/**
 *                                                                            
 *  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:                                                      
 * 	   Florian Pirchner - Initial implementation
 * 
 */
package org.eclipse.osbp.ecview.extension.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.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;
import org.eclipse.osbp.ecview.core.common.extender.IECViewCache;

/**
 * This extender scans all bundles about .ecview_xmi files. Any of them will be
 * passed to the {@link IECViewCache}. If bundles are being stopped, the
 * contained .ecview_xmi files will be unregistered from {@link IECViewCache}.
 */
@Component
public class ECViewCacheBuilder {

	/** The Constant FACTORY_MODEL_EXTENDER. */
	public static final String FACTORY_MODEL_EXTENDER = "Factory-Model";
	
	/** The context. */
	@SuppressWarnings("unused")
	private ComponentContext context;

	/** The tracker. */
	private BundleTracker<List<URL>> tracker;
	
	/** The cache. */
	private IECViewCache cache;

	/**
	 * Instantiates a new EC view cache builder.
	 */
	public ECViewCacheBuilder() {

	}

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

	/**
	 * State criteria.
	 *
	 * @return the int
	 */
	protected int stateCriteria() {
		return Bundle.RESOLVED | Bundle.STARTING | Bundle.ACTIVE
				| Bundle.STOPPING;
	}

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

	/**
	 * Returns true, if the bundle contains the header.
	 *
	 * @param bundle
	 *            the bundle
	 * @param header
	 *            the header
	 * @return true, if successful
	 */
	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
	 *            the bundle
	 * @return the list
	 */
	private List<URL> internalFindURLs(Bundle bundle) {
		List<URL> results = new ArrayList<URL>();
		BundleWiring wiring = bundle.adapt(BundleWiring.class);
		results.addAll(wiring.findEntries("/", "*." + ECViewCache.ECVIEW_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;
	}

	/**
	 * Bind cache.
	 *
	 * @param cache
	 *            the cache
	 */
	@Reference(cardinality = ReferenceCardinality.MANDATORY, policy = ReferencePolicy.STATIC, unbind = "unbindCache")
	protected void bindCache(IECViewCache cache) {
		this.cache = cache;
	}

	/**
	 * Unbind cache.
	 *
	 * @param cache
	 *            the cache
	 */
	protected void unbindCache(IECViewCache cache) {
		tracker.close();
		tracker = null;
		this.cache = null;
	}

	/**
	 * The Class Customizer.
	 */
	private class Customizer implements BundleTrackerCustomizer<List<URL>> {

		/* (non-Javadoc)
		 * @see org.osgi.util.tracker.BundleTrackerCustomizer#addingBundle(org.osgi.framework.Bundle, org.osgi.framework.BundleEvent)
		 */
		@Override
		public List<URL> addingBundle(Bundle bundle, BundleEvent event) {
			if (!containsHeader(bundle, FACTORY_MODEL_EXTENDER)) {
				return null;
			}

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

		/* (non-Javadoc)
		 * @see org.osgi.util.tracker.BundleTrackerCustomizer#modifiedBundle(org.osgi.framework.Bundle, org.osgi.framework.BundleEvent, java.lang.Object)
		 */
		@Override
		public void modifiedBundle(Bundle bundle, BundleEvent event,
				List<URL> object) {

		}

		/* (non-Javadoc)
		 * @see org.osgi.util.tracker.BundleTrackerCustomizer#removedBundle(org.osgi.framework.Bundle, org.osgi.framework.BundleEvent, java.lang.Object)
		 */
		@Override
		public void removedBundle(Bundle bundle, BundleEvent event,
				List<URL> urls) {
			cache.unregisterViews(urls);
		}
	}

}