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use crate::reactor::*;
use derive_deref::{Deref, DerefMut};
use futures::executor::block_on;
use futures::sink::{Sink, SinkExt};
use futures::task::{Context, Poll};
use std::{ops::DerefMut, pin::Pin};

#[derive(Deref, DerefMut)]
struct SinkAsReactor<T> {
    sink: T,
}

impl<S, T> Reactor<S> for SinkAsReactor<T>
where
    S: Clone,
    T: Sink<S> + Unpin,
{
    type Error = T::SinkError;

    fn react(&mut self, state: &S) -> Result<(), Self::Error> {
        block_on(self.send(state.clone()))
    }
}

impl<S, T> Sink<S> for SinkAsReactor<T>
where
    T: Sink<S> + Unpin,
{
    type SinkError = T::SinkError;

    fn poll_ready(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::SinkError>> {
        Pin::new(&mut self.sink).poll_ready(cx)
    }

    fn start_send(mut self: Pin<&mut Self>, state: S) -> Result<(), Self::SinkError> {
        Pin::new(&mut self.sink).start_send(state)
    }

    fn poll_flush(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::SinkError>> {
        Pin::new(&mut self.sink).poll_flush(cx)
    }

    fn poll_close(
        mut self: Pin<&mut Self>,
        cx: &mut Context<'_>,
    ) -> Poll<Result<(), Self::SinkError>> {
        Pin::new(&mut self.sink).poll_close(cx)
    }
}

impl<S, E> dyn Reactor<S, Error = E>
where
    S: Clone,
{
    /// Adapts any type that implements [`Sink`] as a [`Reactor`] (requires [`async`]).
    ///
    /// [`async`]: index.html#optional-features
    ///
    /// # Example
    /// ```rust
    /// use reducer::*;
    /// use futures::channel::mpsc::channel;
    /// use futures::executor::block_on_stream;
    /// use std::thread;
    ///
    /// let (tx, rx) = channel(0);
    /// let mut reactor = Reactor::<Error = _>::from_sink(tx);
    ///
    /// thread::spawn(move || {
    ///     reactor.react(&1);
    ///     reactor.react(&1);
    ///     reactor.react(&3);
    ///     reactor.react(&5);
    ///     reactor.react(&8);
    /// });
    ///
    /// assert_eq!(block_on_stream(rx).collect::<Vec<_>>(), vec![1, 1, 3, 5, 8]);
    /// ```
    #[cfg(feature = "async")]
    pub fn from_sink<T>(
        sink: T,
    ) -> impl Reactor<S, Error = E> + Sink<S, SinkError = E> + DerefMut<Target = T>
    where
        T: Sink<S, SinkError = E> + Unpin,
    {
        SinkAsReactor { sink }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::mock::*;
    use proptest::*;

    proptest! {
        #[test]
        fn ok(states: Vec<u8>) {
            let mut reactor = Reactor::<Error = _>::from_sink(Mock::<_>::default());

            for (i, state) in states.iter().enumerate() {
                assert_eq!(react(&mut reactor, state), Ok(()));
                assert_eq!(reactor.calls(), &states[0..=i])
            }
        }
    }

    proptest! {
        #[test]
        fn err(state: u8, error: String) {
            let mut reactor = Reactor::<Error = _>::from_sink(Mock::default());
            reactor.fail_if(state, &error[..]);

            assert_eq!(react(&mut reactor, &state), Err(&error[..]));
            assert_eq!(reactor.calls(), &[state]);
        }
    }
}