/*******************************************************************************
 * Copyright (c) 2000, 2006 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.jface.text.IUndoManager;

import dwtx.jface.text.ITextViewer; // packageimport

import dwt.dwthelper.utils;

/**
 * An undo manager is connected to at most one
 * {@link dwtx.jface.text.ITextViewer}.
 * <p>
 * It monitors the text viewer and keeps a history of the changes applied to the
 * viewer. The undo manager groups those changes into user interactions which on
 * an undo request are rolled back in one atomic change.</p>
 * <p>
 * In order to provide backward compatibility for clients of
 * <code>IUndoManager</code>, extension interfaces are used as a means of
 * evolution. The following extension interfaces exist:
 * <ul>
 * <li>{@link dwtx.jface.text.IUndoManagerExtension} since version 3.1
 * introducing access to the undo context.</li>
 * </ul></p>
 * <p>
 * Clients may implement this interface or use the standard implementation
 * <code>TextViewerUndoManager</code>.
 * </p>
 *
 * @see TextViewerUndoManager
 * @see IUndoManagerExtension
 */
public interface IUndoManager {

    /**
     * Connects this undo manager to the given text viewer.
     *
     * @param viewer the viewer the undo manager is connected to
     */
    void connect(ITextViewer viewer);

    /**
     * Disconnects this undo manager from its text viewer.
     * If this undo manager hasn't been connected before this
     * operation has no effect.
     */
    void disconnect();

    /**
     * Signals the undo manager that all subsequent changes until
     * <code>endCompoundChange</code> is called are to be undone in one piece.
     */
    void beginCompoundChange();

    /**
     * Signals the undo manager that the sequence of changes which started with
     * <code>beginCompoundChange</code> has been finished. All subsequent changes
     * are considered to be individually undo-able.
     */
    void endCompoundChange();

    /**
     * Resets the history of the undo manager. After that call,
     * there aren't any undo-able or redo-able text changes.
     */
    void reset();

    /**
     * The given parameter determines the maximal length of the history
     * remembered by the undo manager.
     *
     * @param undoLevel the length of this undo manager's history
     */
    void setMaximalUndoLevel(int undoLevel);

    /**
     * Returns whether at least one text change can be rolled back.
     *
     * @return <code>true</code> if at least one text change can be rolled back
     */
    bool undoable();

    /**
     * Returns whether at least one text change can be repeated. A text change
     * can be repeated only if it was executed and rolled back.
     *
     * @return <code>true</code> if at least on text change can be repeated
     */
    bool redoable();

    /**
     * Rolls back the most recently executed text change.
     */
    void undo();

    /**
     * Repeats the most recently rolled back text change.
     */
    void redo();

}