//! ANSI escape-sequence stripping — keeps bench/console logs readable in
//! `sm121 report` and under grep/less (the pty-wrapped tool emits colors,
//! cursor moves, and OSC titles).

/// Strip ANSI escape sequences out of `buf` into `out`, in place. The
/// consumed prefix is drained from `buf`; a trailing partial escape (a
/// sequence split across chunk boundaries) is left in `buf` as the carry
/// for the next call. Handles CSI (`ESC [ ... final`), OSC (`ESC ] ... BEL`
/// or `ST`), and generic escapes with intermediate bytes (`ESC ( B`).
pub(crate) fn strip_ansi_step(buf: &mut Vec<u8>, out: &mut Vec<u8>) {
    let n = buf.len();
    let mut i = 0;
    while i < n {
        if buf[i] != 0x1b {
            out.push(buf[i]);
            i += 1;
            continue;
        }
        let rest = &buf[i + 1..];
        match rest.first() {
            Some(b'[') => match rest.iter().skip(1).position(|c| (0x40..=0x7e).contains(c)) {
                Some(p) => i += 1 + 1 + p + 1, // ESC [ params final
                None => break,                 // incomplete: wait for more data
            },
            Some(b']') => match rest.iter().skip(1).position(|c| *c == 0x07 || *c == 0x1b) {
                Some(p) => {
                    i += 1 + 1 + p + 1;
                    if rest[1 + p] == 0x1b {
                        i += 1; // consume the backslash of the ST
                    }
                }
                None => break,
            },
            None => break, // lone ESC at the chunk end
            Some(_) => {
                // Generic escape: intermediate bytes (0x20-0x2f), then one
                // final byte — drop all of them.
                let mut j = 1;
                while j < rest.len() && (0x20..=0x2f).contains(&rest[j]) {
                    j += 1;
                }
                if j < rest.len() {
                    j += 1; // final byte
                }
                i += 1 + j;
            }
        }
    }
    buf.drain(..i);
}

/// One-shot ANSI strip (whole buffer at once; for files already on disk).
pub(crate) fn strip_ansi(bytes: &[u8]) -> Vec<u8> {
    let mut buf = bytes.to_vec();
    let mut out = Vec::new();
    strip_ansi_step(&mut buf, &mut out);
    out
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn strip_ansi_removes_codes_keeps_text() {
        let raw = b"\x1b[38;5;214mred\x1b[0m plain \x1b]0;title\x07osc \x1b]2;x\x1b\\st \x1b(Bc";
        assert_eq!(strip_ansi(raw), b"red plain osc st c");
        // nothing to strip
        assert_eq!(strip_ansi(b"clean text"), b"clean text".to_vec());
    }

    #[test]
    fn strip_ansi_survives_split_chunks() {
        // the escape sequence straddles the chunk boundary
        let a = b"ab\x1b[38;5;2"; // split inside a CSI parameter
        let b2 = b"14mtext";
        let mut ca = Vec::new();
        ca.extend_from_slice(a);
        let mut out = Vec::new();
        strip_ansi_step(&mut ca, &mut out);
        ca.extend_from_slice(b2);
        strip_ansi_step(&mut ca, &mut out);
        assert_eq!(out, b"abtext");
        assert!(ca.is_empty(), "no dangling carry: {ca:?}");
    }
}