package javax.jnlp;

import java.util.HashMap;
import java.util.Map;

public final class ServiceManager {

    private static ServiceManagerStub stub = null;

    private static Map<String, Object> lookupTable = new HashMap<String, Object>(); // ensure lookup is idempotent

    private ServiceManager() {
        // says it can't be instantiated
    }

    public static java.lang.Object lookup(java.lang.String name) throws UnavailableServiceException {
        if (stub == null) {
            throw new UnavailableServiceException("service stub not set.");
        }

        synchronized (lookupTable) {
            Object result = lookupTable.get(name);

            if (result == null) {
                result = stub.lookup(name);
                if (result != null) {
                    lookupTable.put(name, result);
                }
            }

            if (result == null) {
                throw new UnavailableServiceException("service not available (stub returned null).");
            }

            return result;
        }
    }

    public static java.lang.String[] getServiceNames() {
        // should this return the required ones even though no stub??
        if (stub == null) {
            return new String[0];
        }

        return stub.getServiceNames();
    }

    public static void setServiceManagerStub(ServiceManagerStub stub) {
        if (ServiceManager.stub == null) {
            ServiceManager.stub = stub;
        }
    }

}
