freestanding

tower/src/lib.rs

@@ -1,6 +1,39 @@
-pub mod balance;
+use std::marker::PhantomData;
+use std::{
+    pin::Pin,
+    task::{Context, Poll},
+};
 
-use futures_core::TryStream;
+use core::ops::DerefMut;
+
+pub trait Stream {
+    type Item;
+}
+
+impl<S: ?Sized + Stream + Unpin> Stream for &mut S {
+    type Item = S::Item;
+}
+
+impl<P> Stream for Pin<P>
+where
+    P: DerefMut + Unpin,
+    P::Target: Stream,
+{
+    type Item = <P::Target as Stream>::Item;
+}
+
+pub trait TryStream: Stream {
+    type Ok;
+    type Error;
+}
+
+impl<S, T, E> TryStream for S
+where
+    S: ?Sized + Stream<Item = Result<T, E>>,
+{
+    type Ok = T;
+    type Error = E;
+}
 
 pub type BoxError = Box<dyn std::error::Error + Send + Sync>;
 
@@ -21,7 +54,6 @@ where
 }
 
 pub trait Service<Request> {
-    type Response;
     type Error;
     type Future;
 }
@@ -29,7 +61,82 @@ pub trait Service<Request> {
 pub trait MakeService<Target, Request> {
     type Response;
     type Error;
-    type Service: Service<Request, Response = Self::Response, Error = Self::Error>;
+    type Service: Service<Request, Error = Self::Error>;
     type Future;
 }
 
+pub struct Balance<D, Req> {
+    _req: PhantomData<(D, Req)>,
+}
+
+impl<D, Req> Balance<D, Req>
+where
+    D: Discover,
+    D::Service: Service<Req>,
+    <D::Service as Service<Req>>::Error: Into<crate::BoxError>,
+{
+    pub fn new(_: D) -> Self {
+        todo!()
+    }
+}
+
+impl<D, Req> Service<Req> for Balance<D, Req> {
+    type Error = crate::BoxError;
+    type Future = std::future::Ready<()>;
+}
+
+pub struct PoolDiscoverer<MS, Target, Request>
+where
+    MS: MakeService<Target, Request>,
+{
+    _p: PhantomData<(MS, Target, Request)>,
+}
+
+impl<MS, Target, Request> Stream for PoolDiscoverer<MS, Target, Request>
+where
+    MS: MakeService<Target, Request>,
+{
+    type Item = Result<(usize, DropNotifyService<MS::Service>), MS::Error>;
+}
+
+pub struct Builder {}
+
+impl Builder {
+    pub fn build<MS, Target, Request>() -> ()
+    where
+        MS: MakeService<Target, Request>,
+        MS::Error: Into<crate::BoxError>,
+    {
+        let d: PoolDiscoverer<MS, Target, Request> = todo!();
+
+        // THE CRITICAL STATEMENT
+        let x = Balance::new(Box::pin(d));
+
+        todo!()
+    }
+}
+
+pub struct Pool<MS, Target, Request> {
+    balance: (MS, Target, Request),
+}
+
+type PinBalance<S, Request> = Balance<Pin<Box<S>>, Request>;
+
+impl<MS, Target, Req> Service<Req> for Pool<MS, Target, Req>
+where
+    MS: MakeService<Target, Req>,
+    MS::Error: Into<crate::BoxError>,
+    Target: Clone,
+{
+    type Error = <PinBalance<PoolDiscoverer<MS, Target, Req>, Req> as Service<Req>>::Error;
+    type Future = <PinBalance<PoolDiscoverer<MS, Target, Req>, Req> as Service<Req>>::Future;
+}
+
+pub struct DropNotifyService<Svc> {
+    svc: Svc,
+}
+
+impl<Request, Svc: Service<Request>> Service<Request> for DropNotifyService<Svc> {
+    type Future = Svc::Future;
+    type Error = Svc::Error;
+}