import java.util.HashMap;

public class ServiceMonitor {
	public static final String SERVICERUNNING = "service_running";
	public static final String SERVICESTOPPED = "service_stopped";

	private static final boolean DEBUG = false;
	private static ServiceMonitor instance;
	private HashMap<String, Object> services;
	private BundleContext context;
	private String[] infos;

	private ServiceMonitor() {
		// construct the singleton instance
	}
	
	public static final ServiceMonitor getInstance() {
		if (instance == null) {
			instance = new ServiceMonitor();
		}
		return instance;
	}

	public static void start(final BundleContext context) throws Exception {
		System.err.println(ServiceMonitor.class.getName() + " started.");
		System.out.println("context = " + context);
		if (getInstance().context == null) {
			getInstance().context = context;
			getInstance().services = new HashMap<String, Object>();
		}
		if (DEBUG) {
			System.out.println(String.format(
					"ServiceMonitor is NOW ready @ %s", instance.context));
		}
	}

	public static void stop() {
	}

	public static String[] getServices() {
		final String filter = "(objectclass=lumo.osgi.service.*)";
		System.out.println("getInstance().context = " + getInstance().context);
		if (getInstance().infos == null) {
			try {
				
				final ServiceReference<?>[] refs = getInstance().context
						.getAllServiceReferences(null, filter);
// refs is null here!!
				System.out.println("refs == null " + (refs == null));
				getInstance().infos = new String[refs.length];
				for (int i = 0; i < refs.length; i++) {
					String name = (String) refs[i]
							.getProperty("component.name");
					name = name.substring(name.lastIndexOf(".") + 1);
					System.err.println(String.format(
							"Service %d [%s] of %d Services checked.", i + 1,
							name, refs.length));
					final String clazz = (String) refs[i]
							.getProperty("component.name");
					if (!getInstance().services.containsKey(clazz)) {
						getInstance().services.put(clazz,
								getInstance().context.getService(refs[i]));
					}
					getInstance().infos[i] = clazz;
				}
			} catch (final InvalidSyntaxException e) {
				e.printStackTrace();
			}
		}
		return getInstance().infos;
	}

	public static boolean isServiceRunning(final Class<?> clazz) {
		final String[] infos = getServices();
		for (final String info : infos) {
			if (info.equals(clazz.getName())) {
				return true;
			}
		}
		return false;
	}

	/**
	 * alias for getService
	 * 
	 * @param clazz
	 * @return
	 * @see #getService(Class)
	 */
	public static Object addService(final Class<?> clazz) {
		return getService(clazz);
	}

	/**
	 * this function automatically adds a service if its not there...
	 * 
	 * @param clazz
	 * @return
	 */
	public static Object getService(final Class<?> clazz) {
		if (clazz != null) {
			if (!getInstance().services.containsKey(clazz.getName())) {
				final ServiceReference<?> ref = getInstance().context
						.getServiceReference(clazz.getName());
				if (ref == null) {
					return null;
				} else {
					getInstance().services.put(clazz.getName(),
							getInstance().context.getService(ref));
					return getInstance().services.get(clazz.getName());
				}
			}
			return getInstance().services.get(clazz.getName());
		}
		return null;
	}

	/**
	 * true, if the service got removed, otherwise false (even if class == null)<br>
	 * not working yet
	 * 
	 * @param clazz
	 * @return
	 */
	public static Boolean removeService(final Class<?> clazz) {
		if (clazz != null) {
			boolean result = false;
			if (getInstance().services.containsKey(clazz.getName())) {
				final ServiceReference<?> ref = getInstance().context
						.getServiceReference(clazz.getName());
				if (ref == null) {
					return Boolean.valueOf(false);
				} else {
					result = getInstance().context.ungetService(ref);
					getInstance().services.remove(clazz.getName());
					if (DEBUG) {
						System.out.println(String.format("%s got %s removed.",
								clazz.getSimpleName(), result ? "successfully"
										: "not"));
					}
					return result;
				}
			}
			if (DEBUG) {
				System.out
						.println(String.format("%s got %s removed.", clazz
								.getSimpleName(), result ? "successfully"
								: "not"));
			}
			return result;
		}
		return Boolean.valueOf(false);
	}
}