/*
 * 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.onlab.osgi;

import org.osgi.framework.BundleContext;
import org.osgi.framework.FrameworkUtil;
import org.osgi.framework.ServiceReference;

/**
 * Default implementation of the service directory using OSGi framework utilities.
 */
public class DefaultServiceDirectory implements ServiceDirectory {

    /**
     * Returns the reference to the implementation of the specified service.
     *
     * @param serviceClass service class
     * @param <T>          type of service
     * @return service implementation
     */
    public static <T> T getService(Class<T> serviceClass) {
        BundleContext bc = FrameworkUtil.getBundle(serviceClass).getBundleContext();
        if (bc != null) {
            ServiceReference<T> reference = bc.getServiceReference(serviceClass);
            if (reference != null) {
                T impl = bc.getService(reference);
                if (impl != null) {
                    return impl;
                }
            }
        }
        throw new ServiceNotFoundException("Service " + serviceClass.getName() + " not found");
    }

    @Override
    public <T> T get(Class<T> serviceClass) {
        return getService(serviceClass);
    }

}