/*******************************************************************************
 * Copyright (c) 2004, 2012, 2015 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Dirk Fauth <dirk.fauth@googlemail.com> - Bug 463043
 *******************************************************************************/
package org.eclipse.ui.internal;

import org.eclipse.core.runtime.Adapters;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.e4.core.services.events.IEventBroker;
import org.eclipse.e4.ui.model.application.ui.MUIElement;
import org.eclipse.e4.ui.model.application.ui.basic.MPart;
import org.eclipse.e4.ui.model.application.ui.basic.MPartStack;
import org.eclipse.e4.ui.workbench.IPresentationEngine;
import org.eclipse.e4.ui.workbench.UIEvents;
import org.eclipse.e4.ui.workbench.UIEvents.EventTags;
import org.eclipse.swt.custom.BusyIndicator;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.ui.IMemento;
import org.eclipse.ui.IViewSite;
import org.eclipse.ui.PartInitException;
import org.eclipse.ui.internal.intro.IntroMessages;
import org.eclipse.ui.intro.IIntroPart;
import org.eclipse.ui.intro.IIntroSite;
import org.eclipse.ui.part.ViewPart;
import org.osgi.service.event.EventHandler;

/**
 * Simple view that will wrap an <code>IIntroPart</code>.
 *
 * @since 3.0
 */
public final class ViewIntroAdapterPart extends ViewPart {

	private IIntroPart introPart;

	private IIntroSite introSite;

	private boolean handleZoomEvents = true;

	private IEventBroker eventBroker;

	private EventHandler zoomChangeListener = event -> {
		if (!handleZoomEvents)
			return;

		Object changedObj = event.getProperty(EventTags.ELEMENT);
		if (!(changedObj instanceof MPartStack))
			return;

		if (changedObj != getIntroStack())
			return;

		if (UIEvents.isADD(event)
				&& UIEvents.contains(event, UIEvents.EventTags.NEW_VALUE, IPresentationEngine.MAXIMIZED)) {
			setStandby(false);
		} else if (UIEvents.isREMOVE(event)
				&& UIEvents.contains(event, UIEvents.EventTags.OLD_VALUE, IPresentationEngine.MAXIMIZED)) {
			setStandby(true);
		}
	};

	/**
	 * Adds a listener that toggles standby state if the view pane is zoomed.
	 */
	private void addZoomListener() {
		ViewSite site = (ViewSite) getViewSite();
		MPart introModelPart = site.getModel();
		if (introModelPart == null || introModelPart.getContext() == null)
			return;

		eventBroker = introModelPart.getContext().get(IEventBroker.class);
		eventBroker.subscribe(UIEvents.ApplicationElement.TOPIC_TAGS, zoomChangeListener);
	}

	private MPartStack getIntroStack() {
		ViewSite site = (ViewSite) getViewSite();

		MPart introModelPart = site.getModel();
		if (introModelPart.getCurSharedRef() != null) {
			MUIElement introPartParent = introModelPart.getCurSharedRef().getParent();
			if (introPartParent instanceof MPartStack) {
				return (MPartStack) introPartParent;
			}
		}

		return null;
	}

	/**
	 * Forces the standby state of the intro part.
	 *
	 * @param standby update the standby state
	 */
	public void setStandby(final boolean standby) {
		final Control control = (Control) ((PartSite) getSite()).getModel().getWidget();
		BusyIndicator.showWhile(control.getDisplay(), () -> {
			try {
				control.setRedraw(false);
				introPart.standbyStateChanged(standby);
			} finally {
				control.setRedraw(true);
			}

		});
	}

	/**
	 * Toggles handling of zoom events.
	 *
	 * @param handle whether to handle zoom events
	 */
	public void setHandleZoomEvents(boolean handle) {
		handleZoomEvents = handle;
	}

	@Override
	public void createPartControl(Composite parent) {
		addZoomListener();
		introPart.createPartControl(parent);

		ViewSite site = (ViewSite) getViewSite();
		MPart introModelPart = site.getModel();
		if (introModelPart.getCurSharedRef() != null) {
			MUIElement parentElement = introModelPart.getCurSharedRef().getParent();
			if (parentElement instanceof MPartStack) {
				setStandby(!parentElement.getTags().contains(IPresentationEngine.MAXIMIZED));
			}
		}
	}

	@Override
	public void dispose() {
		eventBroker.unsubscribe(zoomChangeListener);

		getSite().getWorkbenchWindow().getWorkbench().getIntroManager().closeIntro(introPart);
		introPart.dispose();
		super.dispose();
	}

	@Override
	public <T> T getAdapter(Class<T> adapter) {
		return Adapters.adapt(introPart, adapter);
	}

	@Override
	public Image getTitleImage() {
		return introPart.getTitleImage();
	}

	@Override
	public String getTitle() {
		// this method is called eagerly before our init method is called (and
		// therefore before our intropart is created). By default return
		// the view title from the view declaration. We will fire a property
		// change to set the title to the proper value in the init method.
		return introPart == null ? super.getTitle() : introPart.getTitle();
	}

	@Override
	public void init(IViewSite site, IMemento memento) throws PartInitException {
		super.init(site);
		Workbench workbench = (Workbench) site.getWorkbenchWindow().getWorkbench();
		try {
			introPart = workbench.getWorkbenchIntroManager().createNewIntroPart();
			// reset the part name of this view to be that of the intro title
			setPartName(introPart.getTitle());
			introPart.addPropertyListener((source, propId) -> firePropertyChange(propId));
			introSite = new ViewIntroAdapterSite(site, workbench.getIntroDescriptor());
			introPart.init(introSite, memento);

		} catch (CoreException e) {
			WorkbenchPlugin.log(IntroMessages.Intro_could_not_create_proxy, new Status(IStatus.ERROR,
					WorkbenchPlugin.PI_WORKBENCH, IStatus.ERROR, IntroMessages.Intro_could_not_create_proxy, e));
		}
	}

	@Override
	public void setFocus() {
		introPart.setFocus();
	}

	@Override
	public void saveState(IMemento memento) {
		introPart.saveState(memento);
	}
}