UndoCommand.java

////////////////////////////////////////////////////////////////////////////////
// Copyright 2013 Michael Schmalle - Teoti Graphix, LLC
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
// http://www.apache.org/licenses/LICENSE-2.0 
// 
// Unless required by applicable law or agreed to in writing, software 
// distributed under the License is distributed on an "AS IS" BASIS, 
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and 
// limitations under the License
// 
// Author: Michael Schmalle, Principal Architect
// mschmalle at teotigraphix dot com
////////////////////////////////////////////////////////////////////////////////

package com.teotigraphix.caustk.controller.command;

/**
 * This command handles adding itself to the provided/injected CommandHistory.
 * <p>
 * UndoableCommands are pushed to the CommandHistory only once the Command has
 * been executed, and are removed once the Command has been undone.
 * <p>
 * Undoable commands can be cancelled by calling cancel() from within their
 * doExecute() function, and they will not be added to the history. All
 * functions assume the CommandHistory dependency has been provided as the
 * public property 'history'.
 */
public abstract class UndoCommand extends UndoCommandBase {

    ICommandHistory history;

    private boolean isCancelled = false;

    protected boolean isCanceled() {
        return isCancelled;
    }

    private boolean hasRegisteredWithHistory;

    protected boolean hasSteppedBack = false;

    /**
     * All injected members are guaranteed to be set when this commit is called.
     * <p>
     * Setup all persistent state that is needed for undo here.
     * </p>
     */
    protected void commitState() {
    }

    public UndoCommand() {
        super();
    }

    @Override
    public void cancel() {
        isCancelled = true;
    }

    @Override
    protected abstract void doExecute();

    @Override
    protected abstract void undoExecute();

    /**
     * Checks if this command has added itself to the command history. Ensures
     * we don't let this Command push to the CommandHistory more than once.
     */
    @SuppressWarnings("unused")
    private void registerIfRequired() {
        if (!hasRegisteredWithHistory) {
            hasRegisteredWithHistory = true;
            history.execute(this);
        }
    }
}