/// Benchmark various implementations of and_then

use criterion::{criterion_main, Criterion};
use futures_util::future::join_all;
use std::cell::{RefCell, UnsafeCell};
use std::task::{Context, Poll};
use std::rc::Rc;
use actix_service::{Service};
use actix_service::IntoService;
use std::future::Future;
use std::pin::Pin;
use futures_util::future::TryFutureExt;
use actix_service::boxed::BoxFuture;


/*
 * Test services A,B for AndThen service implementations
 */

async fn svc1(_: ()) -> Result<usize, ()> {
	Ok(1)
}

async fn svc2(req: usize) -> Result<usize, ()> {
	Ok(req + 1)
}

/*
 * AndThenUC - original AndThen service based on UnsafeCell
 * Cut down version of actix_service::AndThenService based on actix-service::Cell
 */


struct AndThenUC<A,B>(Rc<UnsafeCell<(A, B)>>);

impl<A,B> AndThenUC<A,B> {
	fn new(a: A, b: B) -> Self
	where
		A: Service,
		B: Service<Request = A::Response, Error = A::Error>,
	{
		Self(Rc::new(UnsafeCell::new((a,b))))
	}
}

impl<A,B> Clone for AndThenUC<A,B> {
	fn clone(&self) -> Self {
		Self(self.0.clone())
	}
}

impl<A,B> Service for AndThenUC<A,B>
where
    A: Service,
    B: Service<Request = A::Response, Error = A::Error>
{
	type Request = A::Request;
	type Response = B::Response;
	type Error = A::Error;
	type Future = AndThenServiceResponse<A,B>;

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

	fn call(&mut self, req: A::Request) -> Self::Future {
		let fut = unsafe { &mut *(*self.0).get() }.0.call(req);
		AndThenServiceResponse {
			state: State::A(fut, Some(self.0.clone()))
		}
	}
}

#[pin_project::pin_project]
pub(crate) struct AndThenServiceResponse<A, B>
where
    A: Service,
    B: Service<Request = A::Response, Error = A::Error>,
{
    #[pin]
    state: State<A, B>,
}

#[pin_project::pin_project]
enum State<A, B>
where
    A: Service,
    B: Service<Request = A::Response, Error = A::Error>,
{
    A(#[pin] A::Future, Option<Rc<UnsafeCell<(A, B)>>>),
    B(#[pin] B::Future),
    Empty,
}

impl<A, B> Future for AndThenServiceResponse<A, B>
where
    A: Service,
    B: Service<Request = A::Response, Error = A::Error>,
{
    type Output = Result<B::Response, A::Error>;

    #[pin_project::project]
    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let mut this = self.as_mut().project();

        #[project]
        match this.state.as_mut().project() {
            State::A(fut, b) => match fut.poll(cx)? {
                Poll::Ready(res) => {
                    let b = b.take().unwrap();
                    this.state.set(State::Empty); // drop fut A
                    let fut = unsafe { &mut (*b.get()).1 }.call(res);
                    this.state.set(State::B(fut));
                    self.poll(cx)
                }
                Poll::Pending => Poll::Pending,
            },
            State::B(fut) => fut.poll(cx).map(|r| {
                this.state.set(State::Empty);
                r
            }),
            State::Empty => panic!("future must not be polled after it returned `Poll::Ready`"),
        }
    }
}


/*
 * AndThenRC - AndThen service based on RefCell
 */

 struct AndThenRC<A,B>(Rc<RefCell<(A, B)>>);

 impl<A,B> AndThenRC<A,B> {
	 fn new(a: A, b: B) -> Self
	 where
		 A: Service,
		 B: Service<Request = A::Response, Error = A::Error>,
	 {
		 Self(Rc::new(RefCell::new((a,b))))
	 }
 }
 
 impl<A,B> Clone for AndThenRC<A,B> {
	 fn clone(&self) -> Self {
		 Self(self.0.clone())
	 }
 }
 
 impl<A,B> Service for AndThenRC<A,B>
 where
	 A: Service,
	 B: Service<Request = A::Response, Error = A::Error>
 {
	 type Request = A::Request;
	 type Response = B::Response;
	 type Error = A::Error;
	 type Future = AndThenServiceResponseRC<A,B>;
 
	 fn poll_ready(&mut self, _: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
		 Poll::Ready(Ok(()))
	 }
 
	 fn call(&mut self, req: A::Request) -> Self::Future {
		 let fut = self.0.borrow_mut().0.call(req);
		 AndThenServiceResponseRC {
			 state: StateRC::A(fut, Some(self.0.clone()))
		 }
	 }
 }
 
 #[pin_project::pin_project]
 pub(crate) struct AndThenServiceResponseRC<A, B>
 where
	 A: Service,
	 B: Service<Request = A::Response, Error = A::Error>,
 {
	 #[pin]
	 state: StateRC<A, B>,
 }
 
 #[pin_project::pin_project]
 enum StateRC<A, B>
 where
	 A: Service,
	 B: Service<Request = A::Response, Error = A::Error>,
 {
	 A(#[pin] A::Future, Option<Rc<RefCell<(A, B)>>>),
	 B(#[pin] B::Future),
	 Empty,
 }
 
 impl<A, B> Future for AndThenServiceResponseRC<A, B>
 where
	 A: Service,
	 B: Service<Request = A::Response, Error = A::Error>,
 {
	 type Output = Result<B::Response, A::Error>;
 
	 #[pin_project::project]
	 fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
		 let mut this = self.as_mut().project();
 
		 #[project]
		 match this.state.as_mut().project() {
			 StateRC::A(fut, b) => match fut.poll(cx)? {
				 Poll::Ready(res) => {
					 let b = b.take().unwrap();
					 this.state.set(StateRC::Empty); // drop fut A
					 let fut = b.borrow_mut().1.call(res);
					 this.state.set(StateRC::B(fut));
					 self.poll(cx)
				 }
				 Poll::Pending => Poll::Pending,
			 },
			 StateRC::B(fut) => fut.poll(cx).map(|r| {
				 this.state.set(StateRC::Empty);
				 r
			 }),
			 StateRC::Empty => panic!("future must not be polled after it returned `Poll::Ready`"),
		 }
	 }
 }
 

 /*
 * AndThenRCFuture - AndThen service based on RefCell 
 * and standard futures::future::and_then combinator in a Box
 */

 struct AndThenRCFuture<A,B>(Rc<RefCell<(A, B)>>);

 impl<A,B> AndThenRCFuture<A,B> {
	 fn new(a: A, b: B) -> Self
	 where
		 A: Service,
		 B: Service<Request = A::Response, Error = A::Error>,
	 {
		 Self(Rc::new(RefCell::new((a,b))))
	 }
 }
 
 impl<A,B> Clone for AndThenRCFuture<A,B> {
	 fn clone(&self) -> Self {
		 Self(self.0.clone())
	 }
 }
 
 impl<A,B> Service for AndThenRCFuture<A,B>
 where
	A: Service + 'static,
	A::Future: 'static,
	B: Service<Request = A::Response, Error = A::Error> + 'static,
 	B::Future: 'static
 {
	 type Request = A::Request;
	 type Response = B::Response;
	 type Error = A::Error;
	 type Future = BoxFuture<Self::Response, Self::Error>;
 
	 fn poll_ready(&mut self, _: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
		 Poll::Ready(Ok(()))
	 }
 
	 fn call(&mut self, req: A::Request) -> Self::Future {
		 let fut = self.0.borrow_mut().0.call(req);
		 let core = self.0.clone();
		 let fut2 = move |res| (*core).borrow_mut().1.call(res);
		 Box::pin(
			fut.and_then(fut2)
		)
	 }
 }
 

/// Criterion Benchmark for async Service
/// Should be used from within criterion group:
/// ```rust,ignore
/// let mut criterion: ::criterion::Criterion<_> =
///     ::criterion::Criterion::default().configure_from_args();
/// bench_async_service(&mut criterion, ok_service(), "async_service_direct");
/// ```
///
/// Usable for benching Service wrappers:
/// Using minimum service code implementation we first measure
/// time to run minimum service, then measure time with wrapper.
///
/// Sample output
/// async_service_direct    time:   [1.0908 us 1.1656 us 1.2613 us]
pub fn bench_async_service<S>(c: &mut Criterion, srv: S, name: &str)
where
    S: Service<Request = (), Response = usize, Error = ()> + Clone + 'static,
{
    let mut rt = actix_rt::System::new("test");

    // start benchmark loops
    c.bench_function(name, move |b| {
        b.iter_custom(|iters| {
            let mut srvs: Vec<_> = (1..iters).map(|_| srv.clone()).collect();
            // exclude request generation, it appears it takes significant time vs call (3us vs 1us)
            let start = std::time::Instant::now();
            // benchmark body
            rt.block_on(async move {
				join_all(srvs.iter_mut().map(|srv| srv.call(()))).await
			});
            let elapsed = start.elapsed();
            // check that at least first request succeeded
            elapsed
        })
    });
}


pub fn service_benches() {
    let mut criterion: ::criterion::Criterion<_> =
        ::criterion::Criterion::default().configure_from_args();
    bench_async_service(&mut criterion, AndThenUC::new(svc1.into_service(), svc2.into_service()), "AndThen with UnsafeCell");
    bench_async_service(&mut criterion, AndThenRC::new(svc1.into_service(), svc2.into_service()), "AndThen with RefCell");
    bench_async_service(&mut criterion, AndThenUC::new(svc1.into_service(), svc2.into_service()), "AndThen with UnsafeCell");
    bench_async_service(&mut criterion, AndThenRC::new(svc1.into_service(), svc2.into_service()), "AndThen with RefCell");
    bench_async_service(&mut criterion, AndThenRCFuture::new(svc1.into_service(), svc2.into_service()), "AndThen with RefCell via future::and_then");
}

criterion_main!(service_benches);