/*
    * Copyright (C) 2008-2009, Google Inc.
    * Copyright (C) 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
    * 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.treewalk;
  
  import java.io.IOException;
  
  import org.eclipse.jgit.errors.CorruptObjectException;
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectReader;
  
  /**
   * Iterator over an empty tree (a directory with no files).
   */
  public class EmptyTreeIterator extends AbstractTreeIterator {
  	/**
  	 * Create a new iterator with no parent.
  	 */
  	public EmptyTreeIterator() {
  		// Create a root empty tree.
  	}
  
  	EmptyTreeIterator(AbstractTreeIterator p) {
  		super(p);
  		pathLen = pathOffset;
  	}
  
  	/**
  	 * Create an iterator for a subtree of an existing iterator.
  	 * <p>
  	 * The caller is responsible for setting up the path of the child iterator.
  	 *
  	 * @param p
  	 *            parent tree iterator.
  	 * @param childPath
  	 *            path array to be used by the child iterator. This path must
  	 *            contain the path from the top of the walk to the first child
  	 *            and must end with a '/'.
  	 * @param childPathOffset
  	 *            position within <code>childPath</code> where the child can
  	 *            insert its data. The value at
  	 *            <code>childPath[childPathOffset-1]</code> must be '/'.
  	 */
  	public EmptyTreeIterator(final AbstractTreeIterator p,
  			final byte[] childPath, final int childPathOffset) {
  		super(p, childPath, childPathOffset);
  		pathLen = childPathOffset - 1;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public AbstractTreeIterator createSubtreeIterator(ObjectReader reader)
  			throws IncorrectObjectTypeException, IOException {
  		return new EmptyTreeIterator(this);
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public boolean hasId() {
  		return false;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public ObjectId getEntryObjectId() {
  		return ObjectId.zeroId();
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public byte[] idBuffer() {
  		return zeroid;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public int idOffset() {
  		return 0;
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public void reset() {
  		// Do nothing.
  	}
  
  	/** {@inheritDoc} */
  	@Override
  	public boolean first() {
 		return true;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public boolean eof() {
 		return true;
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void next(int delta) throws CorruptObjectException {
 		// Do nothing.
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void back(int delta) throws CorruptObjectException {
 		// Do nothing.
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void stopWalk() {
 		if (parent != null)
 			parent.stopWalk();
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	protected boolean needsStopWalk() {
 		return parent != null && parent.needsStopWalk();
 	}
 }