//! pkt-line framing for smart HTTP.

use crate::service::GitService;

/// The flush packet `0000`.
pub const FLUSH_PKT: &[u8] = b"0000";

/// Frames `data` as a pkt-line (4 hex length digits, including the 4 length bytes).
/// The payload must be at most 65516 bytes; callers pass short protocol strings.
pub fn pkt_line(data: &str) -> Vec<u8> {
    let len = data.len() + 4;
    debug_assert!(len <= 0xffff, "pkt-line payload too long");
    let mut out = format!("{len:04x}").into_bytes();
    out.extend_from_slice(data.as_bytes());
    out
}

/// The smart-HTTP advertisement preamble: `# service=git-<svc>` as a pkt-line, then a flush.
pub fn service_advertisement_header(svc: GitService) -> Vec<u8> {
    let mut out = pkt_line(&format!("# service={}\n", svc.name()));
    out.extend_from_slice(FLUSH_PKT);
    out
}