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//! Infer things from events.
//!
//! Used to share between `to_html` and `to_mdast`.
use crate::mdx_parser::event::{Event, Kind, Name};
use crate::mdx_parser::mdast::AlignKind;
use alloc::{vec, vec::Vec};
/// Whether lists and list items are spread (loose), found in one pass.
#[derive(Debug)]
pub struct ListSpread {
/// For each list and item enter, in order: `(enter, spread, loose)`.
entries: Vec<(usize, bool, bool)>,
}
impl ListSpread {
pub fn new(events: &[Event]) -> ListSpread {
let mut entries: Vec<(usize, bool, bool)> = vec![];
// Per open event: the entry of a list or item.
let mut open: Vec<Option<usize>> = vec![];
for (index, event) in events.iter().enumerate() {
if event.kind == Kind::Enter {
let entry = if matches!(event.name, Name::ListOrdered | Name::ListUnordered | Name::ListItem) {
entries.push((index, false, false));
Some(entries.len() - 1)
} else {
None
};
open.push(entry);
continue;
}
let entry = open.pop().flatten();
if let Some(Some(parent)) = open.last() {
let parent = *parent;
let is_item = events[entries[parent].0].name == Name::ListItem;
if event.name == Name::BlankLineEnding
&& !(if is_item {
item_blank_after_prefix(events, index)
} else {
list_blank_after_empty(events, index)
})
{
entries[parent].1 = true;
entries[parent].2 = true;
}
if let Some(entry) = entry {
if !is_item && events[entries[entry].0].name == Name::ListItem && entries[entry].1 {
entries[parent].2 = true;
}
}
}
}
ListSpread { entries }
}
fn entry(&self, enter: usize) -> (usize, bool, bool) {
let position = self
.entries
.binary_search_by_key(&enter, |entry| entry.0)
.expect("expected list or list item");
self.entries[position]
}
/// Whether the list or item entered at `enter` is spread.
pub fn spread(&self, enter: usize) -> bool {
self.entry(enter).1
}
/// Whether the list entered at `enter` is spread or has a spread item.
pub fn loose(&self, enter: usize) -> bool {
self.entry(enter).2
}
}
/// Whether the blank line ending at `index`, directly in a list, is right
/// after an empty item or block quote prefix.
fn list_blank_after_empty(events: &[Event], index: usize) -> bool {
// Blank line directly after item, which is just a prefix.
//
// ```markdown
// > | -␊
// ^
// | - a
// ```
//
// Blank line at block quote prefix:
//
// ```markdown
// > | * >␊
// ^
// | * a
// ```
let mut before = index - 2;
if events[before].name == Name::ListItem {
before -= 1;
if events[before].name == Name::SpaceOrTab {
before -= 2;
}
(events[before].name == Name::BlockQuote && events[before - 1].name == Name::BlockQuotePrefix)
|| events[before].name == Name::ListItemPrefix
} else {
false
}
}
/// Whether the blank line ending at `index`, directly in a list item, is right
/// after its prefix.
fn item_blank_after_prefix(events: &[Event], index: usize) -> bool {
// Blank line directly after a prefix:
//
// ```markdown
// > | -␊
// ^
// | a
// ```
let mut before = index - 2;
if events[before].name == Name::SpaceOrTab {
before -= 2;
}
events[before].name == Name::ListItemPrefix
}
/// Figure out the alignment of a GFM table.
pub fn gfm_table_align(events: &[Event], mut index: usize) -> Vec<AlignKind> {
debug_assert!(matches!(events[index].name, Name::GfmTable), "expected table");
let mut in_delimiter_row = false;
let mut align = vec![];
while index < events.len() {
let event = &events[index];
if in_delimiter_row {
if event.kind == Kind::Enter {
// Start of alignment value: set a new column.
if event.name == Name::GfmTableDelimiterCellValue {
align.push(if events[index + 1].name == Name::GfmTableDelimiterMarker {
AlignKind::Left
} else {
AlignKind::None
});
}
} else {
// End of alignment value: change the column.
if event.name == Name::GfmTableDelimiterCellValue {
if events[index - 1].name == Name::GfmTableDelimiterMarker {
let align_index = align.len() - 1;
align[align_index] = if align[align_index] == AlignKind::Left {
AlignKind::Center
} else {
AlignKind::Right
}
}
}
// Done!
else if event.name == Name::GfmTableDelimiterRow {
break;
}
}
} else if event.kind == Kind::Enter && event.name == Name::GfmTableDelimiterRow {
in_delimiter_row = true;
}
index += 1;
}
align
}