C++ Tri-state enum method which is nice to use, but bad to write.

tristate.cpp

#include <stdint.h>
#include <stdio.h>

// The processes vision can be running
enum struct Process : uint16_t {
  PROCESS_1,
  PROCESS_2,
};

enum struct Function : uint16_t {
  FUNCTION_1,
  FUNCTION_2,
};

// The steps building the function.
namespace steps {
enum struct Function_1 : uint16_t {
  IDLE,
  STARTUP,
  SHUTDOWN,
};

enum struct Function_2 : uint16_t {
  INIT,
  DOING_STUFF,
  ABORTED,
};
}  // namespace steps

union Step {
  steps::Function_1 func_1;
  steps::Function_2 func_2;
  uint16_t value;
};

struct Status {
  Process process;
  Function function;
  Step step;
};

#define STEP(name, config)                                                  \
  static Status name()  {                                                   \
    return {process_, function_, {.value = static_cast<uint16_t>(config)}}; \
  }


namespace Process1 {
  static constexpr Process process_ = Process::PROCESS_1;
  namespace Function1 {
    static constexpr Function function_ = Function::FUNCTION_1;
    STEP(Idle, steps::Function_1::IDLE)
    STEP(Startup, steps::Function_1::STARTUP)
    STEP(Shutdown, steps::Function_1::SHUTDOWN)
  };
};

namespace Process2 {
  static constexpr Process process_ = Process::PROCESS_2;
  namespace Function1 {
    static constexpr Function function_ = Function::FUNCTION_1;
    STEP(Idle, steps::Function_1::IDLE)
    STEP(Startup, steps::Function_1::STARTUP)
    STEP(Shutdown, steps::Function_1::SHUTDOWN)
  };

  namespace Function2 {
    static constexpr Function function_ = Function::FUNCTION_2;
    STEP(Idle, steps::Function_2::INIT)
    STEP(Startup, steps::Function_2::DOING_STUFF)
    STEP(Shutdown, steps::Function_2::ABORTED)
  };
};

#undef STEP

int main() {
  Status status = Process2::Function1::Shutdown();
  printf("Status: %d %d %d\n", (uint16_t) status.process, (uint16_t) status.function, status.step.value);
}