helix-mods/helix-core/src/surround.rs

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use std::fmt::Display;
use crate::{search, Range, Selection};
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use ropey::RopeSlice;
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pub const PAIRS: &[(char, char)] = &[
('(', ')'),
('[', ']'),
('{', '}'),
('<', '>'),
('«', '»'),
('「', '」'),
('', ''),
];
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#[derive(Debug, PartialEq)]
pub enum Error {
PairNotFound,
CursorOverlap,
RangeExceedsText,
CursorOnAmbiguousPair,
}
impl Display for Error {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.write_str(match *self {
Error::PairNotFound => "Surround pair not found around all cursors",
Error::CursorOverlap => "Cursors overlap for a single surround pair range",
Error::RangeExceedsText => "Cursor range exceeds text length",
Error::CursorOnAmbiguousPair => "Cursor on ambiguous surround pair",
})
}
}
type Result<T> = std::result::Result<T, Error>;
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/// Given any char in [PAIRS], return the open and closing chars. If not found in
/// [PAIRS] return (ch, ch).
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///
/// ```
/// use helix_core::surround::get_pair;
///
/// assert_eq!(get_pair('['), ('[', ']'));
/// assert_eq!(get_pair('}'), ('{', '}'));
/// assert_eq!(get_pair('"'), ('"', '"'));
/// ```
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pub fn get_pair(ch: char) -> (char, char) {
PAIRS
.iter()
.find(|(open, close)| *open == ch || *close == ch)
.copied()
.unwrap_or((ch, ch))
}
/// Find the position of surround pairs of `ch` which can be either a closing
/// or opening pair. `n` will skip n - 1 pairs (eg. n=2 will discard (only)
/// the first pair found and keep looking)
pub fn find_nth_pairs_pos(
text: RopeSlice,
ch: char,
range: Range,
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n: usize,
) -> Result<(usize, usize)> {
if text.len_chars() < 2 {
return Err(Error::PairNotFound);
}
if range.to() >= text.len_chars() {
return Err(Error::RangeExceedsText);
}
let (open, close) = get_pair(ch);
let pos = range.cursor(text);
let (open, close) = if open == close {
if Some(open) == text.get_char(pos) {
// Cursor is directly on match char. We return no match
// because there's no way to know which side of the char
// we should be searching on.
return Err(Error::CursorOnAmbiguousPair);
}
(
search::find_nth_prev(text, open, pos, n),
search::find_nth_next(text, close, pos, n),
)
} else {
(
find_nth_open_pair(text, open, close, pos, n),
find_nth_close_pair(text, open, close, pos, n),
)
};
Option::zip(open, close).ok_or(Error::PairNotFound)
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}
fn find_nth_open_pair(
text: RopeSlice,
open: char,
close: char,
mut pos: usize,
n: usize,
) -> Option<usize> {
let mut chars = text.chars_at(pos + 1);
// Adjusts pos for the first iteration, and handles the case of the
// cursor being *on* the close character which will get falsely stepped over
// if not skipped here
if chars.prev()? == open {
return Some(pos);
}
for _ in 0..n {
let mut step_over: usize = 0;
loop {
let c = chars.prev()?;
pos = pos.saturating_sub(1);
// ignore other surround pairs that are enclosed *within* our search scope
if c == close {
step_over += 1;
} else if c == open {
if step_over == 0 {
break;
}
step_over = step_over.saturating_sub(1);
}
}
}
Some(pos)
}
fn find_nth_close_pair(
text: RopeSlice,
open: char,
close: char,
mut pos: usize,
n: usize,
) -> Option<usize> {
if pos >= text.len_chars() {
return None;
}
let mut chars = text.chars_at(pos);
if chars.next()? == close {
return Some(pos);
}
for _ in 0..n {
let mut step_over: usize = 0;
loop {
let c = chars.next()?;
pos += 1;
if c == open {
step_over += 1;
} else if c == close {
if step_over == 0 {
break;
}
step_over = step_over.saturating_sub(1);
}
}
}
Some(pos)
}
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/// Find position of surround characters around every cursor. Returns None
/// if any positions overlap. Note that the positions are in a flat Vec.
/// Use get_surround_pos().chunks(2) to get matching pairs of surround positions.
/// `ch` can be either closing or opening pair.
pub fn get_surround_pos(
text: RopeSlice,
selection: &Selection,
ch: char,
skip: usize,
) -> Result<Vec<usize>> {
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let mut change_pos = Vec::new();
for &range in selection {
let (open_pos, close_pos) = find_nth_pairs_pos(text, ch, range, skip)?;
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if change_pos.contains(&open_pos) || change_pos.contains(&close_pos) {
return Err(Error::CursorOverlap);
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}
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change_pos.extend_from_slice(&[open_pos, close_pos]);
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}
Ok(change_pos)
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}
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#[cfg(test)]
mod test {
use super::*;
use crate::Range;
use ropey::Rope;
use smallvec::SmallVec;
#[allow(clippy::type_complexity)]
fn check_find_nth_pair_pos(
text: &str,
cases: Vec<(usize, char, usize, Result<(usize, usize)>)>,
) {
let doc = Rope::from(text);
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let slice = doc.slice(..);
for (cursor_pos, ch, n, expected_range) in cases {
let range = find_nth_pairs_pos(slice, ch, (cursor_pos, cursor_pos + 1).into(), n);
assert_eq!(
range, expected_range,
"Expected {:?}, got {:?}",
expected_range, range
);
}
}
#[test]
fn test_find_nth_pairs_pos() {
check_find_nth_pair_pos(
"some (text) here",
vec![
// cursor on [t]ext
(6, '(', 1, Ok((5, 10))),
(6, ')', 1, Ok((5, 10))),
// cursor on so[m]e
(2, '(', 1, Err(Error::PairNotFound)),
// cursor on bracket itself
(5, '(', 1, Ok((5, 10))),
(10, '(', 1, Ok((5, 10))),
],
);
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}
#[test]
fn test_find_nth_pairs_pos_skip() {
check_find_nth_pair_pos(
"(so (many (good) text) here)",
vec![
// cursor on go[o]d
(13, '(', 1, Ok((10, 15))),
(13, '(', 2, Ok((4, 21))),
(13, '(', 3, Ok((0, 27))),
],
);
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}
#[test]
fn test_find_nth_pairs_pos_same() {
check_find_nth_pair_pos(
"'so 'many 'good' text' here'",
vec![
// cursor on go[o]d
(13, '\'', 1, Ok((10, 15))),
(13, '\'', 2, Ok((4, 21))),
(13, '\'', 3, Ok((0, 27))),
// cursor on the quotes
(10, '\'', 1, Err(Error::CursorOnAmbiguousPair)),
],
)
}
#[test]
fn test_find_nth_pairs_pos_step() {
check_find_nth_pair_pos(
"((so)((many) good (text))(here))",
vec![
// cursor on go[o]d
(15, '(', 1, Ok((5, 24))),
(15, '(', 2, Ok((0, 31))),
],
)
}
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#[test]
fn test_find_nth_pairs_pos_mixed() {
check_find_nth_pair_pos(
"(so [many {good} text] here)",
vec![
// cursor on go[o]d
(13, '{', 1, Ok((10, 15))),
(13, '[', 1, Ok((4, 21))),
(13, '(', 1, Ok((0, 27))),
],
)
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}
#[test]
fn test_get_surround_pos() {
let doc = Rope::from("(some) (chars)\n(newline)");
let slice = doc.slice(..);
let selection = Selection::new(
SmallVec::from_slice(&[Range::point(2), Range::point(9), Range::point(20)]),
0,
);
// cursor on s[o]me, c[h]ars, newl[i]ne
assert_eq!(
get_surround_pos(slice, &selection, '(', 1)
.unwrap()
.as_slice(),
&[0, 5, 7, 13, 15, 23]
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);
}
#[test]
fn test_get_surround_pos_bail() {
let doc = Rope::from("[some]\n(chars)xx\n(newline)");
let slice = doc.slice(..);
let selection =
Selection::new(SmallVec::from_slice(&[Range::point(2), Range::point(9)]), 0);
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// cursor on s[o]me, c[h]ars
assert_eq!(
get_surround_pos(slice, &selection, '(', 1),
Err(Error::PairNotFound) // different surround chars
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);
let selection = Selection::new(
SmallVec::from_slice(&[Range::point(14), Range::point(24)]),
0,
);
// cursor on [x]x, newli[n]e
assert_eq!(
get_surround_pos(slice, &selection, '(', 1),
Err(Error::PairNotFound) // overlapping surround chars
);
let selection =
Selection::new(SmallVec::from_slice(&[Range::point(2), Range::point(3)]), 0);
// cursor on s[o][m]e
assert_eq!(
get_surround_pos(slice, &selection, '[', 1),
Err(Error::CursorOverlap)
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);
}
}