/*
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * The Original Code is the Kowari Metadata Store.
 *
 * The Initial Developer of the Original Code is Plugged In Software Pty
 * Ltd (http://www.pisoftware.com, mailto:info@pisoftware.com). Portions
 * created by Plugged In Software Pty Ltd are Copyright (C) 2001,2002
 * Plugged In Software Pty Ltd. All Rights Reserved.
 *
 * Contributor(s): N/A.
 *
 * [NOTE: The text of this Exhibit A may differ slightly from the text
 * of the notices in the Source Code files of the Original Code. You
 * should use the text of this Exhibit A rather than the text found in the
 * Original Code Source Code for Your Modifications.]
 *
 */

package org.mulgara.server.rmi;

// Java 2 standard packages
import java.net.URI;
import java.rmi.*;
import java.util.*;

// Third party packages
import org.apache.log4j.*;

// Locally written packages
import org.mulgara.jrdf.*;
import org.mulgara.query.QueryException;
import org.mulgara.server.ServerInfo;
import org.mulgara.server.Session;
import org.mulgara.server.SessionFactory;
import org.mulgara.util.Rmi;

/**
 * RMI wrapper for {@link SessionFactory} implementations.
 *
 * @author <a href="http://staff.pisoftware.com/raboczi">Simon Raboczi</a>
 * @created 2001-07-14
 * @copyright © 2001-2003 <A href="http://www.PIsoftware.com/">Plugged In Software Pty Ltd</A>
 * @licence <a href="{@docRoot}/../../LICENCE">Mozilla Public License v1.1</a>
 */
class RemoteSessionFactoryImpl implements RemoteSessionFactory {

  /** Logger. This is named after the classname. */
  private final static Logger logger = Logger.getLogger(RemoteSessionFactoryImpl.class);

  /** The local database. */
  private final SessionFactory sessionFactory;
  
  /** Flag to control whether to support interruptible RMI operations on exported sessions. */
  private final boolean interruptible;

  /** The server URI used to create this factory. Used for reconnection */
  private URI serverURI = null;

  /**
   * Set of {@link RemoteSession}s, the local copies of exported stubs. This is
   * necessary to prevent garbage collection.
   */
  private Set<RemoteSession> remoteSessionSet = new HashSet<RemoteSession>();

  /**
   * Constructor to create an RMI database server.
   *
   * @param sessionFactory A local factory that this exports access to.
   * @throws IllegalArgumentException if <var>database</var> is <code>null</code>
   * @throws RemoteException if RMI communication fails
   */
  RemoteSessionFactoryImpl(SessionFactory sessionFactory, boolean interruptible) throws RemoteException {
    // Validate "sessionFactory" parameter
    if (sessionFactory == null) throw new IllegalArgumentException("Null \"sessionFactory\" parameter");

    // Initialize fields
    this.sessionFactory = sessionFactory;
    this.interruptible = interruptible;
  }

  //
  // Methods implementing the RemoteSessionFactory interface
  //

  /**
   * {@inheritDoc RemoteSessionFactory}
   * @return The SecurityDomain value.
   * @throws QueryException Error accessing the domain.
   */
  public URI getSecurityDomain() throws QueryException {
    return sessionFactory.getSecurityDomain();
  }


  /**
   * Get the server URI used to create the current remoteSessionFactory
   */
  public URI getServerURI()  {
    return serverURI;
  }


  /**
   * Set the server URI used to create the current remoteSessionFactory
   */
  public void setServerURI(URI serverURI) {
    this.serverURI = serverURI;
  }


  /**
   * Get the default URI used by this server.
   */
  public URI getDefaultServerURI()  {
    return ServerInfo.getServerURI();
  }


  /**
   * {@inheritDoc RemoteSessionFactory}
   *
   * @return A new remotely exported session
   * @throws QueryException If an error occrred in the network protocol
   */
  public Session newSession() throws QueryException {
    try {
      // Create the session
      RemoteSession remoteSession = new RemoteSessionImpl(sessionFactory.newSession(), this);
      remoteSessionSet.add(remoteSession);

      RemoteSession exportedRemoteSession = (RemoteSession)Rmi.export(remoteSession, interruptible);

      // Apply two wrappers to hide the RemoteExceptions of the
      // RemoteSession interface so everything looks like a Session
      return new RemoteSessionWrapperSession(exportedRemoteSession, getServerURI());
    } catch (RemoteException e) {
      throw new QueryException("Couldn't export session", e);
    }
  }

  /**
   * {@inheritDoc RemoteSessionFactory}
   * @return A new remotely exported JRDF session
   * @throws QueryException If an error occrred in the network protocol
   */
  public Session newJRDFSession() throws QueryException {
    try {
      // Create the session
      RemoteSession remoteSession = new RemoteJRDFSessionImpl((LocalJRDFSession)sessionFactory.newJRDFSession(), this);
      remoteSessionSet.add(remoteSession);

      RemoteJRDFSession exportedRemoteSession = (RemoteJRDFSession)Rmi.export(remoteSession, interruptible);

      // Apply two wrappers to hide the RemoteExceptions of the
      // RemoteSession interface so everything looks like a Session
      return new RemoteSessionWrapperJRDFSession(exportedRemoteSession, getServerURI());
    } catch (RemoteException e) {
      throw new QueryException("Couldn't export session", e);
    }
  }


  /**
   * {@inheritDoc RemoteSessionFactory}
   */
  public RemoteSession newRemoteSession() throws QueryException, RemoteException {
    try {
      // Create the session
      RemoteSession remoteSession = new RemoteSessionImpl(sessionFactory.newSession(), this);
      remoteSessionSet.add(remoteSession);

      return (RemoteSession)Rmi.export(remoteSession, interruptible);
    } catch (RemoteException e) {
      throw new QueryException("Couldn't export session", e);
    }
  }


  /**
   * {@inheritDoc RemoteSessionFactory}
   */
  public void removeSession(RemoteSession session)  {
    remoteSessionSet.remove(session);
    try {
      Rmi.unexportObject(session, true);
    } catch ( NoSuchObjectException ex ) {
      logger.warn("Request to remove an unknown session");
    }
  }


  /**
   * {@inheritDoc RemoteSessionFactory}
   */
  public void close() throws QueryException { }
}