/*******************************************************************************
 * Copyright (c) 2014, 2015 Cisco Systems, Inc. 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
 *  
 *******************************************************************************/
package com.cisco.yangide.ui.internal;

import java.util.HashMap;

import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.resource.ImageDescriptor;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Display;

import com.cisco.yangide.ui.YangUIPlugin;

/**
 * A registry that maps <code>ImageDescriptors</code> to <code>Image</code>.
 *
 * @author Konstantin Zaitsev
 * @date Jul 14, 2014
 */
public class ImageDescriptorRegistry {

    private HashMap<ImageDescriptor, Image> fRegistry = new HashMap<>(10);
    private Display fDisplay;

    /**
     * Creates a new image descriptor registry for the current or default display, respectively.
     */
    public ImageDescriptorRegistry() {
        this(YangUIPlugin.getStandardDisplay());
    }

    /**
     * Creates a new image descriptor registry for the given display. All images managed by this
     * registry will be disposed when the display gets disposed.
     *
     * @param display the display the images managed by this registry are allocated for
     */
    public ImageDescriptorRegistry(Display display) {
        fDisplay = display;
        Assert.isNotNull(fDisplay);
        hookDisplay();
    }

    /**
     * Returns the image associated with the given image descriptor.
     *
     * @param descriptor the image descriptor for which the registry manages an image
     * @return the image associated with the image descriptor or <code>null</code> if the image
     * descriptor can't create the requested image.
     */
    public Image get(ImageDescriptor descriptor) {
        if (descriptor == null) {
            descriptor = ImageDescriptor.getMissingImageDescriptor();
        }

        Image result = fRegistry.get(descriptor);
        if (result != null) {
            return result;
        }

        Assert.isTrue(fDisplay == YangUIPlugin.getStandardDisplay());
        result = descriptor.createImage();
        if (result != null) {
            fRegistry.put(descriptor, result);
        }
        return result;
    }

    /**
     * Disposes all images managed by this registry.
     */
    public void dispose() {
        for (Image image : fRegistry.values()) {
            image.dispose();
        }
        fRegistry.clear();
    }

    private void hookDisplay() {
        fDisplay.disposeExec(new Runnable() {
            @Override
            public void run() {
                dispose();
            }
        });
    }
}