/*!
 * \file utils/timer_delay.h
 * \brief
 *      A CRTP timer delay utility
 *
 * \copyright Copyright (C) 2021 Christos Choutouridis <christos@choutouridis.net>
 *
 * <dl class=\"section copyright\"><dt>License</dt><dd>
 * The MIT License (MIT)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 * </dd></dl>
 */

#ifndef TBX_UTILS_TIMER_DELAY_H_
#define TBX_UTILS_TIMER_DELAY_H_

#include <core/core.h>
#include <core/crtp.h>

#include <type_traits>

namespace tbx {

    /*!
     * \class timer_delay
     * \brief
     *      A CRTP hw timer based, delay implementation.
     *
     * CRTP requirements:
     *  - int set_frequency_impl (size_t freq, Counter_t ticks)
     *    Initialize and start the hw timer with tick frequency \c freq and reload value \c ticks
     *  - volatile Counter_t* get_value_ptr_impl (Counter_t discard)
     *    Return a pointer to hw timer counter value register. The \c discard argument should discarded.
     *
     * \tparam Impl_t       The derived class
     * \tparam Counter_t    The hw timer's type
     */
    template <typename Impl_t, typename Counter_t>
    class timer_delay {
        _CRTP_IMPL(Impl_t);
        using value_t  = volatile Counter_t;
        using marker_t = std::make_signed_t<std::remove_cv_t<Counter_t>>;

    //! \name CRTP requirements
    //! @{
    private:
        int set_frequency (size_t freq, Counter_t ticks) {
            return impl().set_frequency_impl(freq, ticks);
        }
        volatile Counter_t* get_value_ptr (Counter_t discard = Counter_t{}) {
            return impl().get_value_ptr_impl (discard);
        }
    //! @}

    //! \name Object lifetime
    //! @{
    protected:
        //! \brief
        //!     Create and initialize
        //! \param freq     The required hw timer's frequency
        //! \param ticks    The required timer's reload value
        timer_delay (size_t freq, Counter_t ticks) {
            init (freq, ticks);
        }
        timer_delay() noexcept = default;                       //!< Default object is valid, but non-usable
        timer_delay(const timer_delay&)             = delete;   //!< No copies
        timer_delay& operator=(const timer_delay&)  = delete;   //!< No copies
        //! \note
        //! We are not initializing the timer via default ctor, in order to be able to
        //! declare a timer_delay object globally and initialize it after the call to main().
    //! @}

    private:
        //! Period to frequency compile time tool
        constexpr Counter_t period2freq (double period) noexcept {
            return (Counter_t)(1 / period);
        }

        /*!
         * \brief   Return the systems best approximation for ticks per msec
         * \return  The calculated value or zero if no calculation can apply
         */
        Counter_t ticks_per_msec () {
            Counter_t tck = (Counter_t)(frequency / period2freq(0.001));
            return (tck <= 1) ? 1 : tck;
        }

        /*!
         * \brief   Return the systems best approximation for ticks per usec
         * \return  The calculated value or zero if no calculation can apply
         */
        Counter_t ticks_per_usec () {
            Counter_t tck = (Counter_t)(frequency / period2freq(0.000001));
            return (tck <= 1) ? 1 : tck;
        }

        /*!
         * \brief   Return the systems best approximation for ticks per usec
         * \return  The calculated value or zero if no calculation can apply
         */
        Counter_t ticks_per_100nsec () {
            Counter_t tck = (Counter_t)(frequency / period2freq(0.0000001));
            return (tck <= 1) ? 1 : tck;
        }

    public:
        /*!
         * \brief
         *      Initializes both object members and hw timer.
         *
         * \param freq      The required hw timer's frequency
         * \param ticks     The required timer's reload value
         * \return
         */
        bool init (size_t freq, Counter_t ticks) {
            if (set_frequency(freq, ticks))
                return false;
            volatile Counter_t* v = get_value_ptr();

            value     = (v != nullptr) ? v : value;
            frequency = freq;
            max_ticks = ticks;
            tp1ms  = ticks_per_msec();
            tp1us  = ticks_per_usec();
            tp100ns= ticks_per_100nsec();
            return true;
        }

        /*!
         * \brief
         *    A code based delay implementation, using hw timer for timing.
         *    This is NOT accurate but it ensures that the time passed is always
         *    more than the requested value.
         *    The delay values are multiplications of 1 msec.
         * \param   msec     Time in msec for delay
         */
        void delay_ms (int msec) {
            marker_t m, m2, m1 = (marker_t)*value;

            msec *= tp1ms;

            // Eat the time difference from msec value.
            do {
                m2 = (marker_t)(*value);
                m = m2 - m1;
                msec -= (m>=0) ? m : max_ticks + m;
                m1 = m2;
            } while (msec>0);
        }

        /*!
         * \brief
         *    A code based delay implementation, using hw timer for timing.
         *    This is NOT accurate but it ensures that the time passed is always
         *    more than the requested value.
         *    The delay values are multiplications of 1 usec.
         * \param   usec     Time in usec for delay
         */
        void delay_us (int usec) {
            marker_t m, m2, m1 = (marker_t)*value;

            usec *= tp1us;
            if ((marker_t)(*value) - m1 > usec) // Very small delays may return here.
            return;

            // Eat the time difference from usec value.
            do {
                m2 = (marker_t)(*value);
                m = m2 - m1;
                usec -= (m>=0) ? m : max_ticks + m;
                m1 = m2;
            } while (usec>0);
        }

        /*!
         * \brief
         *    A code based delay implementation, using hw timer for timing.
         *    This is NOT accurate but it ensures that the time passed is always
         *    more than the requested value.
         *    The delay values are multiplications of 100 nsec.
         * \param   _100nsec     Time in 100nsec for delay
         */
        void delay_100ns (int _100nsec) {
            marker_t m, m2, m1 = (marker_t)*value;

            _100nsec *= tp100ns;
            if ((marker_t)(*value) - m1 > _100nsec) // Very small delays may return here.
                return;

            // Eat the time difference from _100nsec value.
            do {
                m2 = (marker_t)(*value);
                m = m2 - m1;
                _100nsec -= (m>=0) ? m : max_ticks + m;
                m1 = m2;
            } while (_100nsec>0);
        }

        /*!
         * \brief
         *    A code based polling version delay implementation, using hw timer for timing.
         *    This is NOT accurate but it ensures that the time passed is always
         *    more than the requested value.
         *    The delay values are multiplications of 1 msec.
         * \param   msec     Time in msec for delay
         * \return  The status of ongoing delay
         *    \arg  false:    Delay time has passed
         *    \arg  true:     Delay is ongoing, keep calling
         */
        bool check_msec (int msec) {
            static marker_t m1=-1, cnt;
            marker_t m, m2;

            if (m1 == -1) {
                m1 = *value;
                cnt = tp1ms * msec;
            }

            // Eat the time difference from msec value.
            if (cnt>0) {
                m2 = (marker_t)(*value);
                m = m2-m1;
                cnt -= (m>=0) ? m : max_ticks + m;
                m1 = m2;
                return 1;   // wait
            } else {
                m1 = -1;
                return 0;   // do not wait any more
            }
        }

        /*!
         * \brief
         *    A code based polling version delay implementation, using hw timer for timing.
         *    This is NOT accurate but it ensures that the time passed is always
         *    more than the requested value.
         *    The delay values are multiplications of 1 usec.
         * \param   usec     Time in usec for delay
         * \return  The status of ongoing delay
         *    \arg  false:    Delay time has passed
         *    \arg  true:     Delay is ongoing, keep calling
         */
        bool check_usec (int usec) {
            static marker_t m1=-1, cnt;
            marker_t m, m2;

            if (m1 == -1) {
                m1 = *value;
                cnt = tp1us * usec;
            }

            // Eat the time difference from usec value.
            if (cnt>0) {
                m2 = (marker_t)(*value);
                m = m2-m1;
                cnt -= (m>=0) ? m : max_ticks + m;
                m1 = m2;
                return 1;   // wait
            } else {
                m1 = -1;
                return 0;   // do not wait any more
            }
        }


        /*!
         * \brief
         *    A code based polling version delay implementation, using hw timer for timing.
         *    This is NOT accurate but it ensures that the time passed is always
         *    more than the requested value.
         *    The delay values are multiplications of 100 nsec.
         * \param
         *    _100nsec     Time in 100nsec for delay
         * \return  The status of ongoing delay
         *    \arg  false:    Delay time has passed
         *    \arg  true:     Delay is ongoing, keep calling
         */
        bool check_100nsec (int _100nsec) {
            static marker_t m1=-1, cnt;
            marker_t m, m2;

            if (m1 == -1) {
                m1 = *value;
                cnt = tp100ns * _100nsec;
            }

            // Eat the time difference from _100nsec value.
            if (cnt>0) {
                m2 = (marker_t)(*value);
                m = m2-m1;
                cnt -= (m>=0) ? m : max_ticks + m;
                m1 = m2;
                return 1;   // wait
            }
            else {
                m1 = -1;
                return 0;   // do not wait any more
            }
        }

    private:
        static constexpr Counter_t zero = 0;    //!< A always zero place

        value_t*    value {(value_t*)&zero};    //!< Pointer to hw timer's counter register
                                                //!< We initialize it to &zero to avoid nullptr dereference
        size_t      frequency{};                //!< The frequency of the timer
        Counter_t   max_ticks{};                //!< The reload value of the timer
        Counter_t   tp1ms{};                    //!< ticks per ms temporary variable
        Counter_t   tp1us{};                    //!< ticks per us temporary variable
        Counter_t   tp100ns{};                  //!< ticks per 100ns temporary variable
    };


} // namespace tbx

#endif /* TBX_UTILS_TIMER_DELAY_H_ */