use bytes::Buf;
use h2::{SendStream};
use http::header::{
    HeaderName, CONNECTION, PROXY_AUTHENTICATE, PROXY_AUTHORIZATION, TE, TRAILER,
    TRANSFER_ENCODING, UPGRADE,
};
use http::HeaderMap;

use crate::body::Payload;
use crate::common::{Future, Pin, Poll, task};

pub(crate) mod client;
pub(crate) mod server;

pub(crate) use self::client::ClientTask;
pub(crate) use self::server::Server;

fn strip_connection_headers(headers: &mut HeaderMap, is_request: bool) {
    // List of connection headers from:
    // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Connection
    //
    // TE headers are allowed in HTTP/2 requests as long as the value is "trailers", so they're
    // tested separately.
    let connection_headers = [
        HeaderName::from_lowercase(b"keep-alive").unwrap(),
        HeaderName::from_lowercase(b"proxy-connection").unwrap(),
        PROXY_AUTHENTICATE,
        PROXY_AUTHORIZATION,
        TRAILER,
        TRANSFER_ENCODING,
        UPGRADE,
    ];

    for header in connection_headers.iter() {
        if headers.remove(header).is_some() {
            warn!("Connection header illegal in HTTP/2: {}", header.as_str());
        }
    }

    if is_request {
        if headers.get(TE).map(|te_header| te_header != "trailers").unwrap_or(false) {
            warn!("TE headers not set to \"trailers\" are illegal in HTTP/2 requests");
            headers.remove(TE);
        }
    } else {
        if headers.remove(TE).is_some() {
            warn!("TE headers illegal in HTTP/2 responses");
        }
    }

    if let Some(header) = headers.remove(CONNECTION) {
        warn!(
            "Connection header illegal in HTTP/2: {}",
            CONNECTION.as_str()
        );
        let header_contents = header.to_str().unwrap();

        // A `Connection` header may have a comma-separated list of names of other headers that
        // are meant for only this specific connection.
        //
        // Iterate these names and remove them as headers. Connection-specific headers are
        // forbidden in HTTP2, as that information has been moved into frame types of the h2
        // protocol.
        for name in header_contents.split(',') {
            let name = name.trim();
            headers.remove(name);
        }
    }
}

// body adapters used by both Client and Server

struct PipeToSendStream<S>
where
    S: Payload,
{
    body_tx: SendStream<SendBuf<S::Data>>,
    data_done: bool,
    stream: S,
}

impl<S> PipeToSendStream<S>
where
    S: Payload,
{
    fn new(stream: S, tx: SendStream<SendBuf<S::Data>>) -> PipeToSendStream<S> {
        PipeToSendStream {
            body_tx: tx,
            data_done: false,
            stream: stream,
        }
    }

    fn on_user_err(&mut self, err: S::Error) -> crate::Error {
        let err = crate::Error::new_user_body(err);
        debug!("send body user stream error: {}", err);
        self.body_tx.send_reset(err.h2_reason());
        err
    }

    fn send_eos_frame(&mut self) -> crate::Result<()> {
        trace!("send body eos");
        self.body_tx
            .send_data(SendBuf(None), true)
            .map_err(crate::Error::new_body_write)
    }
}

impl<S> Future for PipeToSendStream<S>
where
    S: Payload + Unpin,
{
    type Output = crate::Result<()>;

    fn poll(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<Self::Output> {
        loop {
            if !self.data_done {
                // we don't have the next chunk of data yet, so just reserve 1 byte to make
                // sure there's some capacity available. h2 will handle the capacity management
                // for the actual body chunk.
                self.body_tx.reserve_capacity(1);

                if self.body_tx.capacity() == 0 {
                    loop {
                        match ready!(self.body_tx.poll_capacity(cx)) {

                            Some(Ok(0)) => {},
                            Some(Ok(_)) => break,
                            Some(Err(e)) => return Poll::Ready(Err(crate::Error::new_body_write(e))) ,
                            None => return Poll::Ready(Err(crate::Error::new_canceled())),
                        }
                    }
                } else {
                    if let Poll::Ready(reason) =
                        self.body_tx.poll_reset(cx).map_err(crate::Error::new_body_write)?
                    {
                        debug!("stream received RST_STREAM: {:?}", reason);
                        return Poll::Ready(Err(crate::Error::new_body_write(::h2::Error::from(reason))));
                    }
                }

                match ready!(Pin::new(&mut self.stream).poll_data(cx)) {
                    Some(Ok(chunk)) => {
                        let is_eos = self.stream.is_end_stream();
                        trace!(
                            "send body chunk: {} bytes, eos={}",
                            chunk.remaining(),
                            is_eos,
                        );

                        let buf = SendBuf(Some(chunk));
                        self.body_tx
                            .send_data(buf, is_eos)
                            .map_err(crate::Error::new_body_write)?;

                        if is_eos {
                            return Poll::Ready(Ok(()));
                        }
                    }
                    Some(Err(e)) => return Poll::Ready(Err(self.on_user_err(e))),
                    None => {
                        self.body_tx.reserve_capacity(0);
                        let is_eos = self.stream.is_end_stream();
                        if is_eos {
                            return Poll::Ready(self.send_eos_frame());
                        } else {
                            self.data_done = true;
                            // loop again to poll_trailers
                        }
                    }
                }
            } else {
                if let Poll::Ready(reason) =
                    self.body_tx.poll_reset(cx).map_err(|e| crate::Error::new_body_write(e))?
                {
                    debug!("stream received RST_STREAM: {:?}", reason);
                    return Poll::Ready(Err(crate::Error::new_body_write(::h2::Error::from(reason))));
                }

                match ready!(Pin::new(&mut self.stream).poll_trailers(cx)) {
                    Ok(Some(trailers)) => {
                        self.body_tx
                            .send_trailers(trailers)
                            .map_err(crate::Error::new_body_write)?;
                        return Poll::Ready(Ok(()));
                    }
                    Ok(None) => {
                        // There were no trailers, so send an empty DATA frame...
                        return Poll::Ready(self.send_eos_frame());
                    }
                    Err(e) => return Poll::Ready(Err(self.on_user_err(e))),
                }
            }
        }
    }
}

struct SendBuf<B>(Option<B>);

impl<B: Buf> Buf for SendBuf<B> {
    #[inline]
    fn remaining(&self) -> usize {
        self.0.as_ref().map(|b| b.remaining()).unwrap_or(0)
    }

    #[inline]
    fn bytes(&self) -> &[u8] {
        self.0.as_ref().map(|b| b.bytes()).unwrap_or(&[])
    }

    #[inline]
    fn advance(&mut self, cnt: usize) {
        self.0.as_mut().map(|b| b.advance(cnt));
    }
}