strykelang 0.7.2

//! Memory-mapped parallel line iteration for `par_lines PATH, sub { ... }`.
//! Splits the file into byte ranges aligned to line starts, then processes each chunk in parallel
//! with rayon (each chunk scans its lines sequentially).

/// Build up to `max_chunks` contiguous byte ranges `[start, end)` covering `data`, where each
/// range starts at a line boundary (byte 0 or immediately after `\n`). Ranges partition the file
/// without splitting lines.
pub fn line_aligned_chunks(data: &[u8], max_chunks: usize) -> Vec<(usize, usize)> {
    let len = data.len();
    if len == 0 {
        return vec![];
    }
    let k = max_chunks.max(1).min(len);
    let mut splits: Vec<usize> = (0..=k).map(|i| i * len / k).collect();
    for split in splits.iter_mut().take(k).skip(1) {
        let mut p = *split;
        while p < len && p > 0 && data[p - 1] != b'\n' {
            p += 1;
        }
        *split = p;
    }
    for i in 1..=k {
        if splits[i] < splits[i - 1] {
            splits[i] = splits[i - 1];
        }
    }
    let mut out = Vec::new();
    for i in 0..k {
        let s = splits[i];
        let e = splits[i + 1];
        if s < e {
            out.push((s, e));
        }
    }
    if out.is_empty() {
        out.push((0, len));
    }
    out
}

/// Count newline-delimited lines (non-empty buffer; last line may omit trailing `\n`).
pub fn line_count_bytes(data: &[u8]) -> usize {
    if data.is_empty() {
        return 0;
    }
    let mut n = data.iter().filter(|&&b| b == b'\n').count();
    if !data.ends_with(b"\n") {
        n += 1;
    }
    n
}

/// Convert one line of bytes (no `\n`) to a Perl string; strips trailing `\r` for CRLF.
pub fn line_to_perl_string(line: &[u8]) -> String {
    let line = if line.ends_with(b"\r") && !line.is_empty() {
        &line[..line.len() - 1]
    } else {
        line
    };
    crate::perl_decode::decode_utf8_or_latin1_line(line)
}

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

    #[test]
    fn line_aligned_chunks_splits_without_breaking_lines() {
        let data = b"a\nbb\nccc\n";
        let chunks = line_aligned_chunks(data, 4);
        let rebuilt: Vec<u8> = chunks
            .iter()
            .flat_map(|(s, e)| data[*s..*e].iter().copied())
            .collect();
        assert_eq!(rebuilt, data);
        for (s, _e) in &chunks {
            if *s > 0 {
                assert_eq!(data[*s - 1], b'\n');
            }
        }
    }

    #[test]
    fn line_count_bytes_matches_scan() {
        assert_eq!(line_count_bytes(b""), 0);
        assert_eq!(line_count_bytes(b"a\nb"), 2);
        assert_eq!(line_count_bytes(b"a\nb\n"), 2);
        assert_eq!(line_count_bytes(b"a"), 1);
    }

    #[test]
    fn scan_lines_in_slice_three_lines() {
        let data = b"one\ntwo\nthree";
        let mut lines = Vec::new();
        let mut s = 0usize;
        while s < data.len() {
            let e = data[s..]
                .iter()
                .position(|&b| b == b'\n')
                .map(|p| s + p)
                .unwrap_or(data.len());
            lines.push(&data[s..e]);
            if e >= data.len() {
                break;
            }
            s = e + 1;
        }
        assert_eq!(lines, vec![&b"one"[..], &b"two"[..], &b"three"[..]]);
    }

    #[test]
    fn line_aligned_chunks_empty_input() {
        assert!(line_aligned_chunks(&[], 8).is_empty());
    }

    #[test]
    fn line_aligned_chunks_single_byte() {
        let c = line_aligned_chunks(b"x", 4);
        assert_eq!(c, vec![(0, 1)]);
    }

    #[test]
    fn line_aligned_chunks_max_chunks_zero_uses_one() {
        let data = b"a\nb\n";
        let c = line_aligned_chunks(data, 0);
        assert!(!c.is_empty());
        let rebuilt: Vec<u8> = c
            .iter()
            .flat_map(|(s, e)| data[*s..*e].iter().copied())
            .collect();
        assert_eq!(rebuilt, data);
    }

    #[test]
    fn line_to_perl_string_strips_cr() {
        assert_eq!(line_to_perl_string(b"row\r"), "row");
    }

    #[test]
    fn line_to_perl_string_invalid_utf8_maps_octets() {
        let s = line_to_perl_string(&[0xff, 0xfe]);
        assert_eq!(s, "\u{00ff}\u{00fe}");
    }
}