/*
 * Copyright (C) 2017, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.internal.revwalk;

import org.eclipse.jgit.lib.BitmapIndex.Bitmap;
import org.eclipse.jgit.lib.BitmapIndex.BitmapBuilder;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.revwalk.filter.RevFilter;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevFlag;

/**
 * A RevFilter that adds the visited commits to {@code bitmap} as a side
 * effect.
 * <p>
 * When the walk hits a commit that is part of {@code bitmap}'s
 * BitmapIndex, that entire bitmap is ORed into {@code bitmap} and the
 * commit and its parents are marked as SEEN so that the walk does not
 * have to visit its ancestors.  This ensures the walk is very short if
 * there is good bitmap coverage.
 * <p>
 * Commits named in {@code seen} are considered already seen.  If one is
 * encountered, that commit and its parents will be marked with the SEEN
 * flag to prevent the walk from visiting its ancestors.
 */
public class AddUnseenToBitmapFilter extends RevFilter {
	private final BitmapBuilder seen;
	private final BitmapBuilder bitmap;

	/**
	 * Create a filter that adds visited commits to the given bitmap, but does not walk
	 * through the objects in {@code seen}.
	 *
	 * @param seen objects that are already seen
	 * @param bitmap bitmap to write visited commits to
	 */
	public AddUnseenToBitmapFilter(BitmapBuilder seen, BitmapBuilder bitmap) {
		this.seen = seen;
		this.bitmap = bitmap;
	}

	/** {@inheritDoc} */
	@Override
	public final boolean include(RevWalk walker, RevCommit cmit) {
		Bitmap visitedBitmap;

		if (seen.contains(cmit) || bitmap.contains(cmit)) {
			// already seen or included
		} else if ((visitedBitmap = bitmap.getBitmapIndex()
				.getBitmap(cmit)) != null) {
			bitmap.or(visitedBitmap);
		} else {
			bitmap.addObject(cmit, Constants.OBJ_COMMIT);
			return true;
		}

		for (RevCommit p : cmit.getParents()) {
			p.add(RevFlag.SEEN);
		}
		return false;
	}

	/** {@inheritDoc} */
	@Override
	public final RevFilter clone() {
		throw new UnsupportedOperationException();
	}

	/** {@inheritDoc} */
	@Override
	public final boolean requiresCommitBody() {
		return false;
	}
}