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repeatable course/process (delta-processing-engine, event sourcing)

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/*
 * File: $HeadURL$
 * Id  : $Id$
 * 
 * created by: Tom
 * created on: 31.03.2017
 * 
 * Copyright: (c) Thomas Schneider 2017, all rights reserved
 */
package de.tsl2.nano.cursus;

import java.io.Serializable;

import de.tsl2.nano.core.util.Util;
import de.tsl2.nano.repeat.IChange;

/**
 * describes the change of an item/res from an old to a new value
 * @author Tom
 */
public class Mutatio implements IChange, Serializable {
	private static final long serialVersionUID = 1L;
	protected V previous;
	protected V next;
	protected Res res;

	public Mutatio() {
	}

	public Mutatio(V next, Res res) {
		this.next = next;
		this.res = res;
	}

	@Override
	public Object getItem() {
		return res;
	}

	@Override
	public V getOld() {
		if (previous == null && res != null) //TODO: constrain, if old value is really null!
			previous = res.getValueAccess().getValue();
		return previous;
	}

	@Override
	public V getNew() {
		return next;
	}

	@Override
	public IChange revert() {
		return new Mutatio(previous, res);
	}

	@Override
	public int hashCode() {
		return Util.hashCode(res, previous, next);
	}

	@Override
	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (!(o instanceof Mutatio))
			return false;
		Mutatio m = (Mutatio) o;
		return Util.equals(this.res, m.res) && Util.equals(previous, m.previous) && Util.equals(next, m.next);
	}

	@Override
	public String toString() {
		return Util.toString(getClass(), res, previous, next);
	}
}