//! HTTP/1 Server Connections

use std::error::Error as StdError;
use std::fmt;
use std::future::Future;
use std::marker::Unpin;
use std::pin::Pin;
use std::task::{Context, Poll};
use std::time::Duration;

use bytes::Bytes;
use tokio::io::{AsyncRead, AsyncWrite};

use crate::body::{Body as IncomingBody, HttpBody as Body};
use crate::proto;
use crate::service::HttpService;

type Http1Dispatcher<T, B, S> = proto::h1::Dispatcher<
    proto::h1::dispatch::Server<S, IncomingBody>,
    B,
    T,
    proto::ServerTransaction,
>;

pin_project_lite::pin_project! {
    /// A future binding an http1 connection with a Service.
    ///
    /// Polling this future will drive HTTP forward.
    #[must_use = "futures do nothing unless polled"]
    pub struct Connection<T, S>
    where
        S: HttpService<IncomingBody>,
    {
        conn: Http1Dispatcher<T, S::ResBody, S>,
    }
}

/// A configuration builder for HTTP/1 server connections.
#[derive(Clone, Debug)]
pub struct Builder {
    h1_half_close: bool,
    h1_keep_alive: bool,
    h1_title_case_headers: bool,
    h1_preserve_header_case: bool,
    h1_header_read_timeout: Option<Duration>,
    h1_writev: Option<bool>,
    max_buf_size: Option<usize>,
    pipeline_flush: bool,
}

/// Deconstructed parts of a `Connection`.
///
/// This allows taking apart a `Connection` at a later time, in order to
/// reclaim the IO object, and additional related pieces.
#[derive(Debug)]
pub struct Parts<T, S> {
    /// The original IO object used in the handshake.
    pub io: T,
    /// A buffer of bytes that have been read but not processed as HTTP.
    ///
    /// If the client sent additional bytes after its last request, and
    /// this connection "ended" with an upgrade, the read buffer will contain
    /// those bytes.
    ///
    /// You will want to check for any existing bytes if you plan to continue
    /// communicating on the IO object.
    pub read_buf: Bytes,
    /// The `Service` used to serve this connection.
    pub service: S,
    _inner: (),
}

// ===== impl Connection =====

impl<I, S> fmt::Debug for Connection<I, S>
where
    S: HttpService<IncomingBody>,
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Connection").finish()
    }
}

impl<I, B, S> Connection<I, S>
where
    S: HttpService<IncomingBody, ResBody = B>,
    S::Error: Into<Box<dyn StdError + Send + Sync>>,
    I: AsyncRead + AsyncWrite + Unpin,
    B: Body + 'static,
    B::Error: Into<Box<dyn StdError + Send + Sync>>,
{
    /// Start a graceful shutdown process for this connection.
    ///
    /// This `Connection` should continue to be polled until shutdown
    /// can finish.
    ///
    /// # Note
    ///
    /// This should only be called while the `Connection` future is still
    /// pending. If called after `Connection::poll` has resolved, this does
    /// nothing.
    pub fn graceful_shutdown(mut self: Pin<&mut Self>) {
        self.conn.disable_keep_alive();
    }

    /// Return the inner IO object, and additional information.
    ///
    /// If the IO object has been "rewound" the io will not contain those bytes rewound.
    /// This should only be called after `poll_without_shutdown` signals
    /// that the connection is "done". Otherwise, it may not have finished
    /// flushing all necessary HTTP bytes.
    ///
    /// # Panics
    /// This method will panic if this connection is using an h2 protocol.
    pub fn into_parts(self) -> Parts<I, S> {
        let (io, read_buf, dispatch) = self.conn.into_inner();
        Parts {
            io,
            read_buf,
            service: dispatch.into_service(),
            _inner: (),
        }
    }

    /// Poll the connection for completion, but without calling `shutdown`
    /// on the underlying IO.
    ///
    /// This is useful to allow running a connection while doing an HTTP
    /// upgrade. Once the upgrade is completed, the connection would be "done",
    /// but it is not desired to actually shutdown the IO object. Instead you
    /// would take it back using `into_parts`.
    pub fn poll_without_shutdown(&mut self, cx: &mut Context<'_>) -> Poll<crate::Result<()>>
    where
        S: Unpin,
        S::Future: Unpin,
        B: Unpin,
    {
        self.conn.poll_without_shutdown(cx)
    }

    /// Prevent shutdown of the underlying IO object at the end of service the request,
    /// instead run `into_parts`. This is a convenience wrapper over `poll_without_shutdown`.
    ///
    /// # Error
    ///
    /// This errors if the underlying connection protocol is not HTTP/1.
    pub fn without_shutdown(self) -> impl Future<Output = crate::Result<Parts<I, S>>>
    where
        S: Unpin,
        S::Future: Unpin,
        B: Unpin,
    {
        let mut zelf = Some(self);
        futures_util::future::poll_fn(move |cx| {
            ready!(zelf.as_mut().unwrap().conn.poll_without_shutdown(cx))?;
            Poll::Ready(Ok(zelf.take().unwrap().into_parts()))
        })
    }

    /// Enable this connection to support higher-level HTTP upgrades.
    ///
    /// See [the `upgrade` module](crate::upgrade) for more.
    pub fn with_upgrades(self) -> upgrades::UpgradeableConnection<I, S>
    where
        I: Send,
    {
        upgrades::UpgradeableConnection { inner: Some(self) }
    }
}

impl<I, B, S> Future for Connection<I, S>
where
    S: HttpService<IncomingBody, ResBody = B>,
    S::Error: Into<Box<dyn StdError + Send + Sync>>,
    I: AsyncRead + AsyncWrite + Unpin + 'static,
    B: Body + 'static,
    B::Error: Into<Box<dyn StdError + Send + Sync>>,
{
    type Output = crate::Result<()>;

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        match ready!(Pin::new(&mut self.conn).poll(cx)) {
            Ok(done) => {
                match done {
                    proto::Dispatched::Shutdown => {}
                    proto::Dispatched::Upgrade(pending) => {
                        // With no `Send` bound on `I`, we can't try to do
                        // upgrades here. In case a user was trying to use
                        // `Body::on_upgrade` with this API, send a special
                        // error letting them know about that.
                        pending.manual();
                    }
                };
                return Poll::Ready(Ok(()));
            }
            Err(e) => Poll::Ready(Err(e)),
        }
    }
}

// ===== impl Builder =====

impl Builder {
    /// Create a new connection builder.
    pub fn new() -> Self {
        Self {
            h1_half_close: false,
            h1_keep_alive: true,
            h1_title_case_headers: false,
            h1_preserve_header_case: false,
            h1_header_read_timeout: None,
            h1_writev: None,
            max_buf_size: None,
            pipeline_flush: false,
        }
    }
    /// 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.h1_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.h1_keep_alive = val;
        self
    }

    /// Set whether HTTP/1 connections will write header names as title case at
    /// the socket level.
    ///
    /// Default is false.
    pub fn title_case_headers(&mut self, enabled: bool) -> &mut Self {
        self.h1_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.
    ///
    /// Default is false.
    pub fn preserve_header_case(&mut self, enabled: bool) -> &mut Self {
        self.h1_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.h1_header_read_timeout = Some(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.h1_writev = Some(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 {
        assert!(
            max >= proto::h1::MINIMUM_MAX_BUFFER_SIZE,
            "the max_buf_size cannot be smaller than the minimum that h1 specifies."
        );
        self.max_buf_size = Some(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.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.timer = Time::Timer(Arc::new(timer));
    //     self
    // }

    /// Bind a connection together with a [`Service`](crate::service::Service).
    ///
    /// This returns a Future that must be polled in order for HTTP to be
    /// driven on the connection.
    ///
    /// # Example
    ///
    /// ```
    /// # use hyper::{Body as Incoming, Request, Response};
    /// # use hyper::service::Service;
    /// # use hyper::server::conn::http1::Builder;
    /// # use tokio::io::{AsyncRead, AsyncWrite};
    /// # async fn run<I, S>(some_io: I, some_service: S)
    /// # where
    /// #     I: AsyncRead + AsyncWrite + Unpin + Send + 'static,
    /// #     S: Service<hyper::Request<Incoming>, Response=hyper::Response<Incoming>> + Send + 'static,
    /// #     S::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
    /// #     S::Future: Send,
    /// # {
    /// let http = Builder::new();
    /// let conn = http.serve_connection(some_io, some_service);
    ///
    /// if let Err(e) = conn.await {
    ///     eprintln!("server connection error: {}", e);
    /// }
    /// # }
    /// # fn main() {}
    /// ```
    pub fn serve_connection<I, S>(&self, io: I, service: S) -> Connection<I, S>
    where
        S: HttpService<IncomingBody>,
        S::Error: Into<Box<dyn StdError + Send + Sync>>,
        S::ResBody: 'static,
        <S::ResBody as Body>::Error: Into<Box<dyn StdError + Send + Sync>>,
        I: AsyncRead + AsyncWrite + Unpin,
    {
        let mut conn = proto::Conn::new(io);
        if !self.h1_keep_alive {
            conn.disable_keep_alive();
        }
        if self.h1_half_close {
            conn.set_allow_half_close();
        }
        if self.h1_title_case_headers {
            conn.set_title_case_headers();
        }
        if self.h1_preserve_header_case {
            conn.set_preserve_header_case();
        }
        if let Some(header_read_timeout) = self.h1_header_read_timeout {
            conn.set_http1_header_read_timeout(header_read_timeout);
        }
        if let Some(writev) = self.h1_writev {
            if writev {
                conn.set_write_strategy_queue();
            } else {
                conn.set_write_strategy_flatten();
            }
        }
        conn.set_flush_pipeline(self.pipeline_flush);
        if let Some(max) = self.max_buf_size {
            conn.set_max_buf_size(max);
        }
        let sd = proto::h1::dispatch::Server::new(service);
        let proto = proto::h1::Dispatcher::new(sd, conn);
        Connection { conn: proto }
    }
}

mod upgrades {
    use crate::upgrade::Upgraded;

    use super::*;

    // A future binding a connection with a Service with Upgrade support.
    //
    // This type is unnameable outside the crate.
    #[must_use = "futures do nothing unless polled"]
    #[allow(missing_debug_implementations)]
    pub struct UpgradeableConnection<T, S>
    where
        S: HttpService<IncomingBody>,
    {
        pub(super) inner: Option<Connection<T, S>>,
    }

    impl<I, B, S> UpgradeableConnection<I, S>
    where
        S: HttpService<IncomingBody, ResBody = B>,
        S::Error: Into<Box<dyn StdError + Send + Sync>>,
        I: AsyncRead + AsyncWrite + Unpin,
        B: Body + 'static,
        B::Error: Into<Box<dyn StdError + Send + Sync>>,
    {
        /// Start a graceful shutdown process for this connection.
        ///
        /// This `Connection` should continue to be polled until shutdown
        /// can finish.
        pub fn graceful_shutdown(mut self: Pin<&mut Self>) {
            Pin::new(self.inner.as_mut().unwrap()).graceful_shutdown()
        }
    }

    impl<I, B, S> Future for UpgradeableConnection<I, S>
    where
        S: HttpService<IncomingBody, ResBody = B>,
        S::Error: Into<Box<dyn StdError + Send + Sync>>,
        I: AsyncRead + AsyncWrite + Unpin + Send + 'static,
        B: Body + 'static,
        B::Error: Into<Box<dyn StdError + Send + Sync>>,
    {
        type Output = crate::Result<()>;

        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
            match ready!(Pin::new(&mut self.inner.as_mut().unwrap().conn).poll(cx)) {
                Ok(proto::Dispatched::Shutdown) => Poll::Ready(Ok(())),
                Ok(proto::Dispatched::Upgrade(pending)) => {
                    let (io, buf, _) = self.inner.take().unwrap().conn.into_inner();
                    pending.fulfill(Upgraded::new(io, buf));
                    Poll::Ready(Ok(()))
                }
                Err(e) => Poll::Ready(Err(e)),
            }
        }
    }
}