/org.eclipse.paho.mqttv5.client/src/main/java/org/eclipse/paho/mqttv5/client/alpha/IMqttClient.java

/*******************************************************************************
 * Copyright (c) 2009, 2015 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
 *    Ian Craggs - per subscription message handlers (bug 466579)
 *    Ian Craggs - ack control (bug 472172)
 */

package org.eclipse.paho.mqttv5.client.alpha;

import org.eclipse.paho.mqttv5.client.MqttConnectionOptions;
import org.eclipse.paho.mqttv5.client.alpha.result.IMqttConnectionResult;
import org.eclipse.paho.mqttv5.common.MqttException;
import org.eclipse.paho.mqttv5.common.MqttSecurityException;

/**
 * Enables an application to communicate with an MQTT server using blocking methods.
 * <p>
 * This interface allows applications to utilize all features of the MQTT version 3.1
 * specification including:</p>
 * <ul>
 * <li>connect
 * <li>publish
 * <li>subscribe
 * <li>unsubscribe
 * <li>disconnect
 * </ul>
 * <p>
 * There are two styles of MQTT client, this one and {@link IMqttAsyncClient}.</p>
 * <ul>
 * <li>IMqttClient provides a set of methods that block and return control to the application
 * program once the MQTT action has completed.</li>
 * <li>IMqttAsyncClient provides a set of non-blocking methods that return control to the
 * invoking application after initial validation of parameters and state. The main processing is
 * performed in the background so as not to block the application programs thread. This non
 * blocking approach is handy when the application wants to carry on processing while the
 * MQTT action takes place. For instance connecting to an MQTT server can take time, using
 * the non-blocking connect method allows an application to display a busy indicator while the
 * connect action is occurring. Non-blocking methods are particularly useful in event-oriented
 * programs and graphical programs where issuing methods that take time to complete on the the
 * main or GUI thread can cause problems.</li>
 * </ul>
 * <p>
 * The non-blocking client can also be used in a blocking form by turning a non-blocking
 * method into a blocking invocation using the following pattern:</p>
 *     <pre>
 *     IMqttToken token;
 *     token = asyncClient.method(parms).getPromise().getValue();
 *     </pre>
 * <p>
 * Using the non-blocking client allows an application to use a mixture of blocking and
 * non-blocking styles. Using the blocking client only allows an application to use one
 * style. The blocking client provides compatibility with earlier versions
 * of the MQTT client.</p>
 */
public interface IMqttClient extends IMqttCommonClient {
	/**
	 * Connects to an MQTT server using the default options.
	 * <p>The default options are specified in {@link MqttConnectionOptions} class.
	 * </p>
	 *
	 * @throws MqttSecurityException when the server rejects the connect for security
	 * reasons
	 * @throws MqttException  for non security related problems
	 * @see #connect(MqttConnectionOptions)
	 */
    void connect() throws MqttSecurityException, MqttException;

	/**
	 * Connects to an MQTT server using the specified options.
	 * 
	 * <p>This is a blocking method that returns once connect completes</p>
	 *
	 * @param options a set of connection parameters that override the defaults.
	 * @throws MqttSecurityException when the server rejects the connect for security
	 * reasons
	 * @throws MqttException  for non security related problems including communication errors
	 */
    void connect(MqttConnectionOptions options) throws MqttSecurityException, MqttException;
  
	/**
	 * Connects to an MQTT server using the specified options.
	 *
	 * <p>This is a blocking method that returns once connect completes</p>
	 *
	 * @param options a set of connection parameters that override the defaults.
	 * @return the MqttToken used for the call.  Can be used to obtain the session present flag
	 * @throws MqttSecurityException when the server rejects the connect for security
	 * reasons
	 * @throws MqttException  for non security related problems including communication errors
	 */
    IMqttConnectionResult<Void> connectWithResult(MqttConnectionOptions options) throws MqttSecurityException, MqttException;

	/**
	 * Disconnects from the server.
	 *
	 * <p>This is a blocking method that returns once disconnect completes</p>
	 *
	 * @throws MqttException if a problem is encountered while disconnecting
	 */
    void disconnect() throws MqttException;

	/**
	 * Disconnects from the server.
	 * <p>
	 * The client will wait for all callback methods to
	 * complete. It will then wait for up to the quiesce timeout to allow for
	 * work which has already been initiated to complete - for example, it will
	 * wait for the QoS 2 flows from earlier publications to complete. When work has
	 * completed or after the quiesce timeout, the client will disconnect from
	 * the server. If the cleanStart flag was set to false and is set to false the
	 * next time a connection is made QoS 1 and 2 messages that
	 * were not previously delivered will be delivered.</p>
	 *
	 * <p>This is a blocking method that returns once disconnect completes</p>
	 *
	 * @param quiesceTimeout the amount of time in milliseconds to allow for
	 * existing work to finish before disconnecting.  A value of zero or less
	 * means the client will not quiesce.
	 * @throws MqttException if a problem is encountered while disconnecting
	 */
    void disconnect(long quiesceTimeout) throws MqttException;
  
  /**
	 * Disconnects from the server forcibly to reset all the states. Could be useful when disconnect attempt failed.
	 * <p>
	 * Because the client is able to establish the TCP/IP connection to a none MQTT server and it will certainly fail to
	 * send the disconnect packet. It will wait for a maximum of 30 seconds for work to quiesce before disconnecting and
	 * wait for a maximum of 10 seconds for sending the disconnect packet to server.
	 * 
	 * @throws MqttException if any unexpected error
	 * @since 0.4.1
	 */
  void disconnectForcibly() throws MqttException;
	
	/**
	 * Disconnects from the server forcibly to reset all the states. Could be useful when disconnect attempt failed.
	 * <p>
	 * Because the client is able to establish the TCP/IP connection to a none MQTT server and it will certainly fail to
	 * send the disconnect packet. It will wait for a maximum of 30 seconds for work to quiesce before disconnecting.
	 * 
	 * @param disconnectTimeout the amount of time in milliseconds to allow send disconnect packet to server.
	 * @throws MqttException if any unexpected error
	 * @since 0.4.1
	 */
    void disconnectForcibly(long disconnectTimeout) throws MqttException;
	
	/**
	 * Disconnects from the server forcibly to reset all the states. Could be useful when disconnect attempt failed.
	 * <p>
	 * Because the client is able to establish the TCP/IP connection to a none MQTT server and it will certainly fail to
	 * send the disconnect packet.
	 * 
	 * @param quiesceTimeout the amount of time in milliseconds to allow for existing work to finish before
	 * disconnecting. A value of zero or less means the client will not quiesce.
	 * @param disconnectTimeout the amount of time in milliseconds to allow send disconnect packet to server.
	 * @throws MqttException if any unexpected error
	 * @since 0.4.1
	 */
    void disconnectForcibly(long quiesceTimeout, long disconnectTimeout) throws MqttException;

	/**
	 * Subscribe to a topic, which may include wildcards using a QoS of 1.
	 *
	 * @see #subscribe(String[], int[])
	 *
	 * @param topicFilter the topic to subscribe to, which can include wildcards.
	 * @return The Subscription Token
	 * @throws MqttException if there was an error registering the subscription.
	 * @throws MqttSecurityException if the client is not authorized to register the subscription
	 */
    IMqttSubscriptionToken<Void> subscribe(String topicFilter) throws MqttException, MqttSecurityException;

	/**
	 * Subscribes to a one or more topics, which may include wildcards using a QoS of 1.
	 *
	 * @see #subscribe(String[], int[])
	 *
	 * @param topicFilters the topic to subscribe to, which can include wildcards.
	 * @return The Subscription Token
	 * @throws MqttException if there was an error registering the subscription.
	 */
    IMqttSubscriptionToken<Void> subscribe(String[] topicFilters) throws MqttException;

	/**
	 * Subscribe to a topic, which may include wildcards.
	 *
	 * @see #subscribe(String[], int[])
	 *
	 * @param topicFilter the topic to subscribe to, which can include wildcards.
	 * @param qos the maximum quality of service at which to subscribe. Messages
	 * published at a lower quality of service will be received at the published
	 * QoS.  Messages published at a higher quality of service will be received using
	 * the QoS specified on the subscribe.
	 * @return The Subscription Token
	 * @throws MqttException if there was an error registering the subscription.
	 */
    IMqttSubscriptionToken<Void> subscribe(String topicFilter, int qos) throws MqttException;

	/**
	 * Subscribes to multiple topics, each of which may include wildcards.
	 * <p>
	 * If (@link MqttConnectOptions#setCleanStart(boolean)} was set to true
	 * when when connecting to the server then the subscription remains in place
	 * until either:
	 * </p>
	 * <ul>
	 * <li>The client disconnects</li>
	 * <li>An unsubscribe method is called to un-subscribe the topic</li>
	 * </ul>
	 * <p>
	 * If (@link MqttConnectOptions#setCleanStart(boolean)} was set to false
	 * when when connecting to the server then the subscription remains in place
	 * until either:</p>
	 * <ul>
	 * <li>An unsubscribe method is called to unsubscribe the topic</li>
	 * <li>The client connects with cleanStart set to true</li>
	 * </ul>
	 * <p>
	 * With cleanStart set to false the MQTT server will store messages on
	 * behalf of the client when the client is not connected. The next time the
	 * client connects with the <b>same client ID</b> the server will
	 * deliver the stored messages to the client.
	 * </p>
	 *
	 * <p>The "topic filter" string used when subscribing
	 * may contain special characters, which allow you to subscribe to multiple topics
	 * at once.</p>
	 * <p>The topic level separator is used to introduce structure into the topic, and
	 * can therefore be specified within the topic for that purpose.  The multi-level
	 * wildcard and single-level wildcard can be used for subscriptions, but they
	 * cannot be used within a topic by the publisher of a message.
	 * <dl>
	 * 	<dt>Topic level separator</dt>
	 * 	<dd>The forward slash (/) is used to separate each level within
	 * 	a topic tree and provide a hierarchical structure to the topic space. The
	 * 	use of the topic level separator is significant when the two wildcard characters
	 * 	are encountered in topics specified by subscribers.</dd>
	 *
	 * 	<dt>Multi-level wildcard</dt>
	 * 	<dd><p>The number sign (#) is a wildcard character that matches
	 * 	any number of levels within a topic. For example, if you subscribe to
	 *  <span><span class="filepath">finance/stock/ibm/#</span></span>, you receive
	 * 	messages on these topics:</p>
	 * <ul>
	 * <li><pre>finance/stock/ibm</pre></li>
	 * <li><pre>finance/stock/ibm/closingprice</pre></li>
	 * <li><pre>finance/stock/ibm/currentprice</pre></li>
	 * </ul>
	 *  
	 *  <p>The multi-level wildcard
	 *  can represent zero or more levels. Therefore, <em>finance/#</em> can also match
	 * 	the singular <em>finance</em>, where <em>#</em> represents zero levels. The topic
	 * 	level separator is meaningless in this context, because there are no levels
	 * 	to separate.</p>
	 *
	 * 	<p>The <span>multi-level</span> wildcard can
	 * 	be specified only on its own or next to the topic level separator character.
	 * 	Therefore, <em>#</em> and <em>finance/#</em> are both valid, but <em>finance#</em> is
	 * 	not valid. <span>The multi-level wildcard must be the last character
	 *  used within the topic tree. For example, <em>finance/#</em> is valid but
	 *  <em>finance/#/closingprice</em> is 	not valid.</span></p></dd>
	 *
	 * 	<dt>Single-level wildcard</dt>
	 * 	<dd><p>The plus sign (+) is a wildcard character that matches only one topic
	 * 	level. For example, <em>finance/stock/+</em> matches
	 * <em>finance/stock/ibm</em> and <em>finance/stock/xyz</em>,
	 * 	but not <em>finance/stock/ibm/closingprice</em>. Also, because the single-level
	 * 	wildcard matches only a single level, <em>finance/+</em> does not match <em>finance</em>.</p>
	 *
	 * 	<p>Use
	 * 	the single-level wildcard at any level in the topic tree, and in conjunction
	 * 	with the multilevel wildcard. Specify the single-level wildcard next to the
	 * 	topic level separator, except when it is specified on its own. Therefore,
	 *  <em>+</em> and <em>finance/+</em> are both valid, but <em>finance+</em> is
	 *  not valid. <span>The single-level wildcard can be used at the end of the
	 *  topic tree or within the topic tree.
	 * 	For example, <em>finance/+</em> and <em>finance/+/ibm</em> are both valid.</span></p>
	 * 	</dd>
	 * </dl>
	 *
	 * <p>This is a blocking method that returns once subscribe completes</p>
	 *
	 * @param topicFilters one or more topics to subscribe to, which can include wildcards.
	 * @param qos the maximum quality of service to subscribe each topic at.Messages
	 * published at a lower quality of service will be received at the published
	 * QoS.  Messages published at a higher quality of service will be received using
	 * the QoS specified on the subscribe.
	 * @return The Subscription Token
	 * @throws MqttException if there was an error registering the subscription.
	 * @throws IllegalArgumentException if the two supplied arrays are not the same size.
	 */
    IMqttSubscriptionToken<Void> subscribe(String[] topicFilters, int[] qos) throws MqttException;

}