/*
    ChibiOS - Copyright (C) 2006..2018 Giovanni Di Sirio.

    This file is part of ChibiOS.

    ChibiOS is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    ChibiOS is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/**
 * @file    chvt.h
 * @brief   Time and Virtual Timers module macros and structures.
 *
 * @addtogroup time
 * @{
 */

#ifndef CHVT_H
#define CHVT_H

/*===========================================================================*/
/* Module constants.                                                         */
/*===========================================================================*/

/*===========================================================================*/
/* Module pre-compile time settings.                                         */
/*===========================================================================*/

/*===========================================================================*/
/* Derived constants and error checks.                                       */
/*===========================================================================*/

#if (CH_CFG_ST_TIMEDELTA < 0) || (CH_CFG_ST_TIMEDELTA == 1)
#error "invalid CH_CFG_ST_TIMEDELTA specified, must "                       \
       "be zero or greater than one"
#endif

#if (CH_CFG_ST_TIMEDELTA > 0) && (CH_CFG_TIME_QUANTUM > 0)
#error "CH_CFG_TIME_QUANTUM not supported in tickless mode"
#endif

#if (CH_CFG_ST_TIMEDELTA > 0) && (CH_DBG_THREADS_PROFILING == TRUE)
#error "CH_DBG_THREADS_PROFILING not supported in tickless mode"
#endif

/*===========================================================================*/
/* Module data structures and types.                                         */
/*===========================================================================*/

/*===========================================================================*/
/* Module macros.                                                            */
/*===========================================================================*/

/*===========================================================================*/
/* External declarations.                                                    */
/*===========================================================================*/

/*
 * Virtual Timers APIs.
 */
#ifdef __cplusplus
extern "C" {
#endif
  void _vt_init(void);
  void chVTDoSetI(virtual_timer_t *vtp, sysinterval_t delay,
                  vtfunc_t vtfunc, void *par);
  void chVTDoResetI(virtual_timer_t *vtp);
#ifdef __cplusplus
}
#endif

/*===========================================================================*/
/* Module inline functions.                                                  */
/*===========================================================================*/

/**
 * @brief   Initializes a @p virtual_timer_t object.
 * @note    Initializing a timer object is not strictly required because
 *          the function @p chVTSetI() initializes the object too. This
 *          function is only useful if you need to perform a @p chVTIsArmed()
 *          check before calling @p chVTSetI().
 *
 * @param[out] vtp      the @p virtual_timer_t structure pointer
 *
 * @init
 */
static inline void chVTObjectInit(virtual_timer_t *vtp) {

  vtp->func = NULL;
}

/**
 * @brief   Current system time.
 * @details Returns the number of system ticks since the @p chSysInit()
 *          invocation.
 * @note    The counter can reach its maximum and then restart from zero.
 * @note    This function can be called from any context but its atomicity
 *          is not guaranteed on architectures whose word size is less than
 *          @p systime_t size.
 *
 * @return              The system time in ticks.
 *
 * @xclass
 */
static inline systime_t chVTGetSystemTimeX(void) {

#if CH_CFG_ST_TIMEDELTA == 0
  return ch.vtlist.systime;
#else /* CH_CFG_ST_TIMEDELTA > 0 */
  return port_timer_get_time();
#endif /* CH_CFG_ST_TIMEDELTA > 0 */
}

/**
 * @brief   Current system time.
 * @details Returns the number of system ticks since the @p chSysInit()
 *          invocation.
 * @note    The counter can reach its maximum and then restart from zero.
 *
 * @return              The system time in ticks.
 *
 * @api
 */
static inline systime_t chVTGetSystemTime(void) {
  systime_t systime;

  chSysLock();
  systime = chVTGetSystemTimeX();
  chSysUnlock();

  return systime;
}

/**
 * @brief   Returns the elapsed time since the specified start time.
 *
 * @param[in] start     start time
 * @return              The elapsed time.
 *
 * @xclass
 */
static inline sysinterval_t chVTTimeElapsedSinceX(systime_t start) {

  return chTimeDiffX(start, chVTGetSystemTimeX());
}

/**
 * @brief   Checks if the current system time is within the specified time
 *          window.
 * @note    When start==end then the function returns always true because the
 *          whole time range is specified.
 *
 * @param[in] start     the start of the time window (inclusive)
 * @param[in] end       the end of the time window (non inclusive)
 * @retval true         current time within the specified time window.
 * @retval false        current time not within the specified time window.
 *
 * @xclass
 */
static inline bool chVTIsSystemTimeWithinX(systime_t start, systime_t end) {

  return chTimeIsInRangeX(chVTGetSystemTimeX(), start, end);
}

/**
 * @brief   Checks if the current system time is within the specified time
 *          window.
 * @note    When start==end then the function returns always true because the
 *          whole time range is specified.
 *
 * @param[in] start     the start of the time window (inclusive)
 * @param[in] end       the end of the time window (non inclusive)
 * @retval true         current time within the specified time window.
 * @retval false        current time not within the specified time window.
 *
 * @api
 */
static inline bool chVTIsSystemTimeWithin(systime_t start, systime_t end) {

  return chTimeIsInRangeX(chVTGetSystemTime(), start, end);
}

/**
 * @brief   Returns the time interval until the next timer event.
 * @note    The return value is not perfectly accurate and can report values
 *          in excess of @p CH_CFG_ST_TIMEDELTA ticks.
 * @note    The interval returned by this function is only meaningful if
 *          more timers are not added to the list until the returned time.
 *
 * @param[out] timep    pointer to a variable that will contain the time
 *                      interval until the next timer elapses. This pointer
 *                      can be @p NULL if the information is not required.
 * @return              The time, in ticks, until next time event.
 * @retval false        if the timers list is empty.
 * @retval true         if the timers list contains at least one timer.
 *
 * @iclass
 */
static inline bool chVTGetTimersStateI(sysinterval_t *timep) {

  chDbgCheckClassI();

  if (&ch.vtlist == (virtual_timers_list_t *)ch.vtlist.next) {
    return false;
  }

  if (timep != NULL) {
#if CH_CFG_ST_TIMEDELTA == 0
    *timep = ch.vtlist.next->delta;
#else
    *timep = chTimeDiffX(chVTGetSystemTimeX(),
                         chTimeAddX(ch.vtlist.lasttime,
                                    ch.vtlist.next->delta +
                                    (sysinterval_t)CH_CFG_ST_TIMEDELTA));
#endif
  }

  return true;
}

/**
 * @brief   Returns @p true if the specified timer is armed.
 * @pre     The timer must have been initialized using @p chVTObjectInit()
 *          or @p chVTDoSetI().
 *
 * @param[in] vtp       the @p virtual_timer_t structure pointer
 * @return              true if the timer is armed.
 *
 * @iclass
 */
static inline bool chVTIsArmedI(const virtual_timer_t *vtp) {

  chDbgCheckClassI();

  return (bool)(vtp->func != NULL);
}

/**
 * @brief   Returns @p true if the specified timer is armed.
 * @pre     The timer must have been initialized using @p chVTObjectInit()
 *          or @p chVTDoSetI().
 *
 * @param[in] vtp       the @p virtual_timer_t structure pointer
 * @return              true if the timer is armed.
 *
 * @api
 */
static inline bool chVTIsArmed(const virtual_timer_t *vtp) {
  bool b;

  chSysLock();
  b = chVTIsArmedI(vtp);
  chSysUnlock();

  return b;
}

/**
 * @brief   Disables a Virtual Timer.
 * @note    The timer is first checked and disabled only if armed.
 * @pre     The timer must have been initialized using @p chVTObjectInit()
 *          or @p chVTDoSetI().
 *
 * @param[in] vtp       the @p virtual_timer_t structure pointer
 *
 * @iclass
 */
static inline void chVTResetI(virtual_timer_t *vtp) {

  if (chVTIsArmedI(vtp)) {
    chVTDoResetI(vtp);
  }
}

/**
 * @brief   Disables a Virtual Timer.
 * @note    The timer is first checked and disabled only if armed.
 * @pre     The timer must have been initialized using @p chVTObjectInit()
 *          or @p chVTDoSetI().
 *
 * @param[in] vtp       the @p virtual_timer_t structure pointer
 *
 * @api
 */
static inline void chVTReset(virtual_timer_t *vtp) {

  chSysLock();
  chVTResetI(vtp);
  chSysUnlock();
}

/**
 * @brief   Enables a virtual timer.
 * @details If the virtual timer was already enabled then it is re-enabled
 *          using the new parameters.
 * @pre     The timer must have been initialized using @p chVTObjectInit()
 *          or @p chVTDoSetI().
 *
 * @param[in] vtp       the @p virtual_timer_t structure pointer
 * @param[in] delay     the number of ticks before the operation timeouts, the
 *                      special values are handled as follow:
 *                      - @a TIME_INFINITE is allowed but interpreted as a
 *                        normal time specification.
 *                      - @a TIME_IMMEDIATE this value is not allowed.
 *                      .
 * @param[in] vtfunc    the timer callback function. After invoking the
 *                      callback the timer is disabled and the structure can
 *                      be disposed or reused.
 * @param[in] par       a parameter that will be passed to the callback
 *                      function
 *
 * @iclass
 */
static inline void chVTSetI(virtual_timer_t *vtp, sysinterval_t delay,
                            vtfunc_t vtfunc, void *par) {

  chVTResetI(vtp);
  chVTDoSetI(vtp, delay, vtfunc, par);
}

/**
 * @brief   Enables a virtual timer.
 * @details If the virtual timer was already enabled then it is re-enabled
 *          using the new parameters.
 * @pre     The timer must have been initialized using @p chVTObjectInit()
 *          or @p chVTDoSetI().
 *
 * @param[in] vtp       the @p virtual_timer_t structure pointer
 * @param[in] delay     the number of ticks before the operation timeouts, the
 *                      special values are handled as follow:
 *                      - @a TIME_INFINITE is allowed but interpreted as a
 *                        normal time specification.
 *                      - @a TIME_IMMEDIATE this value is not allowed.
 *                      .
 * @param[in] vtfunc    the timer callback function. After invoking the
 *                      callback the timer is disabled and the structure can
 *                      be disposed or reused.
 * @param[in] par       a parameter that will be passed to the callback
 *                      function
 *
 * @api
 */
static inline void chVTSet(virtual_timer_t *vtp, sysinterval_t delay,
                           vtfunc_t vtfunc, void *par) {

  chSysLock();
  chVTSetI(vtp, delay, vtfunc, par);
  chSysUnlock();
}

/**
 * @brief   Virtual timers ticker.
 * @note    The system lock is released before entering the callback and
 *          re-acquired immediately after. It is callback's responsibility
 *          to acquire the lock if needed. This is done in order to reduce
 *          interrupts jitter when many timers are in use.
 *
 * @iclass
 */
static inline void chVTDoTickI(void) {

  chDbgCheckClassI();

#if CH_CFG_ST_TIMEDELTA == 0
  ch.vtlist.systime++;
  if (&ch.vtlist != (virtual_timers_list_t *)ch.vtlist.next) {
    /* The list is not empty, processing elements on top.*/
    --ch.vtlist.next->delta;
    while (ch.vtlist.next->delta == (sysinterval_t)0) {
      virtual_timer_t *vtp;
      vtfunc_t fn;

      vtp = ch.vtlist.next;
      fn = vtp->func;
      vtp->func = NULL;
      vtp->next->prev = (virtual_timer_t *)&ch.vtlist;
      ch.vtlist.next = vtp->next;
      chSysUnlockFromISR();
      fn(vtp->par);
      chSysLockFromISR();
    }
  }
#else /* CH_CFG_ST_TIMEDELTA > 0 */
  virtual_timer_t *vtp;
  systime_t now;
  sysinterval_t delta, nowdelta;

  /* Looping through timers.*/
  vtp = ch.vtlist.next;
  while (true) {

    /* Getting the system time as reference.*/
    now = chVTGetSystemTimeX();
    nowdelta = chTimeDiffX(ch.vtlist.lasttime, now);

    /* The list scan is limited by the timers header having
       "ch.vtlist.vt_delta == (sysinterval_t)-1" which is
       greater than all deltas.*/
    if (nowdelta < vtp->delta) {
      break;
    }

    /* Consuming all timers between "vtp->lasttime" and now.*/
    do {
      vtfunc_t fn;

      /* The "last time" becomes this timer's expiration time.*/
      ch.vtlist.lasttime += vtp->delta;
      nowdelta -= vtp->delta;

      vtp->next->prev = (virtual_timer_t *)&ch.vtlist;
      ch.vtlist.next = vtp->next;
      fn = vtp->func;
      vtp->func = NULL;

      /* if the list becomes empty then the timer is stopped.*/
      if (ch.vtlist.next == (virtual_timer_t *)&ch.vtlist) {
        port_timer_stop_alarm();
      }

      /* The callback is invoked outside the kernel critical zone.*/
      chSysUnlockFromISR();
      fn(vtp->par);
      chSysLockFromISR();

      /* Next element in the list.*/
      vtp = ch.vtlist.next;
    }
    while (vtp->delta <= nowdelta);
  }

  /* if the list is empty, nothing else to do.*/
  if (ch.vtlist.next == (virtual_timer_t *)&ch.vtlist) {
    return;
  }

  /* The "unprocessed nowdelta" time slice is added to "last time"
     and subtracted to next timer's delta.*/
  ch.vtlist.lasttime += nowdelta;
  ch.vtlist.next->delta -= nowdelta;

  /* Recalculating the next alarm time.*/
  delta = vtp->delta - chTimeDiffX(ch.vtlist.lasttime, now);
  if (delta < (sysinterval_t)CH_CFG_ST_TIMEDELTA) {
    delta = (sysinterval_t)CH_CFG_ST_TIMEDELTA;
  }
#if CH_CFG_INTERVALS_SIZE > CH_CFG_ST_RESOLUTION
  /* The delta could be too large for the physical timer to handle.*/
  else if (delta > (sysinterval_t)TIME_MAX_SYSTIME) {
    delta = (sysinterval_t)TIME_MAX_SYSTIME;
  }
#endif
  port_timer_set_alarm(chTimeAddX(now, delta));

  chDbgAssert(chTimeDiffX(ch.vtlist.lasttime, chVTGetSystemTimeX()) <=
              chTimeDiffX(ch.vtlist.lasttime, chTimeAddX(now, delta)),
              "exceeding delta");
#endif /* CH_CFG_ST_TIMEDELTA > 0 */
}

#endif /* CHVT_H */

/** @} */