/*
 *   Copyright 2006 The Apache Software Foundation
 *
 *   Licensed 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.felix.dependencymanager;

import java.util.List;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;

/**
 * Base bundle activator class. Subclass this activator if you want to use dependency
 * management in your bundle. There are two methods you should implement:
 * <code>init()</code> and <code>destroy()</code>. Both methods take two arguments,
 * the bundle context and the dependency manager. The dependency manager can be used
 * to define all the dependencies.
 * 
 * @author <a href="mailto:felix-dev@incubator.apache.org">Felix Project Team</a>
 */
public abstract class DependencyActivatorBase implements BundleActivator {
    private BundleContext m_context;
    private DependencyManager m_manager;
    
    /**
     * Initialize the dependency manager. Here you can add all services and their dependencies.
     * If something goes wrong and you do not want your bundle to be started, you can throw an
     * exception. This exception will be passed on to the <code>start()</code> method of the
     * bundle activator, causing the bundle not to start.
     * 
     * @param context the bundle context
     * @param manager the dependency manager
     * @throws Exception if the initialization fails
     */
    public abstract void init(BundleContext context, DependencyManager manager) throws Exception;
    
    /**
     * Destroy the dependency manager. Here you can remove all services and their dependencies.
     * Actually, the base class will clean up your dependencies anyway, so most of the time you
     * don't need to do anything here.
     * If something goes wrong and you do not want your bundle to be stopped, you can throw an
     * exception. This exception will be passed on to the <code>stop()</code> method of the
     * bundle activator, causing the bundle not to stop.
     * 
     * @param context the bundle context
     * @param manager the dependency manager
     * @throws Exception if the destruction fails
     */
    public abstract void destroy(BundleContext context, DependencyManager manager) throws Exception;

    /**
     * Start method of the bundle activator. Initializes the dependency manager
     * and calls <code>init()</code>.
     * 
     * @param context the bundle context
     */
    public void start(BundleContext context) throws Exception {
        m_context = context;
        m_manager = new DependencyManager(context);
        init(m_context, m_manager);
    }

    /**
     * Stop method of the bundle activator. Calls the <code>destroy()</code> method
     * and cleans up all left over dependencies.
     * 
     * @param context the bundle context
     */
    public void stop(BundleContext context) throws Exception {
        destroy(m_context, m_manager);
        cleanup(m_manager);
        m_manager = null;
        m_context = null;
    }
    
    /**
     * Creates a new service.
     * 
     * @return the new service
     */
    public Service createService() {
        return new ServiceImpl(m_context);
    }
    
    /**
     * Creates a new service dependency.
     * 
     * @return the service dependency
     */
    public ServiceDependency createServiceDependency() {
        return new ServiceDependency(m_context);
    }

    /**
     * Cleans up all services and their dependencies.
     * 
     * @param manager the dependency manager
     */
    private void cleanup(DependencyManager manager) {
        List services = manager.getServices();
        for (int i = services.size() - 1; i >= 0; i--) {
            Service service = (Service) services.get(i);
            manager.remove(service);
            // remove any state listeners that are still registered
            if (service instanceof ServiceImpl) {
                ServiceImpl si = (ServiceImpl) service;
                si.removeStateListeners();
            }
        }
    }
}