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/**
 *
 * All rights reserved. Licensed 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.jivesoftware.smack;

import java.util.Random;

import org.apache.log4j.Logger;
import org.jivesoftware.smack.packet.StreamError;

/**
 * Handles the automatic reconnection process. Every time a connection is
 * dropped without the application explictly closing it, the manager
 * automatically tries to reconnect to the server.
 * 
 * 
 * The reconnection mechanism will try to reconnect periodically:
 * 

 * For the first minute it will attempt to connect once every ten seconds.
 * 
For the next five minutes it will attempt to connect once a minute.
 * 
If that fails it will indefinitely try to connect once every five
 * minutes.
 * 
 * 
 * @author Francisco Vives
 */
public class ReconnectionManager implements ConnectionListener {
    private static Logger log = Logger.getLogger(ReconnectionManager.class
            .getName());

    // Holds the connection to the server
    private Connection connection;
    private Thread reconnectionThread;
    private int randomBase = new Random().nextInt(11) + 5; // between 5 and 15
                                                           // seconds

    // Holds the state of the reconnection
    boolean done = false;

    static {
        // Create a new PrivacyListManager on every established connection. In
        // the init()
        // method of PrivacyListManager, we'll add a listener that will delete
        // the
        // instance when the connection is closed.
        Connection
                .addConnectionCreationListener(new ConnectionCreationListener() {
                    public void connectionCreated(Connection connection) {
                        connection
                                .addConnectionListener(new ReconnectionManager(
                                        connection));
                    }
                });
    }

    private ReconnectionManager(Connection connection) {
        this.connection = connection;
    }

    /**
     * Returns true if the reconnection mechanism is enabled.
     * 
     * @return true if automatic reconnections are allowed.
     */
    private boolean isReconnectionAllowed() {
        return !done && !connection.isConnected()
                && connection.isReconnectionAllowed();
    }

    /**
     * Starts a reconnection mechanism if it was configured to do that. The
     * algorithm is been executed when the first connection error is detected.
     * 
     * The reconnection mechanism will try to reconnect periodically in this
     * way:
     * 

     * First it will try 6 times every 10 seconds.
     * 
Then it will try 10 times every 1 minute.
     * 
Finally it will try indefinitely every 5 minutes.
     * 
     */
    synchronized protected void reconnect() {
        if (this.isReconnectionAllowed()) {
            // Since there is no thread running, creates a new one to attempt
            // the reconnection.
            // avoid to run duplicated reconnectionThread -- fd: 16/09/2010
            if (reconnectionThread != null && reconnectionThread.isAlive())
                return;

            reconnectionThread = new Thread() {

                /**
                 * Holds the current number of reconnection attempts
                 */
                private int attempts = 0;

                /**
                 * Returns the number of seconds until the next reconnection
                 * attempt.
                 * 
                 * @return the number of seconds until the next reconnection
                 *         attempt.
                 */
                private int timeDelay() {
                    attempts++;
                    if (attempts > 13) {
                        return randomBase * 6 * 5; // between 2.5 and 7.5
                                                   // minutes (~5 minutes)
                    }
                    if (attempts > 7) {
                        return randomBase * 6; // between 30 and 90 seconds (~1
                                               // minutes)
                    }
                    return randomBase; // 10 seconds
                }

                /**
                 * The process will try the reconnection until the connection
                 * succeed or the user cancell it
                 */
                public void run() {
                    // The process will try to reconnect until the connection is
                    // established or
                    // the user cancel the reconnection process {@link
                    // Connection#disconnect()}
                    while (ReconnectionManager.this.isReconnectionAllowed()) {
                        // Find how much time we should wait until the next
                        // reconnection
                        int remainingSeconds = timeDelay();
                        // Sleep until we're ready for the next reconnection
                        // attempt. Notify
                        // listeners once per second about how much time remains
                        // before the next
                        // reconnection attempt.
                        while (ReconnectionManager.this.isReconnectionAllowed()
                                && remainingSeconds > 0) {
                            try {
                                Thread.sleep(1000);
                                remainingSeconds--;
                                ReconnectionManager.this
                                        .notifyAttemptToReconnectIn(remainingSeconds);
                            } catch (InterruptedException e1) {
                                log.warn("Sleeping thread interrupted");
                                // Notify the reconnection has failed
                                ReconnectionManager.this
                                        .notifyReconnectionFailed(e1);
                            }
                        }

                        // Makes a reconnection attempt
                        try {
                            if (ReconnectionManager.this
                                    .isReconnectionAllowed()) {
                                connection.connect();
                            }
                        } catch (XMPPException e) {
                            // Fires the failed reconnection notification
                            ReconnectionManager.this
                                    .notifyReconnectionFailed(e);
                        }
                    }
                }
            };
            reconnectionThread.setName("Smack Reconnection Manager");
            reconnectionThread.setDaemon(true);
            reconnectionThread.start();
        }
    }

    /**
     * Fires listeners when a reconnection attempt has failed.
     * 
     * @param exception
     *            the exception that occured.
     */
    protected void notifyReconnectionFailed(Exception exception) {
        if (isReconnectionAllowed()) {
            for (ConnectionListener listener : connection.connectionListeners) {
                listener.reconnectionFailed(exception);
            }
        }
    }

    /**
     * Fires listeners when The Connection will retry a reconnection. Expressed
     * in seconds.
     * 
     * @param seconds
     *            the number of seconds that a reconnection will be attempted
     *            in.
     */
    protected void notifyAttemptToReconnectIn(int seconds) {
        if (isReconnectionAllowed()) {
            for (ConnectionListener listener : connection.connectionListeners) {
                listener.reconnectingIn(seconds);
            }
        }
    }

    public void connectionClosed() {
        done = true;
    }

    public void connectionClosedOnError(Exception e) {
        done = false;
        if (e instanceof XMPPException) {
            XMPPException xmppEx = (XMPPException) e;
            StreamError error = xmppEx.getStreamError();

            // Make sure the error is not null
            if (error != null) {
                String reason = error.getCode();

                if ("conflict".equals(reason)) {
                    return;
                }
            }
        }

        if (this.isReconnectionAllowed()) {
            this.reconnect();
        }
    }

    public void reconnectingIn(int seconds) {
        // ignore
    }

    public void reconnectionFailed(Exception e) {
        // ignore
    }

    /**
     * The connection has successfull gotten connected.
     */
    public void reconnectionSuccessful() {
        // ignore
    }

}