#[derive(Debug, Hash, Copy, Clone)]
enum Action {
    Begin(NaiveDateTime, usize),
    Asleep(NaiveDateTime),
    Wake(NaiveDateTime),
}

impl FromStr for Action {
    type Err = ();

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let (date, action) = s.split_at(18);
        let date = NaiveDateTime::parse_from_str(date, "[%Y-%m-%d %H:%M]").unwrap();

        Ok(match &action[1..] {
            "falls asleep" => Action::Asleep(date),
            "wakes up" => Action::Wake(date),
            _ => {
                let guard_id = action.split_whitespace().nth(1).unwrap()[1..]
                    .parse()
                    .unwrap();
                Action::Begin(date, guard_id)
            }
        })
    }
}