xy.reflect.ui.undo.IModification Maven / Gradle / Ivy

/*******************************************************************************
 * Copyright (C) 2018 OTK Software
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * The GNU General Public License allows you also to freely redistribute 
 * the libraries under the same license, if you provide the terms of the 
 * GNU General Public License with them and add the following 
 * copyright notice at the appropriate place (with a link to 
 * http://javacollection.net/reflectionui/ web site when possible).
 ******************************************************************************/
package xy.reflect.ui.undo;

/**
 * This is the base interface of every object state modification made through an
 * abstract UI model element.
 * 
 * @author olitank
 *
 */
public interface IModification {

	/**
	 * Dummy instance of this class made available for utilitarian purposes.
	 * Represents a null (no impact on the object state) modification.
	 */
	IModification NULL_MODIFICATION = new IModification() {
		@Override
		public IModification applyAndGetOpposite() {
			return NULL_MODIFICATION;
		}

		@Override
		public boolean isNull() {
			return true;
		}

		@Override
		public String toString() {
			return getTitle();
		}

		@Override
		public String getTitle() {
			return "NULL_MODIFICATION";
		}

	};

	/**
	 * Dummy instance of this class made available for utilitarian purposes.
	 * Represents a fake (simulated impact on the object state) modification.
	 */
	IModification FAKE_MODIFICATION = new IModification() {
		@Override
		public IModification applyAndGetOpposite() {
			return FAKE_MODIFICATION;
		}

		@Override
		public boolean isNull() {
			return false;
		}

		@Override
		public String toString() {
			return getTitle();
		}

		@Override
		public String getTitle() {
			return "FAKE_MODIFICATION";
		}

	};;

	/**
	 * Applies the current modification.
	 * 
	 * @return the opposite modification.
	 */
	IModification applyAndGetOpposite();

	/**
	 * @return true if and only if this modification should be considered as empty,
	 *         with no impact on the target object state.
	 */
	boolean isNull();

	/**
	 * @return the title of this modification.
	 */
	String getTitle();
}