struct Init;
struct Master;
struct Backup;

enum Event {
    Startup,
    Shutdown,
    MasterDownTimer,
    AdvertTimer,
}

impl Init {
    fn new() -> Init {
        Init {}
    }
}

trait VRRPv2StateMachine {
    fn next(&self, event: Event) -> impl VRRPv2StateMachine;
}

impl VRRPv2StateMachine for Init {
    fn next(&self, _event: Event) -> impl VRRPv2StateMachine {
        Master {}
    }
}

impl VRRPv2StateMachine for Master {
    fn next(&self, _event: Event) -> impl VRRPv2StateMachine {
        Backup {}
    }
}

impl VRRPv2StateMachine for Backup {
    fn next(&self, _event: Event) -> impl VRRPv2StateMachine {
        Init {}
    }
}

pub fn run() {
    let sm = Init::new();
    loop {
        let _ = sm.next(Event::Startup);
    }
}