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use crate::{Dt, Scale};
use chrono::{DateTime, Datelike, Duration, TimeDelta, Timelike, Utc};
impl Dt {
/// Converts this [`Dt`] to a [`chrono::DateTime`].
///
/// - Sub-nanosecond attoseconds are truncated toward zero.
/// - Saturates at the minimum/maximum representable `DateTime<Utc>`
/// (roughly years 1678–2262) if the instant is out of range.
#[inline]
pub fn to_chrono_datetime_utc(&self) -> DateTime<Utc> {
DateTime::<Utc>::from_timestamp_nanos(Dt::to_i64(
self.target(Scale::UTC).to_unix().to_ns().0,
))
}
/// Creates a TAI [`Dt`] from a [`chrono::DateTime`].
///
/// This is the inverse of [`Dt::to_chrono_datetime_utc`].
pub fn from_chrono_datetime_utc(dt: DateTime<Utc>) -> Dt {
let yr = dt.year() as i64;
let mo = dt.month().clamp(1, 12) as u8;
let day = dt.day().clamp(1, 31) as u8;
let hr = dt.hour().clamp(0, 23) as u8;
let min = dt.minute().clamp(0, 59) as u8;
let sec = dt.second().clamp(0, 60) as u8;
let subsec_nanos = dt.nanosecond();
let attos = Dt::from_ns_floor(subsec_nanos as i128, 0, Scale::TAI).to_attos();
Dt::from_ymd(yr, mo, day, Scale::UTC, hr, min, sec, Dt::to_u64(attos))
}
/// Creates a [`Dt`] from a [`chrono::Duration`] (nanosecond precision).
pub fn from_chrono_duration(dur: Duration) -> Dt {
match dur.num_nanoseconds() {
Some(ns) => Self::from_ns_floor(ns as i128, 0, Scale::TAI),
None => {
let ns = if dur > Duration::zero() {
i64::MAX
} else {
i64::MIN
};
Self::from_ns_floor(ns as i128, 0, Scale::TAI)
}
}
}
/// Converts this [`Dt`] to a `chrono::Duration` (nanosecond precision).
///
/// - Sub-nanosecond attoseconds are **truncated toward zero**.
/// - The conversion is fully exact up to the nanosecond (128-bit integer arithmetic).
/// - **Saturates** at `chrono::Duration::MIN` / `chrono::Duration::MAX`
/// (roughly ±292 million years) if the value is out of range.
#[inline]
pub fn to_chrono_duration(&self) -> Duration {
TimeDelta::nanoseconds(Dt::to_i64(self.to_ns().0))
}
}