package org.simantics.district.route.internal;

import java.util.Hashtable;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.Constants;
import org.osgi.framework.ServiceEvent;
import org.osgi.framework.ServiceListener;
import org.osgi.framework.ServiceReference;
import org.osgi.framework.ServiceRegistration;
import org.osgi.util.tracker.ServiceTracker;
import org.simantics.district.route.RouteService;
import org.simantics.district.route.Router;

/**
 * @author Tuukka Lehtonen
 * @since 6.09
 */
public class Activator implements BundleActivator, ServiceListener {

    private static BundleContext context;
    private static Activator instance;

    static BundleContext getContext() {
        return context;
    }

    public static Activator getInstance() {
        return instance;
    }

    private RouteServiceImpl                routeService;
    private ServiceRegistration<?>          routeServiceRegistration;
    private ServiceTracker<RouteService, ?> routeServiceTracker;
    private ServiceTracker<Router, ?>       routerTracker;

    @Override
    public void start(BundleContext context) throws Exception {
        Activator.instance = this;
        Activator.context = context;
        routeService = new RouteServiceImpl();

        // register the service
        routeServiceRegistration = context.registerService(RouteService.class.getName(), routeService, new Hashtable<>());

        // create a tracker and track the service
        routeServiceTracker = new ServiceTracker<>(context, RouteService.class.getName(), null);
        routeServiceTracker.open();

        // Register initially availble routers
        routerTracker = new ServiceTracker<>(context, Router.class.getName(), null);
        routerTracker.open();
        Object[] routers = routerTracker.getServices();
        if (routers != null) {
            for (Object router : routers)
                routeService.registerRouter((Router) router);
        }

        // have a service listener to implement the whiteboard pattern
        context.addServiceListener(this, "(" + Constants.OBJECTCLASS + "=" + Router.class.getName() + ")"); //$NON-NLS-1$ //$NON-NLS-2$

        // grab the service
        routeService = (RouteServiceImpl) routeServiceTracker.getService();
    }

    @Override
    public void stop(BundleContext context) throws Exception {
        // close the service tracker
        routeServiceTracker.close();
        routeServiceTracker = null;

        routeServiceRegistration.unregister();

        routeService.close();
        routeService = null;
        context = null;
        instance = null;
    }

    public void serviceChanged(ServiceEvent ev) {
        ServiceReference<?> sr = ev.getServiceReference();
        switch (ev.getType()) {
            case ServiceEvent.REGISTERED:
                routeService.registerRouter((Router) context.getService(sr));
                break;
            case ServiceEvent.UNREGISTERING:
                routeService.unregisterRouter((Router) context.getService(sr));
                break;
        }
    }

    public RouteService getRouteService() {
        return routeService;
    }

}