/*******************************************************************************
 * Copyright (c) 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module dwtx.core.commands.operations.IAdvancedUndoableOperation;

import dwtx.core.commands.ExecutionException;
import dwtx.core.runtime.IProgressMonitor;
import dwtx.core.runtime.IStatus;

import dwtx.core.commands.operations.OperationHistoryEvent;

import dwt.dwthelper.utils;

/**
 * <p>
 * IAdvancedUndoableOperation defines an interface for undoable operations that
 * modify one or more elements in a model and attempt to keep model listeners up
 * to date with changes that occur in the undo and redo history involving particular
 * model elements.  It also defines methods for computing the validity of an operation
 * for undo or redo before attempting to perform the undo or redo.
 * </p>
 * <p>
 * This interface is intended to be used by legacy frameworks that are adapting
 * their original undo and redo support to this framework. The methods in this
 * interface allow legacy clients to maintain features not supported in the
 * basic operations framework.
 * </p>
 *
 * @since 3.1
 *
 */
public interface IAdvancedUndoableOperation {

    /**
     * <p>
     * An operation history notification about this operation is about to be
     * sent to operation history listeners. Any preparation needed before
     * listeners are notified about this operation should be performed here.
     *
     * <p>
     * This method has been added to support legacy undo frameworks that are
     * adapting to IUndoableOperation. Operations that previously relied on
     * notification from their containing history or stack before any listeners
     * are notified about changes to the operation should implement this
     * interface.
     *
     * @param event
     *            the event that is about to be sent with the pending
     *            notification
     *
     */
    void aboutToNotify(OperationHistoryEvent event);

    /**
     * <p>
     * Return an array of objects that are affected by executing, undoing, or
     * redoing this operation. If it cannot be determined which objects are
     * affected, return null.
     * </p>
     *
     * @return the array of Objects modified by this operation, or
     *         <code>null</code> if the affected objects cannot be determined.
     */
    Object[] getAffectedObjects();

    /**
     * Return a status indicating the projected outcome of undoing the receiver.
     *
     * This method should be used to report the possible outcome of an undo and
     * is used when computing the validity of an undo is too expensive to
     * perform in {@link IUndoableOperation#canUndo()}. It is not called by the
     * operation history, but instead is used by clients (such as implementers
     * of {@link IOperationApprover}) who wish to perform advanced validation of
     * an operation before attempting to undo it.
     *
     * If the result of this method is the discovery that an operation can in
     * fact not be undone, then the operation is expected to correctly answer
     * <code>false</code> on subsequent calls to
     * {@link IUndoableOperation#canUndo()}.
     *
     * @param monitor
     *            the progress monitor (or <code>null</code>) to use for
     *            reporting progress to the user while computing the validity.
     *
     * @return the IStatus indicating the validity of the undo. The status
     *         severity should be set to <code>OK</code> if the undo can
     *         successfully be performed, and <code>ERROR</code> if it
     *         cannnot. Any other status is assumed to represent an ambiguous
     *         state.
     * @throws ExecutionException
     *             if an exception occurs while computing the validity.
     */
    IStatus computeUndoableStatus(IProgressMonitor monitor);

    /**
     * Return a status indicating the projected outcome of redoing the receiver.
     *
     * This method should be used to report the possible outcome of a redo and
     * is used when computing the validity of a redo is too expensive to perform
     * in {@link IUndoableOperation#canRedo()}. It is not called by the
     * operation history, but instead is used by clients (such as implementers
     * of {@link IOperationApprover}) who wish to perform advanced validation of
     * an operation before attempting to redo it.
     *
     * If the result of this method is the discovery that an operation can in
     * fact not be redone, then the operation is expected to correctly answer
     * <code>false</code> on subsequent calls to
     * {@link IUndoableOperation#canRedo()}.
     *
     * @param monitor
     *            the progress monitor (or <code>null</code>) to use for
     *            reporting progress to the user while computing the validity.
     *
     * @return the IStatus indicating the validity of the redo. The status
     *         severity should be set to <code>OK</code> if the redo can
     *         successfully be performed, and <code>ERROR</code> if it
     *         cannnot. Any other status is assumed to represent an ambiguous
     *         state.
     * @throws ExecutionException
     *             if an exception occurs while computing the validity.
     */
    IStatus computeRedoableStatus(IProgressMonitor monitor);

}