright (c) 2009, 2011 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation

/*******************************************************************************
 * Copyright (c) 2009, 2011 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.compare.patch;

import java.util.Arrays;
import java.util.Comparator;

import org.eclipse.compare.internal.core.patch.FilePatch2;
import org.eclipse.compare.internal.core.patch.Hunk;
import org.eclipse.core.runtime.IPath;


Builder for creating IFilePatch2 and IHunk objects as well as building
relationship between them.

@noextendThis class is not intended to be subclassed by clients.
@noinstantiateThis class is not intended to be instantiated by clients.
Since:org.eclipse.compare.core 3.5
/**
 * Builder for creating IFilePatch2 and IHunk objects as well as building
 * relationship between them.
 *
 * @noextend This class is not intended to be subclassed by clients.
 * @noinstantiate This class is not intended to be instantiated by clients.
 *
 * @since org.eclipse.compare.core 3.5
 */
public class PatchBuilder {

	
Line prefix used to mark context lines.

/**
	 * Line prefix used to mark context lines.
	 */
	public static final char CONTEXT_PREFIX = ' ';
	
Line prefix used to mark an added lines.

/**
	 * Line prefix used to mark an added lines.
	 */
	public static final char ADDITION_PREFIX = '+';
	
Line prefix used to mark an removed lines.

/**
	 * Line prefix used to mark an removed lines.
	 */
	public static final char REMOVAL_PREFIX = '-';

	
Creates an IHunk instance.

Params:
  • start – 
           the start position in the before file
  • lines – 
           content of the hunk. Each line starts with a control
           character. Their meaning is as follows:
           
      
           
    • 
           '+': add the line
           
    • 
           '-': delete the line
           
    • 
           ' ': no change, context line
           
Returns:IHunk instance
/**
	 * Creates an IHunk instance.
	 *
	 * @param start
	 *            the start position in the before file
	 * @param lines
	 *            content of the hunk. Each line starts with a control
	 *            character. Their meaning is as follows:
	 *            <ul>
	 *            <li>
	 *            '+': add the line
	 *            <li>
	 *            '-': delete the line
	 *            <li>
	 *            ' ': no change, context line
	 *            </ul>
	 * @return IHunk instance
	 */
	public static IHunk createHunk(int start, String[] lines) {
		int type = getHunkType(lines);
		int oldLength = getHunkLength(lines, true);
		int newLength = getHunkLength(lines, false);
		return new Hunk(null, type, start, oldLength, start, newLength, lines);
	}

	
Creates an IFilePatch2 instance and performs recalculation of all hunks'
after positions. Hunk's after position is position in the file state
after applying a patch. It is affected by all the hunks that are to be
applied before a given one. This recalculation is necessary to keep
IFilePatch2's state coherent.

Params:
  • oldPath – 
           the path of the before state of the file
  • oldDate –  the timestamp of the before state of the file, see also IFilePatch2.DATE_UNKNOWN
  • newPath – 
           the path of the after state of the file
  • newDate –  the timestamp of the after state of the file, see also IFilePatch2.DATE_UNKNOWN
  • hunks – 
           a set of hunks to insert into IFilePatch2
Returns:IFilePatch2 instance
/**
	 * Creates an IFilePatch2 instance and performs recalculation of all hunks'
	 * after positions. Hunk's after position is position in the file state
	 * after applying a patch. It is affected by all the hunks that are to be
	 * applied before a given one. This recalculation is necessary to keep
	 * IFilePatch2's state coherent.
	 *
	 * @param oldPath
	 *            the path of the before state of the file
	 * @param oldDate
	 *            the timestamp of the before state of the file, see also
	 *            {@link IFilePatch2#DATE_UNKNOWN}
	 * @param newPath
	 *            the path of the after state of the file
	 * @param newDate
	 *            the timestamp of the after state of the file, see also
	 *            {@link IFilePatch2#DATE_UNKNOWN}
	 * @param hunks
	 *            a set of hunks to insert into IFilePatch2
	 * @return IFilePatch2 instance
	 */
	public static IFilePatch2 createFilePatch(IPath oldPath, long oldDate,
			IPath newPath, long newDate, IHunk[] hunks) {
		reorder(hunks);
		FilePatch2 fileDiff = new FilePatch2(oldPath, oldDate, newPath, newDate);
		for (IHunk hunk : hunks) {
			fileDiff.add((Hunk) hunk);
		}
		return fileDiff;
	}

	
Adds IHunks to a given IFilePatch2 and performs recalculation of all
hunks' after positions. Hunk's after position is position in the file
state after applying a patch. It is affected by all the hunks that are to
be applied before a given one. This recalculation is necessary to keep
IFilePatch2's state coherent.

Params:
  • filePatch – 
           a file patch to add hunks to
  • toAdd – 
           a set of IHunks to add
Returns:newly created file patch with added hunks
/**
	 * Adds IHunks to a given IFilePatch2 and performs recalculation of all
	 * hunks' after positions. Hunk's after position is position in the file
	 * state after applying a patch. It is affected by all the hunks that are to
	 * be applied before a given one. This recalculation is necessary to keep
	 * IFilePatch2's state coherent.
	 *
	 * @param filePatch
	 *            a file patch to add hunks to
	 * @param toAdd
	 *            a set of IHunks to add
	 * @return newly created file patch with added hunks
	 */
	public static IFilePatch2 addHunks(IFilePatch2 filePatch, IHunk[] toAdd) {
		IHunk[] result = addHunks(filePatch.getHunks(), toAdd);
		reorder(result);
		return createFilePatch(filePatch, result);
	}

	
Removes IHunks from a given IFilePatch2 and performs recalculation of all
hunks' after positions. Hunk's after position is position in the file
state after applying a patch. It is affected by all the hunks that are to
be applied before a given one. This recalculation is necessary to keep
IFilePatch2's state coherent.

Params:
  • filePatch – 
           a file patch to add hunks to
  • toRemove – 
           a set of IHunks to add
Returns:newly created file patch with removed hunks
/**
	 * Removes IHunks from a given IFilePatch2 and performs recalculation of all
	 * hunks' after positions. Hunk's after position is position in the file
	 * state after applying a patch. It is affected by all the hunks that are to
	 * be applied before a given one. This recalculation is necessary to keep
	 * IFilePatch2's state coherent.
	 *
	 * @param filePatch
	 *            a file patch to add hunks to
	 * @param toRemove
	 *            a set of IHunks to add
	 * @return newly created file patch with removed hunks
	 */
	public static IFilePatch2 removeHunks(IFilePatch2 filePatch,
			IHunk[] toRemove) {
		IHunk[] result = removeHunks(filePatch.getHunks(), toRemove);
		reorder(result);
		return createFilePatch(filePatch, result);
	}

	private static IFilePatch2 createFilePatch(IFilePatch2 filePatch,
			IHunk[] hunks) {
		PatchConfiguration config = new PatchConfiguration();
		IPath beforePath = filePatch.getTargetPath(config);
		config.setReversed(true);
		IPath afterPath = filePatch.getTargetPath(config);
		return createFilePatch(beforePath, filePatch.getBeforeDate(),
				afterPath, filePatch.getAfterDate(), hunks);
	}

	private static int getHunkType(String[] lines) {
		boolean hasContextLines = checkForPrefix(CONTEXT_PREFIX, lines);
		if (!hasContextLines) {
			boolean hasLineAdditions = checkForPrefix(ADDITION_PREFIX, lines);
			boolean hasLineDeletions = checkForPrefix(REMOVAL_PREFIX, lines);
			if (hasLineAdditions && !hasLineDeletions) {
				return FilePatch2.ADDITION;
			} else if (!hasLineAdditions && hasLineDeletions) {
				return FilePatch2.DELETION;
			}
		}
		return FilePatch2.CHANGE;
	}

	private static int getHunkLength(String[] lines, boolean old) {
		int length = 0;
		for (String line : lines) {
			if (line.length() > 0) {
				switch (line.charAt(0)) {
				case ' ':
					length++;
					break;
				case '+':
					if (!old) {
						length++;
					}
					break;
				case '-':
					if (old) {
						length++;
					}
					break;
				default:
					throw new IllegalArgumentException(""); //$NON-NLS-1$
				}
			}
		}
		return length;
	}

	private static boolean checkForPrefix(char prefix, String[] lines) {
		for (String line : lines) {
			if (line.length() > 0) {
				if (line.charAt(0) == prefix) {
					return true;
				}
			}
		}
		return false;
	}

	private static IHunk[] addHunks(IHunk[] hunks, IHunk[] toAdd) {
		IHunk[] ret = new IHunk[hunks.length + toAdd.length];
		System.arraycopy(hunks, 0, ret, 0, hunks.length);
		System.arraycopy(toAdd, 0, ret, hunks.length, toAdd.length);
		return ret;
	}

	private static IHunk[] removeHunks(IHunk[] hunks, IHunk[] toRemove) {
		int removed = 0;
		for (int i = 0; i < hunks.length; i++) {
			for (IHunk r : toRemove) {
				if (r == hunks[i]) {
					hunks[i] = null;
					removed++;
				}
			}
		}
		IHunk[] ret = new IHunk[hunks.length - removed];
		for (int i = 0, j = 0; i < hunks.length; i++) {
			if (hunks[i] != null) {
				ret[j++] = hunks[i];
			}
		}
		return ret;
	}

	private static void reorder(IHunk[] hunks) {
		Arrays.sort(hunks, new HunkComparator());
		int shift = 0;
		for (IHunk h : hunks) {
			Hunk hunk = (Hunk) h;
			int start = hunk.getStart(false) + shift;
			hunk.setStart(start, true);
			shift += hunk.getLength(true) - hunk.getLength(false);
		}
	}

	static class HunkComparator implements Comparator<IHunk> {
		@Override
		public int compare(IHunk arg0, IHunk arg1) {
			if ((arg0 != null && arg0 instanceof Hunk)
					&& (arg1 != null && arg1 instanceof Hunk)) {
				Hunk hunk0 = (Hunk) arg0;
				Hunk hunk1 = (Hunk) arg1;
				int shift = hunk0.getStart(true) - hunk1.getStart(true);
				return shift;
			}
			return 0;
		}
	}

}