//! Http1 or Http2 connection.

use futures_util::ready;
use std::future::Future;
use std::io::{Error as IoError, ErrorKind, Result as IoResult};
use std::marker::PhantomPinned;
use std::pin::Pin;
use std::task::{Context, Poll};
use std::{error::Error as StdError, marker::Unpin, time::Duration};

use bytes::Bytes;
use http::{Request, Response};
use http_body::Body;
use hyper::{
    body::Incoming,
    rt::{bounds::Http2ServerConnExec, Read, ReadBuf, Timer, Write},
    server::conn::{http1, http2},
    service::Service,
};
use pin_project_lite::pin_project;

use crate::common::rewind::Rewind;

type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;

const H2_PREFACE: &[u8] = b"PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n";

/// Http1 or Http2 connection builder.
pub struct Builder<E> {
    http1: http1::Builder,
    http2: http2::Builder<E>,
}

impl<E> Builder<E> {
    /// Create a new auto connection builder.
    ///
    /// `executor` parameter should be a type that implements
    /// [`Executor`](hyper::rt::Executor) trait.
    ///
    /// # Example
    ///
    /// ```
    /// use hyper_util::{
    ///     rt::tokio_executor::TokioExecutor,
    ///     server::conn::auto,
    /// };
    ///
    /// auto::Builder::new(TokioExecutor::new());
    /// ```
    pub fn new(executor: E) -> Self {
        Self {
            http1: http1::Builder::new(),
            http2: http2::Builder::new(executor),
        }
    }

    /// Http1 configuration.
    pub fn http1(&mut self) -> Http1Builder<'_, E> {
        Http1Builder { inner: self }
    }

    /// Http2 configuration.
    pub fn http2(&mut self) -> Http2Builder<'_, E> {
        Http2Builder { inner: self }
    }

    /// Bind a connection together with a [`Service`].
    pub async fn serve_connection<I, S, B>(&self, io: I, service: S) -> Result<()>
    where
        S: Service<Request<Incoming>, Response = Response<B>>,
        S::Future: 'static,
        S::Error: Into<Box<dyn StdError + Send + Sync>>,
        B: Body + 'static,
        B::Error: Into<Box<dyn StdError + Send + Sync>>,
        I: Read + Write + Unpin + 'static,
        E: Http2ServerConnExec<S::Future, B>,
    {
        let (version, io) = read_version(io).await?;
        match version {
            Version::H1 => self.http1.serve_connection(io, service).await?,
            Version::H2 => self.http2.serve_connection(io, service).await?,
        }

        Ok(())
    }

    /// Bind a connection together with a [`Service`], with the ability to
    /// handle HTTP upgrades. This requires that the IO object implements
    /// `Send`.
    pub async fn serve_connection_with_upgrades<I, S, B>(&self, io: I, service: S) -> Result<()>
    where
        S: Service<Request<Incoming>, Response = Response<B>>,
        S::Future: 'static,
        S::Error: Into<Box<dyn StdError + Send + Sync>>,
        B: Body + 'static,
        B::Error: Into<Box<dyn StdError + Send + Sync>>,
        I: Read + Write + Unpin + Send + 'static,
        E: Http2ServerConnExec<S::Future, B>,
    {
        let (version, io) = read_version(io).await?;
        match version {
            Version::H1 => {
                self.http1
                    .serve_connection(io, service)
                    .with_upgrades()
                    .await?
            }
            Version::H2 => self.http2.serve_connection(io, service).await?,
        }

        Ok(())
    }
}
#[derive(Copy, Clone)]
enum Version {
    H1,
    H2,
}
async fn read_version<'a, A>(mut reader: A) -> IoResult<(Version, Rewind<A>)>
where
    A: Read + Unpin,
{
    use std::mem::MaybeUninit;

    let mut buf = [MaybeUninit::uninit(); 24];
    let (version, buf) = ReadVersion {
        reader: &mut reader,
        buf: ReadBuf::uninit(&mut buf),
        version: Version::H1,
        _pin: PhantomPinned,
    }
    .await?;
    Ok((version, Rewind::new_buffered(reader, Bytes::from(buf))))
}
pin_project! {
    struct ReadVersion<'a, A: ?Sized> {
        reader: &'a mut A,
        buf: ReadBuf<'a>,
        version: Version,
        // Make this future `!Unpin` for compatibility with async trait methods.
        #[pin]
        _pin: PhantomPinned,
    }
}

impl<A> Future for ReadVersion<'_, A>
where
    A: Read + Unpin + ?Sized,
{
    type Output = IoResult<(Version, Vec<u8>)>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<IoResult<(Version, Vec<u8>)>> {
        let this = self.project();

        while this.buf.filled().len() < H2_PREFACE.len() {
            if this.buf.filled() != &H2_PREFACE[0..this.buf.filled().len()] {
                return Poll::Ready(Ok((*this.version, this.buf.filled().to_vec())));
            }
            // if our buffer is empty, then we need to read some data to continue.
            let len = this.buf.filled().len();
            ready!(Pin::new(&mut *this.reader).poll_read(cx, this.buf.unfilled()))?;
            if this.buf.filled().len() == len {
                return Err(IoError::new(ErrorKind::UnexpectedEof, "early eof")).into();
            }
        }
        if this.buf.filled() == H2_PREFACE {
            *this.version = Version::H2;
        }
        return Poll::Ready(Ok((*this.version, this.buf.filled().to_vec())));
    }
}

/// Http1 part of builder.
pub struct Http1Builder<'a, E> {
    inner: &'a mut Builder<E>,
}

impl<E> Http1Builder<'_, E> {
    /// Http2 configuration.
    pub fn http2(&mut self) -> Http2Builder<'_, E> {
        Http2Builder {
            inner: &mut self.inner,
        }
    }

    /// Set whether HTTP/1 connections should support half-closures.
    ///
    /// Clients can chose to shutdown their write-side while waiting
    /// for the server to respond. Setting this to `true` will
    /// prevent closing the connection immediately if `read`
    /// detects an EOF in the middle of a request.
    ///
    /// Default is `false`.
    pub fn half_close(&mut self, val: bool) -> &mut Self {
        self.inner.http1.half_close(val);
        self
    }

    /// Enables or disables HTTP/1 keep-alive.
    ///
    /// Default is true.
    pub fn keep_alive(&mut self, val: bool) -> &mut Self {
        self.inner.http1.keep_alive(val);
        self
    }

    /// Set whether HTTP/1 connections will write header names as title case at
    /// the socket level.
    ///
    /// Note that this setting does not affect HTTP/2.
    ///
    /// Default is false.
    pub fn title_case_headers(&mut self, enabled: bool) -> &mut Self {
        self.inner.http1.title_case_headers(enabled);
        self
    }

    /// Set whether to support preserving original header cases.
    ///
    /// Currently, this will record the original cases received, and store them
    /// in a private extension on the `Request`. It will also look for and use
    /// such an extension in any provided `Response`.
    ///
    /// Since the relevant extension is still private, there is no way to
    /// interact with the original cases. The only effect this can have now is
    /// to forward the cases in a proxy-like fashion.
    ///
    /// Note that this setting does not affect HTTP/2.
    ///
    /// Default is false.
    pub fn preserve_header_case(&mut self, enabled: bool) -> &mut Self {
        self.inner.http1.preserve_header_case(enabled);
        self
    }

    /// Set a timeout for reading client request headers. If a client does not
    /// transmit the entire header within this time, the connection is closed.
    ///
    /// Default is None.
    pub fn header_read_timeout(&mut self, read_timeout: Duration) -> &mut Self {
        self.inner.http1.header_read_timeout(read_timeout);
        self
    }

    /// Set whether HTTP/1 connections should try to use vectored writes,
    /// or always flatten into a single buffer.
    ///
    /// Note that setting this to false may mean more copies of body data,
    /// but may also improve performance when an IO transport doesn't
    /// support vectored writes well, such as most TLS implementations.
    ///
    /// Setting this to true will force hyper to use queued strategy
    /// which may eliminate unnecessary cloning on some TLS backends
    ///
    /// Default is `auto`. In this mode hyper will try to guess which
    /// mode to use
    pub fn writev(&mut self, val: bool) -> &mut Self {
        self.inner.http1.writev(val);
        self
    }

    /// Set the maximum buffer size for the connection.
    ///
    /// Default is ~400kb.
    ///
    /// # Panics
    ///
    /// The minimum value allowed is 8192. This method panics if the passed `max` is less than the minimum.
    pub fn max_buf_size(&mut self, max: usize) -> &mut Self {
        self.inner.http1.max_buf_size(max);
        self
    }

    /// Aggregates flushes to better support pipelined responses.
    ///
    /// Experimental, may have bugs.
    ///
    /// Default is false.
    pub fn pipeline_flush(&mut self, enabled: bool) -> &mut Self {
        self.inner.http1.pipeline_flush(enabled);
        self
    }

    /// Set the timer used in background tasks.
    pub fn timer<M>(&mut self, timer: M) -> &mut Self
    where
        M: Timer + Send + Sync + 'static,
    {
        self.inner.http1.timer(timer);
        self
    }

    /// Bind a connection together with a [`Service`].
    pub async fn serve_connection<I, S, B>(&self, io: I, service: S) -> Result<()>
    where
        S: Service<Request<Incoming>, Response = Response<B>>,
        S::Future: 'static,
        S::Error: Into<Box<dyn StdError + Send + Sync>>,
        B: Body + 'static,
        B::Error: Into<Box<dyn StdError + Send + Sync>>,
        I: Read + Write + Unpin + 'static,
        E: Http2ServerConnExec<S::Future, B>,
    {
        self.inner.serve_connection(io, service).await
    }
}

/// Http2 part of builder.
pub struct Http2Builder<'a, E> {
    inner: &'a mut Builder<E>,
}

impl<E> Http2Builder<'_, E> {
    /// Http1 configuration.
    pub fn http1(&mut self) -> Http1Builder<'_, E> {
        Http1Builder {
            inner: &mut self.inner,
        }
    }

    /// Sets the [`SETTINGS_INITIAL_WINDOW_SIZE`][spec] option for HTTP2
    /// stream-level flow control.
    ///
    /// Passing `None` will do nothing.
    ///
    /// If not set, hyper will use a default.
    ///
    /// [spec]: https://http2.github.io/http2-spec/#SETTINGS_INITIAL_WINDOW_SIZE
    pub fn initial_stream_window_size(&mut self, sz: impl Into<Option<u32>>) -> &mut Self {
        self.inner.http2.initial_stream_window_size(sz);
        self
    }

    /// Sets the max connection-level flow control for HTTP2.
    ///
    /// Passing `None` will do nothing.
    ///
    /// If not set, hyper will use a default.
    pub fn initial_connection_window_size(&mut self, sz: impl Into<Option<u32>>) -> &mut Self {
        self.inner.http2.initial_connection_window_size(sz);
        self
    }

    /// Sets whether to use an adaptive flow control.
    ///
    /// Enabling this will override the limits set in
    /// `http2_initial_stream_window_size` and
    /// `http2_initial_connection_window_size`.
    pub fn adaptive_window(&mut self, enabled: bool) -> &mut Self {
        self.inner.http2.adaptive_window(enabled);
        self
    }

    /// Sets the maximum frame size to use for HTTP2.
    ///
    /// Passing `None` will do nothing.
    ///
    /// If not set, hyper will use a default.
    pub fn max_frame_size(&mut self, sz: impl Into<Option<u32>>) -> &mut Self {
        self.inner.http2.max_frame_size(sz);
        self
    }

    /// Sets the [`SETTINGS_MAX_CONCURRENT_STREAMS`][spec] option for HTTP2
    /// connections.
    ///
    /// Default is no limit (`std::u32::MAX`). Passing `None` will do nothing.
    ///
    /// [spec]: https://http2.github.io/http2-spec/#SETTINGS_MAX_CONCURRENT_STREAMS
    pub fn max_concurrent_streams(&mut self, max: impl Into<Option<u32>>) -> &mut Self {
        self.inner.http2.max_concurrent_streams(max);
        self
    }

    /// Sets an interval for HTTP2 Ping frames should be sent to keep a
    /// connection alive.
    ///
    /// Pass `None` to disable HTTP2 keep-alive.
    ///
    /// Default is currently disabled.
    ///
    /// # Cargo Feature
    ///
    pub fn keep_alive_interval(&mut self, interval: impl Into<Option<Duration>>) -> &mut Self {
        self.inner.http2.keep_alive_interval(interval);
        self
    }

    /// Sets a timeout for receiving an acknowledgement of the keep-alive ping.
    ///
    /// If the ping is not acknowledged within the timeout, the connection will
    /// be closed. Does nothing if `http2_keep_alive_interval` is disabled.
    ///
    /// Default is 20 seconds.
    ///
    /// # Cargo Feature
    ///
    pub fn keep_alive_timeout(&mut self, timeout: Duration) -> &mut Self {
        self.inner.http2.keep_alive_timeout(timeout);
        self
    }

    /// Set the maximum write buffer size for each HTTP/2 stream.
    ///
    /// Default is currently ~400KB, but may change.
    ///
    /// # Panics
    ///
    /// The value must be no larger than `u32::MAX`.
    pub fn max_send_buf_size(&mut self, max: usize) -> &mut Self {
        self.inner.http2.max_send_buf_size(max);
        self
    }

    /// Enables the [extended CONNECT protocol].
    ///
    /// [extended CONNECT protocol]: https://datatracker.ietf.org/doc/html/rfc8441#section-4
    pub fn enable_connect_protocol(&mut self) -> &mut Self {
        self.inner.http2.enable_connect_protocol();
        self
    }

    /// Sets the max size of received header frames.
    ///
    /// Default is currently ~16MB, but may change.
    pub fn max_header_list_size(&mut self, max: u32) -> &mut Self {
        self.inner.http2.max_header_list_size(max);
        self
    }

    /// Set the timer used in background tasks.
    pub fn timer<M>(&mut self, timer: M) -> &mut Self
    where
        M: Timer + Send + Sync + 'static,
    {
        self.inner.http2.timer(timer);
        self
    }

    /// Bind a connection together with a [`Service`].
    pub async fn serve_connection<I, S, B>(&self, io: I, service: S) -> Result<()>
    where
        S: Service<Request<Incoming>, Response = Response<B>>,
        S::Future: 'static,
        S::Error: Into<Box<dyn StdError + Send + Sync>>,
        B: Body + 'static,
        B::Error: Into<Box<dyn StdError + Send + Sync>>,
        I: Read + Write + Unpin + 'static,
        E: Http2ServerConnExec<S::Future, B>,
    {
        self.inner.serve_connection(io, service).await
    }
}

#[cfg(test)]
mod tests {
    use crate::{
        rt::{tokio_executor::TokioExecutor, TokioIo},
        server::conn::auto,
    };
    use http::{Request, Response};
    use http_body::Body;
    use http_body_util::{BodyExt, Empty, Full};
    use hyper::{body, body::Bytes, client, service::service_fn};
    use std::{convert::Infallible, error::Error as StdError, net::SocketAddr};
    use tokio::net::{TcpListener, TcpStream};

    const BODY: &[u8] = b"Hello, world!";

    #[test]
    fn configuration() {
        // One liner.
        auto::Builder::new(TokioExecutor::new())
            .http1()
            .keep_alive(true)
            .http2()
            .keep_alive_interval(None);
        //  .serve_connection(io, service);

        // Using variable.
        let mut builder = auto::Builder::new(TokioExecutor::new());

        builder.http1().keep_alive(true);
        builder.http2().keep_alive_interval(None);
        // builder.serve_connection(io, service);
    }

    #[cfg(not(miri))]
    #[tokio::test]
    async fn http1() {
        let addr = start_server().await;
        let mut sender = connect_h1(addr).await;

        let response = sender
            .send_request(Request::new(Empty::<Bytes>::new()))
            .await
            .unwrap();

        let body = response.into_body().collect().await.unwrap().to_bytes();

        assert_eq!(body, BODY);
    }

    #[cfg(not(miri))]
    #[tokio::test]
    async fn http2() {
        let addr = start_server().await;
        let mut sender = connect_h2(addr).await;

        let response = sender
            .send_request(Request::new(Empty::<Bytes>::new()))
            .await
            .unwrap();

        let body = response.into_body().collect().await.unwrap().to_bytes();

        assert_eq!(body, BODY);
    }

    async fn connect_h1<B>(addr: SocketAddr) -> client::conn::http1::SendRequest<B>
    where
        B: Body + Send + 'static,
        B::Data: Send,
        B::Error: Into<Box<dyn StdError + Send + Sync>>,
    {
        let stream = TokioIo::new(TcpStream::connect(addr).await.unwrap());
        let (sender, connection) = client::conn::http1::handshake(stream).await.unwrap();

        tokio::spawn(connection);

        sender
    }

    async fn connect_h2<B>(addr: SocketAddr) -> client::conn::http2::SendRequest<B>
    where
        B: Body + Unpin + Send + 'static,
        B::Data: Send,
        B::Error: Into<Box<dyn StdError + Send + Sync>>,
    {
        let stream = TokioIo::new(TcpStream::connect(addr).await.unwrap());
        let (sender, connection) = client::conn::http2::Builder::new(TokioExecutor::new())
            .handshake(stream)
            .await
            .unwrap();

        tokio::spawn(connection);

        sender
    }

    async fn start_server() -> SocketAddr {
        let addr: SocketAddr = ([127, 0, 0, 1], 0).into();
        let listener = TcpListener::bind(addr).await.unwrap();

        let local_addr = listener.local_addr().unwrap();

        tokio::spawn(async move {
            loop {
                let (stream, _) = listener.accept().await.unwrap();
                let stream = TokioIo::new(stream);
                tokio::task::spawn(async move {
                    let _ = auto::Builder::new(TokioExecutor::new())
                        .serve_connection(stream, service_fn(hello))
                        .await;
                });
            }
        });

        local_addr
    }

    async fn hello(_req: Request<body::Incoming>) -> Result<Response<Full<Bytes>>, Infallible> {
        Ok(Response::new(Full::new(Bytes::from(BODY))))
    }
}