bach 0.1.2

Discrete-event simulation environment for async workflows
Documentation 
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use super::{CloseError, PopError, PushError, Pushable};
use crate::{
    ext::*,
    time::{Duration, Instant},
    tracing::{debug_span, Instrument},
};
use std::{marker::PhantomData, task::Context};

pub trait Latency<T> {
    fn for_value(&self, value: &T) -> Duration;
}

impl<T> Latency<T> for Duration {
    fn for_value(&self, _value: &T) -> Duration {
        *self
    }
}

pub struct Queue<T, Q, L> {
    inner: Q,
    latency: L,
    value: PhantomData<T>,
}

impl<T, Q, L> Queue<T, Q, L> {
    pub fn new(inner: Q, latency: L) -> Self {
        Self {
            inner,
            latency,
            value: PhantomData,
        }
    }

    pub fn inner(&self) -> &Q {
        &self.inner
    }
}

impl<T, Q, L> Queue<T, Q, L>
where
    Q: super::Conditional<(Instant, T)>,
    L: Latency<T>,
{
    fn push_with_latency<P: Pushable<T> + ?Sized>(
        &mut self,
        value: &mut P,
    ) -> Result<(Instant, Option<T>), PushError> {
        self.inner.check_push()?;

        let value = value.produce();
        let latency = self.latency.for_value(&value);
        let target = Instant::now() + latency;
        let value = (target, value);

        match self.inner.push_lazy(&mut Some(value))? {
            None => Ok((target, None)),
            Some((_t, value)) => Ok((target, Some(value))),
        }
    }
}

impl<T, Q, L> super::Queue<T> for Queue<T, Q, L>
where
    Q: super::Conditional<(Instant, T)>,
    L: Latency<T>,
    T: 'static + Sync + Send,
{
    fn push_lazy(&mut self, value: &mut dyn Pushable<T>) -> Result<Option<T>, PushError> {
        let (_target, value) = self.push_with_latency(value)?;
        Ok(value)
    }

    fn push_with_notify(
        &mut self,
        value: &mut dyn Pushable<T>,
        cx: &mut Context,
    ) -> Result<Option<T>, PushError> {
        let (target, value) = self.push_with_latency(value)?;

        if target == Instant::now() {
            cx.waker().wake_by_ref();
            return Ok(value);
        }

        let waker = cx.waker().clone();
        async move {
            crate::time::sleep_until(target).await;
            waker.wake();
        }
        .instrument(debug_span!("message"))
        .spawn();

        Ok(value)
    }

    fn pop(&mut self) -> Result<T, PopError> {
        let now = Instant::now();
        let (_t, value) = self.inner.find_pop(|(t, _)| t.le(&now))?;
        Ok(value)
    }

    fn pop_with_notify(&mut self, cx: &mut Context) -> Result<T, PopError> {
        let value = self.pop()?;
        cx.waker().wake_by_ref();
        Ok(value)
    }

    fn close(&mut self) -> Result<(), CloseError> {
        self.inner.close()
    }

    fn is_closed(&self) -> bool {
        self.inner.is_closed()
    }

    fn is_empty(&self) -> bool {
        self.inner.is_empty()
    }

    fn is_full(&self) -> bool {
        self.inner.is_full()
    }

    fn len(&self) -> usize {
        self.inner.len()
    }

    fn capacity(&self) -> Option<usize> {
        self.inner.capacity()
    }
}