/*
 * 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;

abstract class AbstractRevQueue extends Generator {
	static final AbstractRevQueue EMPTY_QUEUE = new AlwaysEmptyQueue();

	
Current output flags set for this generator instance. /** Current output flags set for this generator instance. */
	int outputType;

	AbstractRevQueue(boolean firstParent) {
		super(firstParent);
	}

	
Add a commit to the queue.
 This method always adds the commit, even if it is already in the queue or previously was in the queue but has already been removed. To control queue admission use add(RevCommit, RevFlag). 
Params:
c – 
           commit to add./**
	 * Add a commit to the queue.
	 * <p>
	 * This method always adds the commit, even if it is already in the queue or
	 * previously was in the queue but has already been removed. To control
	 * queue admission use {@link #add(RevCommit, RevFlag)}.
	 *
	 * @param c
	 *            commit to add.
	 */
	public abstract void add(RevCommit c);

	
Add a commit if it does not have a flag set yet, then set the flag.

This method permits the application to test if the commit has the given
flag; if it does not already have the flag than the commit is added to
the queue and the flag is set. This later will prevent the commit from
being added twice.
Params:
c – 
           commit to add.
queueControl – 
           flag that controls admission to the queue./**
	 * Add a commit if it does not have a flag set yet, then set the flag.
	 * <p>
	 * This method permits the application to test if the commit has the given
	 * flag; if it does not already have the flag than the commit is added to
	 * the queue and the flag is set. This later will prevent the commit from
	 * being added twice.
	 *
	 * @param c
	 *            commit to add.
	 * @param queueControl
	 *            flag that controls admission to the queue.
	 */
	public final void add(RevCommit c, RevFlag queueControl) {
		if (!c.has(queueControl)) {
			c.add(queueControl);
			add(c);
		}
	}

	
Add a commit's parents if one does not have a flag set yet.

This method permits the application to test if the commit has the given
flag; if it does not already have the flag than the commit is added to
the queue and the flag is set. This later will prevent the commit from
being added twice.
Params:
c – 
           commit whose parents should be added.
queueControl – 
           flag that controls admission to the queue./**
	 * Add a commit's parents if one does not have a flag set yet.
	 * <p>
	 * This method permits the application to test if the commit has the given
	 * flag; if it does not already have the flag than the commit is added to
	 * the queue and the flag is set. This later will prevent the commit from
	 * being added twice.
	 *
	 * @param c
	 *            commit whose parents should be added.
	 * @param queueControl
	 *            flag that controls admission to the queue.
	 */
	public final void addParents(RevCommit c, RevFlag queueControl) {
		final RevCommit[] pList = c.parents;
		if (pList == null) {
			return;
		}
		for (int i = 0; i < pList.length; i++) {
			if (firstParent && i > 0) {
				break;
			}
			add(pList[i], queueControl);
		}
	}

	
{@inheritDoc}

Remove the first commit from the queue.
/**
	 * {@inheritDoc}
	 * <p>
	 * Remove the first commit from the queue.
	 */
	@Override
	public abstract RevCommit next();

	
Remove all entries from this queue.
/**
	 * Remove all entries from this queue.
	 */
	public abstract void clear();

	abstract boolean everbodyHasFlag(int f);

	abstract boolean anybodyHasFlag(int f);

	@Override
	int outputType() {
		return outputType;
	}

	
Describe this queue
Params:
s – 
           a StringBuilder
c –  a RevCommit/**
	 * Describe this queue
	 *
	 * @param s
	 *            a StringBuilder
	 * @param c
	 *            a {@link org.eclipse.jgit.revwalk.RevCommit}
	 */
	protected static void describe(StringBuilder s, RevCommit c) {
		s.append(c.toString());
		s.append('\n');
	}

	private static class AlwaysEmptyQueue extends AbstractRevQueue {
		private AlwaysEmptyQueue() {
			super(false);
		}

		@Override
		public void add(RevCommit c) {
			throw new UnsupportedOperationException();
		}

		@Override
		public RevCommit next() {
			return null;
		}

		@Override
		boolean anybodyHasFlag(int f) {
			return false;
		}

		@Override
		boolean everbodyHasFlag(int f) {
			return true;
		}

		@Override
		public void clear() {
			// Nothing to clear, we have no state.
		}

	}
}