/*
 * Copyright (C) 2009, Google Inc.
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
 * 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;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.revwalk;

import java.io.IOException;

import org.eclipse.jgit.errors.IncorrectObjectTypeException;
import org.eclipse.jgit.errors.MissingObjectException;

Delays commits to be at least PendingGenerator.OVER_SCAN late. 
 This helps to "fix up" weird corner cases resulting from clock skew, by slowing down what we produce to the caller we get a better chance to ensure PendingGenerator reached back far enough in the graph to correctly mark commits RevWalk.UNINTERESTING if necessary. 
 This generator should appear before FixUninterestingGenerator if the lower level pending isn't already fully buffered. /**
 * Delays commits to be at least {@link PendingGenerator#OVER_SCAN} late.
 * <p>
 * This helps to "fix up" weird corner cases resulting from clock skew, by
 * slowing down what we produce to the caller we get a better chance to ensure
 * PendingGenerator reached back far enough in the graph to correctly mark
 * commits {@link RevWalk#UNINTERESTING} if necessary.
 * <p>
 * This generator should appear before {@link FixUninterestingGenerator} if the
 * lower level {@link #pending} isn't already fully buffered.
 */
final class DelayRevQueue extends Generator {
	private static final int OVER_SCAN = PendingGenerator.OVER_SCAN;

	private final Generator pending;

	private final FIFORevQueue delay;

	private int size;

	DelayRevQueue(Generator g) {
		super(g.firstParent);
		pending = g;
		delay = new FIFORevQueue();
	}

	@Override
	int outputType() {
		return pending.outputType();
	}

	@Override
	RevCommit next() throws MissingObjectException,
			IncorrectObjectTypeException, IOException {
		while (size < OVER_SCAN) {
			final RevCommit c = pending.next();
			if (c == null)
				break;
			delay.add(c);
			size++;
		}

		final RevCommit c = delay.next();
		if (c == null)
			return null;
		size--;
		return c;
	}
}