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