/*
 * @(#)RMIServerImpl.java	1.54 04/06/03
 * 
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package javax.management.remote.rmi;

import java.io.IOException;
import java.lang.ref.WeakReference;
import java.rmi.Remote;
import java.rmi.server.RemoteObject;
import java.rmi.server.RemoteServer;
import java.rmi.server.ServerNotActiveException;
import java.security.Principal;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.management.MBeanServer;
import javax.management.remote.JMXAuthenticator;
import javax.management.remote.JMXConnectorFactory;
import javax.management.remote.JMXConnectorServer;

import javax.security.auth.Subject;

import com.sun.jmx.remote.security.JMXPluggableAuthenticator;
import com.sun.jmx.remote.util.ClassLogger;
import com.sun.jmx.remote.internal.ArrayNotificationBuffer;
import com.sun.jmx.remote.internal.NotificationBuffer;

/**
 * <p>An RMI object representing a connector server.  Remote clients
 * can make connections using the {@link #newClient(Object)} method.  This
 * method returns an RMI object representing the connection.</p>
 *
 * <p>User code does not usually reference this class directly.  RMI
 * connection servers are usually created with the class {@link
 * RMIConnectorServer}.  Remote clients usually create connections
 * either with {@link JMXConnectorFactory} or by instantiating {@link
 * RMIConnector}.</p>
 *
 * <p>This is an abstract class.  Concrete subclasses define the
 * details of the client connection objects, such as whether they use
 * JRMP or IIOP.</p>
 *
 * @since 1.5
 * @since.unbundled 1.0
 */
public abstract class RMIServerImpl implements RMIServer {
    /**
     * <p>Constructs a new <code>RMIServerImpl</code>.</p>
     *
     * @param env the environment containing attributes for the new
     * <code>RMIServerImpl</code>.  Can be null, which is equivalent
     * to an empty Map.
     */
    public RMIServerImpl(Map<String,?> env) {
        this.env = (env == null) ? Collections.EMPTY_MAP : env;
	if (logger.debugOn()) 
	    logger.trace("RMIServerImpl","class="+this.getClass().getName());
    }

    void setRMIConnectorServer(RMIConnectorServer connServer)
	    throws IOException {
	this.connServer = connServer;
    }

    /**
     * <p>Exports this RMI object.</p>
     *
     * @exception IOException if this RMI object cannot be exported.
     */
    protected abstract void export() throws IOException;

    /**
     * Returns a remotable stub for this server object.
     * @return a remotable stub.
     * @exception IOException if the stub cannot be obtained - e.g the
     *            RMIServerImpl has not been exported yet.
     **/
    public abstract Remote toStub() throws IOException;  

    /**
     * <p>Sets the default <code>ClassLoader</code> for this connector
     * server. New client connections will use this classloader.
     * Existing client connections are unaffected.</p>
     *
     * @param cl the new <code>ClassLoader</code> to be used by this
     * connector server.
     *
     * @see #getDefaultClassLoader
     */
    public synchronized void setDefaultClassLoader(ClassLoader cl) {
        this.cl = cl;
    }

    /**
     * <p>Gets the default <code>ClassLoader</code> used by this connector
     * server.</p>
     *
     * @return the default <code>ClassLoader</code> used by this
     * connector server.</p>
     *
     * @see #setDefaultClassLoader
     */
    public synchronized ClassLoader getDefaultClassLoader() {
        return cl;
    }

    /**
     * <p>Sets the <code>MBeanServer</code> to which this connector
     * server is attached. New client connections will interact
     * with this <code>MBeanServer</code>. Existing client connections are
     * unaffected.</p>
     *
     * @param mbs the new <code>MBeanServer</code>.  Can be null, but
     * new client connections will be refused as long as it is.
     *
     * @see #getMBeanServer
     */
    public synchronized void setMBeanServer(MBeanServer mbs) {
        this.mbeanServer = mbs;
    }

    /**
     * <p>The <code>MBeanServer</code> to which this connector server
     * is attached.  This is the last value passed to {@link
     * #setMBeanServer} on this object, or null if that method has
     * never been called.</p>
     *
     * @return the <code>MBeanServer</code> to which this connector
     * is attached.
     *
     * @see #setMBeanServer
     */
    public synchronized MBeanServer getMBeanServer() {
        return mbeanServer;
    }

    public String getVersion() {
	// Expected format is: "protocol-version implementation-name"
	return "1.0 java_runtime_" + (String)
	    AccessController.doPrivileged(new PrivilegedAction() {
		    public Object run() {
			return System.getProperty("java.runtime.version");
		    }
		});
    }

    /**
     * <p>Creates a new client connection.  This method calls {@link
     * #makeClient makeClient} and adds the returned client connection
     * object to an internal list.  When this
     * <code>RMIServerImpl</code> is shut down via its {@link
     * #close()} method, the {@link RMIConnection#close() close()}
     * method of each object remaining in the list is called.</p>
     *
     * <p>The fact that a client connection object is in this internal
     * list does not prevent it from being garbage collected.</p>
     *
     * @param credentials this object specifies the user-defined
     * credentials to be passed in to the server in order to
     * authenticate the caller before creating the
     * <code>RMIConnection</code>.  Can be null.
     *
     * @return the newly-created <code>RMIConnection</code>.  This is
     * usually the object created by <code>makeClient</code>, though
     * an implementation may choose to wrap that object in another
     * object implementing <code>RMIConnection</code>.
     *
     * @exception IOException if the new client object cannot be
     * created or exported.
     *
     * @exception SecurityException if the given credentials do not allow
     * the server to authenticate the user successfully.
     *
     * @exception IllegalStateException if {@link #getMBeanServer()}
     * is null.
     */
    public RMIConnection newClient(Object credentials) throws IOException {
	final boolean tracing = logger.traceOn();

	if (tracing) logger.trace("newClient","making new client");

	if (getMBeanServer() == null)
	    throw new IllegalStateException("Not attached to an MBean server");

        Subject subject = null;
        JMXAuthenticator authenticator =
            (JMXAuthenticator) env.get(JMXConnectorServer.AUTHENTICATOR);
	if (authenticator == null) {
	    /*
	     * Create the JAAS-based authenticator only if authentication
	     * has been enabled
	     */
	    if (env.get("jmx.remote.x.password.file") != null ||
		env.get("jmx.remote.x.login.config") != null) {
		authenticator = new JMXPluggableAuthenticator(env);
	    }
	}
        if (authenticator != null) {
	    if (tracing) logger.trace("newClient","got authenticator: " +
			       authenticator.getClass().getName());
	    try {
		subject = authenticator.authenticate(credentials);
	    } catch (SecurityException e) {
		logger.trace("newClient", "Authentication failed: " + e);
		throw e;
	    }
        }

	if (tracing) {
	    if (subject != null) 
		logger.trace("newClient","subject is not null");
	    else logger.trace("newClient","no subject");
	}

	final String connectionId = makeConnectionId(getProtocol(), subject);

	if (tracing) 
	    logger.trace("newClient","making new connection: " + connectionId);

        RMIConnection client = makeClient(connectionId, subject);

	connServer.connectionOpened(connectionId, "Connection opened", null);

        dropDeadReferences();
        WeakReference wr = new WeakReference(client);
        synchronized (clientList) {
            clientList.add(wr);
        }

	if (tracing) 
	    logger.trace("newClient","new connection done: " + connectionId );

        return client;
    }

    /**
     * <p>Creates a new client connection.  This method is called by
     * the public method {@link #newClient(Object)}.</p>
     *
     * @param connectionId the ID of the new connection.  Every
     * connection opened by this connector server will have a
     * different ID.  The behavior is unspecified if this parameter is
     * null.
     *
     * @param subject the authenticated subject.  Can be null.
     *
     * @return the newly-created <code>RMIConnection</code>.
     *
     * @exception IOException if the new client object cannot be
     * created or exported.
     */
    protected abstract RMIConnection makeClient(String connectionId,
						Subject subject)
	    throws IOException;

    /**
     * <p>Closes a client connection made by {@link #makeClient makeClient}.
     *
     * @param client a connection previously returned by
     * <code>makeClient</code> on which the <code>closeClient</code>
     * method has not previously been called.  The behavior is
     * unspecified if these conditions are violated, including the
     * case where <code>client</code> is null.
     *
     * @exception IOException if the client connection cannot be
     * closed.
     */
    protected abstract void closeClient(RMIConnection client)
	    throws IOException;

    /**
     * <p>Returns the protocol string for this object.  The string is
     * <code>rmi</code> for RMI/JRMP and <code>iiop</code> for RMI/IIOP.
     *
     * @return the protocol string for this object.
     */
    protected abstract String getProtocol();

    /**
     * <p>Method called when a client connection created by {@link
     * #makeClient makeClient} is closed.  A subclass that defines
     * <code>makeClient</code> must arrange for this method to be
     * called when the resultant object's {@link RMIConnection#close()
     * close} method is called.  This enables it to be removed from
     * the <code>RMIServerImpl</code>'s list of connections.  It is
     * not an error for <code>client</code> not to be in that
     * list.</p>
     *
     * <p>After removing <code>client</code> from the list of
     * connections, this method calls {@link #closeClient
     * closeClient(client)}.</p>
     *
     * @param client the client connection that has been closed.
     *
     * @exception IOException if {@link #closeClient} throws this
     * exception.
     *
     * @exception NullPointerException if <code>client</code> is null.
     */
    protected void clientClosed(RMIConnection client) throws IOException {
	final boolean debug = logger.debugOn();

	if (debug) logger.trace("clientClosed","client="+client);

	if (client == null)
	    throw new NullPointerException("Null client");

        synchronized (clientList) {
            dropDeadReferences();
            for (Iterator it = clientList.iterator(); it.hasNext(); ) {
                WeakReference wr = (WeakReference) it.next();
                if (wr.get() == client) {
                    it.remove();
                    break;
                }
            }
            /* It is not a bug for this loop not to find the client.  In
               our close() method, we remove a client from the list before
               calling its close() method.  */
        }

	if (debug) logger.trace("clientClosed", "closing client.");
        closeClient(client);

	if (debug) logger.trace("clientClosed", "sending notif");
	connServer.connectionClosed(client.getConnectionId(),
				    "Client connection closed", null);

	if (debug) logger.trace("clientClosed","done");
    }

    /**
     * <p>Closes this connection server.  This method first calls the
     * {@link #closeServer()} method so that no new client connections
     * will be accepted.  Then, for each remaining {@link
     * RMIConnection} object returned by {@link #makeClient
     * makeClient}, its {@link RMIConnection#close() close} method is
     * called.</p>
     *
     * <p>The behaviour when this method is called more than once is
     * unspecified.</p>
     *
     * <p>If {@link #closeServer()} throws an
     * <code>IOException</code>, the individual connections are
     * nevertheless closed, and then the <code>IOException</code> is
     * thrown from this method.</p>
     *
     * <p>If {@link #closeServer()} returns normally but one or more
     * of the individual connections throws an
     * <code>IOException</code>, then, after closing all the
     * connections, one of those <code>IOException</code>s is thrown
     * from this method.  If more than one connection throws an
     * <code>IOException</code>, it is unspecified which one is thrown
     * from this method.</p>
     *
     * @exception IOException if {@link #closeServer()} or one of the
     * {@link RMIConnection#close()} calls threw
     * <code>IOException</code>.
     */
    public synchronized void close() throws IOException {
	final boolean tracing = logger.traceOn();
	final boolean debug   = logger.debugOn();
	
	if (tracing) logger.trace("close","closing");

        IOException ioException = null;
        try {
	    if (debug)   logger.debug("close","closing Server");
            closeServer();
        } catch (IOException e) {
	    if (tracing) logger.trace("close","Failed to close server: " + e);
	    if (debug)   logger.debug("close",e);
            ioException = e;
        }

	if (debug)   logger.debug("close","closing Clients");
        // Loop to close all clients
        while (true) {
            synchronized (clientList) {
		if (debug) logger.debug("close","droping dead references");
                dropDeadReferences();

		if (debug) logger.debug("close","client count: "+clientList.size());
                if (clientList.size() == 0) 
                    break;
                /* Loop until we find a non-null client.  Because we called
                   dropDeadReferences(), this will usually be the first
                   element of the list, but a garbage collection could have
                   happened in between.  */
                for (Iterator it = clientList.iterator(); it.hasNext(); ) {
                    WeakReference wr = (WeakReference) it.next();
                    RMIConnection client = (RMIConnection) wr.get();
                    it.remove();
                    if (client != null) {
                        try {
                            client.close();
                        } catch (IOException e) {
			    if (tracing) 
				logger.trace("close","Failed to close client: " + e);
			    if (debug) logger.debug("close",e);
                            if (ioException == null)
                                ioException = e;
                        }
                        break;
                    }
                }
            }
        }

	if(notifBuffer != null)
	    notifBuffer.dispose();
	
        if (ioException != null) {
	    if (tracing) logger.trace("close","close failed.");
            throw ioException;
	}

	if (tracing) logger.trace("close","closed.");
    }

    /**
     * <p>Called by {@link #close()} to close the connector server.
     * After returning from this method, the connector server must
     * not accept any new connections.</p>
     *
     * @exception IOException if the attempt to close the connector
     * server failed.
     */
    protected abstract void closeServer() throws IOException;

    private static synchronized String makeConnectionId(String protocol,
							Subject subject) {
        connectionIdNumber++;

	String clientHost = "";
	try {
	    clientHost = RemoteServer.getClientHost();
	} catch (ServerNotActiveException e) {
	    logger.trace("makeConnectionId", "getClientHost", e);
	}

	StringBuffer buf = new StringBuffer();
	buf.append(protocol).append(":");
	if (clientHost.length() > 0)
	    buf.append("//").append(clientHost);
	buf.append(" ");
	if (subject != null) {
	    Set principals = subject.getPrincipals();
	    String sep = "";
	    for (Iterator it = principals.iterator(); it.hasNext(); ) {
		Principal p = (Principal) it.next();
		String name = p.getName().replace(' ', '_').replace(';', ':');
		buf.append(sep).append(name);
		sep = ";";
	    }
	}
	buf.append(" ").append(connectionIdNumber);
	if (logger.traceOn()) 
	    logger.trace("newConnectionId","connectionId="+buf);
        return buf.toString();
    }

    private void dropDeadReferences() {
        synchronized (clientList) {
            for (Iterator it = clientList.iterator(); it.hasNext(); ) {
                WeakReference wr = (WeakReference) it.next();
                if (wr.get() == null)
                    it.remove();
            }
        }
    }
    
    synchronized NotificationBuffer getNotifBuffer() {
	//Notification buffer is lazily created when the first client connects
	if(notifBuffer == null)
	    notifBuffer = 
		ArrayNotificationBuffer.getNotificationBuffer(mbeanServer,
							      env);
	return notifBuffer;
    }
    
    private static final ClassLogger logger =
	new ClassLogger("javax.management.remote.rmi", "RMIServerImpl");

    /** List of WeakReference values.  Each one references an
        RMIConnection created by this object, or null if the
        RMIConnection has been garbage-collected.  */
    private final List clientList = new ArrayList();

    private ClassLoader cl;

    private MBeanServer mbeanServer;

    private final Map env;

    private RMIConnectorServer connServer;

    private static int connectionIdNumber;

    private NotificationBuffer notifBuffer;
}