//! Buffered newline framing shared by stdin and endpoint connections.
#[cfg(any(target_os = "wasi", test))]
#[derive(Default)]
pub(crate) struct Lines {
    bytes: Vec<u8>,
    scanned: usize,
}
#[cfg(any(target_os = "wasi", test))]
impl Lines {
    fn frame(&mut self) -> Option<Vec<u8>> {
        if let Some(end) = self.bytes[self.scanned..].iter().position(|b| *b == b'\n') {
            let end = self.scanned + end;
            self.scanned = 0;
            return Some(self.bytes.drain(..=end).collect());
        }
        self.scanned = self.bytes.len();
        None
    }
    #[cfg(target_os = "wasi")]
    pub(crate) async fn next(
        &mut self,
        input: &mut impl wstd::io::AsyncRead,
    ) -> std::io::Result<Option<Vec<u8>>> {
        loop {
            if let Some(line) = self.frame() {
                return Ok(Some(line));
            }
            let mut buffer = [0; 8192];
            let count = input.read(&mut buffer).await?;
            if count == 0 {
                self.scanned = 0;
                return Ok(if self.bytes.is_empty() {
                    None
                } else {
                    Some(std::mem::take(&mut self.bytes))
                });
            }
            self.bytes.extend_from_slice(&buffer[..count]);
        }
    }
    #[cfg(target_os = "wasi")]
    pub(crate) async fn rpc(
        &mut self,
        input: &mut impl wstd::io::AsyncRead,
    ) -> std::io::Result<Option<serde_json::Value>> {
        while let Some(bytes) = self.next(input).await? {
            if let Ok(value) = serde_json::from_slice::<serde_json::Value>(&bytes)
                && value.is_object()
                && value["jsonrpc"] == "2.0"
            {
                return Ok(Some(value));
            }
        }
        Ok(None)
    }
}
#[cfg(test)]
mod tests {
    #[test]
    fn incomplete_frames_retain_the_scanned_length() {
        let mut lines = super::Lines::default();
        lines.bytes.extend_from_slice(b"first");
        assert!(lines.frame().is_none());
        assert_eq!(lines.scanned, 5);
        lines.bytes.extend_from_slice(b"\nsecond\n");
        assert_eq!(lines.frame().unwrap(), b"first\n");
        assert_eq!(lines.frame().unwrap(), b"second\n");
        assert!(lines.frame().is_none());
    }
}