fsm.erl

if_true(true, Action) -> Action;
if_true(false, _) -> no_such_tile.

check_tile_exists(ExistsAction, Seat, Tile, Seats) ->
	#desk_seat{ hand=Hand } = lists:nth(Seat, Seats),
	if_true(deck:member(Tile, Hand), ExistsAction).

wait_for_discard({check_discard_possible, Seat, Tile}, S=#state{seat=Seat, seats=Seats}) ->
	wait_for_discard({check_tile_exists(discard, Seat, Tile, Seats), Seat, Tile}, S);

wait_for_discard({no_such_tile, Seat, Tile}, S=#state{}) ->
	error(S, Seat, #no_such_tile{tile=Tile}),
	{next_state, wait_for_discard, S};

% discard
wait_for_discard({discard, Seat, Tile}, S=#state{seat=Seat, seats=Seats}) ->
	notify(S, Seat, #discarded{tile=Tile}),
	next_move(S#state{seats=discard_tile(Seat, Tile, Seats)});