/*
    * Copyright (C) 2008-2009, Google Inc.
    * Copyright (C) 2009, Robin Rosenberg <robin.rosenberg@dewire.com> 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.merge;
  
  import java.io.IOException;
  
  import org.eclipse.jgit.lib.Config;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectInserter;
  import org.eclipse.jgit.lib.Repository;
  
  /**
   * Trivial merge strategy to make the resulting tree exactly match an input.
   * <p>
   * This strategy can be used to cauterize an entire side branch of history, by
   * setting the output tree to one of the inputs, and ignoring any of the paths
   * of the other inputs.
   */
  public class StrategyOneSided extends MergeStrategy {
  	private final String strategyName;
  
  	private final int treeIndex;
  
  	/**
  	 * Create a new merge strategy to select a specific input tree.
  	 *
  	 * @param name
  	 *            name of this strategy.
  	 * @param index
  	 *            the position of the input tree to accept as the result.
  	 */
  	protected StrategyOneSided(String name, int index) {
  		strategyName = name;
  		treeIndex = index;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public String getName() {
  		return strategyName;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public Merger newMerger(Repository db) {
  		return new OneSide(db, treeIndex);
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public Merger newMerger(Repository db, boolean inCore) {
  		return new OneSide(db, treeIndex);
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public Merger newMerger(ObjectInserter inserter, Config config) {
  		return new OneSide(inserter, treeIndex);
  	}
  
  	static class OneSide extends Merger {
  		private final int treeIndex;
  
  		protected OneSide(Repository local, int index) {
  			super(local);
  			treeIndex = index;
  		}
  
  		protected OneSide(ObjectInserter inserter, int index) {
  			super(inserter);
  			treeIndex = index;
  		}
  
  		@Override
  		protected boolean mergeImpl() throws IOException {
  			return treeIndex < sourceTrees.length;
  		}
  
  		@Override
  		public ObjectId getResultTreeId() {
  			return sourceTrees[treeIndex];
  		}
  
  		@Override
  		public ObjectId getBaseCommitId() {
  			return null;
  		}
  	}
  }