#[inline]
pub(crate) fn strip_sse_field<'a>(line: &'a str, field: &str) -> Option<&'a str> {
    line.strip_prefix(&format!("{field}: "))
        .or_else(|| line.strip_prefix(&format!("{field}:")))
}

#[inline]
pub(crate) fn take_sse_block(buffer: &mut String) -> Option<String> {
    let mut best: Option<(usize, usize)> = None;

    for (delimiter, len) in [("\r\n\r\n", 4usize), ("\n\n", 2usize)] {
        if let Some(pos) = buffer.find(delimiter) {
            if best.is_none_or(|(best_pos, _)| pos < best_pos) {
                best = Some((pos, len));
            }
        }
    }

    let (pos, len) = best?;
    let block = buffer[..pos].to_string();
    buffer.drain(..pos + len);
    Some(block)
}

#[cfg(test)]
mod tests {
    use super::{strip_sse_field, take_sse_block};

    #[test]
    fn strip_sse_field_accepts_optional_space() {
        assert_eq!(
            strip_sse_field("data: {\"ok\":true}", "data"),
            Some("{\"ok\":true}")
        );
        assert_eq!(
            strip_sse_field("data:{\"ok\":true}", "data"),
            Some("{\"ok\":true}")
        );
        assert_eq!(
            strip_sse_field("event: message_start", "event"),
            Some("message_start")
        );
        assert_eq!(
            strip_sse_field("event:message_start", "event"),
            Some("message_start")
        );
        assert_eq!(strip_sse_field("id:1", "data"), None);
    }

    #[test]
    fn take_sse_block_supports_lf_delimiters() {
        let mut buffer = "data: {\"ok\":true}\n\nrest".to_string();

        assert_eq!(
            take_sse_block(&mut buffer),
            Some("data: {\"ok\":true}".to_string())
        );
        assert_eq!(buffer, "rest");
    }

    #[test]
    fn take_sse_block_supports_crlf_delimiters() {
        let mut buffer = "data: {\"ok\":true}\r\n\r\nrest".to_string();

        assert_eq!(
            take_sse_block(&mut buffer),
            Some("data: {\"ok\":true}".to_string())
        );
        assert_eq!(buffer, "rest");
    }
}