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use std::{
    cmp::Ordering,
    time::{Duration, Instant},
};

pub const INFINITE_DURATION: Duration = Duration::new(u64::MAX, 1_000_000_000 - 1);

#[derive(Clone, Copy, PartialEq, Eq)]
pub enum TimerDuration {
    Elapsed,
    Real(Duration),
    Infinite,
}
impl TimerDuration {
    pub fn from_difference(a: TimerDuration, b: Duration) -> TimerDuration {
        let a = a.to_real();
        if a < b {
            TimerDuration::Elapsed
        } else {
            TimerDuration::Real(a - b)
        }
    }

    pub fn to_real(&self) -> Duration {
        match *self {
            Self::Real(d) if d > Duration::ZERO => d,
            Self::Infinite => INFINITE_DURATION,
            _ => Duration::new(0, 0),
        }
    }
}
impl From<Duration> for TimerDuration {
    fn from(value: Duration) -> Self {
        if value == Duration::ZERO {
            return Self::Elapsed;
        }
        Self::Real(value)
    }
}
impl PartialOrd for TimerDuration {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}
impl Ord for TimerDuration {
    fn cmp(&self, other: &Self) -> Ordering {
        match (self, other) {
            (TimerDuration::Elapsed, TimerDuration::Elapsed) => Ordering::Equal,
            (TimerDuration::Elapsed, _) => Ordering::Less,
            (TimerDuration::Real(_), TimerDuration::Elapsed) => Ordering::Greater,
            (TimerDuration::Real(a), TimerDuration::Real(b)) => a.cmp(b),
            (TimerDuration::Real(_), TimerDuration::Infinite) => Ordering::Less,
            (TimerDuration::Infinite, TimerDuration::Infinite) => Ordering::Equal,
            (TimerDuration::Infinite, _) => Ordering::Greater,
        }
    }
}

#[derive(Clone, Copy)]
pub struct Timer(Instant, TimerDuration);
impl Timer {
    pub fn new(d: TimerDuration) -> Self {
        Self(Instant::now(), d)
    }

    pub fn time_elapsed(&self) -> Duration {
        self.0.elapsed()
    }
}

pub trait Timed {
    fn has_elapsed(&self) -> bool;
    fn time_left(&self) -> TimerDuration;
}
impl Timed for Timer {
    fn has_elapsed(&self) -> bool {
        self.0.elapsed() >= self.1.to_real()
    }
    fn time_left(&self) -> TimerDuration {
        TimerDuration::from_difference(self.1, self.0.elapsed())
    }
}