time_limited.hpp

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/*!
 * \file
 * \brief Implementation of time-limited asynchronous one-time operation.
 *
 * \since
 * v.1.0.4
 */

#pragma once

#include <so_5_extra/async_op/details.hpp>
#include <so_5_extra/async_op/errors.hpp>

#include <so_5/details/h/invoke_noexcept_code.hpp>

#include <so_5/rt/impl/h/internal_env_iface.hpp>

#include <so_5/rt/h/agent.hpp>
#include <so_5/rt/h/send_functions.hpp>

#include <so_5/h/timers.hpp>

#include <so_5/h/outliving.hpp>

#if defined(SO_5_VERSION)
    #if (SO_5_VERSION < SO_5_VERSION_MAKE(5, 21, 0))
        #error "SObjectizer v.5.5.21 or above is required"
    #endif
#else
        #error "SObjectizer v.5.5.21 or above is required"
#endif

#include <chrono>
#include <vector>

namespace so_5 {

namespace extra {

namespace async_op {

namespace time_limited {

//! Enumeration for status of operation.
enum class status_t
    {
        //! Status of operation is unknown because the
        //! operation data has been moved to another proxy-object.
        unknown_moved_away,
        //! Operation is not activated yet.
        not_activated,
        //! Operation is activated.
        activated,
        //! Operation is completed.
        completed,
        //! Operation is cancelled.
        cancelled,
        //! Operation is timed-out.
        timedout
    };

namespace details {

/*!
 * \brief Container of all data related to async operation.
 *
 * \attention
 * There can be cyclic references from op_data_t instance to
 * completion/timeout handlers and back from completion/timeout
 * handlers to op_data_t. Because of that op_data_t can't
 * perform cleanup in its destructor because the destructor
 * will not be called until these cyclic references exist.
 * It requires special attention: content of op_data_t must
 * be cleared by owners of op_data_t instances.
 *
 * \since
 * v.1.0.4
 */
class op_data_t : protected ::so_5::atomic_refcounted_t
    {
    private :
        friend class ::so_5::intrusive_ptr_t<op_data_t>;

        //! Description of one completion handler subscription.
        struct completion_handler_subscription_t
            {
                //! Mbox from that a message is expected.
                ::so_5::mbox_t m_mbox;

                //! State for that a subscription should be created.
                ::so_5::outliving_reference_t< const ::so_5::state_t > m_state;

                //! Subscription type.
                /*!
                 * \note
                 * This is a subscription type. Not a type which will
                 * be passed to the event handler.
                 */
                std::type_index m_subscription_type;

                //! Event handler.
                ::so_5::event_handler_method_t m_handler;

                //! Initializing constructor.
                completion_handler_subscription_t(
                    so_5::mbox_t mbox,
                    const so_5::state_t & state,
                    std::type_index subscription_type,
                    so_5::event_handler_method_t handler )
                    :   m_mbox( std::move(mbox) )
                    ,   m_state( ::so_5::outliving_const(state) )
                    ,   m_subscription_type( std::move(subscription_type) )
                    ,   m_handler( std::move(handler) )
                    {}
            };

        //! Description of one timeout handler subscription.
        struct timeout_handler_subscription_t
            {
                //! State for that a subscription should be created.
                ::so_5::outliving_reference_t< const ::so_5::state_t > m_state;

                //! Event handler.
                ::so_5::event_handler_method_t m_handler;

                //! Initializing constructor.
                timeout_handler_subscription_t(
                    const so_5::state_t & state,
                    so_5::event_handler_method_t handler )
                    :   m_state( ::so_5::outliving_const(state) )
                    ,   m_handler( std::move(handler) )
                    {}
            };

        //! Owner of async operation.
        ::so_5::outliving_reference_t<::so_5::agent_t> m_owner;

        //! Type of timeout message.
        const std::type_index m_timeout_msg_type;

        //! The status of the async operation.
        status_t m_status = status_t::not_activated;

        //! Subscriptions for completion handlers which should be created on
        //! activation.
        std::vector< completion_handler_subscription_t > m_completion_handlers;

        //! Subscriptions for timeout handlers which should be created on
        //! activation.
        std::vector< timeout_handler_subscription_t > m_timeout_handlers;

        //! A default timeout handler which will be used as
        //! deadletter handler for timeout message/signal.
        /*!
         * \note
         * Can be nullptr. If so the default timeout handler will
         * be created during activation procedure.
         */
        ::so_5::event_handler_method_t m_default_timeout_handler;

        //! A mbox to which timeout message/signal will be sent.
        /*!
         * \note
         * It will be limitless MPSC-mbox.
         */
        const ::so_5::mbox_t m_timeout_mbox;

        //! An ID of timeout message/signal.
        /*!
         * Will be used for cancellation of async operation.
         */
        ::so_5::timer_id_t m_timeout_timer_id;

        //! Create subscriptions for all defined completion handlers.
        /*!
         * This method will rollback all subscriptions made in case of
         * an exception. It means that if an exception is throw during
         * subscription then all already subscribed completion handlers
         * will be removed.
         */
        void
        create_completion_handlers_subscriptions()
            {
                std::size_t i = 0;
                ::so_5::details::do_with_rollback_on_exception( [&] {
                        for(; i != m_completion_handlers.size(); ++i )
                            {
                                auto & ch = m_completion_handlers[ i ];
                                m_owner.get().so_create_event_subscription(
                                        ch.m_mbox,
                                        ch.m_subscription_type,
                                        ch.m_state.get(),
                                        ch.m_handler,
                                        ::so_5::thread_safety_t::unsafe );
                            }
                    },
                    [&] {
                        drop_completion_handlers_subscriptions_up_to( i );
                    } );
            }

        //! Removes subscription for the first N completion handlers.
        void
        drop_completion_handlers_subscriptions_up_to(
            //! Upper bound in m_completion_handlers (not included).
            std::size_t upper_border ) noexcept
            {
                for( std::size_t i = 0; i != upper_border; ++i )
                    {
                        const auto & ch = m_completion_handlers[ i ];
                        m_owner.get().so_destroy_event_subscription(
                                ch.m_mbox,
                                ch.m_subscription_type,
                                ch.m_state.get() );
                    }
            }

        //! Create subscriptions for all defined timeout handlers
        //! (including default handler).
        /*!
         * This method will rollback all subscriptions made in case of
         * an exception. It means that if an exception is throw during
         * subscription then all already subscribed timeout handlers
         * will be removed.
         */
        void
        create_timeout_handlers_subscriptions()
            {
                do_subscribe_timeout_handlers();
                ::so_5::details::do_with_rollback_on_exception( [&] {
                        do_subscribe_default_timeout_handler();
                    },
                    [&] {
                        do_unsubscribe_default_timeout_handler();
                    } );
            }

        //! An implementation of subscription of timeout handlers.
        /*!
         * Default timeout handler is not subscribed by this method.
         */
        void
        do_subscribe_timeout_handlers()
            {
                std::size_t i = 0;
                ::so_5::details::do_with_rollback_on_exception( [&] {
                        for(; i != m_timeout_handlers.size(); ++i )
                            {
                                auto & th = m_timeout_handlers[ i ];
                                m_owner.get().so_create_event_subscription(
                                        m_timeout_mbox,
                                        m_timeout_msg_type,
                                        th.m_state,
                                        th.m_handler,
                                        ::so_5::thread_safety_t::unsafe );
                            }
                    },
                    [&] {
                        drop_timeout_handlers_subscriptions_up_to( i );
                    } );
            }

        //! An implementation of subscription of default timeout handler.
        void
        do_subscribe_default_timeout_handler()
            {
                m_owner.get().so_create_deadletter_subscription(
                        m_timeout_mbox,
                        m_timeout_msg_type,
                        m_default_timeout_handler,
                        ::so_5::thread_safety_t::unsafe );
            }

        //! An implementation of unsubscription of the first N timeout handlers.
        /*!
         * The default timeout handler is not unsubscribed by this method.
         */
        void
        drop_timeout_handlers_subscriptions_up_to(
            //! Upper bound in m_timeout_handlers (not included).
            std::size_t upper_border ) noexcept
            {
                for( std::size_t i = 0; i != upper_border; ++i )
                    {
                        const auto & th = m_timeout_handlers[ i ];
                        m_owner.get().so_destroy_event_subscription(
                                m_timeout_mbox,
                                m_timeout_msg_type,
                                th.m_state.get() );
                    }
            }

        //! Remove subscriptions for all completion handlers.
        void
        drop_all_completion_handlers_subscriptions() noexcept
            {
                drop_completion_handlers_subscriptions_up_to(
                        m_completion_handlers.size() );
            }

        //! Remove subscriptions for all timeout handlers
        //! (including the default timeout handler).
        void
        drop_all_timeout_handlers_subscriptions() noexcept
            {
                do_unsubscribe_default_timeout_handler();
                do_unsubscribe_timeout_handlers();
            }

        //! Actual unsubscription for the default timeout handler.
        void
        do_unsubscribe_default_timeout_handler() noexcept
            {
                m_owner.get().so_destroy_deadletter_subscription(
                        m_timeout_mbox,
                        m_timeout_msg_type );
            }

        //! Actual unsubscription for timeout handlers.
        /*!
         * The default timeout handler is not unsubscribed by this method.
         */
        void
        do_unsubscribe_timeout_handlers() noexcept
            {
                drop_timeout_handlers_subscriptions_up_to(
                        m_timeout_handlers.size() );
            }

        //! Performs total cleanup of the operation data.
        /*!
         * All subscriptions are removed.
         * The delayed message is released.
         *
         * Content of m_completion_handlers, m_timeout_handlers and
         * m_default_timeout_handler will be erased.
         */
        void
        do_cancellation_actions() noexcept
            {
                // All subscriptions must be removed.
                drop_all_timeout_handlers_subscriptions();
                drop_all_completion_handlers_subscriptions();

                // Timer is no more needed.
                m_timeout_timer_id.release();

                // Information about completion and timeout handlers
                // is no more needed.
                m_completion_handlers.clear();
                m_timeout_handlers.clear();
                m_default_timeout_handler = ::so_5::event_handler_method_t{};
            }

        //! Creates the default timeout handler if it is not set
        //! by the user.
        void
        make_default_timeout_handler_if_necessary()
            {
                if( !m_default_timeout_handler )
                    {
                        m_default_timeout_handler =
                            [op = ::so_5::intrusive_ptr_t<op_data_t>(this)](
                                ::so_5::invocation_type_t /*invoke_type*/,
                                ::so_5::message_ref_t & /*msg*/ )
                            {
                                op->timedout();
                            };
                    }
            }

        //! Cleans the operation data and sets the status specified.
        void
        clean_with_status(
            //! A new status to be set.
            status_t status )
            {
                do_cancellation_actions();
                m_status = status;
            }

    public :
        //! Initializing constructor.
        op_data_t(
            //! Owner of the async operation.
            ::so_5::outliving_reference_t< ::so_5::agent_t > owner,
            //! Type of the timeout message/signal.
            const std::type_index & timeout_msg_type )
            :   m_owner( owner )
            ,   m_timeout_msg_type( timeout_msg_type )
                // Timeout mbox must be created right now.
                // It will be used during timeout_handlers processing.
            ,   m_timeout_mbox(
                        ::so_5::impl::internal_env_iface_t{ this->environment() }
                        .create_mpsc_mbox(
                                &m_owner.get(),
                                // No message limits for this mbox.
                                nullptr ) )
            {}

        //! Access to timeout mbox.
        SO_5_NODISCARD const ::so_5::mbox_t &
        timeout_mbox() const noexcept
            {
                return m_timeout_mbox;
            }

        //! Access to type of timeout message/signal.
        SO_5_NODISCARD const std::type_index &
        timeout_msg_type() const noexcept
            {
                return m_timeout_msg_type;
            }

        //! Access to owner of the async operation.
        SO_5_NODISCARD ::so_5::agent_t &
        owner() noexcept
            {
                return m_owner.get();
            }

        //! Access to SObjectizer Environment in that the owner is working.
        SO_5_NODISCARD ::so_5::environment_t &
        environment() noexcept
            {
                return m_owner.get().so_environment();
            }

        //! Reserve a space for storage of completion handlers.
        void
        reserve_completion_handlers_capacity(
            //! A required capacity.
            std::size_t capacity )
            {
                m_completion_handlers.reserve( capacity );
            }

        //! Reserve a space for storage of timeout handlers.
        void
        reserve_timeout_handlers_capacity(
            //! A required capacity.
            std::size_t capacity )
            {
                m_timeout_handlers.reserve( capacity );
            }

        //! Performs activation actions.
        /*!
         * The default timeout handler is created if necessary.
         *
         * Subscriptions for completion handlers and timeout handler are created.
         * If an exception is thrown during subscription then all already
         * subscribed completion and timeout handler will be unsubscribed.
         */
        void
        do_activation_actions()
            {
                make_default_timeout_handler_if_necessary();

                create_completion_handlers_subscriptions();

                ::so_5::details::do_with_rollback_on_exception(
                    [&] {
                        create_timeout_handlers_subscriptions();
                    },
                    [&] {
                        drop_all_completion_handlers_subscriptions();
                    } );
            }

        //! Change the status of async operation.
        void
        change_status(
            //! A new status to be set.
            status_t status ) noexcept
            {
                m_status = status;
            }

        //! Get the current status of async operation.
        SO_5_NODISCARD status_t
        current_status() const noexcept
            {
                return m_status;
            }

        //! Add a new completion handler for the async operation.
        void
        add_completion_handler(
            //! A mbox from which the completion message/signal is expected.
            const ::so_5::mbox_t & mbox,
            //! A state for completion handler.
            const ::so_5::state_t & state,
            //! A type of the completion message/signal.
            const std::type_index msg_type,
            //! Completion handler itself.
            ::so_5::event_handler_method_t evt_handler )
            {
                m_completion_handlers.emplace_back(
                        mbox,
                        state,
                        msg_type,
                        std::move(evt_handler) );
            }

        //! Add a new timeout handler for the async operation.
        void
        add_timeout_handler(
            //! A state for timeout handler.
            const ::so_5::state_t & state,
            //! Timeout handler itself.
            ::so_5::event_handler_method_t evt_handler )
            {
                m_timeout_handlers.emplace_back(
                        state,
                        std::move(evt_handler) );
            }

        //! Set the default timeout handler.
        /*!
         * \note
         * If there already is the default timeout handler then the old
         * one will be replaced by new handler.
         */
        void
        default_timeout_handler(
            //! Timeout handler itself.
            ::so_5::event_handler_method_t evt_handler )
            {
                m_default_timeout_handler = std::move(evt_handler);
            }

        //! Set the ID of timeout message/signal timer.
        void
        setup_timer_id(
            //! Timer ID of delayed timeout message/signal.
            ::so_5::timer_id_t id )
            {
                m_timeout_timer_id = std::move(id);
            }

        //! Mark the async operation as completed.
        void
        completed() noexcept
            {
                clean_with_status( status_t::completed );
            }

        //! Mark the async operation as timedout.
        void
        timedout() noexcept
            {
                clean_with_status( status_t::timedout );
            }

        //! Mark the async operation as cancelled.
        void
        cancelled() noexcept
            {
                clean_with_status( status_t::cancelled );
            }
    };

/*!
 * \brief An alias for smart pointer to operation data.
 *
 * \tparam Operation_Data Type of actual operation data representation.
 * It is expected to be op_data_t or some of its derivatives.
 */
template< typename Operation_Data >
using op_shptr_t = ::so_5::intrusive_ptr_t< Operation_Data >;

} /* namespace details */

/*!
 * \brief An object that allows to cancel async operation.
 *
 * Usage example:
 * \code
 * namespace asyncop = so_5::extra::async_op::time_limited;
 * class demo : public so_5::agent_t {
 *  asyncop::cancellation_point_t<> cp_;
 *  ...
 *  void initiate_async_op() {
 *      auto op = asyncop::make<timeout>(*this);
 *      op.completed_on(...);
 *      op.timeout_handler(...);
 *      cp_ = op.activate(std::chrono::milliseconds(300), ...);
 *  }
 *  void on_operation_aborted(mhood_t<op_aborted_notify> cmd) {
 *      // Operation aborted. There is no need to wait for
 *      // completion of operation.
 *      cp_.cancel();
 *  }
 * };
 * \endcode
 *
 * \note
 * This class is DefaultConstructible and Moveable, but not Copyable.
 *
 * \attention
 * Objects of this class are not thread safe. It means that cancellation
 * point should be used only by agent which created it. And the cancellation
 * point can't be used inside thread-safe event handlers of that agent.
 *
 * \tparam Operation_Data Type of actual operation data representation.
 * Please note that this template parameter is indended to be used for
 * debugging and testing purposes only.
 *
 * \since
 * v.1.0.4
 */
template< typename Operation_Data = details::op_data_t >
class cancellation_point_t
    {
    private :
        template<typename Msg, typename Op_Data> friend class definition_point_t;

        //! Actual data for async op.
        /*!
         * \note
         * This can be a nullptr if the default constructor was used,
         * or if operation is already cancelled, or if the content of
         * the cancellation_point was moved to another object.
         */
        details::op_shptr_t< Operation_Data > m_op;

        //! Initializing constructor to be used by definition_point.
        cancellation_point_t(
            //! Actual data for async operation.
            //! Can't be null.
            details::op_shptr_t< Operation_Data > op )
            :   m_op( std::move(op) )
            {}

    public :
        cancellation_point_t() = default;

        cancellation_point_t( const cancellation_point_t & ) = delete;
        cancellation_point_t( cancellation_point_t && ) = default;

        cancellation_point_t &
        operator=( const cancellation_point_t & ) = delete;

        cancellation_point_t &
        operator=( cancellation_point_t && ) = default;

        //! Get the status of the operation.
        /*!
         * \note
         * The value status_t::unknown_moved_away can be returned if
         * the actual data of the async operation was moved to another object
         * (like another cancellation_point_t). Or after a call to
         * cleanup() method.
         */
        SO_5_NODISCARD status_t
        status() const noexcept
            {
                if( m_op)
                    return m_op->current_status();
                return status_t::unknown_moved_away;
            }

        //! Can the async operation be cancelled via this cancellation point?
        /*!
         * \return true if the cancellation_point holds actual async operation's
         * data and this async operation is not completed nor timedout yet.
         */
        SO_5_NODISCARD bool
        is_cancellable() const noexcept
            {
                return m_op && status_t::activated == m_op->current_status();
            }

        //! An attempt to cancel the async operation.
        /*!
         * \note
         * Operation will be cancelled only if (true == is_cancellable()).
         *
         * It is safe to call cancel() if the operation is already
         * cancelled or completed, or timed out. In that case the call to
         * cancel() will have no effect.
         */
        void
        cancel() noexcept
            {
                if( is_cancellable() )
                    {
                        m_op->cancelled();
                    }
            }

        //! Throw out a reference to the async operation data.
        /*!
         * A cancellation_point holds a reference to the async operation
         * data. It means that the async operation data will be destroyed
         * only when the cancellation_point will be destroyed. For example,
         * in that case:
         * \code
         * namespace asyncop = so_5::extra::async_op::time_limited;
         * class demo : public so_5::agent_t {
         *  ...
         *  asyncop::cancellation_point_t<> cp_;
         *  ...
         *  void initiate_async_op() {
         *      cp_ = asyncop::make<timeout_msg>(*this)
         *              ...
         *              .activate(...);
         *      ...
         *  }
         *  ...
         *  void on_some_interruption() {
         *      // Cancel asyncop.
         *      cp_.cancel();
         *      // Async operation is cancelled, but the async operation
         *      // data is still in memory. The data will be deallocated
         *      // only when cp_ receives new value or when cp_ will be
         *      // destroyed (e.g. after destruction of demo agent).
         *  }
         * \endcode
         *
         * A call to cleanup() method removes the reference to the async
         * operation data. It means that if the operation is already
         * completed, timed out or cancelled, then the operation data
         * fill be deallocated.
         *
         * \note
         * If the operation is still in progress then a call to cleanup()
         * doesn't break the operation. You need to call cancel() manually
         * before calling cleanup() to cancel the operation.
         */
        void
        cleanup() noexcept
            {
                m_op.reset();
            }
    };

namespace details
{

/*!
 * \brief A basic part of implementation of definition_point.
 *
 * This part is independent from timeout message/signal type.
 *
 * \note
 * This is Moveable class. But not DefaultConstructible.
 * And not Copyable.
 *
 * \note
 * Most of methods are declared as protected to be used only in
 * derived class.
 *
 * \since
 * v.1.0.4
 */
template< typename Operation_Data >
class msg_independent_part_of_definition_point_t
    {
    protected :
        //! Actual async operation data.
        /*!
         * \note This pointer can be nullptr after activation or
         * when the object is move away.
         */
        details::op_shptr_t< Operation_Data > m_op;

        //! Initializing constructor.
        msg_independent_part_of_definition_point_t(
            //! Actual async operation data.
            //! This pointer can't be nullptr.
            details::op_shptr_t< Operation_Data > op )
            :   m_op( std::move(op) )
            {}

        msg_independent_part_of_definition_point_t(
            const msg_independent_part_of_definition_point_t & ) = delete;
        msg_independent_part_of_definition_point_t &
        operator=( const msg_independent_part_of_definition_point_t & ) = delete;

        msg_independent_part_of_definition_point_t(
            msg_independent_part_of_definition_point_t && ) = default;
        msg_independent_part_of_definition_point_t &
        operator=( msg_independent_part_of_definition_point_t && ) = default;

        //! Can the async_op be activated?
        /*!
         * The async operation can't be activated if it is already activated.
         * Or if the content of the definition_point is moved to another
         * definition_point.
         */
        SO_5_NODISCARD bool
        is_activable() const noexcept
            {
                return m_op;
            }

        //! Throws an exception if the async operation can't be activated.
        void
        ensure_activable() const
            {
                if( !is_activable() )
                    SO_5_THROW_EXCEPTION(
                            ::so_5::extra::async_op::errors::rc_op_cant_be_activated,
                            "An attempt to do something on non-activable async_op" );
            }

        //! Reserve a space for storage of completion handlers.
        void
        reserve_completion_handlers_capacity_impl(
            //! A required capacity.
            std::size_t capacity )
            {
                ensure_activable();

                m_op->reserve_completion_handlers_capacity( capacity );
            }

        //! Reserve a space for storage of timeout handlers.
        void
        reserve_timeout_handlers_capacity_impl(
            //! A required capacity.
            std::size_t capacity )
            {
                ensure_activable();

                m_op->reserve_timeout_handlers_capacity( capacity );
            }

        //! The actual implementation of addition of completion handler.
        /*!
         * \tparam Msg_Target It can be a mbox, or a reference to an agent.
         * In the case if Msg_Target if a reference to an agent the agent's
         * direct mbox will be used as message source.
         *
         * \tparam Event_Handler Type of actual handler for message/signal.
         * It can be a pointer to agent's method or lambda (or another
         * type of functional object).
         */
        template<
                typename Msg_Target,
                typename Event_Handler >
        void
        completed_on_impl(
            //! A source from which a completion message/signal is expected.
            //! It can be a mbox or an agent (in that case the agent's direct
            //! mbox will be used).
            Msg_Target && msg_target,
            //! A state for that a completion handler is defined.
            const ::so_5::state_t & state,
            //! Completion handler itself.
            Event_Handler && evt_handler )
            {
                ensure_activable();

                const auto mbox = ::so_5::extra::async_op::details::target_to_mbox(
                        msg_target );

                auto evt_handler_info =
                        ::so_5::preprocess_agent_event_handler(
                                mbox,
                                m_op->owner(),
                                std::forward<Event_Handler>(evt_handler) );

                ::so_5::event_handler_method_t actual_handler =
                    [op = m_op,
                    user_handler = std::move(evt_handler_info.m_handler)](
                        ::so_5::invocation_type_t invoke_type,
                        ::so_5::message_ref_t & msg )
                    {
                        op->completed();
                        user_handler( invoke_type, msg );
                    };

                m_op->add_completion_handler(
                        mbox,
                        state,
                        evt_handler_info.m_msg_type,
                        std::move(actual_handler) );
            }

        //! The actual implementation of addition of timeout handler.
        /*!
         * \tparam Event_Handler Type of actual handler for message/signal.
         * It can be a pointer to agent's method or lambda (or another
         * type of functional object).
         */
        template< typename Event_Handler >
        void
        timeout_handler_impl(
            //! A state for that a timeout handler is defined.
            const ::so_5::state_t & state,
            //! Timeout handler itself.
            Event_Handler && evt_handler )
            {
                ensure_activable();

                m_op->add_timeout_handler(
                        state,
                        create_actual_timeout_handler(
                                std::forward<Event_Handler>(evt_handler) ) );
            }

        //! The actual implementation of addition of the default timeout handler.
        /*!
         * \tparam Event_Handler Type of actual handler for message/signal.
         * It can be a pointer to agent's method or lambda (or another
         * type of functional object).
         */
        template< typename Event_Handler >
        void
        default_timeout_handler_impl(
            //! The default timeout handler itself.
            Event_Handler && evt_handler )
            {
                ensure_activable();

                m_op->default_timeout_handler(
                        create_actual_timeout_handler(
                                std::forward<Event_Handler>(evt_handler) ) );
            }

    private :
        //! A helper method for creation a wrapper for a timeout handler.
        template< typename Event_Handler >
        SO_5_NODISCARD ::so_5::event_handler_method_t
        create_actual_timeout_handler(
            //! Timeout handler to be wrapped.
            Event_Handler && evt_handler )
            {
                auto evt_handler_info =
                        ::so_5::preprocess_agent_event_handler(
                                m_op->timeout_mbox(),
                                m_op->owner(),
                                std::forward<Event_Handler>(evt_handler) );
                if( evt_handler_info.m_msg_type != m_op->timeout_msg_type() )
                    SO_5_THROW_EXCEPTION(
                            ::so_5::extra::async_op::errors::rc_msg_type_mismatch,
                            std::string(
                                    "An attempt to register timeout handler for "
                                    "different message type. Expected type: " )
                            + m_op->timeout_msg_type().name()
                            + ", actual type: " + evt_handler_info.m_msg_type.name() );

                return
                    [op = m_op,
                    user_handler = std::move(evt_handler_info.m_handler)](
                        ::so_5::invocation_type_t invoke_type,
                        ::so_5::message_ref_t & msg )
                    {
                        op->timedout();
                        user_handler( invoke_type, msg );
                    };
            }
    };

} /* namespace details */

/*!
 * \brief An interface for definition of async operation.
 *
 * Object of this type is usually created by make() function and
 * is used for definition of async operation. Completion and timeout
 * handlers are set for async operation by using definition_point object.
 *
 * Then an user calls activate() method and the definition_point transfers
 * the async operation data into cancellation_point object. It means that
 * after a call to activate() method the definition_point object should
 * not be used. Because it doesn't hold any async operation anymore.
 *
 * A simple usage without storing the cancellation_point:
 * \code
 * namespace asyncop = so_5::extra::async_op::time_limited;
 * class demo : public so_5::agent_t {
 *  struct timeout final : public so_5::signal_t {};
 *  ...
 *  void initiate_async_op() {
 *      // Create a definition_point for a new async operation...
 *      asyncop::make<timeout>(*this)
 *          // ...then set up completion handler(s)...
 *          .completed_on(
 *              *this,
 *              so_default_state(),
 *              &demo::on_first_completion_msg )
 *          .completed_on(
 *              some_external_mbox_,
 *              some_user_defined_state_,
 *              [this](mhood_t<another_completion_msg> cmd) {...})
 *          // ...then set up timeout handler(s)...
 *          .timeout_handler(
 *              so_default_state(),
 *              &demo::on_timeout )
 *          .timeout_handler(
 *              some_user_defined_state_,
 *              [this](mhood_t<timeout> cmd) {...})
 *          // ...and now we can activate the operation.
 *          .activate(std::chrono::milliseconds(300));
 *      ...
 *  }
 * };
 * \endcode
 * \note
 * There is no need to hold definition_point object after activation
 * of the async operation. This object can be safely discarded.
 *
 * A more complex example using cancellation_point for
 * cancelling the operation.
 * \code
 * namespace asyncop = so_5::extra::async_op::time_limited;
 * class demo : public so_5::agent_t {
 *  struct timeout final : public so_5::signal_t {};
 *  ...
 *  // Cancellation point for the async operation.
 *  asyncop::cancellation_point_t<> cp_;
 *  ...
 *  void initiate_async_op() {
 *      // Create a definition_point for a new async operation
 *      // and store the cancellation point after activation.
 *      cp_ = asyncop::make<timeout>(*this)
 *          // ...then set up completion handler(s)...
 *          .completed_on(
 *              *this,
 *              so_default_state(),
 *              &demo::on_first_completion_msg )
 *          .completed_on(
 *              some_external_mbox_,
 *              some_user_defined_state_,
 *              [this](mhood_t<another_completion_msg> cmd) {...})
 *          // ...then set up timeout handler(s)...
 *          .timeout_handler(
 *              so_default_state(),
 *              &demo::on_timeout )
 *          .timeout_handler(
 *              some_user_defined_state_,
 *              [this](mhood_t<timeout> cmd) {...})
 *          // ...and now we can activate the operation.
 *          .activate(std::chrono::milliseconds(300));
 *      ...
 *  }
 *  ...
 *  void on_abortion_signal(mhood_t<abort_signal>) {
 *      // The current async operation should be cancelled.
 *      cp_.cancel();
 *  }
 * };
 * \endcode
 *
 * \note
 * This class is Moveable, but not DefaultConstructible nor Copyable.
 *
 * \attention
 * Objects of this class are not thread safe. It means that a definition
 * point should be used only by agent which created it. And the definition
 * point can't be used inside thread-safe event handlers of that agent.
 *
 * \since
 * v.1.0.4
 */
template<
    typename Message,
    typename Operation_Data = details::op_data_t >
class definition_point_t
    :   protected details::msg_independent_part_of_definition_point_t< Operation_Data >
    {
        //! A short alias for base type.
        using base_type_t =
                details::msg_independent_part_of_definition_point_t< Operation_Data >;

    public :
        //! Initializing constructor.
        definition_point_t(
            //! The owner of the async operation.
            ::so_5::outliving_reference_t< ::so_5::agent_t > owner )
            :   base_type_t(
                    details::op_shptr_t< Operation_Data >(
                            new Operation_Data( owner, typeid(Message) ) ) )
            {}

        ~definition_point_t()
            {
                // If operation data is still here then it means that
                // there wasn't call to `activate()` and we should cancel
                // all described handlers.
                // This will lead to deallocation of operation data.
                if( this->m_op )
                    this->m_op->cancelled();
            }

        definition_point_t( const definition_point_t & ) = delete;
        definition_point_t &
        operator=( const definition_point_t & ) = delete;

        definition_point_t( definition_point_t && ) = default;
        definition_point_t &
        operator=( definition_point_t && ) = default;

        using base_type_t::is_activable;

        /*!
         * \brief Reserve a space for storage of completion handlers.
         *
         * Usage example:
         * \code
         * namespace asyncop = so_5::extra::async_op::time_limited;
         * auto op = asyncop::make<timeout>(some_agent);
         * // Reserve space for four completion handlers.
         * op.reserve_completion_handlers_capacity(4);
         * op.completed_on(...);
         * op.completed_on(...);
         * op.completed_on(...);
         * op.completed_on(...);
         * op.activate(...);
         * \endcode
         */
        definition_point_t &
        reserve_completion_handlers_capacity(
            //! A required capacity.
            std::size_t capacity ) &
            {
                this->reserve_completion_handlers_capacity_impl( capacity );
                return *this;
            }

        //! Just a proxy for actual version of %reserve_completion_handlers_capacity.
        template< typename... Args >
        auto
        reserve_completion_handlers_capacity( Args && ...args ) &&
            {
                return std::move(this->reserve_completion_handlers_capacity(
                            std::forward<Args>(args)... ));
            }

        /*!
         * \brief Reserve a space for storage of timeout handlers.
         *
         * Usage example:
         * \code
         * namespace asyncop = so_5::extra::async_op::time_limited;
         * auto op = asyncop::make<timeout>(some_agent);
         * // Reserve space for eight timeout handlers.
         * op.reserve_timeout_handlers_capacity(8);
         * op.timeout_handler(...);
         * op.timeout_handler(...);
         * ...
         * op.activate(...);
         * \endcode
         */
        definition_point_t &
        reserve_timeout_handlers_capacity(
            //! A required capacity.
            std::size_t capacity ) &
            {
                this->reserve_timeout_handlers_capacity_impl( capacity );
                return *this;
            }

        //! Just a proxy for actual version of %reserve_timeout_handlers_capacity.
        template< typename... Args >
        auto
        reserve_timeout_handlers_capacity( Args && ...args ) &&
            {
                return std::move(this->reserve_timeout_handlers_capacity(
                            std::forward<Args>(args)... ));
            }

        /*!
         * \brief Add a completion handler for the async operation.
         *
         * Usage example:
         * \code
         * namespace asyncop = so_5::extra::async_op::time_limited;
         * class demo : public so_5::agent_t {
         *  ...
         *  void initiate_async_op() {
         *          asyncop::make<timeout>(*this)
         *              .completed_on(
         *                  *this,
         *                  so_default_state(),
         *                  &demo::some_event )
         *              .completed_on(
         *                  some_mbox_,
         *                  some_agent_state_,
         *                  [this](mhood_t<some_msg> cmd) {...})
         *              ...
         *              .activate(...);
         *  }
         * };
         * \endcode
         *
         * \note
         * The completion handler will be stored inside async operation
         * data. Actual subscription for it will be made during activation
         * of the async operation.
         *
         * \tparam Msg_Target It can be a mbox, or a reference to an agent.
         * In the case if Msg_Target if a reference to an agent the agent's
         * direct mbox will be used as message source.
         *
         * \tparam Event_Handler Type of actual handler for message/signal.
         * It can be a pointer to agent's method or lambda (or another
         * type of functional object).
         */
        template<
                typename Msg_Target,
                typename Event_Handler >
        definition_point_t &
        completed_on(
            //! A source from which a completion message is expected.
            //! It \a msg_target is a reference to an agent then
            //! the agent's direct mbox will be used.
            Msg_Target && msg_target,
            //! A state for which that completion handler will be subscribed.
            const ::so_5::state_t & state,
            //! The completion handler itself.
            Event_Handler && evt_handler ) &
            {
                this->completed_on_impl(
                        std::forward<Msg_Target>(msg_target),
                        state,
                        std::forward<Event_Handler>(evt_handler) );

                return *this;
            }

        //! Just a proxy for the main version of %completed_on.
        template< typename... Args >
        definition_point_t &&
        completed_on( Args && ...args ) &&
            {
                return std::move(this->completed_on(std::forward<Args>(args)...));
            }

        /*!
         * \brief Add a timeout handler for the async operation.
         *
         * Usage example:
         * \code
         * namespace asyncop = so_5::extra::async_op::time_limited;
         * class demo : public so_5::agent_t {
         *  ...
         *  void initiate_async_op() {
         *          asyncop::make<timeout>(*this)
         *              .timeout_handler(
         *                  so_default_state(),
         *                  &demo::some_event )
         *              .timeout_handler(
         *                  some_agent_state_,
         *                  [this](mhood_t<timeout> cmd) {...})
         *              ...
         *              .activate(...);
         *  }
         * };
         * \endcode
         *
         * \note
         * The timeout handler will be stored inside async operation
         * data. Actual subscription for it will be made during activation
         * of the async operation.
         *
         * \tparam Event_Handler Type of actual handler for message/signal.
         * It can be a pointer to agent's method or lambda (or another
         * type of functional object).
         * Please notice that Event_Handler must receive a message/signal
         * of type \a Message. It means that Event_Handler can have one of the
         * following formats:
         * \code
         * ret_type handler(Message);
         * ret_type handler(const Message &);
         * ret_type handler(mhood_t<Message>); // This is the recommended format.
         * \endcode
         */
        template< typename Event_Handler >
        definition_point_t &
        timeout_handler(
            const ::so_5::state_t & state,
            Event_Handler && evt_handler ) &
            {
                this->timeout_handler_impl(
                        state,
                        std::forward<Event_Handler>(evt_handler) );

                return *this;
            }

        //! Just a proxy for the main version of %timeout_handler.
        template< typename... Args >
        definition_point_t &&
        timeout_handler( Args && ...args ) &&
            {
                return std::move(this->timeout_handler(
                        std::forward<Args>(args)...));
            }

        /*!
         * \brief Add the default timeout handler for the async operation.
         *
         * The default timeout handler will be called if no timeout
         * handler was called for timeout message/signal.
         * A deadletter handlers from SObjectizer-5.5.21 are used for
         * implementation of the default timeout handler for async
         * operation.
         *
         * There can be only one the default timeout handler.
         * If the default timeout handler is already specified a new call
         * to default_timeout_handler() will replace the old handler with
         * new one (the old default timeout handler will be lost).
         *
         * Usage example:
         * \code
         * namespace asyncop = so_5::extra::async_op::time_limited;
         * class demo : public so_5::agent_t {
         *  ...
         *  void initiate_async_op() {
         *          asyncop::make<timeout>(*this)
         *              .default_timeout_handler(
         *                  &demo::some_deadletter_handler )
         *              ...
         *              .activate(...);
         *  }
         * };
         * \endcode
         *
         * \note
         * The default timeout handler will be stored inside async operation
         * data. Actual subscription for it will be made during activation
         * of the async operation.
         *
         * \tparam Event_Handler Type of actual handler for message/signal.
         * It can be a pointer to agent's method or lambda (or another
         * type of functional object).
         * Please notice that Event_Handler must receive a message/signal
         * of type \a Message. It means that Event_Handler can have one of the
         * following formats:
         * \code
         * ret_type handler(Message);
         * ret_type handler(const Message &);
         * ret_type handler(mhood_t<Message>); // This is the recommended format.
         * \endcode
         */
        template< typename Event_Handler >
        definition_point_t &
        default_timeout_handler(
            //! The default timeout handler itself.
            Event_Handler && evt_handler ) &
            {
                this->default_timeout_handler_impl(
                        std::forward<Event_Handler>(evt_handler) );

                return *this;
            }

        //! Just a proxy for the main version of %default_timeout_handler.
        template< typename... Args >
        definition_point_t &&
        default_timeout_handler( Args && ...args ) &&
            {
                return std::move(this->timeout_handler(
                        std::forward<Args>(args)...));
            }

        /*!
         * \brief Activation of the async operation.
         *
         * All subscriptions for completion and timeout handlers will be made
         * here. Then the timeout message/signal will be sent. And then
         * a cancellation_point for that async operation will be returned.
         *
         * An example of activation of the async operation in the case
         * when \a Message is a signal:
         * \code
         * namespace asyncop = so_5::extra::async_op::time_limited;
         * class demo : public so_5::agent_t {
         *  struct timeout final : public so_5::signal_t {};
         *  ...
         *  void initiate_async_op() {
         *      asyncop::make<timeout>()
         *          ... // Set up completion and timeout handlers...
         *          // Activation with just one argument - timeout duration.
         *          .activate(std::chrono::milliseconds(200));
         *      ...
         *  }
         * };
         * \endcode
         *
         * An example of activation of the async operation in the case
         * when \a Message is a message:
         * \code
         * namespace asyncop = so_5::extra::async_op::time_limited;
         * class demo : public so_5::agent_t {
         *  struct timeout final : public so_5::message_t {
         *      int id_;
         *      const std::string reply_payload_;
         *          const so_5::mbox_t reply_mbox_;
         *
         *          timeout(int id, std::string playload, so_5::mbox_t mbox)
         *              : id_(id), reply_payload_(std::move(payload), reply_mbox_(std::move(mbox))
         *              {}
         *  };
         *  ...
         *  void initiate_async_op() {
         *      asyncop::make<timeout>()
         *          ... // Set up completion and timeout handlers...
         *          // Activation with several arguments.
         *          .activate(
         *              // This is timeout duration.
         *              std::chrono::milliseconds(200),
         *              // All these arguments will be passed to the constructor of timeout message.
         *              current_op_id,
         *              op_reply_payload,
         *              op_result_consumer_mbox);
         *      ...
         *  }
         * };
         * \endcode
         *
         * \note
         * There is no need to store the cancellation_point returned if you
         * don't want to cancel async operation. The return value of
         * activate() can be safely discarded in that case.
         *
         * \attention
         * If cancellation_point is stored then it should be used only on
         * the working context of the agent for that the async operation is
         * created. And the cancellation_point should not be used in the
         * thread-safe event handlers of that agent. It is because
         * cancellation_point is not a thread safe object.
         *
         * \note
         * If an exception is thrown during the activation procedure all
         * completion and timeout handlers which were subscribed before
         * the exception will be unsubscribed. And the async operation
         * data will be deleted. It means that after an exception in
         * activate() method the definition_point can't be used anymore.
         */
        template< typename... Args >
        cancellation_point_t< Operation_Data >
        activate(
            //! The maximum duration for the async operation.
            //! Note: this should be non-negative value.
            std::chrono::steady_clock::duration timeout,
            //! Arguments for the construction of timeout message/signal
            //! of the type \a Message.
            //! This arguments will be passed to so_5::send_delayed
            //! function.
            Args && ...args ) &
            {
                this->ensure_activable();

                // From this point the definition_point will be detached
                // from operation data. It means that is_activable() will
                // return false.
                auto op = std::move(this->m_op);

                ::so_5::details::do_with_rollback_on_exception( [&] {
                        op->do_activation_actions();
                        op->setup_timer_id(
                                ::so_5::send_periodic<Message>(
                                        op->environment(),
                                        op->timeout_mbox(),
                                        timeout,
                                        std::chrono::steady_clock::duration::zero(),
                                        std::forward<Args>(args)... ) );
                        op->change_status( status_t::activated );
                    },
                    [&] {
                        op->cancelled();
                    } );

                return cancellation_point_t< Operation_Data >( std::move(op) );
            }

        //! Just a proxy for the main version of %activate.
        template< typename... Args >
        auto
        activate( Args && ...args ) &&
            {
                return this->activate( std::forward<Args>(args)... );
            }
    };

//
// make
//
/*!
 * \brief A factory for creation definition points of async operations.
 *
 * Instead of creation of definition_point_t object by hand this
 * helper function should be used.
 *
 * Usage examples:
 * \code
 * namespace asyncop = so_5::extra::async_op::time_limited;
 * class demo : public so_5::agent_t {
 *  struct timeout final : public so_5::signal_t {};
 *  ...
 *  void initiate_async_op() {
 *      // Create a definition_point for a new async operation...
 *      asyncop::make<timeout>(*this)
 *          // ...then set up completion handler(s)...
 *          .completed_on(
 *              *this,
 *              so_default_state(),
 *              &demo::on_first_completion_msg )
 *          .completed_on(
 *              some_external_mbox_,
 *              some_user_defined_state_,
 *              [this](mhood_t<another_completion_msg> cmd) {...})
 *          // ...then set up timeout handler(s)...
 *          .timeout_handler(
 *              so_default_state(),
 *              &demo::on_timeout )
 *          .timeout_handler(
 *              some_user_defined_state_,
 *              [this](mhood_t<timeout> cmd) {...})
 *          // ...and now we can activate the operation.
 *          .activate(std::chrono::milliseconds(300));
 *      ...
 *  }
 * };
 * \endcode
 *
 * \since
 * v.1.0.4
 */
template< typename Message >
SO_5_NODISCARD definition_point_t< Message >
make(
    //! Agent for that this async operation will be created.
    ::so_5::agent_t & owner )
    {
        return definition_point_t<Message>( ::so_5::outliving_mutable(owner) );
    }

} /* namespace time_limited */

} /* namespace async_op */

} /* namespace extra */

} /* namespace so_5 */