etl/include/etl/callback_timer_deferred_locked.h

/******************************************************************************
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Embedded Template Library.
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Copyright(c) 2025 John Wellbelove

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#ifndef ETL_CALLBACK_TIMER_DEFERRED_LOCKED_INCLUDED
#define ETL_CALLBACK_TIMER_DEFERRED_LOCKED_INCLUDED

#include "callback_timer_locked.h"
#include "etl/nullptr.h"
#include "etl/optional.h"
#include "priority_queue.h"
#include "delegate.h"

namespace etl
{
  //***************************************************************************
  /// The deferred callback timer
  //***************************************************************************
  template <uint_least8_t Max_Timers_, uint32_t Max_Handlers_>
  class callback_timer_deferred_locked : public etl::icallback_timer_locked
  {
  public:

    ETL_STATIC_ASSERT(Max_Timers_ <= 254U, "No more than 254 timers are allowed");

    typedef icallback_timer_locked::callback_type callback_type;
    typedef icallback_timer_locked::try_lock_type try_lock_type;
    typedef icallback_timer_locked::lock_type     lock_type;
    typedef icallback_timer_locked::unlock_type   unlock_type;

  private:

    class CallbackNode 
    {
    public:

      CallbackNode(callback_type &callback_,uint_least8_t priority_) : callback(callback_), priority(priority_) 
      {
      }
            
      bool operator < (const CallbackNode& p) const
      {
        return this->priority > p.priority; // comparison was inverted here to easy the code design
      }

      callback_type callback;
      uint_least8_t priority;
    };

  public:

    //*******************************************
    /// Constructor.
    //*******************************************
    callback_timer_deferred_locked()
      : icallback_timer_locked(timer_array, Max_Timers_)
    {
    }

    //*******************************************
    /// Constructor.
    //*******************************************
    callback_timer_deferred_locked(try_lock_type try_lock_, lock_type lock_, unlock_type unlock_)
      : icallback_timer_locked(timer_array, Max_Timers_)
    {
      this->set_locks(try_lock_, lock_, unlock_);
    }

    //*******************************************
    /// Handle the tick call
    //*******************************************
    bool tick(uint32_t count) final
    {
      if (enabled)
      {
        if (try_lock())
        {
          // We have something to do?
          bool has_active = !active_list.empty();

          if (has_active)
          {
            while (has_active && (count >= active_list.front().delta))
            {
              timer_data& timer = active_list.front();

              count -= timer.delta;

              active_list.remove(timer.id, true);

              if (timer.callback.is_valid())
              {
                if (!handler_queue.full())
                {
                    handler_queue.push(CallbackNode(timer.callback, timer_priorities[timer.id]));
                }
              }

              if (timer.repeating)
              {
                // Reinsert the timer.
                timer.delta = timer.period;
                active_list.insert(timer.id);
              }

              has_active = !active_list.empty();
            }

            if (has_active)
            {
              // Subtract any remainder from the next due timeout.
              active_list.front().delta -= count;
            }
          }

          unlock();

          return true;
        }
      }

      return false;
    }

    //*******************************************
    /// Handles the work collected during the tick() call
    /// You can call this function after tick()
    /// or you can call this on another task to handle the timer events.
    //*******************************************
    void handle_deferred(void)
    {
      callback_type work_todo_callback;

      do
      {
        lock();
        
        if (handler_queue.empty())
        {
          work_todo_callback.clear();
        }
        else
        {
          CallbackNode &work_todo_callback_node = handler_queue.top();
          work_todo_callback = work_todo_callback_node.callback;
          handler_queue.pop();
        }

        unlock();

        work_todo_callback.call_if();
      } while (work_todo_callback.is_valid());
    }

    // Overloads

    //*******************************************
    /// Register a timer.
    //*******************************************
    etl::timer::id::type register_timer(const callback_type& callback_,
                                        uint32_t             period_,
                                        bool                 repeating_)
    {
        return register_timer(callback_, period_, repeating_, 0);
    }

    //*******************************************
    /// Register a timer with priority.
    /// priority_ 0 is highest priority, 255 is lowest
    /// Suggestion: this could be used as amonth of work to do and
    /// less work will be done in first place.
    //*******************************************
    etl::timer::id::type register_timer(const callback_type& callback_,
                                        uint32_t             period_,
                                        bool                 repeating_,
                                        uint_least8_t        priority_)
    {
        etl::timer::id::type id = icallback_timer_locked::register_timer(callback_, period_, repeating_);

        if (id != etl::timer::id::NO_TIMER)
        {
            timer_priorities[id] = priority_;
        }

        return id;
    }

  private:

    priority_queue<CallbackNode, Max_Handlers_> handler_queue;
    uint_least8_t timer_priorities[Max_Timers_];
    timer_data timer_array[Max_Timers_];
  };
}

#endif