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#![doc(html_root_url = "https://docs.rs/tower-pipeline/0.1.0")]
#![warn(
missing_debug_implementations,
missing_docs,
rust_2018_idioms,
unreachable_pub
)]
#![deny(broken_intra_doc_links)]
#![allow(elided_lifetimes_in_paths, clippy::type_complexity)]
#![cfg_attr(test, allow(clippy::float_cmp))]
#![cfg_attr(docsrs, feature(doc_cfg))]
use futures_util::ready;
use pin_project_lite::pin_project;
use std::future::Future;
use std::{
pin::Pin,
task::{Context, Poll},
};
use tower_service::Service;
#[derive(Debug, Clone, Copy, Default)]
pub struct Pipeline<A, B> {
first: A,
second: B,
}
impl<A, B> Pipeline<A, B> {
pub fn new(first: A, second: B) -> Self {
Self { first, second }
}
pub fn first_as_ref(&self) -> &A {
&self.first
}
pub fn first_as_mut(&mut self) -> &mut A {
&mut self.first
}
pub fn into_first(self) -> A {
self.first
}
pub fn second_as_ref(&self) -> &B {
&self.second
}
pub fn second_as_mut(&mut self) -> &mut B {
&mut self.second
}
pub fn into_second(self) -> B {
self.second
}
}
impl<R, A, B> Service<R> for Pipeline<A, B>
where
A: Service<R>,
B: Service<A::Response> + Clone,
A::Error: Into<B::Error>,
{
type Response = B::Response;
type Error = B::Error;
type Future = ResponseFuture<R, A, B>;
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
self.first.poll_ready(cx).map_err(Into::into)
}
fn call(&mut self, req: R) -> Self::Future {
ResponseFuture {
state: State::FirstFuturePending {
future: self.first.call(req),
},
second: Some(self.second.clone()),
}
}
}
pin_project! {
pub struct ResponseFuture<R, A, B>
where
A: Service<R>,
B: Service<A::Response>,
{
#[pin]
state: State<R, A, B>,
second: Option<B>,
}
}
pin_project! {
#[project = StateProj]
enum State<R, A, B>
where
A: Service<R>,
B: Service<A::Response>,
{
FirstFuturePending { #[pin] future: A::Future },
PollReadySecond { first_res: Option<A::Response>, second: B },
SecondFuturePending { #[pin] future: B::Future },
}
}
impl<R, A, B> Future for ResponseFuture<R, A, B>
where
A: Service<R>,
B: Service<A::Response>,
A::Error: Into<B::Error>,
{
type Output = Result<B::Response, B::Error>;
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
loop {
let mut this = self.as_mut().project();
let new_state = match this.state.as_mut().project() {
StateProj::FirstFuturePending { future } => {
let first_res = ready!(future.poll(cx).map_err(Into::into)?);
let second = this.second.take().unwrap();
State::PollReadySecond {
first_res: Some(first_res),
second,
}
}
StateProj::PollReadySecond { first_res, second } => {
let _ready: () = ready!(second.poll_ready(cx)?);
State::SecondFuturePending {
future: second.call(first_res.take().unwrap()),
}
}
StateProj::SecondFuturePending { future } => return future.poll(cx),
};
this.state.set(new_state);
}
}
}
pub trait PipelineExt<R>: Service<R> {
fn pipeline<B>(self, second: B) -> Pipeline<Self, B>
where
Self: Service<R> + Sized,
B: Service<Self::Response> + Clone,
Self::Error: Into<B::Error>;
}
impl<R, T> PipelineExt<R> for T
where
T: Service<R>,
{
fn pipeline<B>(self, second: B) -> Pipeline<Self, B>
where
Self: Service<R> + Sized,
B: Service<Self::Response> + Clone,
Self::Error: Into<B::Error>,
{
Pipeline::new(self, second)
}
}