/*!@file
  \brief   Trigger Mechanism
  \details includes a small, 15 (by default) element list of function pointers
           that may be registered and triggered like a stack of functions.
           Useful for synchronizing function calls.

           Usage example:
           #include <trigger.h>

           void trigger_test(void);

           extern void hack_the_planet(void);
           extern void hack_the_plants(void);
           extern void hack_robert_plant(void);

           void
           trigger_test()
           { TRIGGER_SET(hack_the_planet);
             TRIGGER_SET(hack_the_plants);
             TRIGGER_SET(hack_robert_plant);

             //Don't worry robert!
             TRIGGER_POP();

             TRIGGER();
           }

           Advanced Usage Example:
           #define MAX_TRIGGER_FUNCS 2
           #define TRIGGERS kill_trigger flush_trigger
           #include <trigger.h>
           #include <hack_functions.h>

           void
           advanced_trigger_test()
           { TRIGGER_SET(kill_trigger, hack_the_planet);
             TRIGGER_SET(kill_trigger, hack_the_missiles);
             TRIGGER_SET(flush_trigger, hack_the_government);
             TRIGGER_SET(flush trigger, hack_my_tax_bill);

             if (robert_plant_hacked())
               { TRIGGER(kill_trigger);

                 TRIGGER_POP(flush_trigger);
                 TRIGGER_SET(flush_trigger, hack_the_missile_defenses);
               }
             TRIGGER(flush_trigger);
           }


  \author  Mihrtec
  \date    2016
  -----------------------------------------------------------------------------*/

#ifndef _TRIGGER_H_
#define _TRIGGER_H_

/** The number of trigger functions per trigger */
#ifndef MAX_TRIGGER_FUNCS
#define MAX_TRIGGER_FUNCS 15
#endif

/* Internal macro prototypes */
#define _TRIGGER_DEL(TARG) --((TARG).num_funcs)
#define _TRIGGER_POP(TARG) ((TARG).func[_TRIGGER_DEL(TARG)])()
#define _TRIGGER_SET(TARG, FUNC) (TARG).func[(TARG).num_funcs++] = (FUNC)
#define _TRIGGER(TARG) while((TARG).num_funcs) TRIGGER_POP(TARG)

/* If TRIGGERS is not defined, use only a default trigger and define shorthand
   functions for easy use. */
#ifndef TRIGGERS
#define TRIGGERS default_trigger
#define TRIGGER_DEL() _TRIGGER_DEL(default_trigger)
#define TRIGGER_POP() _TRIGGER_POP(default_trigger)
#define TRIGGER_SET(FUNC) _TRIGGER_SET(default_trigger, FUNC)
#define TRIGGER() _TRIGGER(default_trigger)
#else
#define TRIGGER_DEL(TARG) _TRIGGER_DEL(TARG)
#define TRIGGER_POP(TARG) _TRIGGER_POP(TARG)
#define TRIGGER_SET(TARG,FUNC) _TRIGGER_SET(TARG,FUNC)
#define TRIGGER(TARG) _TRIGGER(TARG)
#endif

static struct call_trigger
{ int num_funcs;
  void (*func[MAX_TRIGGER_FUNCS])(void);
} TRIGGERS;

#endif //_TRIGGER_H_