/*
 * Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.
 *  
 * Redistribution and use in source and binary forms, with or 
 * without modification, are permitted provided that the following 
 * conditions are met:
 * 
 * -Redistributions of source code must retain the above copyright  
 *  notice, this list of conditions and the following disclaimer.
 * 
 * -Redistribution in binary form must reproduce the above copyright 
 *  notice, this list of conditions and the following disclaimer in 
 *  the documentation and/or other materials provided with the 
 *  distribution.
 *  
 * Neither the name of Oracle or the names of 
 * contributors may be used to endorse or promote products derived 
 * from this software without specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND
 * WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY
 * EXCLUDED. SUN MICROSYSTEMS, INC. ("SUN") AND ITS LICENSORS SHALL
 * NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF
 * USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
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 * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF
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 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *  
 * You acknowledge that Software is not designed, licensed or 
 * intended for use in the design, construction, operation or 
 * maintenance of any nuclear facility.
 */
package example.inetd;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketAddress;
import java.net.SocketException;
import java.nio.channels.Channel;
import java.nio.channels.ServerSocketChannel;
import java.rmi.AlreadyBoundException;
import java.rmi.Remote;
import java.rmi.RemoteException;
import java.rmi.registry.LocateRegistry;
import java.rmi.registry.Registry;
import java.rmi.server.RMIServerSocketFactory;

/**
 * A utility to export a registry (using an inherited channel if launched
 * from <code>inetd</code>) and to bind a remote service's proxy in that
 * registry for clients to look up.
 **/
public class InitializeRegistry {

    private static final Object lock = new Object();
    private static boolean serviceAvailable = false;
    private static boolean initialized = false;

    /**
     * Prevents instantiation.
     */
    private InitializeRegistry() {
	throw new AssertionError();
    }
    
    /**
     * Creates and exports a registry (using an inherited channel, if any,
     * as specified below), and binds the specified name to the specified
     * proxy in that registry.
     *
     * First, the registry is exported as follows:
     * <ul>
     * <li>If the <code>System.inheritedChannel</code> method returns a
     * <code>ServerSocketChannel</code> instance, the registry is exported
     * with an <code>RMIServerSocketFactory</code> whose
     * <code>createServerSocket</code> method returns a
     * <code>ServerSocket</code> for the inherited
     * <code>ServerSocketChannel</code> that delays accepting
     * requests until the specified proxy is bound in the
     * registry.
     *
     * <li>If the <code>System.inheritedChannel</code> method returns
     * <code>null</code>, then the registry is exported with an
     * <code>RMIServerSocketFactory</code> whose
     * <code>createServerSocket</code> method returns a
     * <code>ServerSocket</code> constructed with the specified
     * port that delays accepting requests until the specified proxy is
     * bound in the registry.  In this case, if the port is <code>0</code>,
     * then an <code>IllegalArgumentException</code> is thrown.
     *
     * <li>Otherwise, if the <code>System.inheritedChannel</code> returns
     * an instance of any other type, an <code>IOException</code> is
     * thrown.
     * </ul>
     *
     * <p>Once the registry is exported, the registry's <code>bind</code>
     * method is invoked with the specified name and proxy as arguments.
     *
     * @param obj the proxy for a remote object
     * @param name the name for the remote object in the registry
     * @param port a port to export the registry on if there is no
     * inherited channel
     * @throws IllegalArgumentException if the inherited channel is 
     * <code>null</code> and the port is <code>0</code>
     * @throws IllegalStateException if this method was called previously
     * @throws IOException if the inherited channel is not an instance 
     * of <code>ServerSocketChannel</code> or <code>null</code>
     * @throws RemoteException if the registry could not be exported
     **/
    public static void initializeWithInheritedChannel(Remote proxy,
						      String name,
						      int port)
    	throws IOException
    {
	/*
	 * Only allow this method to be invoked once.
	 */
	synchronized (InitializeRegistry.class) {
	    if (initialized) {
		throw new IllegalStateException("already invoked");
	    }
	    initialized = true;
	}
	
	Channel channel = System.inheritedChannel();
	ServerSocket serverSocket = null;

	/*
	 * Handle inherited channel, if any.
	 */
	if (channel instanceof ServerSocketChannel) {
	    /*
	     * Service launched from inetd.  Get server socket from
	     * inherited server socket channel.
	     */
	    serverSocket = ((ServerSocketChannel) channel).socket();

	} else if (channel == null) {
	    /*
	     * Service launched from the command line.  In this case, the
	     * port specified for the registry must be nonzero
	     */
	    if  (port == 0) {
		throw new IllegalArgumentException("port must be nonzero");
	    }
	    serverSocket = new ServerSocket(port);
	    
	} else {
	    throw new IOException(
		"unexpected channel returned from inheritedChannel: " +
		channel.toString());
	}

	/*
	 * Create server socket factory for registry to delay accepting
	 * calls until a service is bound in the registry.
	 */
	RMIServerSocketFactory ssf =
	    new RegistryServerSocketFactory(serverSocket);

	/*
	 * Create/export registry and bind name to proxy in registry.
	 */
	Registry registry = LocateRegistry.createRegistry(port, null, ssf);
	try {
	    registry.bind(name, proxy);
	} catch (RemoteException impossible) {
	    throw new AssertionError(impossible);
	} catch (AlreadyBoundException impossible) {
	    throw new AssertionError(impossible);
	}

	/*
	 * Notify registry's socket factory that the service proxy is
	 * bound in the registry, so that the registry can accept
	 * incoming requests to look up the service.
	 */
	synchronized (lock) {
	    serviceAvailable = true;
	    lock.notifyAll();
	}
    }

    /**
     * A server socket factory to use when exporting a registry launched
     * from 'inetd' with 'wait' status.  This socket factory's
     * 'createServerSocket' method returns a server socket that wraps the
     * server socket specified during construction and is specialized to
     * delay accepting requests until a remote service is bound in the
     * registry (when the 'serviceAvailable' flag is 'true').  The server
     * socket supplied to the constructor should be the server socket
     * obtained from the 'System.inheritedChannel' method.
     *
     * Note that only a single instance of this class should be created.
     **/
    private static class RegistryServerSocketFactory
	implements RMIServerSocketFactory
    {
	private final ServerSocket serverSocket;

	/**
	 * Constructs a 'RegistryServerSocketFactory' with the specified
	 * 'serverSocket'.
	 **/
	RegistryServerSocketFactory(ServerSocket serverSocket) {
	    this.serverSocket = serverSocket;
	}

	/**
	 * Returns the server socket specified during construction wrapped
	 * in a 'DelayedAcceptServerSocket'.  The port argument is ignored.
	 **/
	public ServerSocket createServerSocket(int port)
	    throws IOException
	{
	    return new DelayedAcceptServerSocket(serverSocket);
	}

    }

    /**
     * A server socket that delegates all public methods to the underlying
     * server socket specified at construction.  The accept method is
     * overridden to delay calling accept on the underlying server socket
     * until a remote service is bound in the registry (when the
     * 'serviceAvailable' flag is 'true').
     **/
    private static class DelayedAcceptServerSocket extends ServerSocket {

	private final ServerSocket serverSocket;

	/**
	 * Constructs a 'DelayedAcceptServerSocket' with the specified
	 * 'serverSocket'.
	 */
	DelayedAcceptServerSocket(ServerSocket serverSocket)
	    throws IOException
	{
	    this.serverSocket = serverSocket;
	}

	public void bind(SocketAddress endpoint) throws IOException {
	    serverSocket.bind(endpoint);
	}
	
	public void bind(SocketAddress endpoint, int backlog)
	    	throws IOException
	{
	    serverSocket.bind(endpoint, backlog);
	}
	
	public InetAddress getInetAddress() {
	    return serverSocket.getInetAddress();
	}

	public int getLocalPort() {
	    return serverSocket.getLocalPort();
	}
	
	public SocketAddress getLocalSocketAddress() {
	    return serverSocket.getLocalSocketAddress();
	}

	/**
	 * Delays calling accept on the underlying server socket until the
	 * remote service is bound in the registry.
	 **/
	public Socket accept() throws IOException {
	    synchronized (lock) {
		try {
		    while (!serviceAvailable) {
			lock.wait();
		    }
		} catch (InterruptedException e) {
		    throw (IOException)
			(new InterruptedIOException()).initCause(e);
		}
	    }
	    return serverSocket.accept();
	}

	public void close() throws IOException {
	    serverSocket.close();
	}
	
	public ServerSocketChannel getChannel() {
	    return serverSocket.getChannel();
	}
	
	public boolean isBound() {
	    return serverSocket.isBound();
	}

	public boolean isClosed() {
	    return serverSocket.isClosed();
	}
	
	public void setSoTimeout(int timeout)
	    throws SocketException
	{
	    serverSocket.setSoTimeout(timeout);
	}

	public int getSoTimeout() throws IOException {
	    return serverSocket.getSoTimeout();
	}
	
	public void setReuseAddress(boolean on) throws SocketException {
	    serverSocket.setReuseAddress(on);
	}

	public boolean getReuseAddress() throws SocketException {
	    return serverSocket.getReuseAddress();
	}

	public String toString() {
	    return serverSocket.toString();
	}
	
	public void setReceiveBufferSize(int size)
	    throws SocketException
	{
	    serverSocket.setReceiveBufferSize(size);
	}

	public int getReceiveBufferSize()
	    throws SocketException
	{
	    return serverSocket.getReceiveBufferSize();
	}
    }
}