/*
 * Copyright (C) 2010, Sasa Zivkov <sasa.zivkov@sap.com>
 * 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.notes;

import java.io.IOException;

import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectInserter;
import org.eclipse.jgit.lib.ObjectLoader;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.util.io.UnionInputStream;

Default implementation of the NoteMerger. 

If ours and theirs are both non-null, which means they are either both edits
or both adds, then this merger will simply join the content of ours and
theirs (in that order) and return that as the merge result.

If one or ours/theirs is non-null and the other one is null then the non-null
value is returned as the merge result. This means that an edit/delete
conflict is resolved by keeping the edit version.

If both ours and theirs are null then the result of the merge is also null.
/**
 * Default implementation of the {@link org.eclipse.jgit.notes.NoteMerger}.
 * <p>
 * If ours and theirs are both non-null, which means they are either both edits
 * or both adds, then this merger will simply join the content of ours and
 * theirs (in that order) and return that as the merge result.
 * <p>
 * If one or ours/theirs is non-null and the other one is null then the non-null
 * value is returned as the merge result. This means that an edit/delete
 * conflict is resolved by keeping the edit version.
 * <p>
 * If both ours and theirs are null then the result of the merge is also null.
 */
public class DefaultNoteMerger implements NoteMerger {

	
{@inheritDoc} /** {@inheritDoc} */
	@Override
	public Note merge(Note base, Note ours, Note theirs, ObjectReader reader,
			ObjectInserter inserter) throws IOException {
		if (ours == null)
			return theirs;

		if (theirs == null)
			return ours;

		if (ours.getData().equals(theirs.getData()))
			return ours;

		ObjectLoader lo = reader.open(ours.getData());
		ObjectLoader lt = reader.open(theirs.getData());
		try (UnionInputStream union = new UnionInputStream(lo.openStream(),
				lt.openStream())) {
			ObjectId noteData = inserter.insert(Constants.OBJ_BLOB,
					lo.getSize() + lt.getSize(), union);
			return new Note(ours, noteData);
		}
	}
}