/* Elevator Controller in Golog */

/* Primitive actions */
prim_action(open_door).
prim_action(close_door).
prim_action(move_up).
prim_action(move_down).

/* Preconditions */
poss(open_door, S) :- at_floor(F, S), not(door_open(S)).
poss(close_door, S) :- door_open(S).
poss(move_up, S) :- current_floor(F, S), F < 10, not(door_open(S)).
poss(move_down, S) :- current_floor(F, S), F > 1, not(door_open(S)).

/* Main control procedure */
proc(serve_floor(F),
    [current_floor(F)?;
     open_door;
     wait(3);
     close_door]
).

proc(go_to_floor(Target),
    while(current_floor(F) & F < Target, move_up);
    while(current_floor(F) & F > Target, move_down)
).

proc(elevator_control,
    while(true,
        pi(f, requested(f)?; go_to_floor(f); serve_floor(f))
    )
).