#include <boost/sml.hpp>

#include <cassert>

#include <iostream>

namespace sml = boost::sml;

struct e1 {};

struct e2 {};

struct e3 {};

struct e4 {};

struct e5 {};

struct sub {

auto operator()() const {

using namespace sml;

// clang-format off

return make_transition_table(

*"idle"_s + event<e3> = "sub1"_s

, "sub1"_s + event<e4> = X

);

// clang-format on

}

};

struct composite {

auto operator()() const {

using namespace sml;

// clang-format off

return make_transition_table(

*"idle"_s + event<e1> = "s1"_s

, "s1"_s + event<e2> = state<sub>

, state<sub> + event<e5> = X

);

// clang-format on

}

};

template <class TSM>

class state_name_visitor {

public:

explicit state_name_visitor(const TSM& sm) : sm_{sm} {}

template <class TSub>

void operator()(boost::sml::aux::string<boost::sml::sm<TSub>>) const {

std::cout << boost::sml::aux::get_type_name<TSub>() << ':';

sm_.template visit_current_states<boost::sml::aux::identity<TSub>>(*this);

}

template <class TState>

void operator()(TState state) const {

std::cout << state.c_str() << '\n';

}

private:

const TSM& sm_;

};

int main() {

sml::sm<composite> sm{};

const auto state_name = state_name_visitor<decltype(sm)>{sm};

sm.process_event(e1{});

sm.visit_current_states(state_name); // s1

sm.process_event(e2{});

sm.visit_current_states(state_name); // sub:idle

sm.process_event(e3{});

sm.visit_current_states(state_name); // sub:sub1

sm.process_event(e4{});

sm.visit_current_states(state_name); // sub:terminate

sm.process_event(e5{});

sm.visit_current_states(state_name); // terminate

}