/////////////////////////////////////////////////////////////////////////////
/// @file iasync_client.h
/// Implementation of the interface for the asynchronous clients,
/// 'iasync_client'
/// @date 25-Aug-2016
/////////////////////////////////////////////////////////////////////////////

/*******************************************************************************
 * Copyright (c) 2013-2016 Frank Pagliughi <fpagliughi@mindspring.com>
 *
 * 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
 *    http://www.eclipse.org/legal/epl-v20.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Frank Pagliughi - initial implementation and documentation
 *******************************************************************************/

#ifndef __mqtt_iasync_client_h
#define __mqtt_iasync_client_h

#include <vector>

#include "mqtt/callback.h"
#include "mqtt/connect_options.h"
#include "mqtt/delivery_token.h"
#include "mqtt/disconnect_options.h"
#include "mqtt/event.h"
#include "mqtt/exception.h"
#include "mqtt/iaction_listener.h"
#include "mqtt/iclient_persistence.h"
#include "mqtt/message.h"
#include "mqtt/subscribe_options.h"
#include "mqtt/token.h"
#include "mqtt/types.h"

namespace mqtt {

/////////////////////////////////////////////////////////////////////////////

/**
 * Enables an application to communicate with an MQTT server using
 * non-blocking methods.
 *
 * It provides applications a simple programming interface to all features
 * of the MQTT version 3.1 specification including:
 *
 * @li connect
 * @li publish
 * @li subscribe
 * @li unsubscribe
 * @li disconnect
 */
class iasync_client
{
    friend class token;
    virtual void remove_token(token* tok) = 0;

public:
    /** Type for a collection of QOS values */
    using qos_collection = std::vector<int>;

    /**
     * Virtual destructor
     */
    virtual ~iasync_client() {}
    /**
     * Connects to an MQTT server using the default options.
     * @return token used to track and wait for the connect to complete. The
     *  	   token will be passed to any callback that has been set.
     * @throw exception for non security related problems
     * @throw security_exception for security related problems
     */
    virtual token_ptr connect() = 0;
    /**
     * Connects to an MQTT server using the provided connect options.
     * @param options a set of connection parameters that override the
     *  			  defaults.
     * @return token used to track and wait for the connect to complete. The
     *  	   token will be passed to any callback that has been set.
     * @throw exception for non security related problems
     * @throw security_exception for security related problems
     */
    virtual token_ptr connect(connect_options options) = 0;
    /**
     * Connects to an MQTT server using the specified options.
     *
     * @param options a set of connection parameters that override the
     *  			  defaults.
     * @param userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param cb callback listener that will be notified when the connect
     *  			   completes.
     * @return token used to track and wait for the connect to complete. The
     *  	   token will be passed to any callback that has been set.
     * @throw exception for non security related problems
     * @throw security_exception for security related problems
     */
    virtual token_ptr connect(
        connect_options options, void* userContext, iaction_listener& cb
    ) = 0;
    /**
     *
     * @param userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param cb listener that will be notified when the connect completes.
     * @return token used to track and wait for the connect to complete. The
     *  	   token will be passed to any callback that has been set.
     * @throw exception for non security related problems
     * @throw security_exception for security related problems
     */
    virtual token_ptr connect(void* userContext, iaction_listener& cb) = 0;
    /**
     * Reconnects the client using options from the previous connect.
     * The client must have previously called connect() for this to work.
     * @return token used to track the progress of the reconnect.
     */
    virtual token_ptr reconnect() = 0;
    /**
     * Disconnects from the server.
     * @return token used to track and wait for the disconnect to complete.
     *  	   The token will be passed to any callback that has been set.
     * @throw exception for problems encountered while disconnecting
     */
    virtual token_ptr disconnect() = 0;
    /**
     * Disconnects from the server.
     * @param opts Options for disconnecting.
     * @return token used to track and wait for the disconnect to complete.
     *  	   The token will be passed to any callback that has been set.
     * @throw exception for problems encountered while disconnecting
     */
    virtual token_ptr disconnect(disconnect_options opts) = 0;
    /**
     * Disconnects from the server.
     * @param timeout 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.
     * @return token used to track and wait for the disconnect to complete.
     *  	   The token will be passed to any callback that has been set.
     * @throw exception for problems encountered while disconnecting
     */
    virtual token_ptr disconnect(int timeout) = 0;
    /**
     * Disconnects from the server.
     * @param timeout 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 userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param cb listener that will be notified when the disconnect
     *  		 completes.
     * @return token used to track and wait for the disconnect to complete.
     *  	   The token will be passed to any callback that has been set.
     * @throw exception for problems encountered while disconnecting
     */
    virtual token_ptr disconnect(int timeout, void* userContext, iaction_listener& cb) = 0;
    /**
     * Disconnects from the server.
     * @param userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param cb listener that will be notified when the disconnect
     *  		 completes.
     * @return token used to track and wait for the disconnect to complete.
     *  	   The token will be passed to any callback that has been set.
     * @throw exception for problems encountered while disconnecting
     */
    virtual token_ptr disconnect(void* userContext, iaction_listener& cb) = 0;
    /**
     * Returns the delivery token for the specified message ID.
     * @return delivery_token
     */
    virtual delivery_token_ptr get_pending_delivery_token(int msgID) const = 0;
    /**
     * Returns the delivery tokens for any outstanding publish operations.
     * @return delivery_token[]
     */
    virtual std::vector<delivery_token_ptr> get_pending_delivery_tokens() const = 0;
    /**
     * Returns the client ID used by this client.
     * @return string
     */
    virtual string get_client_id() const = 0;
    /**
     * Returns the address of the server used by this client.
     */
    virtual string get_server_uri() const = 0;
    /**
     * Determines if this client is currently connected to the server.
     */
    virtual bool is_connected() const = 0;
    /**
     * Publishes a message to a topic on the server
     * @param topic The topic to deliver the message to
     * @param payload The bytes to use as the message payload
     * @param n The number of bytes in the payload
     * @param qos The Quality of Service to deliver the message at. Valid
     *  		  values are 0, 1 or 2.
     * @param retained Whether or not this message should be retained by the
     *  			   server.
     * @return token used to track and wait for the publish to complete. The
     *  	   token will be passed to callback methods if set.
     */
    virtual delivery_token_ptr publish(
        string_ref topic, const void* payload, size_t n, int qos, bool retained,
        const properties& props = properties()
    ) = 0;
    /**
     * Publishes a message to a topic on the server
     * @param topic The topic to deliver the message to
     * @param payload the bytes to use as the message payload
     * @param n the number of bytes in the payload
     * @return token used to track and wait for the publish to complete. The
     *  	   token will be passed to callback methods if set.
     */
    virtual delivery_token_ptr publish(string_ref topic, const void* payload, size_t n) = 0;
    /**
     * Publishes a message to a topic on the server
     * @param topic The topic to deliver the message to
     * @param payload The bytes to use as the message payload
     * @param n The number of bytes in the payload
     * @param qos The Quality of Service to deliver the message at. Valid
     *  		  values are 0, 1 or 2.
     * @param retained whether or not this message should be retained by the
     *  			   server.
     * @param userContext Optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param cb The listener callback object
     * @return token used to track and wait for the publish to complete. The
     *  	   token will be passed to callback methods if set.
     */
    virtual delivery_token_ptr publish(
        string_ref topic, const void* payload, size_t n, int qos, bool retained,
        void* userContext, iaction_listener& cb
    ) = 0;
    /**
     * Publishes a message to a topic on the server
     * @param topic The topic to deliver the message to
     * @param payload the bytes to use as the message payload
     * @param qos the Quality of Service to deliver the message at. Valid
     *  		  values are 0, 1 or 2.
     * @param retained whether or not this message should be retained by the
     *  			   server.
     * @return token used to track and wait for the publish to complete. The
     *  	   token will be passed to callback methods if set.
     */
    virtual delivery_token_ptr publish(
        string_ref topic, binary_ref payload, int qos, bool retained,
        const properties& props = properties()
    ) = 0;
    /**
     * Publishes a message to a topic on the server.
     * @param topic The topic to deliver the message to
     * @param payload the bytes to use as the message payload
     * @return token used to track and wait for the publish to complete. The
     *  	   token will be passed to callback methods if set.
     */
    virtual delivery_token_ptr publish(string_ref topic, binary_ref payload) = 0;
    /**
     * Publishes a message to a topic on the server Takes an Message
     * message and delivers it to the server at the requested quality of
     * service.
     * @param msg the message to deliver to the server
     * @return token used to track and wait for the publish to complete. The
     *  	   token will be passed to callback methods if set.
     */
    virtual delivery_token_ptr publish(const_message_ptr msg) = 0;
    /**
     * Publishes a message to a topic on the server.
     * @param msg the message to deliver to the server
     * @param userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param cb optional listener that will be notified when message
     *  		 delivery has completed to the requested quality of service
     * @return token used to track and wait for the publish to complete. The
     *  	   token will be passed to callback methods if set.
     */
    virtual delivery_token_ptr publish(
        const_message_ptr msg, void* userContext, iaction_listener& cb
    ) = 0;
    /**
     * Sets a callback listener to use for events that happen
     * asynchronously.
     * @param cb callback which will be invoked for certain asynchronous
     *  		 events
     */
    virtual void set_callback(callback& cb) = 0;
    /**
     * Stops the callbacks.
     */
    virtual void disable_callbacks() = 0;
    /**
     * Subscribe to a topic, which may include wildcards.
     * @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.
     * @param opts The options for the subscription.
     * @param props The MQTT v5 properties.
     * @return token used to track and wait for the subscribe to complete.
     *  	   The token will be passed to callback methods if set.
     */
    virtual token_ptr subscribe(
        const string& topicFilter, int qos,
        const subscribe_options& opts = subscribe_options(),
        const properties& props = properties()
    ) = 0;
    /**
     * Subscribe to a topic, which may include wildcards.
     * @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.
     * @param userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param callback listener that will be notified when subscribe has
     *  			   completed
     * @param opts The options for the subscription.
     * @param props The MQTT v5 properties.
     * @return token used to track and wait for the subscribe to complete.
     *  	   The token will be passed to callback methods if set.
     */
    virtual token_ptr subscribe(
        const string& topicFilter, int qos, void* userContext, iaction_listener& callback,
        const subscribe_options& opts = subscribe_options(),
        const properties& props = properties()
    ) = 0;
    /**
     * Subscribe to multiple topics, each of which may include wildcards.
     * Provides an optimized way to subscribe to multiple topics compared to
     * subscribing to each one individually.
     * @param topicFilters one or more topics 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.
     * @param opts A collection of subscription options (one for each
     *  		   topic)
     * @param props The MQTT v5 properties.
     * @return token used to track and wait for the subscribe to complete.
     *  	   The token will be passed to callback methods if set.
     */
    virtual token_ptr subscribe(
        const_string_collection_ptr topicFilters, const qos_collection& qos,
        const std::vector<subscribe_options>& opts = std::vector<subscribe_options>(),
        const properties& props = properties()
    ) = 0;
    /**
     * Subscribes to multiple topics, each of which may include wildcards.
     * @param topicFilters one or more topics 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.
     * @param userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param callback listener that will be notified when subscribe has
     *  			   completed
     * @param opts A collection of subscription options (one for each
     *  		   topic)
     * @param props The MQTT v5 properties.
     * @return token used to track and wait for the subscribe to complete.
     *  	   The token will be passed to callback methods if set.
     */
    virtual token_ptr subscribe(
        const_string_collection_ptr topicFilters, const qos_collection& qos,
        void* userContext, iaction_listener& callback,
        const std::vector<subscribe_options>& opts = std::vector<subscribe_options>(),
        const properties& props = properties()
    ) = 0;
    /**
     * Requests the server unsubscribe the client from a topic.
     * @param topicFilter the topic to unsubscribe from. It must match a
     *  				  topicFilter specified on an earlier subscribe.
     * @param props The MQTT v5 properties.
     * @return token used to track and wait for the unsubscribe to complete.
     *  	   The token will be passed to callback methods if set.
     */
    virtual token_ptr unsubscribe(
        const string& topicFilter, const properties& props = properties()
    ) = 0;
    /**
     * Requests the server unsubscribe the client from one or more topics.
     * @param topicFilters one or more topics to unsubscribe from. Each
     *  				   topicFilter must match one specified on an
     *  				   earlier subscribe.
     * @param props The MQTT v5 properties.
     * @return token used to track and wait for the unsubscribe to complete.
     *  	   The token will be passed to callback methods if set.
     */
    virtual token_ptr unsubscribe(
        const_string_collection_ptr topicFilters, const properties& props = properties()
    ) = 0;
    /**
     * Requests the server unsubscribe the client from one or more topics.
     * @param topicFilters one or more topics to unsubscribe from. Each
     *  				   topicFilter must match one specified on an
     *  				   earlier subscribe.
     * @param userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param cb listener that will be notified when unsubscribe has
     *  		 completed
     * @param props The MQTT v5 properties.
     * @return token used to track and wait for the unsubscribe to complete.
     *  	   The token will be passed to callback methods if set.
     */
    virtual token_ptr unsubscribe(
        const_string_collection_ptr topicFilters, void* userContext, iaction_listener& cb,
        const properties& props = properties()
    ) = 0;
    /**
     * Requests the server unsubscribe the client from a topics.
     * @param topicFilter the topic to unsubscribe from. It must match a
     *  				  topicFilter specified on an earlier subscribe.
     * @param userContext optional object used to pass context to the
     *  				  callback. Use @em nullptr if not required.
     * @param cb listener that will be notified when unsubscribe has
     *  		 completed.
     * @param props The MQTT v5 properties.
     * @return Token used to track and wait for the unsubscribe to complete.
     *  	   The token will be passed to callback methods if set.
     */
    virtual token_ptr unsubscribe(
        const string& topicFilter, void* userContext, iaction_listener& cb,
        const properties& props = properties()
    ) = 0;
    /**
     * Start consuming messages.
     * This initializes the client to receive messages through a queue that
     * can be read synchronously.
     */
    virtual void start_consuming() = 0;
    /**
     * Stop consuming messages.
     * This shuts down the internal callback and discards any unread
     * messages.
     */
    virtual void stop_consuming() = 0;
    /**
     * This clears the consumer queue, discarding any pending event.
     */
    virtual void clear_consumer() {}
    /**
     * Determines if the consumer queue has been closed.
     * Once closed, any events in the queue can still be read, but no new
     * events can be added to it.
     * @return @true if the consumer queue has been closed, @false
     *         otherwise.
     */
    virtual bool consumer_closed() noexcept { return false; }
    /**
     * Determines if the consumer queue is "done" (closed and empty).
     * Once the queue is done, no more events can be added or removed from
     * the queue.
     * @return @true if the consumer queue is closed and empty, @false
     *         otherwise.
     */
    virtual bool consumer_done() noexcept { return false; }
    /**
     * Gets the number of events available for immediate consumption.
     * Note that this retrieves the number of "raw" events, not messages,
     * e.g. may include a connected_event which is not returned by try_consume_message().
     * When polling the queue from multiple threads, prefer using try_consume_event(),
     * as the event count may change between checking the size and actual retrieval.
     * @return the number of events in the queue.
     */
    virtual std::size_t consumer_queue_size() const { return 0; }
    /**
     * Read the next message from the queue.
     * This blocks until a new message arrives.
     * @return The message and topic.
     */
    virtual const_message_ptr consume_message() = 0;
    /**
     * Try to read the next message from the queue without blocking.
     * @param msg Pointer to the value to receive the message
     * @return @em true is a message was read, @em false if no message was
     *  	   available.
     */
    virtual bool try_consume_message(const_message_ptr* msg) = 0;
    /**
     * Read the next event from the queue.
     * This blocks until a new message arrives.
     * @return The message and topic.
     */
    virtual event consume_event() { return event{}; }
    /**
     * Try to read the next message from the queue without blocking.
     * @param evt Pointer to the value to receive the event
     * @return @em true is an event was received, @em false if no event was
     *  	   available.
     */
    virtual bool try_consume_event(event* evt) {
        (void)evt;
        return false;
    }
};

/////////////////////////////////////////////////////////////////////////////
}  // namespace mqtt

#endif  // __mqtt_iasync_client_h