/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership. The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
    * with the License. You may obtain a copy of the License at
    * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.river.reggie.proxy;
  
  import java.io.IOException;
  import java.io.InvalidObjectException;
  import java.io.ObjectInputStream;
  import java.io.ObjectOutputStream;
  import java.io.Serializable;
  import java.rmi.RemoteException;
  import net.jini.core.constraint.RemoteMethodControl;
  import net.jini.core.lookup.ServiceID;
  import net.jini.security.TrustVerifier;
  import net.jini.security.proxytrust.TrustEquivalence;
  
  /**
   * Trust verifier for smart proxies used by Reggie.
   *
   * @author Sun Microsystems, Inc.
   *
   */
  public final class ProxyVerifier implements TrustVerifier, Serializable {
  
      private static final long serialVersionUID = 2L;
  
      /**
       * Canonical service reference, used for comparison with inner server
       * references extracted from smart proxies to verify.
       *
       * @serial
       */
      private final RemoteMethodControl server;
      /**
       * The registrar's service ID, used for comparison with registrar service
       * IDs extracted from smart proxies to verify.
       */
      private transient ServiceID registrarID;
  
      /**
       * Constructs proxy verifier which compares server references extracted
       * from smart proxies with the given canonical server reference, which must
       * implement both RemoteMethodControl and TrustEquivalence.  For proxies
       * which contain a copy of the registrar's service ID, that copy is
       * compared against the given service ID to ensure consistency.
       */
      public ProxyVerifier(Registrar server, ServiceID registrarID) {
  	if (!(server instanceof RemoteMethodControl)) {
  	    throw new UnsupportedOperationException(
  		"server does not implement RemoteMethodControl");
  	} else if (!(server instanceof TrustEquivalence)) {
  	    throw new UnsupportedOperationException(
  		"server does not implement TrustEquivalence");
  	}
  	this.server = (RemoteMethodControl) server;
  	this.registrarID = registrarID;
      }
  
      /**
       * Returns true if the given object is a trusted proxy, or false otherwise.
       * The given object is trusted if it is trust equivalent to the canonical
       * server reference carried by this trust verifier, or if it is an instance
       * of one of Reggie's constrainable smart proxy classes, and all component
       * proxies it contains are trusted, and its inner server reference is trust
       * equivalent to the canonical server reference, and its inner copy of the
       * registrar's service ID (if it has one) is equal to the service ID
       * carried by this verifier.
       */
      public boolean isTrustedObject(Object obj, TrustVerifier.Context ctx)
  	throws RemoteException
      {
  	if (obj == null || ctx == null) {
  	    throw new NullPointerException();
  	}
  	RemoteMethodControl inputServer;
  	ServiceID inputRegistrarID;
  	if (obj instanceof ConstrainableRegistrarProxy) {
  	    RegistrarProxy proxy = (RegistrarProxy) obj;
  	    inputServer = (RemoteMethodControl) proxy.server;
  	    inputRegistrarID = proxy.registrarID;
  	} else if (obj instanceof ConstrainableAdminProxy) {
  	    AdminProxy proxy = (AdminProxy) obj;
  	    inputServer = (RemoteMethodControl) proxy.server;
  	    inputRegistrarID = proxy.registrarID;
  	} else if (obj instanceof ConstrainableRegistration) {
 	    Registration reg = (Registration) obj;
 	    if (!isTrustedObject(reg.lease, ctx)) {
 		return false;
 	    }
 	    inputServer = (RemoteMethodControl) reg.server;
 	    inputRegistrarID = registrarID;
 	} else if (obj instanceof ConstrainableEventLease ||
 		   obj instanceof ConstrainableServiceLease)
 	{
 	    RegistrarLease lease = (RegistrarLease) obj;
 	    inputServer = (RemoteMethodControl) lease.server;
 	    inputRegistrarID = lease.registrarID;
 	} else if (obj instanceof RemoteMethodControl) {
 	    inputServer = (RemoteMethodControl) obj;
 	    inputRegistrarID = registrarID;
 	} else {
 	    return false;
 	}
 
 	TrustEquivalence trustEquiv = (TrustEquivalence)
 	    server.setConstraints(inputServer.getConstraints());
 	return trustEquiv.checkTrustEquivalence(inputServer) &&
 	       registrarID.equals(inputRegistrarID);
     }
 
     /**
      * Writes the default serializable field value for this instance, followed
      * by the registrar's service ID encoded as specified by the
      * ServiceID.writeBytes method.
      */
     private void writeObject(ObjectOutputStream out) throws IOException {
 	out.defaultWriteObject();
 	registrarID.writeBytes(out);
     }
 
     /**
      * Reads the default serializable field value for this instance, followed
      * by the registrar's service ID encoded as specified by the
      * ServiceID.writeBytes method.  Verifies that the deserialized registrar
      * reference implements both RemoteMethodControl and TrustEquivalence.
      */
     private void readObject(ObjectInputStream in)
 	throws IOException, ClassNotFoundException
     {
 	in.defaultReadObject();
 	registrarID = new ServiceID(in);
 	if (!(server instanceof RemoteMethodControl)) {
 	    throw new InvalidObjectException(
 		"server does not implement RemoteMethodControl");
 	} else if (!(server instanceof TrustEquivalence)) {
 	    throw new InvalidObjectException(
 		"server does not implement TrustEquivalence");
 	}
     }
 }