/*
 * Copyright (C) 2009, Google Inc.
 * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> 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
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

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;
	}
}