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package org.glassfish.jersey.server.internal;

import java.util.LinkedList;

import javax.ws.rs.core.Application;

import org.glassfish.jersey.internal.inject.Providers;
import org.glassfish.jersey.server.ApplicationHandler;
import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.server.spi.AbstractContainerLifecycleListener;
import org.glassfish.jersey.server.spi.Container;
import org.glassfish.jersey.server.spi.ContainerLifecycleListener;

import com.google.common.collect.Iterables;

/**
 * Helper class to provide some common functionality related to {@link org.glassfish.jersey.server.ResourceConfig application configuration}.
 *
 * @author Jakub Podlesak (jakub.podlesak at oracle.com)
 */
public final class ConfigHelper {

    /**
     * Prevents instantiation.
     */
    private ConfigHelper() {
    }

    /**
     * Provides a single ContainerLifecycleListener instance based on the {@link ApplicationHandler application} configuration.
     * This method looks for providers implementing {@link ContainerLifecycleListener} interface and aggregates them into
     * a single umbrella listener instance that is returned.
     *
     * @param applicationHandler actual application from where to get the listener.
     * @return a single instance of a ContainerLifecycleListener, can not be null.
     */
    public static ContainerLifecycleListener getContainerLifecycleListener(final ApplicationHandler applicationHandler) {

        final ContainerLifecycleListener appPreDestroyInvoker = new AbstractContainerLifecycleListener() {

            @Override
            public void onShutdown(Container container) {
                applicationHandler.getServiceLocator().preDestroy(getWrappedApplication(applicationHandler.getConfiguration()));
            }
        };

        final Iterable<ContainerLifecycleListener> listeners = Iterables.concat(
                Providers.getAllProviders(applicationHandler.getServiceLocator(), ContainerLifecycleListener.class),
                new LinkedList<ContainerLifecycleListener>(){{add(appPreDestroyInvoker);}});

        return new ContainerLifecycleListener() {

            @Override
            public void onStartup(Container container) {
                for (ContainerLifecycleListener listener : listeners) {
                    listener.onStartup(container);
                }
            }

            @Override
            public void onReload(Container container) {
                for (ContainerLifecycleListener listener : listeners) {
                    listener.onReload(container);
                }
            }

            @Override
            public void onShutdown(Container container) {
                for (ContainerLifecycleListener listener : listeners) {
                    listener.onShutdown(container);
                }
            }
        };
    }

    /**
     * Gets the most internal wrapped {@link Application application} class. This method is similar to {@link ResourceConfig#getApplication()}
     * except if provided application was created by wrapping multiple {@link ResourceConfig} instances this method returns the original application
     * and not a resource config wrapper.
     *
     * @return the original {@link Application} subclass.
     */
    public static Application getWrappedApplication(Application app) {
        while (app instanceof  ResourceConfig) {
            final Application wrappedApplication = ((ResourceConfig) app).getApplication();
            if (wrappedApplication == app) {
                break;
            }
            app = wrappedApplication;
        }
        return app;
    }
}
