use ConnectionError;
use frame::{Frame, StreamId};
use proto::*;

/// Tracks a connection's streams.
#[derive(Debug)]
pub struct StreamRecvOpen<T> {
    inner: T,
    max_concurrency: Option<u32>,
    initial_window_size: WindowSize,
    pending_refuse: Option<StreamId>,
}

impl<T> StreamRecvOpen<T> {

    pub fn new<U>(initial_window_size: WindowSize,
                  max_concurrency: Option<u32>,
                  inner: T)
            -> StreamRecvOpen<T>
        where T: Stream<Item = Frame, Error = ConnectionError>,
            T: Sink<SinkItem = Frame<U>, SinkError = ConnectionError>,
            T: ControlStreams,
    {
        StreamRecvOpen {
            inner,
            max_concurrency,
            initial_window_size,
            pending_refuse: None,
        }
    }

}

impl<T, U> StreamRecvOpen<T>
    where T: Sink<SinkItem = Frame<U>, SinkError = ConnectionError>,
          T: ControlStreams,
{
    fn send_refusal(&mut self, id: StreamId) -> Poll<(), ConnectionError> {
        debug_assert!(self.pending_refuse.is_none());

        let f = frame::Reset::new(id, Reason::RefusedStream);
        match self.inner.start_send(f.into())? {
            AsyncSink::Ready => {
                self.inner.reset_stream(id, Reason::RefusedStream);
                Ok(Async::Ready(()))
            }
            AsyncSink::NotReady(_) => {
                self.pending_refuse = Some(id);
                Ok(Async::NotReady)
            }
        }
    }
}

/// Handles updates to `SETTINGS_MAX_CONCURRENT_STREAMS`.
///
/// > Indicates the maximum number of concurrent streams that the senderg will allow. This
/// > limit is directional: it applies to the number of streams that the sender permits
/// > the receiver to create. Initially, there is no limit to this value. It is
/// > recommended that this value be no smaller than 100, so as to not unnecessarily limit
/// > parallelism.
/// >
/// > A value of 0 for SETTINGS_MAX_CONCURRENT_STREAMS SHOULD NOT be treated as special by
/// > endpoints. A zero value does prevent the creation of new streams; however, this can
/// > also happen for any limit that is exhausted with active streams. Servers SHOULD only
/// > set a zero value for short durations; if a server does not wish to accept requests,
/// > closing the connection is more appropriate.
///
/// > An endpoint that wishes to reduce the value of SETTINGS_MAX_CONCURRENT_STREAMS to a
/// > value that is below the current number of open streams can either close streams that
/// > exceed the new value or allow streams to complete.
///
/// This module does NOT close streams when the setting changes.
impl<T> ApplySettings for StreamRecvOpen<T>
    where T: ApplySettings
{
    fn apply_local_settings(&mut self, set: &frame::SettingSet) -> Result<(), ConnectionError> {
        self.max_concurrency = set.max_concurrent_streams();
        self.initial_window_size = set.initial_window_size();
        self.inner.apply_local_settings(set)
    }

    fn apply_remote_settings(&mut self, set: &frame::SettingSet) -> Result<(), ConnectionError> {
        self.inner.apply_remote_settings(set)
    }
}

impl<T, U> Stream for StreamRecvOpen<T>
    where T: Stream<Item = Frame, Error = ConnectionError>,
          T: Sink<SinkItem = Frame<U>, SinkError = ConnectionError>,
          T: ControlStreams,
{
    type Item = T::Item;
    type Error = T::Error;

    fn poll(&mut self) -> Poll<Option<T::Item>, T::Error> {
        use frame::Frame::*;

        // Since there's only one slot for pending refused streams, it must be cleared
        // before polling  a frame from the transport.
        if let Some(id) = self.pending_refuse.take() {
            try_ready!(self.send_refusal(id));
        }

        loop {
            let frame = match try_ready!(self.inner.poll()) {
                None => return Ok(Async::Ready(None)),
                Some(f) => f,
            };

            let id = frame.stream_id();
            if id.is_zero() {
                return Ok(Async::Ready(Some(frame)));
            }

            if self.inner.get_reset(id).is_some() {
                // For now, just ignore frames on reset streams.
                // TODO tell the remote to knock it off?
                continue;
            }

            if T::is_valid_remote_id(id) {
                unimplemented!()
            }
        }
    }
}

impl<T, U> Sink for StreamRecvOpen<T>
    where T: Sink<SinkItem = Frame<U>, SinkError = ConnectionError>,
          T: ControlStreams,
{
    type SinkItem = T::SinkItem;
    type SinkError = T::SinkError;

    fn start_send(&mut self, frame: T::SinkItem) -> StartSend<T::SinkItem, T::SinkError> {
        use frame::Frame::*;

        // The local must complete refusing the remote stream before sending any other
        // frames.
        if let Some(id) = self.pending_refuse.take() {
            if self.send_refusal(id)?.is_not_ready() {
                return Ok(AsyncSink::NotReady(frame));
            }
        }

        let id = frame.stream_id();
        if !id.is_zero() {
            // enforced by StreamSend.
            debug_assert!(self.inner.get_reset(id).is_none());

            let eos = frame.is_end_stream();
        }

        self.inner.start_send(frame)
    }

    fn poll_complete(&mut self) -> Poll<(), T::SinkError> {
        if let Some(id) = self.pending_refuse.take() {
            try_ready!(self.send_refusal(id));
        }

        self.inner.poll_complete()
    }
}


impl<T, U> ReadySink for StreamRecvOpen<T>
    where T: Stream<Item = Frame, Error = ConnectionError>,
          T: Sink<SinkItem = Frame<U>, SinkError = ConnectionError>,
          T: ReadySink,
          T: ControlStreams,
{
    fn poll_ready(&mut self) -> Poll<(), ConnectionError> {
        if let Some(id) = self.pending_refuse.take() {
            try_ready!(self.send_refusal(id));
        }

        self.inner.poll_ready()
    }
}


    // Some(Headers(v)) => {
    //     let id = v.stream_id();
    //     let eos = v.is_end_stream();

    //     if self.get_reset(id).is_some() {
    //         // TODO send the remote errors when it sends us frames on reset
    //         // streams.
    //         continue;
    //     }

    //     if let Some(mut s) = self.get_active_mut(id) {
    //         let created = s.recv_headers(eos, self.initial_window_size)?;
    //         assert!(!created);
    //         return Ok(Async::Ready(Some(Headers(v))));
    //     }

    //     // Ensure that receiving this frame will not violate the local max
    //     // stream concurrency setting. Ensure that the stream is refused
    //     // before processing additional frames.
    //     if let Some(max) = self.max_concurrency {
    //         let max = max as usize;
    //         if !self.local.is_active(id) && self.local.active_count() >= max - 1 {
    //             // This frame would violate our local max concurrency, so reject
    //             // the stream.
    //             try_ready!(self.send_refusal(id));

    //             // Try to process another frame (hopefully for an active
    //             // stream).
    //             continue;
    //         }
    //     }

    //     let is_closed = {
    //         let stream = self.active_streams.entry(id)
    //             .or_insert_with(|| StreamState::default());

    //         let initialized =
    //             stream.recv_headers(eos, self.initial_window_size)?;

    //         if initialized {
    //             if !P::is_valid_remote_stream_id(id) {
    //                 return Err(Reason::ProtocolError.into());
    //             }
    //         }

    //         stream.is_closed()
    //     };

    //     if is_closed {
    //         self.active_streams.remove(id);
    //         self.reset_streams.insert(id, Reason::NoError);
    //     }

    //     return Ok(Async::Ready(Some(Headers(v))));
    // }

    // Some(Data(v)) => {
    //     let id = v.stream_id();

    //     if self.get_reset(id).is_some() {
    //         // TODO send the remote errors when it sends us frames on reset
    //         // streams.
    //         continue;
    //     }

    //     let is_closed = {
    //         let stream = match self.active_streams.get_mut(id) {
    //             None => return Err(Reason::ProtocolError.into()),
    //             Some(s) => s,
    //         };
    //         stream.recv_data(v.is_end_stream())?;
    //         stream.is_closed()
    //     };

    //     if is_closed {
    //         self.reset(id, Reason::NoError);
    //     }

    //     return Ok(Async::Ready(Some(Data(v))));
    // }

    // Some(Reset(v)) => {
    //     // Set or update the reset reason.
    //     self.reset(v.stream_id(), v.reason());
    //     return Ok(Async::Ready(Some(Reset(v))));
    // }

    // Some(f) => {
    //     let id = f.stream_id();

    //     if self.get_reset(id).is_some() {
    //         // TODO send the remote errors when it sends us frames on reset
    //         // streams.
    //         continue;
    //     }

    //     return Ok(Async::Ready(Some(f)));
    // }

    // None => {
    //     return Ok(Async::Ready(None));
    // }


impl<T: ControlStreams> ControlStreams for StreamRecvOpen<T> {
    fn is_valid_local_id(id: StreamId) -> bool {
        T::is_valid_local_id(id)
    }

    fn is_valid_remote_id(id: StreamId) -> bool {
        T::is_valid_remote_id(id)
    }

    fn can_create_local_stream() -> bool {
        T::can_create_local_stream()
    }

    fn get_reset(&self, id: StreamId) -> Option<Reason> {
        self.inner.get_reset(id)
    }

    fn reset_stream(&mut self, id: StreamId, cause: Reason) {
        self.inner.reset_stream(id, cause)
    }

    fn is_local_active(&self, id: StreamId) -> bool {
        self.inner.is_local_active(id)
    }

    fn is_remote_active(&self, id: StreamId) -> bool {
        self.inner.is_remote_active(id)
    }

    fn local_active_len(&self) -> usize {
        self.inner.local_active_len()
    }

    fn remote_active_len(&self) -> usize {
        self.inner.remote_active_len()
    }

    fn local_update_inital_window_size(&mut self, old_sz: u32, new_sz: u32) {
        self.inner.local_update_inital_window_size(old_sz, new_sz)
    }

    fn remote_update_inital_window_size(&mut self, old_sz: u32, new_sz: u32) {
        self.inner.remote_update_inital_window_size(old_sz, new_sz)
    }

    fn local_flow_controller(&mut self, id: StreamId) -> Option<&mut FlowControlState> {
        self.inner.local_flow_controller(id)
    }

    fn remote_flow_controller(&mut self, id: StreamId) -> Option<&mut FlowControlState> {
        self.inner.remote_flow_controller(id)
    }
}

impl<T: ControlPing> ControlPing for StreamRecvOpen<T> {
    fn start_ping(&mut self, body: PingPayload) -> StartSend<PingPayload, ConnectionError> {
        self.inner.start_ping(body)
    }

    fn take_pong(&mut self) -> Option<PingPayload> {
        self.inner.take_pong()
    }
}