/** <module> Threads - implements triggers, timers and simultaneous actions.
@author Piotr Hołownia
*/

:- module(threads,[
		  trigger_create/3,
		  timer_create/3,
		  do_simultaneously/1
		  ]).

%%	trigger_create(-ID,+Event,+Action).
%
%	Creates trigger.
%	Action will be fired, when Event is true.
%	Action can be both predicate and list of predicates.

trigger_create(ID,Event,Action) :-
	thread_create(trigger(Event,Action),ID,[]).

fired([Action|Tail]) :-
	Action,
	fired(Tail).

fired([Action]) :-
	Action.

fired(Action) :-
	Action.

trigger(Event,Action) :-
	Event,
	fired(Action).

trigger(Event,Action) :-
       	trigger(Event,Action).

%%	timer_create(-ID,+Time,+Action).
%
%	Creates timer.
%	Action will be fired after specified Time.
%	Action can be both predicate and list of predicates.

timer_create(ID,Time,Action) :-
	get_time(Start_time),
	Finish_time is Start_time+Time,
	thread_create(timer(Finish_time,Action),ID,[]).

timer(Finish_time,Action) :-
	get_time(Time),
	Time >= Finish_time,
	fired(Action).

timer(Finish_time,Action) :-
       	timer(Finish_time,Action).


%%	do_simultaneously(+Action)
%
%	Creats a thread for each action from Action.
%	Last of them runs in the main thread.
%	Action should be a list of predicates.
%	Although Action can be a signle predicate it makes no sense.


do_simultaneously([Action|Tail]) :-
	thread_create(Action,_,[]),
	do_simultaneously(Tail).

do_simultaneously([Action]) :-
	Action.

do_simultaneously(Action) :-
	Action.