/*
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2003 The Apache Software Foundation.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
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 * 5. Products derived from this software may not be called "Apache"
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 *
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 * 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.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.commons.jrcs.diff;

import java.util.List;

/**
 * Holds a "delta" difference between to revisions of a text.
 * 
 * @version $Revision: 15101 $ $Date: 2006-04-12 18:30:19 +0100 (Wed, 12 Apr
 *          2006) $
 * @author <a href="mailto:juanco@suigeneris.org">Juanco Anez</a>
 * @author <a href="mailto:bwm@hplb.hpl.hp.com">Brian McBride</a>
 * @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 org.apache.commons.jrcs.util.ToString
{

	protected Chunk original;

	protected Chunk revised;

	static Class[][] DeltaClass;

	static
	{
		DeltaClass = new Class[2][2];
		DeltaClass[0][0] = org.apache.commons.jrcs.diff.ChangeDelta.class;
		DeltaClass[0][1] = org.apache.commons.jrcs.diff.AddDelta.class;
		DeltaClass[1][0] = org.apache.commons.jrcs.diff.DeleteDelta.class;
		DeltaClass[1][1] = org.apache.commons.jrcs.diff.ChangeDelta.class;
	}

	/**
	 * 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.
	 */
	public static Delta newDelta(Chunk orig, Chunk rev)
	{
		Class c = DeltaClass[orig.size() > 0 ? 1 : 0][rev.size() > 0 ? 1 : 0];
		Delta result;
		try
		{
			result = (Delta) c.newInstance();
		}
		catch (InstantiationException e)
		{
			return null;
		}
		catch (IllegalAccessException e)
		{
			return null;
		}
		result.init(orig, rev);
		return result;
	}

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

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

	/**
	 * Initializaes the delta with the given chunks from the original and
	 * revised texts.
	 */
	protected void init(Chunk orig, 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 target) throws PatchFailedException;

	/**
	 * Applies this delta as a patch to the given text.
	 * 
	 * @param target
	 *        the text to patch.
	 * @throws PatchFailedException
	 *         if the patch cannot be applied.
	 */
	public final void patch(List target) throws PatchFailedException
	{
		verify(target);
		try
		{
			applyTo(target);
		}
		catch (Exception e)
		{
			throw new PatchFailedException(e.getMessage(), e);
		}
	}

	/**
	 * Applies this delta as a patch to the given text.
	 * 
	 * @param target
	 *        the text to patch.
	 * @throws PatchFailedException
	 *         if the patch cannot be applied.
	 */
	public abstract void applyTo(List target);

	/**
	 * Converts this delta into its Unix diff style string representation.
	 * 
	 * @param s
	 *        a {@link StringBuffer StringBuffer} to which the string
	 *        representation will be appended.
	 */
	public void toString(StringBuffer s)
	{
		original.rangeString(s);
		s.append("x");
		revised.rangeString(s);
		s.append(Diff.NL);
		original.toString(s, "> ", "\n");
		s.append("---");
		s.append(Diff.NL);
		revised.toString(s, "< ", "\n");
	}

	/**
	 * Converts this delta into its RCS style string representation.
	 * 
	 * @param s
	 *        a {@link StringBuffer StringBuffer} to which the string
	 *        representation will be appended.
	 * @param EOL
	 *        the string to use as line separator.
	 */
	public abstract void toRCSString(StringBuffer s, String EOL);

	/**
	 * Converts this delta into its RCS style string representation.
	 * 
	 * @param EOL
	 *        the string to use as line separator.
	 */
	public String toRCSString(String EOL)
	{
		StringBuffer s = new StringBuffer();
		toRCSString(s, EOL);
		return s.toString();
	}

	/**
	 * Accessor method to return the chunk representing the original sequence of
	 * items
	 * 
	 * @return the original sequence
	 */
	public Chunk getOriginal()
	{
		return original;
	}

	/**
	 * Accessor method to return the chunk representing the updated sequence of
	 * items.
	 * 
	 * @return the updated sequence
	 */
	public Chunk getRevised()
	{
		return revised;
	}

	/**
	 * Accepts a visitor.
	 * <p>
	 * See the Visitor pattern in "Design Patterns" by the GOF4.
	 * 
	 * @param visitor
	 *        The visitor.
	 */
	public abstract void accept(RevisionVisitor visitor);
}
