//! `WebSocket` support.
//!
//! To setup a `WebSocket`, first do web socket handshake then on success
//! convert `Payload` into a `WsStream` stream and then use `WsWriter` to
//! communicate with the peer.
//! ```
use bytes::Bytes;
use futures::{Async, Poll, Stream};
use http::{header, Method, StatusCode};

use body::Binary;
use error::{PayloadError, ResponseError};
use httpresponse::{ConnectionType, HttpResponse, HttpResponseBuilder};
use payload::PayloadBuffer;
use request::Request;

mod frame;
mod mask;
mod proto;

pub use self::frame::{Frame, FramedMessage};
pub use self::proto::{CloseCode, CloseReason, OpCode};

/// Websocket protocol errors
#[derive(Fail, Debug)]
pub enum ProtocolError {
    /// Received an unmasked frame from client
    #[fail(display = "Received an unmasked frame from client")]
    UnmaskedFrame,
    /// Received a masked frame from server
    #[fail(display = "Received a masked frame from server")]
    MaskedFrame,
    /// Encountered invalid opcode
    #[fail(display = "Invalid opcode: {}", _0)]
    InvalidOpcode(u8),
    /// Invalid control frame length
    #[fail(display = "Invalid control frame length: {}", _0)]
    InvalidLength(usize),
    /// Bad web socket op code
    #[fail(display = "Bad web socket op code")]
    BadOpCode,
    /// A payload reached size limit.
    #[fail(display = "A payload reached size limit.")]
    Overflow,
    /// Continuation is not supported
    #[fail(display = "Continuation is not supported.")]
    NoContinuation,
    /// Bad utf-8 encoding
    #[fail(display = "Bad utf-8 encoding.")]
    BadEncoding,
    /// Payload error
    #[fail(display = "Payload error: {}", _0)]
    Payload(#[cause] PayloadError),
}

impl ResponseError for ProtocolError {}

impl From<PayloadError> for ProtocolError {
    fn from(err: PayloadError) -> ProtocolError {
        ProtocolError::Payload(err)
    }
}

/// Websocket handshake errors
#[derive(Fail, PartialEq, Debug)]
pub enum HandshakeError {
    /// Only get method is allowed
    #[fail(display = "Method not allowed")]
    GetMethodRequired,
    /// Upgrade header if not set to websocket
    #[fail(display = "Websocket upgrade is expected")]
    NoWebsocketUpgrade,
    /// Connection header is not set to upgrade
    #[fail(display = "Connection upgrade is expected")]
    NoConnectionUpgrade,
    /// Websocket version header is not set
    #[fail(display = "Websocket version header is required")]
    NoVersionHeader,
    /// Unsupported websocket version
    #[fail(display = "Unsupported version")]
    UnsupportedVersion,
    /// Websocket key is not set or wrong
    #[fail(display = "Unknown websocket key")]
    BadWebsocketKey,
}

impl ResponseError for HandshakeError {
    fn error_response(&self) -> HttpResponse {
        match *self {
            HandshakeError::GetMethodRequired => HttpResponse::MethodNotAllowed()
                .header(header::ALLOW, "GET")
                .finish(),
            HandshakeError::NoWebsocketUpgrade => HttpResponse::BadRequest()
                .reason("No WebSocket UPGRADE header found")
                .finish(),
            HandshakeError::NoConnectionUpgrade => HttpResponse::BadRequest()
                .reason("No CONNECTION upgrade")
                .finish(),
            HandshakeError::NoVersionHeader => HttpResponse::BadRequest()
                .reason("Websocket version header is required")
                .finish(),
            HandshakeError::UnsupportedVersion => HttpResponse::BadRequest()
                .reason("Unsupported version")
                .finish(),
            HandshakeError::BadWebsocketKey => HttpResponse::BadRequest()
                .reason("Handshake error")
                .finish(),
        }
    }
}

/// `WebSocket` Message
#[derive(Debug, PartialEq)]
pub enum Message {
    /// Text message
    Text(String),
    /// Binary message
    Binary(Binary),
    /// Ping message
    Ping(String),
    /// Pong message
    Pong(String),
    /// Close message with optional reason
    Close(Option<CloseReason>),
}

/// Prepare `WebSocket` handshake response.
///
/// This function returns handshake `HttpResponse`, ready to send to peer.
/// It does not perform any IO.
///
// /// `protocols` is a sequence of known protocols. On successful handshake,
// /// the returned response headers contain the first protocol in this list
// /// which the server also knows.
pub fn handshake(req: &Request) -> Result<HttpResponseBuilder, HandshakeError> {
    // WebSocket accepts only GET
    if *req.method() != Method::GET {
        return Err(HandshakeError::GetMethodRequired);
    }

    // Check for "UPGRADE" to websocket header
    let has_hdr = if let Some(hdr) = req.headers().get(header::UPGRADE) {
        if let Ok(s) = hdr.to_str() {
            s.to_lowercase().contains("websocket")
        } else {
            false
        }
    } else {
        false
    };
    if !has_hdr {
        return Err(HandshakeError::NoWebsocketUpgrade);
    }

    // Upgrade connection
    if !req.upgrade() {
        return Err(HandshakeError::NoConnectionUpgrade);
    }

    // check supported version
    if !req.headers().contains_key(header::SEC_WEBSOCKET_VERSION) {
        return Err(HandshakeError::NoVersionHeader);
    }
    let supported_ver = {
        if let Some(hdr) = req.headers().get(header::SEC_WEBSOCKET_VERSION) {
            hdr == "13" || hdr == "8" || hdr == "7"
        } else {
            false
        }
    };
    if !supported_ver {
        return Err(HandshakeError::UnsupportedVersion);
    }

    // check client handshake for validity
    if !req.headers().contains_key(header::SEC_WEBSOCKET_KEY) {
        return Err(HandshakeError::BadWebsocketKey);
    }
    let key = {
        let key = req.headers().get(header::SEC_WEBSOCKET_KEY).unwrap();
        proto::hash_key(key.as_ref())
    };

    Ok(HttpResponse::build(StatusCode::SWITCHING_PROTOCOLS)
        .connection_type(ConnectionType::Upgrade)
        .header(header::UPGRADE, "websocket")
        .header(header::TRANSFER_ENCODING, "chunked")
        .header(header::SEC_WEBSOCKET_ACCEPT, key.as_str())
        .take())
}

/// Maps `Payload` stream into stream of `ws::Message` items
pub struct WsStream<S> {
    rx: PayloadBuffer<S>,
    closed: bool,
    max_size: usize,
}

impl<S> WsStream<S>
where
    S: Stream<Item = Bytes, Error = PayloadError>,
{
    /// Create new websocket frames stream
    pub fn new(stream: S) -> WsStream<S> {
        WsStream {
            rx: PayloadBuffer::new(stream),
            closed: false,
            max_size: 65_536,
        }
    }

    /// Set max frame size
    ///
    /// By default max size is set to 64kb
    pub fn max_size(mut self, size: usize) -> Self {
        self.max_size = size;
        self
    }
}

impl<S> Stream for WsStream<S>
where
    S: Stream<Item = Bytes, Error = PayloadError>,
{
    type Item = Message;
    type Error = ProtocolError;

    fn poll(&mut self) -> Poll<Option<Self::Item>, Self::Error> {
        if self.closed {
            return Ok(Async::Ready(None));
        }

        match Frame::parse(&mut self.rx, true, self.max_size) {
            Ok(Async::Ready(Some(frame))) => {
                let (finished, opcode, payload) = frame.unpack();

                // continuation is not supported
                if !finished {
                    self.closed = true;
                    return Err(ProtocolError::NoContinuation);
                }

                match opcode {
                    OpCode::Continue => Err(ProtocolError::NoContinuation),
                    OpCode::Bad => {
                        self.closed = true;
                        Err(ProtocolError::BadOpCode)
                    }
                    OpCode::Close => {
                        self.closed = true;
                        let close_reason = Frame::parse_close_payload(&payload);
                        Ok(Async::Ready(Some(Message::Close(close_reason))))
                    }
                    OpCode::Ping => Ok(Async::Ready(Some(Message::Ping(
                        String::from_utf8_lossy(payload.as_ref()).into(),
                    )))),
                    OpCode::Pong => Ok(Async::Ready(Some(Message::Pong(
                        String::from_utf8_lossy(payload.as_ref()).into(),
                    )))),
                    OpCode::Binary => Ok(Async::Ready(Some(Message::Binary(payload)))),
                    OpCode::Text => {
                        let tmp = Vec::from(payload.as_ref());
                        match String::from_utf8(tmp) {
                            Ok(s) => Ok(Async::Ready(Some(Message::Text(s)))),
                            Err(_) => {
                                self.closed = true;
                                Err(ProtocolError::BadEncoding)
                            }
                        }
                    }
                }
            }
            Ok(Async::Ready(None)) => Ok(Async::Ready(None)),
            Ok(Async::NotReady) => Ok(Async::NotReady),
            Err(e) => {
                self.closed = true;
                Err(e)
            }
        }
    }
}

/// Common writing methods for a websocket.
pub trait WsWriter {
    /// Send a text
    fn send_text<T: Into<Binary>>(&mut self, text: T);
    /// Send a binary
    fn send_binary<B: Into<Binary>>(&mut self, data: B);
    /// Send a ping message
    fn send_ping(&mut self, message: &str);
    /// Send a pong message
    fn send_pong(&mut self, message: &str);
    /// Close the connection
    fn send_close(&mut self, reason: Option<CloseReason>);
}

#[cfg(test)]
mod tests {
    use super::*;
    use http::{header, Method};
    use test::TestRequest;

    #[test]
    fn test_handshake() {
        let req = TestRequest::default().method(Method::POST).finish();
        assert_eq!(
            HandshakeError::GetMethodRequired,
            handshake(&req).err().unwrap()
        );

        let req = TestRequest::default().finish();
        assert_eq!(
            HandshakeError::NoWebsocketUpgrade,
            handshake(&req).err().unwrap()
        );

        let req = TestRequest::default()
            .header(header::UPGRADE, header::HeaderValue::from_static("test"))
            .finish();
        assert_eq!(
            HandshakeError::NoWebsocketUpgrade,
            handshake(&req).err().unwrap()
        );

        let req = TestRequest::default()
            .header(
                header::UPGRADE,
                header::HeaderValue::from_static("websocket"),
            ).finish();
        assert_eq!(
            HandshakeError::NoConnectionUpgrade,
            handshake(&req).err().unwrap()
        );

        let req = TestRequest::default()
            .header(
                header::UPGRADE,
                header::HeaderValue::from_static("websocket"),
            ).header(
                header::CONNECTION,
                header::HeaderValue::from_static("upgrade"),
            ).finish();
        assert_eq!(
            HandshakeError::NoVersionHeader,
            handshake(&req).err().unwrap()
        );

        let req = TestRequest::default()
            .header(
                header::UPGRADE,
                header::HeaderValue::from_static("websocket"),
            ).header(
                header::CONNECTION,
                header::HeaderValue::from_static("upgrade"),
            ).header(
                header::SEC_WEBSOCKET_VERSION,
                header::HeaderValue::from_static("5"),
            ).finish();
        assert_eq!(
            HandshakeError::UnsupportedVersion,
            handshake(&req).err().unwrap()
        );

        let req = TestRequest::default()
            .header(
                header::UPGRADE,
                header::HeaderValue::from_static("websocket"),
            ).header(
                header::CONNECTION,
                header::HeaderValue::from_static("upgrade"),
            ).header(
                header::SEC_WEBSOCKET_VERSION,
                header::HeaderValue::from_static("13"),
            ).finish();
        assert_eq!(
            HandshakeError::BadWebsocketKey,
            handshake(&req).err().unwrap()
        );

        let req = TestRequest::default()
            .header(
                header::UPGRADE,
                header::HeaderValue::from_static("websocket"),
            ).header(
                header::CONNECTION,
                header::HeaderValue::from_static("upgrade"),
            ).header(
                header::SEC_WEBSOCKET_VERSION,
                header::HeaderValue::from_static("13"),
            ).header(
                header::SEC_WEBSOCKET_KEY,
                header::HeaderValue::from_static("13"),
            ).finish();
        assert_eq!(
            StatusCode::SWITCHING_PROTOCOLS,
            handshake(&req).unwrap().finish().status()
        );
    }

    #[test]
    fn test_wserror_http_response() {
        let resp: HttpResponse = HandshakeError::GetMethodRequired.error_response();
        assert_eq!(resp.status(), StatusCode::METHOD_NOT_ALLOWED);
        let resp: HttpResponse = HandshakeError::NoWebsocketUpgrade.error_response();
        assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
        let resp: HttpResponse = HandshakeError::NoConnectionUpgrade.error_response();
        assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
        let resp: HttpResponse = HandshakeError::NoVersionHeader.error_response();
        assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
        let resp: HttpResponse = HandshakeError::UnsupportedVersion.error_response();
        assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
        let resp: HttpResponse = HandshakeError::BadWebsocketKey.error_response();
        assert_eq!(resp.status(), StatusCode::BAD_REQUEST);
    }
}