rok-cache 0.1.0

use std::{
    future::Future,
    pin::Pin,
    sync::Arc,
    task::{Context, Poll},
};

use axum::http::Request;
use tower::{Layer, Service};

use crate::{
    cache::scope_cache,
    driver::{CacheHandle, Driver},
};

/// Tower layer that scopes a `CacheHandle` into every request via task-local
/// storage. After installing this layer, call `Cache::get/set/remember` from
/// anywhere inside a request handler without threading a handle through params.
#[derive(Clone)]
pub struct CacheLayer {
    handle: Arc<CacheHandle>,
}

impl CacheLayer {
    /// Build a layer from a pre-constructed driver and key prefix.
    pub fn new(driver: Driver, prefix: impl Into<String>) -> Self {
        Self {
            handle: Arc::new(CacheHandle::new(driver, prefix)),
        }
    }
}

impl<S> Layer<S> for CacheLayer {
    type Service = CacheService<S>;

    fn layer(&self, inner: S) -> Self::Service {
        CacheService {
            inner,
            handle: self.handle.clone(),
        }
    }
}

#[derive(Clone)]
pub struct CacheService<S> {
    inner: S,
    handle: Arc<CacheHandle>,
}

impl<S, ReqBody> Service<Request<ReqBody>> for CacheService<S>
where
    S: Service<Request<ReqBody>> + Send + Clone + 'static,
    S::Future: Send + 'static,
    ReqBody: Send + 'static,
{
    type Response = S::Response;
    type Error = S::Error;
    type Future = Pin<Box<dyn Future<Output = Result<S::Response, S::Error>> + Send + 'static>>;

    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.inner.poll_ready(cx)
    }

    fn call(&mut self, req: Request<ReqBody>) -> Self::Future {
        let handle = self.handle.clone();
        let future = self.inner.call(req);
        Box::pin(scope_cache(handle, future))
    }
}