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

import java.rmi.Naming;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.RMISecurityManager;
import java.rmi.registry.Registry;
import java.rmi.server.UnicastRemoteObject;

/**
 * Remote Object Registry.  This class allows one to register remote objects
 * using an arbitrary identifier string.  Unlike rmiregistry the registry and
 * service can be on different hosts. One can also have more than one service
 * registered with the same identifier.
 * <p>
 * This is intended to be example code to give one some idea of how one can
 * develop a remote object registry.  It has not been tested.
 * @author Ken Baclawski
 */
@Copyright
public class MyRegistry extends UnicastRemoteObject implements Registry {
    /**
     * Map from identifiers to sets of remote objects.
     */
    private Map<String, ServiceGroup> map = new HashMap<String, ServiceGroup>();

    /**
     * Construct a registry.
     * @throws RemoteException if an I/O error occurs.
     */
    public MyRegistry() throws RemoteException {
    }

    /**
     * Bind a remote reference to the specified identifier in this registry.
     * @param id The identifier string to be bound. It can be any string.
     * @param obj The remote object being bound.
     */
    public void bind(String id, Remote obj) {
        ServiceGroup group = map.get(id);
        if (group == null) {
            group = new ServiceGroup();
            map.put(id, group);
        }
        group.add(obj);
    }

    /**
     * Get a list of all identifiers currently bound in this registry.
     * @return The array of bound identifiers.
     */
    public String[] list() {
        Set<String> identifiers = map.keySet();
        int length = identifiers.size();
        String[] array = new String[length];
        identifiers.toArray(array);
        return array;
    }

    /**
     * Get a remote reference bound to the specified identifier in this registry.
     * @param id The identifier of the remote object.
     * @return A remote object in the service group of the identifier or null
     * if there is no service group or if there is no remote object in the
     * service group.
     */
    public Remote lookup(String id) {
        ServiceGroup group = map.get(id);
        if (group == null) {
            return null;
        }
        return group.getNext();
    }

    /**
     * Bind a remote reference to the specified identifier in this registry.
     * @param identifier The identifier string to be bound. It can be any string.
     * @param obj The remote object being bound.
     */
    public void rebind(String id, Remote obj) {
        bind(id, obj);
    }

    /**
     * Remove the binding for the specified id in this registry.
     * The entire service group is removed.
     * @param id The identifier string to be unbound.
     */
    public void unbind(String id) {
        map.remove(id);
    }

    /**
     * Server program for the MyRegistry example.
     * @param args Only the first command-line argument is used. It specifies
     * the name to be used for registering MyRegistry with the local
     * rmiregistry.  If it is not specified, then "//localhost/MyRegistry" is
     * used.
     */
    public static void main (String[] args) {
        System.setSecurityManager(new RMISecurityManager() {
                public void checkConnect(String host, int port) {}
                public void checkAccept(String host, int port) {}});
        try {
            String name = (args.length > 0)? args[0] : "//localhost/MyRegistry";
            Naming.rebind(name, new MyRegistry());
            System.out.println("MyRegistry service is ready.");
        } catch (Exception e) {
            System.out.println("MyRegistry service failed: " + e);
        }
    }
}