bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/operations/LinearUndoViolationDetector.java

/*******************************************************************************
 * Copyright (c) 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.commands.operations;

import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;

/**
 * <p>
 * An abstract class for detecting violations in a strict linear undo/redo
 * model. Once a violation is detected, subclasses implement the specific
 * behavior for allowing whether or not the undo/redo should proceed.
 * </p>
 * <p>
 * Note: This class/interface is part of a new API under development. It has
 * been added to builds so that clients can start using the new features.
 * However, it may change significantly before reaching stability. It is being
 * made available at this early stage to solicit feedback with the understanding
 * that any code that uses this API may be broken as the API evolves.
 * </p>
 * 
 * @since 3.1
 * @experimental
 */
public abstract class LinearUndoViolationDetector implements
		IContextOperationApprover {

	protected abstract IStatus allowLinearRedoViolation(IUndoableOperation operation,
			UndoContext context, IOperationHistory history);

	protected abstract IStatus allowLinearUndoViolation(IUndoableOperation operation,
			UndoContext context, IOperationHistory history);

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.core.operations.IOperationApprover#proceedRedoing(org.eclipse.core.operations.IOperation,
	 *      org.eclipse.core.operations.IOperationHistory)
	 */
	public IStatus proceedRedoing(IUndoableOperation operation,
			UndoContext context, IOperationHistory history) {
		if (history.getRedoOperation(context) != operation)
			return allowLinearRedoViolation(operation, context, history);

		return Status.OK_STATUS;
	}

	public IStatus proceedUndoing(IUndoableOperation operation,
			UndoContext context, IOperationHistory history) {
		if (history.getUndoOperation(context) != operation)
			return allowLinearUndoViolation(operation, context, history);

		return Status.OK_STATUS;
	}

}