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 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2003 The Apache Software Foundation.
 * All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
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 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
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 *    any, must include the following acknowledgement:
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 *    if and wherever such third-party acknowledgements normally appear.
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package org.apache.commons.jrcs.diff.myers;

/**
 * A node in a diffpath.
 * 
 * @version $Revision: 7756 $ $Date: 2006-04-12 18:30:19 +0100 (Wed, 12 Apr
 *          2006) $
 * @author <a href="mailto:juanco@suigeneris.org">Juanco Anez</a>
 * @see DiffNode
 * @see Snake
 */
public abstract class PathNode
{
	/** Position in the original sequence. */
	public final int i;

	/** Position in the revised sequence. */
	public final int j;

	/** The previous node in the path. */
	public final PathNode prev;

	/**
	 * Concatenates a new path node with an existing diffpath.
	 * 
	 * @param i
	 *        The position in the original sequence for the new node.
	 * @param j
	 *        The position in the revised sequence for the new node.
	 * @param prev
	 *        The previous node in the path.
	 */
	public PathNode(int i, int j, PathNode prev)
	{
		this.i = i;
		this.j = j;
		this.prev = prev;
	}

	/**
	 * Is this node a {@link Snake Snake node}?
	 * 
	 * @return true if this is a {@link Snake Snake node}
	 */
	public abstract boolean isSnake();

	/**
	 * Is this a bootstrap node?
	 * <p>
	 * In bottstrap nodes one of the two corrdinates is less than zero.
	 * 
	 * @return tru if this is a bootstrap node.
	 */
	public boolean isBootstrap()
	{
		return i < 0 || j < 0;
	}

	/**
	 * Skips sequences of {@link DiffNode DiffNodes} until a {@link Snake} or
	 * bootstrap node is found, or the end of the path is reached.
	 * 
	 * @return The next first {@link Snake} or bootstrap node in the path, or
	 *         <code>null</code> if none found.
	 */
	public final PathNode previousSnake()
	{
		if (isBootstrap()) return null;
		if (!isSnake() && prev != null) return prev.previousSnake();
		return this;
	}

	/**
	 * {@inheritDoc}
	 */
	public String toString()
	{
		StringBuffer buf = new StringBuffer("[");
		PathNode node = this;
		while (node != null)
		{
			buf.append("(");
			buf.append(Integer.toString(node.i));
			buf.append(",");
			buf.append(Integer.toString(node.j));
			buf.append(")");
			node = node.prev;
		}
		buf.append("]");
		return buf.toString();
	}
}