time_limited_delivery.hpp

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/*!
 * \file
 * \brief An implementation of time_limited_delivery envelope.
 *
 * \since
 * v.1.2.0
 */

#pragma once

#include <so_5_extra/enveloped_msg/just_envelope.hpp>

#include <chrono>

namespace so_5 {

namespace extra {

namespace enveloped_msg {

//
// time_limited_delivery_t
//
/*!
 * \brief A special envelope to perform time-limited delivery.
 *
 * This envelope checks the current time before processing/transformation
 * of the enveloped message. If the current time is equal or greater than
 * the specified deadline then message won't be processed/transformed.
 *
 * Usage example:
 * \code
 * namespace msg_ns = so_5::extra::enveloped_msg;
 *
 * // Use time_limited_delivery_t with wallclock deadline.
 * msg_ns::make<my_message>(...)
 *      .envelope<msg_ns::time_limited_delivery_t>(
 *              // Limit lifetime of the message by 5 seconds from now.
 *              std::chrono::steady_clock::now() + 5s)
 *      .send_to(destination);
 *
 * // The same thing but less verbose:
 * msg_ns::make<my_message>(...)
 *      .envelope<msg_ns::time_limited_delivery_t>(
 *              // Limit lifetime of the message by 5 seconds from now.
 *              5s)
 *      .send_to(destination);
 * \endcode
 *
 * \since
 * v.1.2.0
 */
class time_limited_delivery_t final : public just_envelope_t
    {
        //! Delivery deadline.
        const std::chrono::steady_clock::time_point m_deadline;

    public :
        //! Initializing constructor.
        /*!
         * Receives wallclock time as deadline.
         */
        time_limited_delivery_t(
            //! Message to be delivered.
            message_ref_t message,
            //! Delivery deadline.
            std::chrono::steady_clock::time_point deadline )
            :   just_envelope_t{ std::move(message) }
            ,   m_deadline{ deadline }
            {}

        //! Initializing constructor.
        /*!
         * Receives time interval. Deadline will be calculated automatically
         * from the current time.
         */
        time_limited_delivery_t(
            //! Message to be delivered.
            message_ref_t message,
            //! Time interval for calculation of deadline value.
            std::chrono::steady_clock::duration deadline )
            :   time_limited_delivery_t{
                    std::move(message),
                    std::chrono::steady_clock::now() + deadline }
            {}

        // Implementation of inherited methods.
        void
        access_hook(
            access_context_t /*context*/,
            handler_invoker_t & invoker ) noexcept override
            {
                if( m_deadline > std::chrono::steady_clock::now() )
                    invoker.invoke( whole_payload() );
            }
    };

} /* namespace enveloped_msg */

} /* namespace extra */

} /* namespace so_5 */