utcnow 0.2.2

use core::fmt;

use wasi::{clock_time_get, Errno, CLOCKID_REALTIME};

use crate::{Result, UtcTime};

pub(crate) const IMPLEMENTED: bool = true;
pub(crate) const INFALLIBLE: bool = false;

#[allow(clippy::cast_possible_truncation)]
#[allow(clippy::cast_possible_wrap)]
pub(crate) fn utcnow() -> Result<UtcTime> {
    let nanos = unsafe { clock_time_get(CLOCKID_REALTIME, 100) }.map_err(OsError)?;
    let secs = nanos.div_euclid(1_000_000_000) as i64;
    let nanos = nanos.rem_euclid(1_000_000_000) as u32;
    Ok(unsafe { UtcTime::new_unchecked(secs, nanos) })
}

#[derive(Debug, Clone, Copy)]
pub(crate) struct OsError(Errno);

impl fmt::Display for OsError {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "could not query clock_gettime(): {}", self.0.message())
    }
}