/*******************************************************************************
 * Copyright (c) 2009, 2010 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
 ******************************************************************************/

package org.eclipse.e4.workbench.ui.internal;

import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
import javax.inject.Inject;
import javax.inject.Named;
import org.eclipse.e4.core.services.annotations.Optional;
import org.eclipse.e4.core.services.annotations.PostConstruct;
import org.eclipse.e4.core.services.annotations.PreDestroy;
import org.eclipse.e4.core.services.context.IEclipseContext;
import org.eclipse.e4.ui.model.application.MElementContainer;
import org.eclipse.e4.ui.model.application.MPart;
import org.eclipse.e4.ui.model.application.MWindow;
import org.eclipse.e4.ui.services.IServiceConstants;
import org.eclipse.e4.ui.services.events.IEventBroker;
import org.eclipse.e4.workbench.modeling.EPartService;
import org.eclipse.e4.workbench.modeling.ESelectionService;
import org.eclipse.e4.workbench.modeling.ISelectionListener;
import org.eclipse.e4.workbench.ui.UIEvents;
import org.osgi.service.event.Event;
import org.osgi.service.event.EventHandler;

public class SelectionServiceImpl implements ESelectionService {

	static final String OUT_SELECTION = "output.selection"; //$NON-NLS-1$

	private Set<ISelectionListener> genericListeners = new HashSet<ISelectionListener>();
	private Map<String, Set<ISelectionListener>> targetedListeners = new HashMap<String, Set<ISelectionListener>>();
	private Set<IEclipseContext> tracked = new HashSet<IEclipseContext>();

	@Inject
	private IEclipseContext context;

	@Inject
	private EPartService partService;

	/**
	 * This is the specific implementation. TODO: generalize it
	 */
	@Inject
	@Named(EPartService.PART_SERVICE_ROOT)
	private MWindow serviceRoot;

	@Inject
	private IEventBroker eventBroker;

	private EventHandler eventHandler = new EventHandler() {
		public void handleEvent(Event event) {
			Object element = event.getProperty(UIEvents.EventTags.ELEMENT);
			if (element instanceof MPart) {
				MPart part = (MPart) element;
				IEclipseContext context = part.getContext();
				if (context != null && isInContainer(part)) {
					track(part);
				}
			}
		}
	};

	private MPart activePart;

	@PreDestroy
	void preDestroy() {
		IEclipseContext rootContext = serviceRoot.getContext();
		if (rootContext != context) {
			ESelectionService selectionService = (ESelectionService) rootContext
					.get(ESelectionService.class.getName());
			for (ISelectionListener listener : genericListeners) {
				selectionService.removeSelectionListener(listener);
			}

			for (Entry<String, Set<ISelectionListener>> entry : targetedListeners.entrySet()) {
				String partId = entry.getKey();
				for (ISelectionListener listener : entry.getValue()) {
					selectionService.removeSelectionListener(partId, listener);
				}
			}
		}

		genericListeners.clear();
		targetedListeners.clear();

		eventBroker.unsubscribe(eventHandler);
	}

	@PostConstruct
	void postConstruct() {
		eventBroker
				.subscribe(UIEvents.buildTopic(UIEvents.Context.TOPIC, UIEvents.Context.CONTEXT),
						eventHandler);

		for (MPart part : partService.getParts()) {
			track(part);
		}
	}

	@Inject
	void setPart(@Optional @Named(IServiceConstants.ACTIVE_PART) final MPart part) {
		if (part != null) {
			activePart = part;
			IEclipseContext rootContext = serviceRoot.getContext();
			if (rootContext == context) {
				final IEclipseContext partContext = part.getContext();
				Object selection = partContext.get(OUT_SELECTION);
				notifyListeners(part, selection);

				track(part);
			}
		}
	}

	private boolean isInContainer(MPart part) {
		return isInContainer(serviceRoot, part);
	}

	private boolean isInContainer(MElementContainer<?> container, MPart part) {
		for (Object object : container.getChildren()) {
			if (object == part) {
				return true;
			} else if (object instanceof MElementContainer<?>) {
				if (isInContainer((MElementContainer<?>) object, part)) {
					return true;
				}
			}
		}

		return false;
	}

	private void notifyListeners(MPart part, Object selection) {
		for (ISelectionListener listener : genericListeners) {
			listener.selectionChanged(part, selection);
		}

		notifyTargetedListeners(part, selection);
	}

	private void notifyTargetedListeners(MPart part, Object selection) {
		String id = part.getId();
		if (id != null) {
			Set<ISelectionListener> listeners = targetedListeners.get(id);
			if (listeners != null) {
				for (ISelectionListener listener : listeners) {
					listener.selectionChanged(part, selection);
				}
			}
		}
	}

	private void track(final MPart part) {
		final IEclipseContext context = part.getContext();
		if (context != null && tracked.add(context)) {
			context.runAndTrack(new Runnable() {

				private boolean initial = true;

				public void run() {
					Object selection = context.get(OUT_SELECTION);
					if (initial) {
						initial = false;
						if (selection == null) {
							return;
						}
					}

					if (activePart == part) {
						notifyListeners(part, selection);
					} else {
						notifyTargetedListeners(part, selection);
					}
				}
			});
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.e4.ui.selection.ESelectionService#setSelection(java.lang.Object)
	 */
	public void setSelection(Object selection) {
		if (selection != null) {
			context.set(OUT_SELECTION, selection);
		} else {
			context.remove(OUT_SELECTION);
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.e4.ui.selection.ESelectionService#getSelection()
	 */
	public Object getSelection() {
		return activePart.getContext().get(ESelectionService.SELECTION);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.eclipse.e4.ui.selection.ESelectionService#addSelectionListener(org.eclipse.e4.ui.selection
	 * .ISelectionListener)
	 */
	public void addSelectionListener(ISelectionListener listener) {
		IEclipseContext rootContext = serviceRoot.getContext();
		if (rootContext != context) {
			ESelectionService selectionService = (ESelectionService) rootContext
					.get(ESelectionService.class.getName());
			selectionService.addSelectionListener(listener);
		}

		genericListeners.add(listener);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see
	 * org.eclipse.e4.ui.selection.ESelectionService#removeSelectionListener(org.eclipse.e4.ui.selection
	 * .ISelectionListener)
	 */
	public void removeSelectionListener(ISelectionListener listener) {
		IEclipseContext rootContext = serviceRoot.getContext();
		if (rootContext != context) {
			ESelectionService selectionService = (ESelectionService) rootContext
					.get(ESelectionService.class.getName());
			selectionService.removeSelectionListener(listener);
		}

		genericListeners.remove(listener);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.e4.ui.selection.ESelectionService#addSelectionListener(java.lang.String,
	 * org.eclipse.e4.ui.selection.ISelectionListener)
	 */
	public void addSelectionListener(String partId, ISelectionListener listener) {
		IEclipseContext rootContext = serviceRoot.getContext();
		if (rootContext != context) {
			ESelectionService selectionService = (ESelectionService) rootContext
					.get(ESelectionService.class.getName());
			selectionService.addSelectionListener(partId, listener);
		}

		Set<ISelectionListener> listeners = targetedListeners.get(partId);
		if (listeners == null) {
			listeners = new HashSet<ISelectionListener>();
			targetedListeners.put(partId, listeners);
		}
		listeners.add(listener);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.e4.ui.selection.ESelectionService#removeSelectionListener(java.lang.String,
	 * org.eclipse.e4.ui.selection.ISelectionListener)
	 */
	public void removeSelectionListener(String partId, ISelectionListener listener) {
		IEclipseContext rootContext = serviceRoot.getContext();
		if (rootContext != context) {
			ESelectionService selectionService = (ESelectionService) rootContext
					.get(ESelectionService.class.getName());
			selectionService.removeSelectionListener(partId, listener);
		}

		Set<ISelectionListener> listeners = targetedListeners.get(partId);
		if (listeners != null) {
			listeners.remove(listener);
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.e4.ui.selection.ESelectionService#getSelection(java.lang.String)
	 */
	public Object getSelection(String partId) {
		MPart part = partService.findPart(partId);
		if (part == null) {
			return null;
		}

		IEclipseContext partContext = part.getContext();
		if (partContext == null) {
			return null;
		}
		return partContext.get(OUT_SELECTION);
	}

}