Implement heading parser.

src/parser/document.rs

@@ -3,8 +3,11 @@ use nom::bytes::complete::tag;
 use nom::character::complete::line_ending;
 use nom::character::complete::space1;
 use nom::combinator::eof;
+use nom::combinator::map;
 use nom::combinator::not;
 use nom::combinator::recognize;
+use nom::combinator::verify;
+use nom::multi::many0;
 use nom::multi::many1;
 use nom::multi::many1_count;
 use nom::sequence::tuple;
@@ -35,6 +38,7 @@ pub struct Document<'s> {
 #[derive(Debug)]
 pub struct Heading<'s> {
     pub source: &'s str,
+    pub stars: usize,
     pub children: Vec<DocumentElement<'s>>,
 }
 
@@ -96,7 +100,25 @@ fn section_end<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str,
 fn heading<'r, 's>(context: Context<'r, 's>, input: &'s str) -> Res<&'s str, Heading<'s>> {
     not(|i| context.check_exit_matcher(i))(input)?;
     let (remaining, (star_count, _ws, title, _ws2)) = headline(context, input)?;
-    todo!()
+    let section_matcher = parser_with_context!(section)(context);
+    // TODO: This needs to only match headings below the current level
+    let heading_matcher = parser_with_context!(heading)(context);
+    let (remaining, children) = many0(alt((
+        map(
+            verify(heading_matcher, |h| h.stars > star_count),
+            DocumentElement::Heading,
+        ),
+        map(section_matcher, DocumentElement::Section),
+    )))(remaining)?;
+    let source = get_consumed(input, remaining);
+    Ok((
+        remaining,
+        Heading {
+            source: source,
+            stars: star_count,
+            children,
+        },
+    ))
 }
 
 fn headline<'r, 's>(