component-dsl/src/main/java/org/apache/aries/component/dsl/internal/ServiceReferenceOSGi.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.aries.component.dsl.internal;

import org.apache.aries.component.dsl.OSGiResult;
import org.apache.aries.component.dsl.CachingServiceReference;
import org.apache.aries.component.dsl.Publisher;
import org.apache.aries.component.dsl.update.UpdateSelector;
import org.apache.aries.component.dsl.update.UpdateTuple;
import org.osgi.framework.ServiceReference;
import org.osgi.util.tracker.ServiceTracker;
import org.osgi.util.tracker.ServiceTrackerCustomizer;

/**
 * @author Carlos Sierra Andrés
 */
public class ServiceReferenceOSGi<T>
	extends OSGiImpl<UpdateTuple<CachingServiceReference<T>>> implements UpdateSelector {

	public ServiceReferenceOSGi(String filterString, Class<T> clazz) {

		super((executionContext, op) -> {
			ServiceTracker<T, Tracked<T>>
				serviceTracker = new ServiceTracker<>(
					executionContext.getBundleContext(),
					buildFilter(executionContext, filterString, clazz),
					new DefaultServiceTrackerCustomizer<>(op));

			serviceTracker.open();

			return new OSGiResultImpl(
				serviceTracker::close,
				us -> serviceTracker.getTracked().values().stream().map(
					tracked -> tracked.runnable.update(us)
				).reduce(
					Boolean.FALSE, Boolean::logicalOr
				)
			);
		});
	}

	private static class DefaultServiceTrackerCustomizer<T>
		implements ServiceTrackerCustomizer<T, Tracked<T>>, UpdateSelector{

		public DefaultServiceTrackerCustomizer(
			Publisher<? super UpdateTuple<CachingServiceReference<T>>> addedSource) {

			_addedSource = addedSource;
		}

		@Override
		public Tracked<T> addingService(ServiceReference<T> reference) {
			CachingServiceReference<T> cachingServiceReference =
				new CachingServiceReference<>(reference);

			return new Tracked<>(
				cachingServiceReference,
				_addedSource.apply(new UpdateTuple<>(this, cachingServiceReference)));
		}

		@Override
		public void modifiedService(
			ServiceReference<T> reference, Tracked<T> tracked) {

			if (tracked.runnable.update(this)) {
				UpdateSupport.runUpdate(() -> {
					tracked.runnable.run();
					tracked.cachingServiceReference = new CachingServiceReference<>(
						reference);
					tracked.runnable =
						_addedSource.apply(
							new UpdateTuple<>(this, tracked.cachingServiceReference));
				});
			}
		}

		@Override
		public void removedService(
			ServiceReference<T> reference, Tracked<T> tracked) {

			tracked.runnable.run();
		}

		private final Publisher<? super UpdateTuple<CachingServiceReference<T>>> _addedSource;

	}

	private static class Tracked<T> {

		public Tracked(
			CachingServiceReference<T> cachingServiceReference,
			OSGiResult osgiResult) {

			this.cachingServiceReference = cachingServiceReference;
			this.runnable = osgiResult;
		}

		volatile CachingServiceReference<T> cachingServiceReference;
		volatile OSGiResult runnable;

	}
}