/*
    * Copyright (c) 2020, Google LLC  and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * http://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  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.lib.AnyObjectId;
  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 the same as {@code cachedCommit} or 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.
   */
  public class AddToBitmapWithCacheFilter extends RevFilter {
  	private final AnyObjectId cachedCommit;
  
  	private final Bitmap cachedBitmap;
  
  	private final BitmapBuilder bitmap;
  
  	/**
  	 * Create a filter with a cached BitmapCommit that adds visited commits to
  	 * the given bitmap.
  	 *
  	 * @param cachedCommit
  	 *            the cached commit
  	 * @param cachedBitmap
  	 *            the bitmap corresponds to {@code cachedCommit}}
  	 * @param bitmap
  	 *            bitmap to write visited commits to
  	 */
  	public AddToBitmapWithCacheFilter(AnyObjectId cachedCommit,
  			Bitmap cachedBitmap,
  			BitmapBuilder bitmap) {
  		this.cachedCommit = cachedCommit;
  		this.cachedBitmap = cachedBitmap;
  		this.bitmap = bitmap;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public final boolean include(RevWalk rw, RevCommit c) {
  		Bitmap visitedBitmap;
  
  		if (bitmap.contains(c)) {
  			// already included
  		} else if ((visitedBitmap = bitmap.getBitmapIndex()
  				.getBitmap(c)) != null) {
  			bitmap.or(visitedBitmap);
  		} else if (cachedCommit.equals(c)) {
  			bitmap.or(cachedBitmap);
  		} else {
  			bitmap.addObject(c, Constants.OBJ_COMMIT);
  			return true;
  		}
  
  		for (RevCommit p : c.getParents()) {
  			p.add(RevFlag.SEEN);
  		}
  		return false;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public final RevFilter clone() {
  		throw new UnsupportedOperationException();
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public final boolean requiresCommitBody() {
  		return false;
  	}
  }