/* 
 * %CopyrightBegin%
 * 
 * Copyright Ericsson AB 2000-2009. All Rights Reserved.
 * 
 * The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved online at http://www.erlang.org/.
 * 
 * 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.
 * 
 * %CopyrightEnd%
 */
package com.ericsson.otp.erlang;

import java.io.IOException;
import java.lang.ref.WeakReference;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Iterator;

/**
 * <p>
 * Represents a local OTP node. This class is used when you do not wish to
 * manage connections yourself - outgoing connections are established as needed,
 * and incoming connections accepted automatically. This class supports the use
 * of a mailbox API for communication, while management of the underlying
 * communication mechanism is automatic and hidden from the application
 * programmer.
 * </p>
 * 
 * <p>
 * Once an instance of this class has been created, obtain one or more mailboxes
 * in order to send or receive messages. The first message sent to a given node
 * will cause a connection to be set up to that node. Any messages received will
 * be delivered to the appropriate mailboxes.
 * </p>
 * 
 * <p>
 * To shut down the node, call {@link #close close()}. This will prevent the
 * node from accepting additional connections and it will cause all existing
 * connections to be closed. Any unread messages in existing mailboxes can still
 * be read, however no new messages will be delivered to the mailboxes.
 * </p>
 * 
 * <p>
 * Note that the use of this class requires that Epmd (Erlang Port Mapper
 * Daemon) is running on each cooperating host. This class does not start Epmd
 * automatically as Erlang does, you must start it manually or through some
 * other means. See the Erlang documentation for more information about this.
 * </p>
 */
public class OtpNode extends OtpLocalNode {
    private boolean initDone = false;

    // thread to manage incoming connections
    private Acceptor acceptor = null;

    // keep track of all connections
    Hashtable<String, OtpCookedConnection> connections = null;

    // keep track of all mailboxes
    Mailboxes mboxes = null;

    // handle status changes
    OtpNodeStatus handler;

    // flags
    private int flags = 0;

    /**
     * <p>
     * Create a node using the default cookie. The default cookie is found by
     * reading the first line of the .erlang.cookie file in the user's home
     * directory. The home directory is obtained from the System property
     * "user.home".
     * </p>
     * 
     * <p>
     * If the file does not exist, an empty string is used. This method makes no
     * attempt to create the file.
     * </p>
     * 
     * @param node
     *            the name of this node.
     * 
     * @exception IOException
     *                if communication could not be initialized.
     * 
     */
    public OtpNode(final String node) throws IOException {
	this(node, defaultCookie, 0);
    }

    /**
     * Create a node.
     * 
     * @param node
     *            the name of this node.
     * 
     * @param cookie
     *            the authorization cookie that will be used by this node when
     *            it communicates with other nodes.
     * 
     * @exception IOException
     *                if communication could not be initialized.
     * 
     */
    public OtpNode(final String node, final String cookie) throws IOException {
	this(node, cookie, 0);
    }

    /**
     * Create a node.
     * 
     * @param node
     *            the name of this node.
     * 
     * @param cookie
     *            the authorization cookie that will be used by this node when
     *            it communicates with other nodes.
     * 
     * @param port
     *            the port number you wish to use for incoming connections.
     *            Specifying 0 lets the system choose an available port.
     * 
     * @exception IOException
     *                if communication could not be initialized.
     * 
     */
    public OtpNode(final String node, final String cookie, final int port)
	    throws IOException {
	super(node, cookie);

	init(port);
    }

    private synchronized void init(final int port) throws IOException {
	if (!initDone) {
	    connections = new Hashtable<String, OtpCookedConnection>(17,
		    (float) 0.95);
	    mboxes = new Mailboxes();
	    acceptor = new Acceptor(port);
	    initDone = true;
	}
    }

    /**
     * Close the node. Unpublish the node from Epmd (preventing new connections)
     * and close all existing connections.
     */
    public synchronized void close() {
	acceptor.quit();
	OtpCookedConnection conn;
	final Collection<OtpCookedConnection> coll = connections.values();
	final Iterator<OtpCookedConnection> it = coll.iterator();

	mboxes.clear();

	while (it.hasNext()) {
	    conn = it.next();
	    it.remove();
	    conn.close();
	}
	initDone = false;
    }

    @Override
    protected void finalize() {
	close();
    }

    /**
     * Create an unnamed {@link OtpMbox mailbox} that can be used to send and
     * receive messages with other, similar mailboxes and with Erlang processes.
     * Messages can be sent to this mailbox by using its associated
     * {@link OtpMbox#self() pid}.
     * 
     * @return a mailbox.
     */
    public OtpMbox createMbox() {
	return mboxes.create();
    }

    /**
     * Close the specified mailbox with reason 'normal'.
     * 
     * @param mbox
     *            the mailbox to close.
     * 
     *            <p>
     *            After this operation, the mailbox will no longer be able to
     *            receive messages. Any delivered but as yet unretrieved
     *            messages can still be retrieved however.
     *            </p>
     * 
     *            <p>
     *            If there are links from the mailbox to other
     *            {@link OtpErlangPid pids}, they will be broken when this
     *            method is called and exit signals with reason 'normal' will be
     *            sent.
     *            </p>
     * 
     */
    public void closeMbox(final OtpMbox mbox) {
	closeMbox(mbox, new OtpErlangAtom("normal"));
    }

    /**
     * Close the specified mailbox with the given reason.
     * 
     * @param mbox
     *            the mailbox to close.
     * @param reason
     *            an Erlang term describing the reason for the termination.
     * 
     *            <p>
     *            After this operation, the mailbox will no longer be able to
     *            receive messages. Any delivered but as yet unretrieved
     *            messages can still be retrieved however.
     *            </p>
     * 
     *            <p>
     *            If there are links from the mailbox to other
     *            {@link OtpErlangPid pids}, they will be broken when this
     *            method is called and exit signals with the given reason will
     *            be sent.
     *            </p>
     * 
     */
    public void closeMbox(final OtpMbox mbox, final OtpErlangObject reason) {
	if (mbox != null) {
	    mboxes.remove(mbox);
	    mbox.name = null;
	    mbox.breakLinks(reason);
	}
    }

    /**
     * Create an named mailbox that can be used to send and receive messages
     * with other, similar mailboxes and with Erlang processes. Messages can be
     * sent to this mailbox by using its registered name or the associated
     * {@link OtpMbox#self() pid}.
     * 
     * @param name
     *            a name to register for this mailbox. The name must be unique
     *            within this OtpNode.
     * 
     * @return a mailbox, or null if the name was already in use.
     * 
     */
    public OtpMbox createMbox(final String name) {
	return mboxes.create(name);
    }

    /**
     * <p>
     * Register or remove a name for the given mailbox. Registering a name for a
     * mailbox enables others to send messages without knowing the
     * {@link OtpErlangPid pid} of the mailbox. A mailbox can have at most one
     * name; if the mailbox already had a name, calling this method will
     * supercede that name.
     * </p>
     * 
     * @param name
     *            the name to register for the mailbox. Specify null to
     *            unregister the existing name from this mailbox.
     * 
     * @param mbox
     *            the mailbox to associate with the name.
     * 
     * @return true if the name was available, or false otherwise.
     */
    public boolean registerName(final String name, final OtpMbox mbox) {
	return mboxes.register(name, mbox);
    }

    /**
     * Get a list of all known registered names on this node.
     * 
     * @return an array of Strings, containins all known registered names on
     *         this node.
     */

    public String[] getNames() {
	return mboxes.names();
    }

    /**
     * Determine the {@link OtpErlangPid pid} corresponding to a registered name
     * on this node.
     * 
     * @return the {@link OtpErlangPid pid} corresponding to the registered
     *         name, or null if the name is not known on this node.
     */
    public OtpErlangPid whereis(final String name) {
	final OtpMbox m = mboxes.get(name);
	if (m != null) {
	    return m.self();
	}
	return null;
    }

    /**
     * Register interest in certain system events. The {@link OtpNodeStatus
     * OtpNodeStatus} handler object contains callback methods, that will be
     * called when certain events occur.
     * 
     * @param handler
     *            the callback object to register. To clear the handler, specify
     *            null as the handler to use.
     * 
     */
    public synchronized void registerStatusHandler(final OtpNodeStatus handler) {
	this.handler = handler;
    }

    /**
     * <p>
     * Determine if another node is alive. This method has the side effect of
     * setting up a connection to the remote node (if possible). Only a single
     * outgoing message is sent; the timeout is how long to wait for a response.
     * </p>
     * 
     * <p>
     * Only a single attempt is made to connect to the remote node, so for
     * example it is not possible to specify an extremely long timeout and
     * expect to be notified when the node eventually comes up. If you wish to
     * wait for a remote node to be started, the following construction may be
     * useful:
     * </p>
     * 
     * <pre>
     * // ping every 2 seconds until positive response
     * while (!me.ping(him, 2000))
     *     ;
     * </pre>
     * 
     * @param node
     *            the name of the node to ping.
     * 
     * @param timeout
     *            the time, in milliseconds, to wait for response before
     *            returning false.
     * 
     * @return true if the node was alive and the correct ping response was
     *         returned. false if the correct response was not returned on time.
     */
    /*
     * internal info about the message formats...
     * 
     * the request: -> REG_SEND {6,#Pid<bingo@aule.1.0>,'',net_kernel}
     * {'$gen_call',{#Pid<bingo@aule.1.0>,#Ref<bingo@aule.2>},{is_auth,bingo@aule}}
     * 
     * the reply: <- SEND {2,'',#Pid<bingo@aule.1.0>} {#Ref<bingo@aule.2>,yes}
     */
    public boolean ping(final String node, final long timeout) {
	if (node.equals(this.node)) {
	    return true;
	} else if (node.indexOf('@', 0) < 0
		&& node.equals(this.node
			.substring(0, this.node.indexOf('@', 0)))) {
	    return true;
	}

	// other node
	OtpMbox mbox = null;
	try {
	    mbox = createMbox();
	    mbox.send("net_kernel", node, getPingTuple(mbox));
	    final OtpErlangObject reply = mbox.receive(timeout);

	    final OtpErlangTuple t = (OtpErlangTuple) reply;
	    final OtpErlangAtom a = (OtpErlangAtom) t.elementAt(1);
	    return "yes".equals(a.atomValue());
	} catch (final Exception e) {
	} finally {
	    closeMbox(mbox);
	}
	return false;
    }

    /* create the outgoing ping message */
    private OtpErlangTuple getPingTuple(final OtpMbox mbox) {
	final OtpErlangObject[] ping = new OtpErlangObject[3];
	final OtpErlangObject[] pid = new OtpErlangObject[2];
	final OtpErlangObject[] node = new OtpErlangObject[2];

	pid[0] = mbox.self();
	pid[1] = createRef();

	node[0] = new OtpErlangAtom("is_auth");
	node[1] = new OtpErlangAtom(node());

	ping[0] = new OtpErlangAtom("$gen_call");
	ping[1] = new OtpErlangTuple(pid);
	ping[2] = new OtpErlangTuple(node);

	return new OtpErlangTuple(ping);
    }

    /*
     * this method simulates net_kernel only for the purpose of replying to
     * pings.
     */
    private boolean netKernel(final OtpMsg m) {
	OtpMbox mbox = null;
	try {
	    final OtpErlangTuple t = (OtpErlangTuple) m.getMsg();
	    final OtpErlangTuple req = (OtpErlangTuple) t.elementAt(1); // actual
	    // request

	    final OtpErlangPid pid = (OtpErlangPid) req.elementAt(0); // originating
	    // pid

	    final OtpErlangObject[] pong = new OtpErlangObject[2];
	    pong[0] = req.elementAt(1); // his #Ref
	    pong[1] = new OtpErlangAtom("yes");

	    mbox = createMbox();
	    mbox.send(pid, new OtpErlangTuple(pong));
	    return true;
	} catch (final Exception e) {
	} finally {
	    closeMbox(mbox);
	}
	return false;
    }

    /*
     * OtpCookedConnection delivers messages here return true if message was
     * delivered successfully, or false otherwise.
     */
    boolean deliver(final OtpMsg m) {
	OtpMbox mbox = null;

	try {
	    final int t = m.type();

	    if (t == OtpMsg.regSendTag) {
		final String name = m.getRecipientName();
		/* special case for netKernel requests */
		if (name.equals("net_kernel")) {
		    return netKernel(m);
		} else {
		    mbox = mboxes.get(name);
		}
	    } else {
		mbox = mboxes.get(m.getRecipientPid());
	    }

	    if (mbox == null) {
		return false;
	    }
	    mbox.deliver(m);
	} catch (final Exception e) {
	    return false;
	}

	return true;
    }

    /*
     * OtpCookedConnection delivers errors here, we send them on to the handler
     * specified by the application
     */
    void deliverError(final OtpCookedConnection conn, final Exception e) {
	removeConnection(conn);
	remoteStatus(conn.name, false, e);
    }

    /*
     * find or create a connection to the given node
     */
    OtpCookedConnection getConnection(final String node) {
	OtpPeer peer = null;
	OtpCookedConnection conn = null;

	synchronized (connections) {
	    // first just try looking up the name as-is
	    conn = connections.get(node);

	    if (conn == null) {
		// in case node had no '@' add localhost info and try again
		peer = new OtpPeer(node);
		conn = connections.get(peer.node());

		if (conn == null) {
		    try {
			conn = new OtpCookedConnection(this, peer);
			conn.setFlags(flags);
			addConnection(conn);
		    } catch (final Exception e) {
			/* false = outgoing */
			connAttempt(peer.node(), false, e);
		    }
		}
	    }
	    return conn;
	}
    }

    void addConnection(final OtpCookedConnection conn) {
	if (conn != null && conn.name != null) {
	    connections.put(conn.name, conn);
	    remoteStatus(conn.name, true, null);
	}
    }

    private void removeConnection(final OtpCookedConnection conn) {
	if (conn != null && conn.name != null) {
	    connections.remove(conn.name);
	}
    }

    /* use these wrappers to call handler functions */
    private synchronized void remoteStatus(final String node, final boolean up,
	    final Object info) {
	if (handler == null) {
	    return;
	}
	try {
	    handler.remoteStatus(node, up, info);
	} catch (final Exception e) {
	}
    }

    synchronized void localStatus(final String node, final boolean up,
	    final Object info) {
	if (handler == null) {
	    return;
	}
	try {
	    handler.localStatus(node, up, info);
	} catch (final Exception e) {
	}
    }

    synchronized void connAttempt(final String node, final boolean incoming,
	    final Object info) {
	if (handler == null) {
	    return;
	}
	try {
	    handler.connAttempt(node, incoming, info);
	} catch (final Exception e) {
	}
    }

    /*
     * this class used to wrap the mailbox hashtables so we can use weak
     * references
     */
    public class Mailboxes {
	// mbox pids here
	private Hashtable<OtpErlangPid, WeakReference<OtpMbox>> byPid = null;
	// mbox names here
	private Hashtable<String, WeakReference<OtpMbox>> byName = null;

	public Mailboxes() {
	    byPid = new Hashtable<OtpErlangPid, WeakReference<OtpMbox>>(17,
		    (float) 0.95);
	    byName = new Hashtable<String, WeakReference<OtpMbox>>(17,
		    (float) 0.95);
	}

	public OtpMbox create(final String name) {
	    OtpMbox m = null;

	    synchronized (byName) {
		if (get(name) != null) {
		    return null;
		}
		final OtpErlangPid pid = createPid();
		m = new OtpMbox(OtpNode.this, pid, name);
		byPid.put(pid, new WeakReference<OtpMbox>(m));
		byName.put(name, new WeakReference<OtpMbox>(m));
	    }
	    return m;
	}

	public OtpMbox create() {
	    final OtpErlangPid pid = createPid();
	    final OtpMbox m = new OtpMbox(OtpNode.this, pid);
	    byPid.put(pid, new WeakReference<OtpMbox>(m));
	    return m;
	}

	public void clear() {
	    byPid.clear();
	    byName.clear();
	}

	public String[] names() {
	    String allnames[] = null;

	    synchronized (byName) {
		final int n = byName.size();
		final Enumeration<String> keys = byName.keys();
		allnames = new String[n];

		int i = 0;
		while (keys.hasMoreElements()) {
		    allnames[i++] = keys.nextElement();
		}
	    }
	    return allnames;
	}

	public boolean register(final String name, final OtpMbox mbox) {
	    if (name == null) {
		if (mbox.name != null) {
		    byName.remove(mbox.name);
		    mbox.name = null;
		}
	    } else {
		synchronized (byName) {
		    if (get(name) != null) {
			return false;
		    }
		    byName.put(name, new WeakReference<OtpMbox>(mbox));
		    mbox.name = name;
		}
	    }
	    return true;
	}

	/*
	 * look up a mailbox based on its name. If the mailbox has gone out of
	 * scope we also remove the reference from the hashtable so we don't
	 * find it again.
	 */
	public OtpMbox get(final String name) {
	    final WeakReference<OtpMbox> wr = byName.get(name);

	    if (wr != null) {
		final OtpMbox m = wr.get();

		if (m != null) {
		    return m;
		}
		byName.remove(name);
	    }
	    return null;
	}

	/*
	 * look up a mailbox based on its pid. If the mailbox has gone out of
	 * scope we also remove the reference from the hashtable so we don't
	 * find it again.
	 */
	public OtpMbox get(final OtpErlangPid pid) {
	    final WeakReference<OtpMbox> wr = byPid.get(pid);

	    if (wr != null) {
		final OtpMbox m = wr.get();

		if (m != null) {
		    return m;
		}
		byPid.remove(pid);
	    }
	    return null;
	}

	public void remove(final OtpMbox mbox) {
	    byPid.remove(mbox.self);
	    if (mbox.name != null) {
		byName.remove(mbox.name);
	    }
	}
    }

    /*
     * this thread simply listens for incoming connections
     */
    public class Acceptor extends Thread {
	private final ServerSocket sock;
	private final int port;
	private volatile boolean done = false;

	Acceptor(final int port) throws IOException {
	    sock = new ServerSocket(port);
	    this.port = sock.getLocalPort();
	    OtpNode.this.port = this.port;

	    setDaemon(true);
	    setName("acceptor");
	    publishPort();
	    start();
	}

	private boolean publishPort() throws IOException {
	    if (getEpmd() != null) {
		return false; // already published
	    }
	    OtpEpmd.publishPort(OtpNode.this);
	    return true;
	}

	private void unPublishPort() {
	    // unregister with epmd
	    OtpEpmd.unPublishPort(OtpNode.this);

	    // close the local descriptor (if we have one)
	    closeSock(epmd);
	    epmd = null;
	}

	public void quit() {
	    unPublishPort();
	    done = true;
	    closeSock(sock);
	    localStatus(node, false, null);
	}

	private void closeSock(final ServerSocket s) {
	    try {
		if (s != null) {
		    s.close();
		}
	    } catch (final Exception e) {
	    }
	}

	private void closeSock(final Socket s) {
	    try {
		if (s != null) {
		    s.close();
		}
	    } catch (final Exception e) {
	    }
	}

	public int port() {
	    return port;
	}

	@Override
	public void run() {
	    Socket newsock = null;
	    OtpCookedConnection conn = null;

	    localStatus(node, true, null);

	    accept_loop: while (!done) {
		conn = null;

		try {
		    newsock = sock.accept();
		} catch (final Exception e) {
		    // Problem in java1.2.2: accept throws SocketException
		    // when socket is closed. This will happen when
		    // acceptor.quit()
		    // is called. acceptor.quit() will call localStatus(...), so
		    // we have to check if that's where we come from.
		    if (!done) {
			localStatus(node, false, e);
		    }
		    break accept_loop;
		}

		try {
		    synchronized (connections) {
			conn = new OtpCookedConnection(OtpNode.this, newsock);
			conn.setFlags(flags);
			addConnection(conn);
		    }
		} catch (final OtpAuthException e) {
		    if (conn != null && conn.name != null) {
			connAttempt(conn.name, true, e);
		    } else {
			connAttempt("unknown", true, e);
		    }
		    closeSock(newsock);
		} catch (final IOException e) {
		    if (conn != null && conn.name != null) {
			connAttempt(conn.name, true, e);
		    } else {
			connAttempt("unknown", true, e);
		    }
		    closeSock(newsock);
		} catch (final Exception e) {
		    closeSock(newsock);
		    closeSock(sock);
		    localStatus(node, false, e);
		    break accept_loop;
		}
	    } // while

	    // if we have exited loop we must do this too
	    unPublishPort();
	}
    }

    public void setFlags(final int flags) {
	this.flags = flags;
    }
}