Simple WASM wait/sleep implementation

wait.rs

use crate::timers::set_timeout;
use std::{
    future::{poll_fn, Future},
    task::Poll,
};
use web_time::{Duration, SystemTime};

pub fn wait(duration: Duration) -> impl Future {
    let dest = SystemTime::now() + duration;
    let mut timer_was_set = false;

    poll_fn(move |cx| {
        if SystemTime::now() >= dest {
            return Poll::Ready(());
        }
        if timer_was_set {
            return Poll::Pending;
        }
        timer_was_set = true;

        let waker = cx.waker().clone();
        // see my timers gist
        set_timeout(
            Box::new(|| {
                waker.wake();
            }),
            duration,
        );

        Poll::Pending
    })
}