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#[derive(Debug, Default)]
pub struct TimeTracker {
    now_sec_f64: f64,
    now_msec_i64: i64,
}

/// Maximum number of seconds we can track. This is related
/// to the limit of a mantissa in 64-bit IEEE numbers, which
/// is about 10^15. Since we count in msec, we have to divide
/// to take away 3 digits. This is still several centuries.
pub const TIME_TRACKER_MAX_SEC: f64 = 1e12;

impl TimeTracker {
    pub fn new() -> TimeTracker {
        TimeTracker::default()
    }

    pub fn add(&mut self, delta: f64) {
        self.now_sec_f64 += delta;
        if self.now_sec_f64 < 0.0 || self.now_sec_f64 >= TIME_TRACKER_MAX_SEC {
            self.now_sec_f64 = 0.0;
        }
        self.now_msec_i64 = (self.now_sec_f64 * 1000.0) as i64;
    }

    pub fn now_sec(self) -> f64 {
        self.now_sec_f64
    }

    pub fn now_msec(self) -> i64 {
        self.now_msec_i64
    }
}

impl std::fmt::Display for TimeTracker {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}.{}",
            self.now_msec_i64 / 1000,
            self.now_msec_i64 % 1000
        )
    }
}