1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133

use async_std::io::{BufRead as AsyncBufRead, Read as AsyncRead};
use async_std::prelude::*;
use async_std::task::{ready, Context, Poll};

use std::io;
use std::pin::Pin;
use std::time::Duration;

pin_project_lite::pin_project! {
    /// An SSE protocol encoder.

    #[derive(Debug)]
    pub struct Encoder {
        buf: Box<[u8]>,
        cursor: usize,
        #[pin]
        receiver: async_channel::Receiver<Vec<u8>>,
    }
}

impl AsyncRead for Encoder {
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut [u8],
    ) -> Poll<io::Result<usize>> {
        let mut this = self.project();
        // Request a new buffer if current one is exhausted.

        if this.buf.len() <= *this.cursor {
            match ready!(this.receiver.as_mut().poll_next(cx)) {
                Some(buf) => {
                    log::trace!("> Received a new buffer with len {}", buf.len());
                    *this.buf = buf.into_boxed_slice();
                    *this.cursor = 0;
                }
                None => {
                    log::trace!("> Encoder done reading");
                    return Poll::Ready(Ok(0));
                }
            };
        }

        // Write the current buffer to completion.

        let local_buf = &this.buf[*this.cursor..];
        let max = buf.len().min(local_buf.len());
        buf[..max].clone_from_slice(&local_buf[..max]);
        *this.cursor += max;

        // Return bytes read.

        Poll::Ready(Ok(max))
    }
}

impl AsyncBufRead for Encoder {
    fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
        let mut this = self.project();
        // Request a new buffer if current one is exhausted.

        if this.buf.len() <= *this.cursor {
            match ready!(this.receiver.as_mut().poll_next(cx)) {
                Some(buf) => {
                    log::trace!("> Received a new buffer with len {}", buf.len());
                    *this.buf = buf.into_boxed_slice();
                    *this.cursor = 0;
                }
                None => {
                    log::trace!("> Encoder done reading");
                    return Poll::Ready(Ok(&[]));
                }
            };
        }
        Poll::Ready(Ok(&this.buf[*this.cursor..]))
    }

    fn consume(self: Pin<&mut Self>, amt: usize) {
        let this = self.project();
        *this.cursor += amt;
    }
}

/// The sending side of the encoder.

#[derive(Debug, Clone)]
pub struct Sender(async_channel::Sender<Vec<u8>>);

/// Create a new SSE encoder.

pub fn encode() -> (Sender, Encoder) {
    let (sender, receiver) = async_channel::bounded(1);
    let encoder = Encoder {
        receiver,
        buf: Box::default(),
        cursor: 0,
    };
    (Sender(sender), encoder)
}

impl Sender {
    async fn inner_send(&self, bytes: impl Into<Vec<u8>>) -> io::Result<()> {
        self.0
            .send(bytes.into())
            .await
            .map_err(|_| io::Error::new(io::ErrorKind::ConnectionAborted, "sse disconnected"))
    }

    /// Send a new message over SSE.

    pub async fn send(&self, name: &str, data: &str, id: Option<&str>) -> io::Result<()> {
        // Write the event name

        let msg = format!("event:{}\n", name);
        self.inner_send(msg).await?;

        // Write the id

        if let Some(id) = id {
            self.inner_send(format!("id:{}\n", id)).await?;
        }

        // Write the data section, and end.

        let msg = format!("data:{}\n\n", data);
        self.inner_send(msg).await?;

        Ok(())
    }

    /// Send a new "retry" message over SSE.

    pub async fn send_retry(&self, dur: Duration, id: Option<&str>) -> io::Result<()> {
        // Write the id

        if let Some(id) = id {
            self.inner_send(format!("id:{}\n", id)).await?;
        }

        // Write the retry section, and end.

        let dur = dur.as_secs_f64() as u64;
        let msg = format!("retry:{}\n\n", dur);
        self.inner_send(msg).await?;
        Ok(())
    }
}