hjkl-engine 0.34.2

//! Pure rope helpers — no editor, host, or vim state involved.
//!
//! These lived in `vim.rs` for historical reasons, which made the
//! mode-agnostic engine core (`substitute.rs`, `editor.rs`) appear to depend
//! on the vim discipline when it only ever wanted rope utilities. Hoisting
//! them here removes the last real engine-core → `vim::` call so `vim.rs` can
//! relocate into `hjkl-vim` (#267 / #265).

/// Return row `r` from a rope as an owned `String`, stripping the
/// trailing `\n` that ropey includes on non-final lines.
pub fn rope_line_to_str(rope: &ropey::Rope, r: usize) -> String {
    let s = rope.line(r).to_string();
    // ropey includes the newline; strip it so callers see bare content.
    if s.ends_with('\n') {
        s[..s.len() - 1].to_string()
    } else {
        s
    }
}

/// Join rows `lo..=hi` from a rope into a single `String` separated by
/// `\n`. Callers must ensure `lo <= hi < rope.len_lines()`.
pub fn rope_row_range_str(rope: &ropey::Rope, lo: usize, hi: usize) -> String {
    let n = rope.len_lines();
    let lo = lo.min(n.saturating_sub(1));
    let hi = hi.min(n.saturating_sub(1));
    if lo > hi {
        return String::new();
    }
    // Use byte-slice to grab the full range in one rope walk.
    let start_byte = rope.line_to_byte(lo);
    // End byte: start of line hi+1, minus the newline separator, or
    // len_bytes() when hi is the last line.
    let end_byte = if hi + 1 < n {
        // line_to_byte(hi+1) points at the \n-terminated start of
        // the next line; step back one byte to drop that trailing \n.
        rope.line_to_byte(hi + 1).saturating_sub(1)
    } else {
        rope.len_bytes()
    };
    rope.byte_slice(start_byte..end_byte).to_string()
}

/// Snapshot all rows from a rope as `Vec<String>` (no trailing `\n`).
/// Use only when the caller truly needs mutable per-row access; prefer
/// rope iterators otherwise.
pub fn rope_to_lines_vec(rope: &ropey::Rope) -> Vec<String> {
    let n = rope.len_lines();
    (0..n).map(|r| rope_line_to_str(rope, r)).collect()
}

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

    #[test]
    fn line_to_str_strips_newline() {
        let rope = Rope::from_str("abc\ndef\n");
        assert_eq!(rope_line_to_str(&rope, 0), "abc");
        assert_eq!(rope_line_to_str(&rope, 1), "def");
    }

    #[test]
    fn line_to_str_final_line_without_newline() {
        let rope = Rope::from_str("abc\ndef");
        assert_eq!(rope_line_to_str(&rope, 1), "def");
    }

    #[test]
    fn row_range_str_joins_inclusive() {
        let rope = Rope::from_str("a\nb\nc\n");
        assert_eq!(rope_row_range_str(&rope, 0, 1), "a\nb");
        assert_eq!(rope_row_range_str(&rope, 1, 2), "b\nc");
    }

    #[test]
    fn row_range_str_single_row() {
        let rope = Rope::from_str("a\nb\nc");
        assert_eq!(rope_row_range_str(&rope, 1, 1), "b");
    }

    #[test]
    fn row_range_str_clamps_out_of_bounds() {
        let rope = Rope::from_str("a\nb");
        // hi past the end clamps to the last row rather than panicking.
        assert_eq!(rope_row_range_str(&rope, 0, 99), "a\nb");
    }

    #[test]
    fn row_range_str_empty_when_lo_gt_hi() {
        let rope = Rope::from_str("a\nb\nc");
        assert_eq!(rope_row_range_str(&rope, 2, 1), "");
    }

    #[test]
    fn to_lines_vec_snapshots_all_rows() {
        let rope = Rope::from_str("a\nb\nc");
        assert_eq!(rope_to_lines_vec(&rope), vec!["a", "b", "c"]);
    }
}