From 1d06d95bb1a788c086a47c5225165cd6212327f8 Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Tue, 29 Aug 2023 13:48:10 -0400
Subject: [PATCH] Add a minimum stars figure to heading parser to reduce
 re-parses.

---
 src/parser/document.rs | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/parser/document.rs b/src/parser/document.rs
index 4d84e5c2..efb85d51 100644
--- a/src/parser/document.rs
+++ b/src/parser/document.rs
@@ -139,7 +139,7 @@ fn _document<'r, 's>(
     input: OrgSource<'s>,
 ) -> Res<OrgSource<'s>, Document<'s>> {
     let zeroth_section_matcher = parser_with_context!(zeroth_section)(context);
-    let heading_matcher = parser_with_context!(heading)(context);
+    let heading_matcher = parser_with_context!(heading(0))(context);
     let (remaining, _blank_lines) = many0(blank_line)(input)?;
     let (remaining, zeroth_section) = opt(zeroth_section_matcher)(remaining)?;
     let (remaining, children) = many0(heading_matcher)(remaining)?;
@@ -266,21 +266,25 @@ fn section_end<'r, 's>(
     recognize(detect_headline)(input)
 }
 
+const fn heading(
+    parent_stars: usize,
+) -> impl for<'r, 's> Fn(Context<'r, 's>, OrgSource<'s>) -> Res<OrgSource<'s>, Heading<'s>> {
+    move |context: Context, input: OrgSource<'_>| _heading(context, input, parent_stars)
+}
+
 #[cfg_attr(feature = "tracing", tracing::instrument(ret, level = "debug"))]
-fn heading<'r, 's>(
+fn _heading<'r, 's>(
     context: Context<'r, 's>,
     input: OrgSource<'s>,
+    parent_stars: usize,
 ) -> Res<OrgSource<'s>, Heading<'s>> {
     not(|i| context.check_exit_matcher(i))(input)?;
     let (remaining, (star_count, _ws, maybe_todo_keyword, title, heading_tags)) =
-        headline(context, input)?;
+        headline(context, input, parent_stars)?;
     let section_matcher = parser_with_context!(section)(context);
-    let heading_matcher = parser_with_context!(heading)(context);
+    let heading_matcher = parser_with_context!(heading(star_count))(context);
     let (remaining, children) = many0(alt((
-        map(
-            verify(heading_matcher, |h| h.stars > star_count),
-            DocumentElement::Heading,
-        ),
+        map(heading_matcher, DocumentElement::Heading),
         map(section_matcher, DocumentElement::Section),
     )))(remaining)?;
     let source = get_consumed(input, remaining);
@@ -308,6 +312,7 @@ fn detect_headline<'s>(input: OrgSource<'s>) -> Res<OrgSource<'s>, ()> {
 fn headline<'r, 's>(
     context: Context<'r, 's>,
     input: OrgSource<'s>,
+    parent_stars: usize,
 ) -> Res<
     OrgSource<'s>,
     (
@@ -330,7 +335,9 @@ fn headline<'r, 's>(
         (_sol, star_count, ws, maybe_todo_keyword, title, maybe_tags, _ws, _line_ending),
     ) = tuple((
         start_of_line,
-        many1_count(tag("*")),
+        verify(many1_count(tag("*")), |star_count| {
+            *star_count > parent_stars
+        }),
         space1,
         opt(tuple((heading_keyword, space1))),
         many1(standard_set_object_matcher),