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

trait Service<Request> {
    type Response;
    type Error;
    type Future: Future<Output = Result<Self::Response, Self::Error>>;
    // perhaps this should return a readiness token
    // that is then passed to `Call`?
    fn poll_ready(self: Pin<&mut Self>, ctx: Context) -> Poll<()>;
    fn call(self: Pin<&mut Self>, req: Request) -> Self::Future;
}