#include <cassert>
#include <cstdio>

#include <boost/sml.hpp>

namespace sml = boost::sml;

// events
struct change_state {};
struct do_a {};
struct do_b {};

// actions
const auto action_a = [] {
	printf("doing action a...\n");
};
const auto entry_action_a = [] {
	printf("-> active state: a...\n");
};

const auto action_b = [] {
	printf("doing action b...\n");
};
const auto entry_action_b = [] {
	printf("-> active state: b...\n");
};

struct hello_world {
  auto operator()() const {
    using namespace sml;
    // clang-format off
    return make_transition_table(
      *"first state"_s  + event<change_state>           = "second state"_s,
       "first state"_s  + on_entry<_> / entry_action_a,
       "first state"_s  + event<do_a> / action_a        = "first state"_s,

       "second state"_s + event<change_state>           = "first state"_s,
       "second state"_s + on_entry<_> / entry_action_b,
       "second state"_s + event<do_b> / action_b
    );
    // clang-format on
  }
};

int main() {
  using namespace sml;

  sm<hello_world> sm;
  static_assert(1 == sizeof(sm), "sizeof(sm) != 1b");

  sm.process_event(do_a{});
  sm.process_event(do_a{});
  sm.process_event(do_a{});

  sm.process_event(change_state{});

  sm.process_event(do_b{});
  sm.process_event(do_b{});
  sm.process_event(do_b{});
}