use futures::unsync::mpsc;
use futures::{Async, Future, Poll, Stream};
use tokio::executor::current_thread::spawn;

use super::{IntoService, Service};

pub struct StreamDispatcher<S: Stream, T> {
    stream: S,
    service: T,
    item: Option<Result<S::Item, S::Error>>,
    stop_rx: mpsc::UnboundedReceiver<()>,
    stop_tx: mpsc::UnboundedSender<()>,
}

impl<S, T> StreamDispatcher<S, T>
where
    S: Stream,
    T: Service<Request = Result<S::Item, S::Error>, Response = (), Error = ()>,
    T::Future: 'static,
{
    pub fn new<F: IntoService<T>>(stream: S, service: F) -> Self {
        let (stop_tx, stop_rx) = mpsc::unbounded();
        StreamDispatcher {
            stream,
            item: None,
            service: service.into_service(),
            stop_rx,
            stop_tx,
        }
    }
}

impl<S, T> Future for StreamDispatcher<S, T>
where
    S: Stream,
    T: Service<Request = Result<S::Item, S::Error>, Response = (), Error = ()>,
    T::Future: 'static,
{
    type Item = ();
    type Error = ();

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        if let Ok(Async::Ready(Some(_))) = self.stop_rx.poll() {
            return Ok(Async::Ready(()));
        }

        let mut item = self.item.take();
        loop {
            if item.is_some() {
                match self.service.poll_ready()? {
                    Async::Ready(_) => spawn(StreamDispatcherService {
                        fut: self.service.call(item.take().unwrap()),
                        stop: self.stop_tx.clone(),
                    }),
                    Async::NotReady => {
                        self.item = item;
                        return Ok(Async::NotReady);
                    }
                }
            }
            match self.stream.poll() {
                Ok(Async::Ready(Some(el))) => item = Some(Ok(el)),
                Err(err) => item = Some(Err(err)),
                Ok(Async::NotReady) => return Ok(Async::NotReady),
                Ok(Async::Ready(None)) => return Ok(Async::Ready(())),
            }
        }
    }
}

struct StreamDispatcherService<F: Future> {
    fut: F,
    stop: mpsc::UnboundedSender<()>,
}

impl<F: Future> Future for StreamDispatcherService<F> {
    type Item = ();
    type Error = ();

    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
        match self.fut.poll() {
            Ok(Async::Ready(_)) => Ok(Async::Ready(())),
            Ok(Async::NotReady) => Ok(Async::NotReady),
            Err(_) => {
                let _ = self.stop.unbounded_send(());
                Ok(Async::Ready(()))
            }
        }
    }
}