/**
* eAdventure (formerly <e-Adventure> and <e-Game>) is a research project of the
* <e-UCM> research group.
*
* Copyright 2005-2010 <e-UCM> research group.
*
* You can access a list of all the contributors to eAdventure at:
* http://e-adventure.e-ucm.es/contributors
*
* <e-UCM> is a research group of the Department of Software Engineering
* and Artificial Intelligence at the Complutense University of Madrid
* (School of Computer Science).
*
* C Profesor Jose Garcia Santesmases sn,
* 28040 Madrid (Madrid), Spain.
*
* For more info please visit: <http://e-adventure.e-ucm.es> or
* <http://www.e-ucm.es>
*
* ****************************************************************************
*
* This file is part of eAdventure, version 2.0
*
* eAdventure is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* eAdventure 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with eAdventure. If not, see <http://www.gnu.org/licenses/>.
*/
package es.eucm.ead.editor.control;
import es.eucm.ead.editor.model.EditorModel;
import es.eucm.ead.editor.model.ModelEvent;
/**
* Actions define tasks that can be performed over the game model.
* This is part of the "Action" pattern, used to allow the easy implementation
* of undo and re-do mechanisms.
*/
public abstract class Command {
/**
* Time stamp of when the action was created
*/
protected long timeStamp = System.currentTimeMillis();
/**
* Get the time when the action was created
*
* @return The time when the action was created
*/
public long getTimeStamp() {
return timeStamp;
}
/**
* Do the actual work. Returns a ChangeEvent if it could be performed,
* null in other case.
*
* @return True if the action was performed correctly
*/
public abstract ModelEvent performCommand(EditorModel em);
/**
* Returns true if the action can be undone
*
* @return True if the action can be undone
*/
public abstract boolean canUndo();
/**
* Undo the work done by the action. Returns true if it could be undone,
* false in other case.
*
* @return a ChangeEvent if it could be performed,
* null in other case.
*/
public abstract ModelEvent undoCommand(EditorModel em);
/**
* Returns true if the action can be redone
*
* @return True if the action can be redone
*/
public abstract boolean canRedo();
/**
* Re-do the work done by the action before it was undone.
*
* @return a ChangeEvent if it could be performed,
* null in other case.
*/
public abstract ModelEvent redoCommand(EditorModel em);
/**
* Combines this action with other similar action (if possible).
* Useful for combining simple changes such as characters typed in the
* same field.
*
* @param other The other action with which this action can
* be combined if possible
* @return true if the actions were combined
*/
public abstract boolean combine(Command other);
}