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JIDE Common Layer (Professional Swing Components)
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/*
 * @(#)DelayUndoManager.java 12/31/2007
 *
 * Copyright 2002 - 2007 JIDE Software Inc. All rights reserved.
 */

package com.jidesoft.swing;

import javax.swing.*;
import javax.swing.undo.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * An undo manager that aggregates UndoableEdits into one CompoundEdit if they are executed very close to each other. By
 * default, the gap is 500 ms. You can control it by passing in a different number in the constructor.
 */
public class DelayUndoManager extends UndoManager {
    private static final long serialVersionUID = -2910365359251677780L;

    private int _delay = 500;
    private CompoundEdit _cache;

    private static final Logger LOGGER = Logger.getLogger(DelayUndoManager.class.getName());
    protected Timer _timer;

    public DelayUndoManager() {
    }

    public DelayUndoManager(int delay) {
        _delay = delay;
    }


    /**
     * Checks if there are pending edits in the DelayUndoManager.
     *
     * @return true if there are pending edits. Otherwise false.
     */
    public boolean isCacheEmpty() {
        return _cache == null;
    }

    /**
     * Commits the cached edit.
     */
    public synchronized void commitCache() {
        if (_cache != null) {
            _cache.end();
            addEditWithoutCaching();
            if (LOGGER.isLoggable(Level.FINE)) {
                LOGGER.fine("Commit cache: " + _cache);
            }
            _cache = null;
        }
    }

    /**
     * Calls super.addEdit without caching.
     */
    public void addEditWithoutCaching() {
        DelayUndoManager.super.addEdit(_cache);
    }

    public synchronized void discardCache() {
        _cache = null;
        if (_timer != null) {
            _timer.stop();
            _timer = null;
        }
    }

    @Override
    public synchronized boolean addEdit(UndoableEdit anEdit) {
        if (_cache == null) {
            if (LOGGER.isLoggable(Level.FINE)) {
                LOGGER.fine("Create cache: " + anEdit);
            }
            _cache = new CompoundEdit();
            boolean ret = _cache.addEdit(anEdit);
            if (ret) {
                _timer = new Timer(_delay, new ActionListener() {
                    public void actionPerformed(ActionEvent e) {
                        commitCache();
                    }
                });
                _timer.setRepeats(false);
                _timer.start();
            }
            return ret;
        }
        else {
            if (LOGGER.isLoggable(Level.FINE)) {
                LOGGER.fine("Add to cache: " + anEdit);
            }
            if (_timer != null) {
                _timer.restart();
            }
            return _cache.addEdit(anEdit);
        }
    }

    /**
     * Override to commit the cache before checking undo status.
     *
     * @return true if an undo operation would be successful now, false otherwise
     */
    @Override
    public synchronized boolean canUndo() {
        commitCache();
        return super.canUndo();
    }

    /**
     * Override to commit the cache before checking redo status.
     *
     * @return true if an redo operation would be successful now, false otherwise
     */
    @Override
    public synchronized boolean canRedo() {
        commitCache();
        return super.canRedo();
    }

    /**
     * Override to commit the cache before undo.
     *
     * @throws CannotUndoException
     */
    @Override
    public synchronized void undo() throws CannotUndoException {
        commitCache();
        super.undo();
    }

    /**
     * Override to commit the cache before redo.
     *
     * @throws CannotRedoException
     */
    @Override
    public synchronized void redo() throws CannotRedoException {
        commitCache();
        super.redo();
    }

    @Override
    public synchronized void discardAllEdits() {
        super.discardAllEdits();
        discardCache();
    }
}