//! Service that applies a timeout to requests.
//!
//! If the response does not complete within the specified timeout, the response
//! will be aborted.
use std::future::Future;
use std::marker::PhantomData;
use std::pin::Pin;
use std::task::{Context, Poll};
use std::{fmt, time};

use actix_rt::time::{delay_for, Delay};
use actix_service::{IntoService, Service, Transform};
use futures_util::future::{ok, Ready};

/// Applies a timeout to requests.
#[derive(Debug)]
pub struct Timeout<E = ()> {
    timeout: time::Duration,
    _t: PhantomData<E>,
}

/// Timeout error
pub enum TimeoutError<E> {
    /// Service error
    Service(E),
    /// Service call timeout
    Timeout,
}

impl<E> From<E> for TimeoutError<E> {
    fn from(err: E) -> Self {
        TimeoutError::Service(err)
    }
}

impl<E: fmt::Debug> fmt::Debug for TimeoutError<E> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            TimeoutError::Service(e) => write!(f, "TimeoutError::Service({:?})", e),
            TimeoutError::Timeout => write!(f, "TimeoutError::Timeout"),
        }
    }
}

impl<E: fmt::Display> fmt::Display for TimeoutError<E> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            TimeoutError::Service(e) => e.fmt(f),
            TimeoutError::Timeout => write!(f, "Service call timeout"),
        }
    }
}

impl<E: PartialEq> PartialEq for TimeoutError<E> {
    fn eq(&self, other: &TimeoutError<E>) -> bool {
        match self {
            TimeoutError::Service(e1) => match other {
                TimeoutError::Service(e2) => e1 == e2,
                TimeoutError::Timeout => false,
            },
            TimeoutError::Timeout => matches!(other, TimeoutError::Timeout),
        }
    }
}

impl<E> Timeout<E> {
    pub fn new(timeout: time::Duration) -> Self {
        Timeout {
            timeout,
            _t: PhantomData,
        }
    }
}

impl<E> Clone for Timeout<E> {
    fn clone(&self) -> Self {
        Timeout::new(self.timeout)
    }
}

impl<S, E> Transform<S> for Timeout<E>
where
    S: Service,
{
    type Request = S::Request;
    type Response = S::Response;
    type Error = TimeoutError<S::Error>;
    type InitError = E;
    type Transform = TimeoutService<S>;
    type Future = Ready<Result<Self::Transform, Self::InitError>>;

    fn new_transform(&self, service: S) -> Self::Future {
        ok(TimeoutService {
            service,
            timeout: self.timeout,
        })
    }
}

/// Applies a timeout to requests.
#[derive(Debug, Clone)]
pub struct TimeoutService<S> {
    service: S,
    timeout: time::Duration,
}

impl<S> TimeoutService<S>
where
    S: Service,
{
    pub fn new<U>(timeout: time::Duration, service: U) -> Self
    where
        U: IntoService<S>,
    {
        TimeoutService {
            timeout,
            service: service.into_service(),
        }
    }
}

impl<S> Service for TimeoutService<S>
where
    S: Service,
{
    type Request = S::Request;
    type Response = S::Response;
    type Error = TimeoutError<S::Error>;
    type Future = TimeoutServiceResponse<S>;

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

    fn call(&mut self, request: S::Request) -> Self::Future {
        TimeoutServiceResponse {
            fut: self.service.call(request),
            sleep: delay_for(self.timeout),
        }
    }
}

/// `TimeoutService` response future
#[pin_project::pin_project]
#[derive(Debug)]
pub struct TimeoutServiceResponse<T: Service> {
    #[pin]
    fut: T::Future,
    sleep: Delay,
}

impl<T> Future for TimeoutServiceResponse<T>
where
    T: Service,
{
    type Output = Result<T::Response, TimeoutError<T::Error>>;

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

        // First, try polling the future
        match this.fut.poll(cx) {
            Poll::Ready(Ok(v)) => return Poll::Ready(Ok(v)),
            Poll::Ready(Err(e)) => return Poll::Ready(Err(TimeoutError::Service(e))),
            Poll::Pending => {}
        }

        // Now check the sleep
        match Pin::new(&mut this.sleep).poll(cx) {
            Poll::Pending => Poll::Pending,
            Poll::Ready(_) => Poll::Ready(Err(TimeoutError::Timeout)),
        }
    }
}

#[cfg(test)]
mod tests {
    use std::task::{Context, Poll};
    use std::time::Duration;

    use super::*;
    use actix_service::{apply, fn_factory, Service, ServiceFactory};
    use futures_util::future::{ok, FutureExt, LocalBoxFuture};

    struct SleepService(Duration);

    impl Service for SleepService {
        type Request = ();
        type Response = ();
        type Error = ();
        type Future = LocalBoxFuture<'static, Result<(), ()>>;

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

        fn call(&mut self, _: ()) -> Self::Future {
            actix_rt::time::delay_for(self.0)
                .then(|_| ok::<_, ()>(()))
                .boxed_local()
        }
    }

    #[actix_rt::test]
    async fn test_success() {
        let resolution = Duration::from_millis(100);
        let wait_time = Duration::from_millis(50);

        let mut timeout = TimeoutService::new(resolution, SleepService(wait_time));
        assert_eq!(timeout.call(()).await, Ok(()));
    }

    #[actix_rt::test]
    async fn test_timeout() {
        let resolution = Duration::from_millis(100);
        let wait_time = Duration::from_millis(500);

        let mut timeout = TimeoutService::new(resolution, SleepService(wait_time));
        assert_eq!(timeout.call(()).await, Err(TimeoutError::Timeout));
    }

    #[actix_rt::test]
    async fn test_timeout_new_service() {
        let resolution = Duration::from_millis(100);
        let wait_time = Duration::from_millis(500);

        let timeout = apply(
            Timeout::new(resolution),
            fn_factory(|| ok::<_, ()>(SleepService(wait_time))),
        );
        let mut srv = timeout.new_service(&()).await.unwrap();

        assert_eq!(srv.call(()).await, Err(TimeoutError::Timeout));
    }
}