use crate::parser::{MarkdownEvent, MarkdownTag, MarkdownTagEnd};use std::ops::Range; struct InlineSpan {    range: Range<usize>,    content: Range<usize>,    is_code: bool,} impl InlineSpan {    fn opening<'a>(&self, source: &'a str) -> &'a str {        source            .get(self.range.start..self.content.start)            .unwrap_or("")    }     fn closing<'a>(&self, source: &'a str) -> &'a str {        source.get(self.content.end..self.range.end).unwrap_or("")    }} fn is_inline_span_tag(tag: &MarkdownTag) -> bool {    matches!(        tag,        MarkdownTag::Emphasis            | MarkdownTag::Strong            | MarkdownTag::Strikethrough            | MarkdownTag::Superscript            | MarkdownTag::Subscript            | MarkdownTag::Link { .. }    )} fn is_inline_span_tag_end(tag: &MarkdownTagEnd) -> bool {    matches!(        tag,        MarkdownTagEnd::Emphasis            | MarkdownTagEnd::Strong            | MarkdownTagEnd::Strikethrough            | MarkdownTagEnd::Superscript            | MarkdownTagEnd::Subscript            | MarkdownTagEnd::Link    )} fn inline_code_full_range(source: &str, content: &Range<usize>) -> Range<usize> {    let opening_ticks = source[..content.start]        .bytes()        .rev()        .take_while(|&byte| byte == b'`')        .count();    let closing_ticks = source[content.end..]        .bytes()        .take_while(|&byte| byte == b'`')        .count();    let ticks = opening_ticks.min(closing_ticks);    content.start - ticks..content.end + ticks} fn collect_inline_spans(source: &str, events: &[(Range<usize>, MarkdownEvent)]) -> Vec<InlineSpan> {    fn note_child(stack: &mut [(Range<usize>, Option<Range<usize>>)], child: &Range<usize>) {        for (_, content) in stack.iter_mut() {            match content {                Some(content) => content.end = content.end.max(child.end),                None => *content = Some(child.clone()),            }        }    }     let mut spans = Vec::new();    let mut stack: Vec<(Range<usize>, Option<Range<usize>>)> = Vec::new();    for (event_range, event) in events {        match event {            MarkdownEvent::Start(tag) if is_inline_span_tag(tag) => {                note_child(&mut stack, event_range);                stack.push((event_range.clone(), None));            }            MarkdownEvent::End(tag) if is_inline_span_tag_end(tag) => {                if let Some((range, content)) = stack.pop() {                    let content = content.unwrap_or(range.clone());                    spans.push(InlineSpan {                        range,                        content,                        is_code: false,                    });                }                note_child(&mut stack, event_range);            }            MarkdownEvent::Code | MarkdownEvent::SubstitutedCode(_) => {                let range = inline_code_full_range(source, event_range);                note_child(&mut stack, &range);                spans.push(InlineSpan {                    range,                    content: event_range.clone(),                    is_code: true,                });            }            _ => note_child(&mut stack, event_range),        }    }    spans} pub(crate) fn rebalanced_markdown_for_selection(    source: &str,    events: &[(Range<usize>, MarkdownEvent)],    root_block_starts: &[usize],    selection: Range<usize>,) -> String {    let Some(selection) = snap_to_char_boundaries(source, selection) else {        return String::new();    };     let (start_events, end_events) = boundary_block_events(events, root_block_starts, &selection);    let mut spans = collect_inline_spans(source, start_events);    spans.extend(collect_inline_spans(source, end_events));     let Some(selection) = snap_out_of_delimiters(&spans, selection) else {        return String::new();    };     if selection_is_only_inside_code_spans(&spans, &selection) {        return source[selection].to_string();    }     rebalance_delimiters(source, &spans, &selection)} /// Returns the events of the root blocks containing each selection boundary./// The second slice is empty when both boundaries share a block.fn boundary_block_events<'a>(    events: &'a [(Range<usize>, MarkdownEvent)],    root_block_starts: &[usize],    selection: &Range<usize>,) -> (    &'a [(Range<usize>, MarkdownEvent)],    &'a [(Range<usize>, MarkdownEvent)],) {    if root_block_starts.is_empty() {        return (events, &[]);    }    let start_block = root_block_index(root_block_starts, selection.start);    let end_block = root_block_index(root_block_starts, selection.end);    let start_events = root_block_events(events, root_block_starts, start_block);    if end_block == start_block {        (start_events, &[])    } else {        (            start_events,            root_block_events(events, root_block_starts, end_block),        )    }} fn root_block_index(root_block_starts: &[usize], offset: usize) -> usize {    root_block_starts        .partition_point(|block_start| *block_start <= offset)        .saturating_sub(1)} fn root_block_events<'a>(    events: &'a [(Range<usize>, MarkdownEvent)],    root_block_starts: &[usize],    block: usize,) -> &'a [(Range<usize>, MarkdownEvent)] {    let Some(&block_start) = root_block_starts.get(block) else {        return events;    };    let start = events.partition_point(|(range, _)| range.start < block_start);    let end = match root_block_starts.get(block + 1) {        Some(&next_block_start) => {            events.partition_point(|(range, _)| range.start < next_block_start)        }        None => events.len(),    };    events.get(start..end).unwrap_or(events)} fn snap_to_char_boundaries(source: &str, selection: Range<usize>) -> Option<Range<usize>> {    let mut start = selection.start.min(source.len());    let mut end = selection.end.min(source.len());    if start >= end {        return None;    }    while start > 0 && !source.is_char_boundary(start) {        start -= 1;    }    while end < source.len() && !source.is_char_boundary(end) {        end += 1;    }    Some(start..end)} /// Shrinks selection boundaries that fall inside delimiter syntax (`**`,/// etc.) so no delimiter is left half-selected:////// - an end in `**bold*|*` snaps back to `**bold|**`/// - a start in `*|*bold**` snaps forward to `**|bold**`////// This repeats until stable, since snapping can land inside a nested span's/// delimiter. Returns `None` if the selection becomes empty.fn snap_out_of_delimiters(spans: &[InlineSpan], selection: Range<usize>) -> Option<Range<usize>> {    let mut start = selection.start;    let mut end = selection.end;    loop {        let mut changed = false;        for span in spans {            if end > span.range.start && end <= span.content.start {                end = span.range.start;                changed = true;            } else if end > span.content.end && end <= span.range.end {                end = span.content.end;                changed = true;            }            if start >= span.range.start && start < span.content.start {                start = span.content.start;                changed = true;            } else if start >= span.content.end && start < span.range.end {                start = span.range.end;                changed = true;            }        }        if !changed {            break;        }    }    (start < end).then(|| start..end)} fn selection_is_only_inside_code_spans(spans: &[InlineSpan], selection: &Range<usize>) -> bool {    let contains = |span: &InlineSpan| {        span.content.start <= selection.start && selection.end <= span.content.end    };    spans.iter().any(|span| span.is_code && contains(span))        && !spans.iter().any(|span| !span.is_code && contains(span))} /// Re-adds delimiters cut off by the selection so the result is well-formed/// markdown:////// - selecting `old te` in `**bold text**` yields `**old te**`/// - nested spans are reopened outermost first: selecting `alic` in///   `**bold _italic_**` yields `**_alic_**`fn rebalance_delimiters(source: &str, spans: &[InlineSpan], selection: &Range<usize>) -> String {    let nesting_order = |a: &&InlineSpan, b: &&InlineSpan| {        a.range            .start            .cmp(&b.range.start)            .then(b.range.end.cmp(&a.range.end))    };     let mut open_at_start = spans        .iter()        .filter(|span| span.content.start <= selection.start && selection.start < span.content.end)        .collect::<Vec<_>>();    open_at_start.sort_by(nesting_order);     let mut open_at_end = spans        .iter()        .filter(|span| span.content.start < selection.end && selection.end <= span.content.end)        .collect::<Vec<_>>();    open_at_end.sort_by(nesting_order);     let mut result = String::new();    for span in &open_at_start {        result.push_str(span.opening(source));    }    result.push_str(&source[selection.clone()]);    for span in open_at_end.iter().rev() {        result.push_str(span.closing(source));    }     result} #[cfg(test)]mod tests {    use super::*;    use crate::parser::parse_markdown_with_options;    use util::test::marked_text_ranges;     fn markdown_for(source: &str, selection: Range<usize>) -> String {        let parsed = parse_markdown_with_options(source, false, false, false);        rebalanced_markdown_for_selection(            source,            &parsed.events,            &parsed.root_block_starts,            selection,        )    }     fn markdown_for_marked(marked_source: &str) -> String {        let (source, selection) = marked_range(marked_source);        markdown_for(&source, selection)    }     #[track_caller]    fn assert_marked_selection(marked_source: &str, expected: &str) {        assert_eq!(            markdown_for_marked(marked_source),            expected,            "source: {marked_source:?}"        );    }     #[track_caller]    fn marked_range(marked_source: &str) -> (String, Range<usize>) {        let (source, ranges) = marked_text_ranges(marked_source, false);        match ranges.as_slice() {            [selection] => (source, selection.clone()),            _ => panic!("expected exactly one «» range in marked source"),        }    }     fn inline_spans(source: &str) -> Vec<InlineSpan> {        let parsed = parse_markdown_with_options(source, false, false, false);        collect_inline_spans(source, &parsed.events)    }     #[track_caller]    fn assert_snapped(marked_selection: &str, marked_expected: Option<&str>, message: &str) {        let (source, selection) = marked_range(marked_selection);        let expected = marked_expected.map(|marked_expected| {            let (expected_source, range) = marked_range(marked_expected);            assert_eq!(                expected_source, source,                "expected must be marked on the same source"            );            range        });        assert_eq!(            snap_out_of_delimiters(&inline_spans(&source), selection),            expected,            "{message}"        );    }     #[test]    fn test_snap_out_of_delimiters() {        assert_snapped(            "**«bold»** rest",            Some("**«bold»** rest"),            "boundaries already in content must be untouched",        );        assert_snapped(            "*«*bold»** rest",            Some("**«bold»** rest"),            "a start in the opening delimiter must advance into the content",        );        assert_snapped(            "**«bold*»* rest",            Some("**«bold»** rest"),            "an end in the closing delimiter must retreat to the content end",        );        assert_snapped(            "**bold*«* rest»",            Some("**bold**« rest»"),            "a start in the closing delimiter must advance past the whole span",        );        assert_snapped(            "«*»*bold** rest",            None,            "an end in the opening delimiter must retreat to before the span",        );        assert_snapped(            "**bold«**» rest",            None,            "a selection covering only delimiter text must collapse",        );    }     #[test]    fn test_snap_out_of_delimiters_cascades_through_nested_spans() {        assert_snapped(            "**`«code`*»*",            Some("**`«code»`**"),            "an end inside bold's closing `**` first snaps to code's closing \             backtick, so it must cascade into the code content",        );    }     #[test]    fn test_snap_to_char_boundaries() {        // `√` occupies bytes 1..4.        let source = "a√b";        assert_eq!(            snap_to_char_boundaries(source, 0..5),            Some(0..5),            "boundaries already on char boundaries must be untouched"        );        assert_eq!(            snap_to_char_boundaries(source, 0..2),            Some(0..4),            "an end mid-character must expand forward to keep the character"        );        assert_eq!(            snap_to_char_boundaries(source, 2..5),            Some(1..5),            "a start mid-character must expand backward to keep the character"        );        assert_eq!(            snap_to_char_boundaries(source, 2..3),            Some(1..4),            "a selection entirely inside a character must cover the whole character"        );        assert_eq!(            snap_to_char_boundaries(source, 2..10),            Some(1..5),            "an end past the source must clamp to its length"        );        assert_eq!(            snap_to_char_boundaries(source, 2..2),            None,            "an empty selection must collapse, even mid-character"        );        assert_eq!(            snap_to_char_boundaries(source, 5..10),            None,            "a selection entirely past the source must collapse"        );        assert_eq!(            snap_to_char_boundaries(source, Range { start: 4, end: 2 }),            None,            "a reversed selection must collapse"        );    }     fn selection_is_plain(marked_source: &str) -> bool {        let (source, selection) = marked_range(marked_source);        selection_is_only_inside_code_spans(&inline_spans(&source), &selection)    }     #[test]    fn test_selection_is_only_inside_code_spans() {        assert!(            selection_is_plain("run `«cargo» test` now"),            "a selection fully inside the code span's content must be plain"        );        assert!(            !selection_is_plain("«run `cargo» test` now"),            "a selection reaching outside the code span must not be plain"        );        assert!(            !selection_is_plain("**`«code»`**"),            "code nested in bold must not be plain: the bold span also contains it"        );    }     #[test]    fn test_markdown_for_selection_balances_inline_spans() {        assert_marked_selection("This is **«bold»** text in a sentence.", "**bold**");        assert_marked_selection("This is **«bold**» text in a sentence.", "**bold**");        assert_marked_selection("Th«is is **bo»ld** text in a sentence.", "is is **bo**");         assert_marked_selection("This is *«italic»* text in a sentence.", "*italic*");        assert_marked_selection("This is *it«al»ic* text in a sentence.", "*al*");         assert_marked_selection("T«his is `cod»e` all `in one` sentence.", "his is `cod`");        assert_marked_selection(            "This is `c«ode` all `in o»ne` sentence.",            "`ode` all `in o`",        );        assert_marked_selection(            "This is `«code` all `in one»` sentence.",            "`code` all `in one`",        );        assert_marked_selection(            "This is `«code` all `in one`» sentence.",            "`code` all `in one`",        );         // Special case for single inline code blocks        assert_marked_selection("This is `«code»` all `in one` sentence.", "code");        assert_marked_selection("This is `«code`» all `in one` sentence.", "code");        assert_marked_selection("This is `c«od»e` all `in one` sentence.", "od");    }     #[test]    fn test_markdown_for_selection_nested_spans() {        assert_marked_selection("**bo«ld wi»th `code` inside**", "**ld wi**");        assert_marked_selection("**bold with `c«od»e` inside**", "**`od`**");        assert_marked_selection("**bold with `«code»` inside**", "**`code`**");        assert_marked_selection(            "**«bold with `code` inside»**",            "**bold with `code` inside**",        );        assert_marked_selection(            "«**bold with `code` inside**»",            "**bold with `code` inside**",        );    }     #[test]    fn test_markdown_for_selection_links() {        assert_marked_selection(            "[Visit Rust's we«bsite»](https://rust.org)",            "[bsite](https://rust.org)",        );        assert_marked_selection(            "[«Visit Rust's website»](https://rust.org)",

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