text: /**************************************************************************
   * Copyright (c) 2009, 2012 IBM Corp.
   *
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v2.0
   * and Eclipse Distribution License v1.0 which accompany this distribution. 
   *
   * The Eclipse Public License is available at 
   *    https://www.eclipse.org/legal/epl-2.0
   * and the Eclipse Distribution License is available at 
   *   https://www.eclipse.org/org/documents/edl-v10.php
   *
   * Contributors:
   *    Dave Locke - initial API and implementation and/or initial documentation
   *    Ian Craggs - MQTT 3.1.1 support
   */
  package org.eclipse.paho.mqttv5.client;
  
  import org.eclipse.paho.mqttv5.common.MqttException;
  import org.eclipse.paho.mqttv5.common.MqttMessage;
  import org.eclipse.paho.mqttv5.common.packet.MqttProperties;
  import org.eclipse.paho.mqttv5.common.packet.MqttWireMessage;
  
  /**
   * Provides a mechanism for tracking the completion of an asynchronous task.
   *
   * <p>When using the asynchronous/non-blocking MQTT programming interface all
   * methods/operations that take any time (and in particular those that involve
   * any network operation) return control to the caller immediately. The operation
   * then proceeds to run in the background so as not to block the invoking thread.
   * An IMqttToken is used to track the state of the operation. An application can use the
   * token to wait for an operation to complete. A token is passed to callbacks
   * once the operation completes and provides context linking it to the original
   * request. A token is associated with a single operation.</p>
   * <p>
   * An action is in progress until either:</p>
   * <ul>
   * <li>isComplete() returns true or</li>
   * <li>getException() is not null.</li>
   * </ul>
   *
   */
  public interface IMqttToken {
  
  	/**
  	 * Blocks the current thread until the action this token is associated with has
  	 * completed.
  	 *
  	 * @throws MqttException if there was a problem with the action associated with the token.
  	 * @see #waitForCompletion(long)
  	 */
          public void waitForCompletion() throws MqttException;
  
  	/**
  	 * Blocks the current thread until the action this token is associated with has
  	 * completed.
  	 * <p>The timeout specifies the maximum time it will block for. If the action
  	 * completes before the timeout then control returns immediately, if not
  	 * it will block until the timeout expires. </p>
  	 * <p>If the action being tracked fails or the timeout expires an exception will
  	 * be thrown. In the event of a timeout the action may complete after timeout.
  	 * </p>
  	 *
  	 * @param timeout the maximum amount of time to wait for, in milliseconds.
  	 * @throws MqttException if there was a problem with the action associated with the token.
  	 */
          public void waitForCompletion(long timeout) throws MqttException;
  
  	/**
  	 * Returns whether or not the action has finished.
  	 * <p>True will be returned both in the case where the action finished successfully
  	 * and in the case where it failed. If the action failed {@link #getException()} will
  	 * be non null.
  	 * </p>
  	 * @return whether or not the action has finished.
  	 */
          public boolean isComplete();
  
  	/**
  	 * Returns an exception providing more detail if an operation failed.
  	 * <p>While an action in in progress and when an action completes successfully
  	 * null will be returned. Certain errors like timeout or shutting down will not
  	 * set the exception as the action has not failed or completed at that time
  	 * </p>
  	 * @return exception may return an exception if the operation failed. Null will be
  	 * returned while action is in progress and if action completes successfully.
  	 */
          public MqttException getException();
  
  	/**
  	 * Register a listener to be notified when an action completes.
  	 * <p>Once a listener is registered it will be invoked when the action the token
  	 * is associated with either succeeds or fails.
  	 * </p>
  	 * @param listener to be invoked once the action completes
  	 */
          public void setActionCallback(MqttActionListener listener);
  
  	/**
  	 * Return the async listener for this token.
  	 * @return listener that is set on the token or null if a listener is not registered.
  	 */
          public MqttActionListener getActionCallback();
  
  	/**
  	 * Returns the MQTT client that is responsible for processing the asynchronous
  	 * action
  	 * @return the client
  	 */
          public MqttClientInterface getClient();
  
  	/**
  	 * Returns the topic string(s) for the action being tracked by this
  	 * token. If the action has not been initiated or the action has not
  	 * topic associated with it such as connect then null will be returned.
  	 *
  	 * @return the topic string(s) for the subscribe being tracked by this token or null
  	 */
          public String[] getTopics();
  
  	/**
  	 * Store some context associated with an action.
  	 * <p>Allows the caller of an action to store some context that can be
  	 * accessed from within the ActionListener associated with the action. This
  	 * can be useful when the same ActionListener is associated with multiple
  	 * actions</p>
  	 * @param userContext to associate with an action
  	 */
          public void setUserContext(Object userContext);
  
  	/**
  	 * Retrieve the context associated with an action.
  	 * <p>Allows the ActionListener associated with an action to retrieve any context
  	 * that was associated with the action when the action was invoked. If not
  	 * context was provided null is returned. </p>
  
  	 * @return Object context associated with an action or null if there is none.
  	 */
          public Object getUserContext();
  
  	/**
  	 * Returns the message ID of the message that is associated with the token.
  	 * A message id of zero will be returned for tokens associated with
  	 * connect, disconnect and ping operations as there can only ever
  	 * be one of these outstanding at a time. For other operations
  	 * the MQTT message id flowed over the network.
  	 * @return the message ID of the message that is associated with the token
  	 */
          public int getMessageId();
  	
  	/**
  	 * @return the granted QoS list from a suback 
  	 */
          public int[] getGrantedQos();
  	
  	/**
  	 * Returns a list of reason codes that were returned as a result of this token's action.
  	 * You will receive reason codes from the following MQTT actions:
  	 * <ul>
  	 * <li>CONNECT - in the corresponding CONNACK Packet.</li>
  	 * <li>PUBLISH - in the corresponding PUBACK, PUBREC, PUBCOMP, PUBREL packets</li>
  	 * <li>SUBSCRIBE - in the corresponding SUBACK Packet.</li>
  	 * <li>UNSUBSCRIBE - in the corresponding UNSUBACK Packet.</li>
  	 * <li>AUTH - in the returned AUTH Packet.</li>
  	 * </ul>
  	 * @return the reason code(s) from the response for this token's action.
  	 * 
  	 */
          public int[] getReasonCodes();
  	
  	/**
  	 * @return the session present flag from a connack 
  	 */
          public boolean getSessionPresent();
  	
  	/**
  	 * @return the response wire message
  	 */
          public MqttWireMessage getResponse();
  
          /**
           * @return the response wire message properties
           */
          public MqttProperties getResponseProperties();
  
          /**
           * Returns the message associated with this token.
           * <p>Until the message has been delivered, the message being delivered will
           * be returned. Once the message has been delivered <code>null</code> will be
           * returned.
           * @return the message associated with this token or null if already delivered.
           * @throws MqttException if there was a problem completing retrieving the message
           */
          public MqttMessage getMessage() throws MqttException;
  
          /**
           * @return the request wire message
           */
          public MqttWireMessage getRequestMessage();
  
          /**
           * @return the request wire message properties
           */
          public MqttProperties getRequestProperties();
  
  }
  