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/*
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 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2003 The Apache Software Foundation.
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 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
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 * .
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package org.apache.wicket.util.diff;

import java.util.List;

/**
 * Holds a "delta" difference between to revisions of a text.
 * 
 * @version $Revision: 1.1 $ $Date: 2006/03/12 00:24:21 $
 * 
 * @author Juanco Anez
 * @author Brian McBride
 * @see Diff
 * @see Chunk
 * @see Revision modifications
 * 
 *      27 Apr 2003 bwm
 * 
 *      Added getOriginal() and getRevised() accessor methods Added visitor pattern accept() method
 */

public abstract class Delta extends ToString
{

	protected Chunk original;

	protected Chunk revised;

	static Class[][] DeltaClass;

	static
	{
		DeltaClass = new Class[2][2];
		try
		{
			DeltaClass[0][0] = ChangeDelta.class;
			DeltaClass[0][1] = AddDelta.class;
			DeltaClass[1][0] = DeleteDelta.class;
			DeltaClass[1][1] = ChangeDelta.class;
		}
		catch (Exception ignored)
		{
		}
	}

	/**
	 * Returns a Delta that corresponds to the given chunks in the original and revised text
	 * respectively.
	 * 
	 * @param orig
	 *            the chunk in the original text.
	 * @param rev
	 *            the chunk in the revised text.
	 * @return Delta
	 */
	public static Delta newDelta(final Chunk orig, final Chunk rev)
	{
		Class c = DeltaClass[orig.size() > 0 ? 1 : 0][rev.size() > 0 ? 1 : 0];
		Delta result;
		try
		{
			result = (Delta)c.newInstance();
		}
		catch (Exception e)
		{
			return null;
		}
		result.init(orig, rev);
		return result;
	}

	/**
	 * Creates an uninitialized delta.
	 */
	protected Delta()
	{
	}

	/**
	 * Creates a delta object with the given chunks from the original and revised texts.
	 * 
	 * @param orig
	 * @param rev
	 */
	protected Delta(final Chunk orig, final Chunk rev)
	{
		init(orig, rev);
	}

	/**
	 * Initializes the delta with the given chunks from the original and revised texts.
	 * 
	 * @param orig
	 * @param rev
	 */
	protected void init(final Chunk orig, final Chunk rev)
	{
		original = orig;
		revised = rev;
	}

	/**
	 * Verifies that this delta can be used to patch the given text.
	 * 
	 * @param target
	 *            the text to patch.
	 * @throws PatchFailedException
	 *             if the patch cannot be applied.
	 */
	public abstract void verify(List