// Copyright (c) 2018-2020 Sean McArthur
// Licensed under the MIT license http://opensource.org/licenses/MIT
// port from https://github.com/seanmonstar/warp/blob/master/src/filters/ws.rs

//! WebSocket

use std::borrow::Cow;
use std::fmt::{self, Formatter};
use std::future::Future;
use std::pin::Pin;
use std::task::{Context, Poll};

use futures_util::sink::{Sink, SinkExt};
use futures_util::stream::{Stream, StreamExt};
use futures_util::{future, ready, FutureExt, TryFutureExt};
use hyper::upgrade::OnUpgrade;
use salvo_core::http::header::{SEC_WEBSOCKET_VERSION, UPGRADE};
use salvo_core::http::headers::{Connection, HeaderMapExt, SecWebsocketAccept, SecWebsocketKey, Upgrade};
use salvo_core::http::{StatusCode, StatusError};
use salvo_core::rt::TokioIo;
use salvo_core::{Error, Request, Response};
use tokio_tungstenite::{
    tungstenite::protocol::{self, WebSocketConfig},
    WebSocketStream,
};

/// Creates a WebSocket Handler.
/// Request:
/// - Method must be `GET`
/// - Header `connection` must be `upgrade`
/// - Header `upgrade` must be `websocket`
/// - Header `sec-websocket-version` must be `13`
/// - Header `sec-websocket-key` must be set.
///
/// Response:
/// - Status of `101 Switching Protocols`
/// - Header `connection: upgrade`
/// - Header `upgrade: websocket`
/// - Header `sec-websocket-accept` with the hash value of the received key.
#[allow(missing_debug_implementations)]
pub struct WebSocketUpgrade {
    config: Option<WebSocketConfig>,
}

impl Default for WebSocketUpgrade {
    #[inline]
    fn default() -> Self {
        Self::new()
    }
}

impl WebSocketUpgrade {
    /// Create new `WebSocketUpgrade`.
    #[inline]
    pub fn new() -> Self {
        WebSocketUpgrade { config: None }
    }

    /// Create new `WebSocketUpgrade` with config.
    #[inline]
    pub fn with_config(config: WebSocketConfig) -> Self {
        WebSocketUpgrade { config: Some(config) }
    }

    /// The target minimum size of the write buffer to reach before writing the data
    /// to the underlying stream.
    /// The default value is 128 KiB.
    ///
    /// If set to `0` each message will be eagerly written to the underlying stream.
    /// It is often more optimal to allow them to buffer a little, hence the default value.
    #[inline]
    pub fn write_buffer_size(mut self, max: usize) -> Self {
        self.config.get_or_insert_with(WebSocketConfig::default).write_buffer_size = max;
        self
    }

    /// The max size of the write buffer in bytes. Setting this can provide backpressure
    /// in the case the write buffer is filling up due to write errors.
    /// The default value is unlimited.
    ///
    /// Note: The write buffer only builds up past [`write_buffer_size`](Self::write_buffer_size)
    /// when writes to the underlying stream are failing. So the **write buffer can not
    /// fill up if you are not observing write errors even if not flushing**.
    ///
    /// Note: Should always be at least [`write_buffer_size + 1 message`](Self::write_buffer_size)
    /// and probably a little more depending on error handling strategy.
    #[inline]
    pub fn max_write_buffer_size(mut self, max: usize) -> Self {
        self.config.get_or_insert_with(WebSocketConfig::default).max_write_buffer_size = max;
        self
    }

    /// The maximum size of a message. `None` means no size limit. The default value is 64 MiB
    /// which should be reasonably big for all normal use-cases but small enough to prevent
    /// memory eating by a malicious user.
    #[inline]
    pub fn max_message_size(mut self, max: usize) -> Self {
        self.config
            .get_or_insert_with(WebSocketConfig::default)
            .max_message_size = Some(max);
        self
    }

    /// The maximum size of a single message frame. `None` means no size limit. The limit is for
    /// frame payload NOT including the frame header. The default value is 16 MiB which should
    /// be reasonably big for all normal use-cases but small enough to prevent memory eating
    /// by a malicious user.
    #[inline]
    pub fn max_frame_size(mut self, max: usize) -> Self {
        self.config.get_or_insert_with(WebSocketConfig::default).max_frame_size = Some(max);
        self
    }

    /// When set to `true`, the server will accept and handle unmasked frames
    /// from the client. According to the RFC 6455, the server must close the
    /// connection to the client in such cases, however it seems like there are
    /// some popular libraries that are sending unmasked frames, ignoring the RFC.
    /// By default this option is set to `false`, i.e. according to RFC 6455.
    #[inline]
    pub fn accept_unmasked_frames(mut self, accept: bool) -> Self {
        self.config.get_or_insert_with(WebSocketConfig::default).accept_unmasked_frames = accept;
        self
    }


    /// Upgrade websocket request.
    #[inline]
    pub async fn upgrade<F, Fut>(&self, req: &mut Request, res: &mut Response, callback: F) -> Result<(), StatusError>
    where
        F: FnOnce(WebSocket) -> Fut + Send + 'static,
        Fut: Future<Output = ()> + Send + 'static,
    {
        let req_headers = req.headers();
        let matched = req_headers
            .typed_get::<Connection>()
            .map(|conn| conn.contains(UPGRADE))
            .unwrap_or(false);
        if !matched {
            tracing::debug!("missing connection upgrade");
            return Err(StatusError::bad_request().brief("Missing connection upgrade."));
        }
        let matched = req_headers
            .get(UPGRADE)
            .and_then(|v| v.to_str().ok())
            .map(|v| v.to_lowercase() == "websocket")
            .unwrap_or(false);
        if !matched {
            tracing::debug!("missing upgrade header or it is not equal websocket");
            return Err(StatusError::bad_request().brief("Missing upgrade header or it is not equal websocket."));
        }
        let matched = !req_headers
            .get(SEC_WEBSOCKET_VERSION)
            .and_then(|v| v.to_str().ok())
            .map(|v| v == "13")
            .unwrap_or(false);
        if matched {
            tracing::debug!("websocket version is not equal 13");
            return Err(StatusError::bad_request().brief("Websocket version is not equal 13."));
        }
        let sec_ws_key = if let Some(key) = req_headers.typed_get::<SecWebsocketKey>() {
            key
        } else {
            tracing::debug!("sec_websocket_key is not exist in request headers");
            return Err(StatusError::bad_request().brief("sec_websocket_key is not exist in request headers."));
        };

        res.status_code(StatusCode::SWITCHING_PROTOCOLS);

        res.headers_mut().typed_insert(Connection::upgrade());
        res.headers_mut().typed_insert(Upgrade::websocket());
        res.headers_mut().typed_insert(SecWebsocketAccept::from(sec_ws_key));

        if let Some(on_upgrade) = req.extensions_mut().remove::<OnUpgrade>() {
            let config = self.config;
            tokio::spawn(async move {
                let socket = on_upgrade
                    .and_then(move |upgraded| {
                        tracing::debug!("websocket upgrade complete");
                        WebSocket::from_raw_socket(upgraded, protocol::Role::Server, config).map(Ok)
                    })
                    .await
                    .expect("connection upgrade failed");
                callback(socket).await;
            });
            Ok(())
        } else {
            tracing::debug!("websocket couldn't be upgraded since no upgrade state was present");
            Err(StatusError::bad_request().brief("Websocket couldn't be upgraded since no upgrade state was present."))
        }
    }
}

/// A websocket `Stream` and `Sink`, provided to `ws` filters.
///
/// Ping messages sent from the client will be handled internally by replying with a Pong message.
/// Close messages need to be handled explicitly: usually by closing the `Sink` end of the
/// `WebSocket`.
pub struct WebSocket {
    inner: WebSocketStream<TokioIo<hyper::upgrade::Upgraded>>,
}

impl WebSocket {
    #[inline]
    pub(crate) async fn from_raw_socket(
        upgraded: hyper::upgrade::Upgraded,
        role: protocol::Role,
        config: Option<protocol::WebSocketConfig>,
    ) -> Self {
        WebSocketStream::from_raw_socket(TokioIo::new(upgraded), role, config)
            .map(|inner| WebSocket { inner })
            .await
    }

    /// Receive another message.
    ///
    /// Returns `None` if the stream has closed.
    pub async fn recv(&mut self) -> Option<Result<Message, Error>> {
        self.next().await
    }

    /// Send a message.
    pub async fn send(&mut self, msg: Message) -> Result<(), Error> {
        self.inner.send(msg.inner).await.map_err(Error::other)
    }

    /// Gracefully close this websocket.
    #[inline]
    pub async fn close(mut self) -> Result<(), Error> {
        future::poll_fn(|cx| Pin::new(&mut self).poll_close(cx)).await
    }
}

impl Stream for WebSocket {
    type Item = Result<Message, Error>;

    #[inline]
    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
        match ready!(Pin::new(&mut self.inner).poll_next(cx)) {
            Some(Ok(item)) => Poll::Ready(Some(Ok(Message { inner: item }))),
            Some(Err(e)) => {
                tracing::debug!("websocket poll error: {}", e);
                Poll::Ready(Some(Err(Error::other(e))))
            }
            None => {
                tracing::debug!("websocket closed");
                Poll::Ready(None)
            }
        }
    }
}

impl Sink<Message> for WebSocket {
    type Error = Error;

    #[inline]
    fn poll_ready(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        Pin::new(&mut self.inner).poll_ready(cx).map_err(Error::other)
    }

    #[inline]
    fn start_send(mut self: Pin<&mut Self>, item: Message) -> Result<(), Self::Error> {
        Pin::new(&mut self.inner).start_send(item.inner).map_err(Error::other)
    }

    #[inline]
    fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Result<(), Self::Error>> {
        Pin::new(&mut self.inner).poll_flush(cx).map_err(Error::other)
    }

    #[inline]
    fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Result<(), Self::Error>> {
        Pin::new(&mut self.inner).poll_close(cx).map_err(Error::other)
    }
}

impl fmt::Debug for WebSocket {
    #[inline]
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        f.debug_struct("WebSocket").finish()
    }
}

/// A WebSocket message.
///
/// This will likely become a `non-exhaustive` enum in the future, once that
/// language feature has stabilized.
#[derive(Eq, PartialEq, Clone)]
pub struct Message {
    inner: protocol::Message,
}

impl Message {
    /// Construct a new Text `Message`.
    #[inline]
    pub fn text<S: Into<String>>(s: S) -> Message {
        Message {
            inner: protocol::Message::text(s),
        }
    }

    /// Construct a new Binary `Message`.
    #[inline]
    pub fn binary<V: Into<Vec<u8>>>(v: V) -> Message {
        Message {
            inner: protocol::Message::binary(v),
        }
    }

    /// Construct a new Ping `Message`.
    #[inline]
    pub fn ping<V: Into<Vec<u8>>>(v: V) -> Message {
        Message {
            inner: protocol::Message::Ping(v.into()),
        }
    }

    /// Construct the default Close `Message`.
    #[inline]
    pub fn close() -> Message {
        Message {
            inner: protocol::Message::Close(None),
        }
    }

    /// Construct a Close `Message` with a code and reason.
    #[inline]
    pub fn close_with(code: impl Into<u16>, reason: impl Into<Cow<'static, str>>) -> Message {
        Message {
            inner: protocol::Message::Close(Some(protocol::frame::CloseFrame {
                code: protocol::frame::coding::CloseCode::from(code.into()),
                reason: reason.into(),
            })),
        }
    }

    /// Returns true if this message is a Text message.
    #[inline]
    pub fn is_text(&self) -> bool {
        self.inner.is_text()
    }

    /// Returns true if this message is a Binary message.
    #[inline]
    pub fn is_binary(&self) -> bool {
        self.inner.is_binary()
    }

    /// Returns true if this message a is a Close message.
    #[inline]
    pub fn is_close(&self) -> bool {
        self.inner.is_close()
    }

    /// Returns true if this message is a Ping message.
    #[inline]
    pub fn is_ping(&self) -> bool {
        self.inner.is_ping()
    }

    /// Returns true if this message is a Pong message.
    #[inline]
    pub fn is_pong(&self) -> bool {
        self.inner.is_pong()
    }

    /// Try to get the close frame (close code and reason).
    #[inline]
    pub fn close_frame(&self) -> Option<(u16, &str)> {
        if let protocol::Message::Close(Some(ref close_frame)) = self.inner {
            Some((close_frame.code.into(), close_frame.reason.as_ref()))
        } else {
            None
        }
    }

    /// Try to get a reference to the string text, if this is a Text message.
    #[inline]
    pub fn to_str(&self) -> Result<&str, Error> {
        match self.inner {
            protocol::Message::Text(ref s) => Ok(s),
            _ => Err(Error::Other("not a text message".into())),
        }
    }

    /// Returns the bytes of this message, if the message can contain data.
    #[inline]
    pub fn as_bytes(&self) -> &[u8] {
        match self.inner {
            protocol::Message::Text(ref s) => s.as_bytes(),
            protocol::Message::Binary(ref v) => v,
            protocol::Message::Ping(ref v) => v,
            protocol::Message::Pong(ref v) => v,
            protocol::Message::Close(_) => &[],
            protocol::Message::Frame(ref v) => v.payload(),
        }
    }

    /// Destructure this message into binary data.
    #[inline]
    pub fn into_bytes(self) -> Vec<u8> {
        self.inner.into_data()
    }
}

impl fmt::Debug for Message {
    #[inline]
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        fmt::Debug::fmt(&self.inner, f)
    }
}

#[allow(clippy::from_over_into)]
impl Into<Vec<u8>> for Message {
    #[inline]
    fn into(self) -> Vec<u8> {
        self.into_bytes()
    }
}

#[cfg(test)]
mod tests {
    use salvo_core::conn::{Acceptor, Listener};
    use salvo_core::http::header::*;
    use salvo_core::prelude::*;
    use salvo_core::rt::TokioIo;

    use super::*;

    #[handler]
    async fn connect(req: &mut Request, res: &mut Response) -> Result<(), StatusError> {
        WebSocketUpgrade::new()
            .upgrade(req, res, |mut ws| async move {
                while let Some(msg) = ws.recv().await {
                    let msg = if let Ok(msg) = msg {
                        msg
                    } else {
                        return;
                    };

                    if ws.send(msg).await.is_err() {
                        return;
                    }
                }
            })
            .await
    }

    #[tokio::test]
    async fn test_websocket() {
        let router = Router::new().handle(connect);
        let acceptor = TcpListener::new("127.0.0.1:0").bind().await;
        let addr = acceptor.holdings()[0].local_addr.clone().into_std().unwrap();

        tokio::spawn(async move {
            Server::new(acceptor).serve(router).await;
        });

        let stream = tokio::net::TcpStream::connect(addr).await.unwrap();

        let (mut sender, conn) = hyper::client::conn::http1::handshake(TokioIo::new(stream)).await.unwrap();
        tokio::task::spawn(async move {
            if let Err(err) = conn.await {
                println!("Connection failed: {:?}", err);
            }
        });

        // Fetch the url...
        let req = hyper::Request::builder()
            .uri(format!("http://{}", addr))
            .header(UPGRADE, "websocket")
            .header(CONNECTION, "Upgrade")
            .header(SEC_WEBSOCKET_KEY, "6D69KGBOr4Re+Nj6zx9aQA==")
            .header(SEC_WEBSOCKET_VERSION, "13")
            .body(http_body_util::Empty::<hyper::body::Bytes>::new())
            .unwrap();

        let res = sender.send_request(req).await.unwrap();

        assert_eq!(res.status(), StatusCode::SWITCHING_PROTOCOLS);
    }
}