expire_cache 0.1.17

use std::{borrow::Borrow, future::Future, hash::Hash, sync::atomic::Ordering};

use crate::Map;

pub trait GetOrInitAsync: Map {
  fn get_or_init_async<'a, Q, E, Fut>(
    &'a self,
    key: &Q,
    func: impl FnOnce(&Q) -> Fut,
  ) -> impl Future<Output = Result<Self::RefVal<'a>, E>>
  where
    Self::Key: Borrow<Q>,
    Q: ToOwned<Owned = Self::Key> + Hash + Eq + ?Sized,
    Fut: Future<Output = Result<Self::Val, E>>;
}

impl<T: GetOrInitAsync + 'static> crate::Expire<T> {
  pub async fn get_or_init_async<'a, Q, E, Fut>(
    &'a self,
    key: &Q,
    func: impl FnOnce(&Q) -> Fut,
  ) -> Result<T::RefVal<'a>, E>
  where
    T::Key: Borrow<Q>,
    Q: ToOwned<Owned = T::Key> + Hash + Eq + ?Sized,
    Fut: Future<Output = Result<T::Val, E>>,
  {
    let inner = self.inner();
    let pos = inner.pos.load(Ordering::Relaxed);
    if let Some(v) = inner.cache[pos].get(key) {
      return Ok(v);
    }
    if let Some(v) = inner.cache[1 - pos].get(key) {
      return Ok(v);
    }
    inner.cache[pos].get_or_init_async(key, func).await
  }
}