org.eclipse.osbp.infogrid.services/src/org/eclipse/osbp/infogrid/services/GridSourceCacheBuilder.java

/**
 *                                                                            
 * Copyright (c) 2011, 2016 - Loetz GmbH&Co.KG (69115 Heidelberg, Germany)
 *                                                                            
 * All rights reserved. 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:   
 * Christophe Loetz (Loetz GmbH&Co.KG) - initial implementation 
 */
package org.eclipse.osbp.infogrid.services;

import java.net.URL;
import java.util.ArrayList;
import java.util.Dictionary;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.eclipse.emf.common.util.URI;
import org.eclipse.osbp.infogrid.api.IGridSourceCache;
import org.osgi.framework.Bundle;
import org.osgi.framework.BundleEvent;
import org.osgi.framework.wiring.BundleWiring;
import org.osgi.service.component.ComponentContext;
import org.osgi.service.component.annotations.Activate;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.Deactivate;
import org.osgi.service.component.annotations.Reference;
import org.osgi.service.component.annotations.ReferenceCardinality;
import org.osgi.service.component.annotations.ReferencePolicy;
import org.osgi.util.tracker.BundleTracker;
import org.osgi.util.tracker.BundleTrackerCustomizer;

/**
 * OSBP uses ECView files directly and does not derive them from the
 * UiDSL-Model. If you have interest using this feature, just provide that class
 * as an OSGi service.
 */
@Component(immediate = true)
public class GridSourceCacheBuilder {

	private static final String OSBP_MODEL_EXTENDER = "Factory-Model";
	@SuppressWarnings("unused")
	private ComponentContext context;

	private BundleTracker<List<URL>> tracker;
	private IGridSourceCache cache;

	public GridSourceCacheBuilder() {

	}

	@Activate
	protected void activate(ComponentContext context) {
		this.context = context;
		tracker = new BundleTracker<>(context.getBundleContext(),
				stateCreteria(), new Customizer());
		tracker.open();
	}

	protected int stateCreteria() {
		return Bundle.RESOLVED | Bundle.STARTING | Bundle.ACTIVE
				| Bundle.STOPPING;
	}

	@Deactivate
	protected void deactivate(ComponentContext context) {
		tracker.close();
		this.context = null;
	}

	/**
	 * Returns true, if the bundle contains the header.
	 * 
	 * @param bundle
	 * @param header
	 * @return
	 */
	private boolean containsHeader(Bundle bundle, String header) {
		Dictionary<String, String> headers = bundle.getHeaders();
		Enumeration<String> keys = headers.keys();
		while (keys.hasMoreElements()) {
			String key = keys.nextElement();
			if (key.equals(header)) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Searches for all ECView translations in the given bundle.
	 * 
	 * @param bundle
	 * @return
	 */
	private List<URL> internalFindURLs(Bundle bundle) {
		List<URL> results = new ArrayList<URL>();
		BundleWiring wiring = bundle.adapt(BundleWiring.class);
		results.addAll(wiring.findEntries("/", "*.gridsource_xmi",
				BundleWiring.LISTRESOURCES_RECURSE));

		Set<String> fragments = new HashSet<String>();
		for (Iterator<URL> iterator = results.iterator(); iterator.hasNext();) {
			URL url = iterator.next();
			URI uri = URI.createURI(url.toString());
			if (fragments.contains(uri.lastSegment())) {
				iterator.remove();
			}
			fragments.add(uri.lastSegment());
		}
		return results;
	}

	@Reference(cardinality = ReferenceCardinality.MANDATORY, policy = ReferencePolicy.STATIC, unbind = "unbindGridSourceCache")
	protected void bindGridSourceCache(IGridSourceCache cache) {
		this.cache = cache;
	}

	protected void unbindGridSourceCache(IGridSourceCache cache) {
		this.cache = null;
		tracker.close();
		tracker = null;
	}

	private class Customizer implements BundleTrackerCustomizer<List<URL>> {

		@Override
		public List<URL> addingBundle(Bundle bundle, BundleEvent event) {
			if (!containsHeader(bundle, OSBP_MODEL_EXTENDER)) {
				return null;
			}

			List<URL> urls = internalFindURLs(bundle);
			cache.registerSources(urls);
			return urls;
		}

		@Override
		public void modifiedBundle(Bundle bundle, BundleEvent event,
				List<URL> object) {

		}

		@Override
		public void removedBundle(Bundle bundle, BundleEvent event,
				List<URL> urls) {
			cache.unregisterSources(urls);
		}
	}

}