-module(crash_statem).
%% we're only going to compile this on OTP 19+
-behaviour(gen_statem).

-export([
   start/0,
   crash/0,
   stop/1,
   timeout/0,
   handle_event/4
]).

-export([terminate/3, code_change/4, init/1, callback_mode/0]).

start() ->
   gen_statem:start({local, ?MODULE}, ?MODULE, [], []).

crash() ->
   gen_statem:call(?MODULE, boom).

stop(Reason) ->
   gen_statem:call(?MODULE, {stop, Reason}).

timeout() ->
   gen_statem:call(?MODULE, timeout).

%% Mandatory callback functions
terminate(_Reason, _State, _Data) -> ok.
code_change(_Vsn, State, Data, _Extra) -> {ok, State, Data}.
init([]) ->
   %% insert rant here about breaking changes in minor versions...
   case erlang:system_info(version) of
      "8.0" -> {callback_mode(), state1, undefined};
      _ -> {ok, state1, undefined}
   end.

callback_mode() -> handle_event_function.

%%% state callback(s)

handle_event(state_timeout, timeout, state1, _) ->
   {stop, timeout};
handle_event({call, _From}, timeout, _Arg, _Data) ->
   {keep_state_and_data, [{state_timeout, 0, timeout}]};
handle_event({call, _From}, {stop, Reason}, state1, _Data) ->
   {stop, Reason}.