From 4359fc92667109e83573730a9c09950a11b3ded0 Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Wed, 27 Sep 2023 15:47:01 -0400
Subject: [PATCH] Introduce a macro for empty iterators.

---
 src/iter/ast_node_iter.rs | 19 ++++++++++++++-----
 src/iter/macros.rs        | 35 +++++++++++++++++++++++++++++++++--
 2 files changed, 47 insertions(+), 7 deletions(-)

diff --git a/src/iter/ast_node_iter.rs b/src/iter/ast_node_iter.rs
index 19b85c1..39d5b58 100644
--- a/src/iter/ast_node_iter.rs
+++ b/src/iter/ast_node_iter.rs
@@ -1,14 +1,21 @@
 use std::marker::PhantomData;
 
 use super::ast_node::AstNode;
-use super::macros::simple_iter;
+use super::macros::children_iter;
+use super::macros::empty_iter;
 use crate::types::Bold;
 use crate::types::Code;
 use crate::types::Italic;
 use crate::types::Object;
 use crate::types::StrikeThrough;
 use crate::types::Underline;
+use crate::types::Verbatim;
 
+/// Iterator over the AST nodes contained within the starting node.
+///
+/// This only iterates over the children, not the starting node itself. So an AstNodeIter::PlainList would only return PlainListItems, not the PlainList.
+///
+/// This only iterates over AST nodes, so an AstNodeIter::Heading would iterate over both the title and section contents, but it would not iterate over simple strings like the TODO keyword or priority.
 pub enum AstNodeIter<'r, 's> {
     // Document Nodes
     // Document(DocumentIter<'r, 's>),
@@ -43,7 +50,7 @@ pub enum AstNodeIter<'r, 's> {
     Underline(UnderlineIter<'r, 's>),
     StrikeThrough(StrikeThroughIter<'r, 's>),
     Code(CodeIter<'r, 's>),
-    // Verbatim(VerbatimIter<'r, 's>),
+    Verbatim(VerbatimIter<'r, 's>),
     // PlainText(PlainTextIter<'r, 's>),
     // RegularLink(RegularLinkIter<'r, 's>),
     // RadioLink(RadioLinkIter<'r, 's>),
@@ -91,13 +98,13 @@ impl<'r, 's> IntoIterator for &'r Bold<'s> {
     }
 }
 
-simple_iter!(Italic<'s>, ItalicIter, std::slice::Iter<'r, Object<'s>>);
-simple_iter!(
+children_iter!(Italic<'s>, ItalicIter, std::slice::Iter<'r, Object<'s>>);
+children_iter!(
     Underline<'s>,
     UnderlineIter,
     std::slice::Iter<'r, Object<'s>>
 );
-simple_iter!(
+children_iter!(
     StrikeThrough<'s>,
     StrikeThroughIter,
     std::slice::Iter<'r, Object<'s>>
@@ -126,3 +133,5 @@ impl<'r, 's> IntoIterator for &'r Code<'s> {
         }
     }
 }
+
+empty_iter!(Verbatim<'s>, VerbatimIter);
diff --git a/src/iter/macros.rs b/src/iter/macros.rs
index acb0f40..07b36fe 100644
--- a/src/iter/macros.rs
+++ b/src/iter/macros.rs
@@ -1,5 +1,5 @@
 /// Create iterators for ast nodes where it only has to iterate over children
-macro_rules! simple_iter {
+macro_rules! children_iter {
     ($astnodetype:ty, $itertype:ident, $innertype:ty) => {
         pub struct $itertype<'r, 's> {
             next: $innertype,
@@ -27,4 +27,35 @@ macro_rules! simple_iter {
     };
 }
 
-pub(crate) use simple_iter;
+pub(crate) use children_iter;
+
+/// Create iterators for ast nodes that do not contain any ast node children.
+macro_rules! empty_iter {
+    ($astnodetype:ty, $itertype:ident) => {
+        pub struct $itertype<'r, 's> {
+            phantom: PhantomData<&'r $astnodetype>,
+        }
+
+        impl<'r, 's> Iterator for $itertype<'r, 's> {
+            type Item = AstNode<'r, 's>;
+
+            fn next(&mut self) -> Option<Self::Item> {
+                None
+            }
+        }
+
+        impl<'r, 's> IntoIterator for &'r $astnodetype {
+            type Item = AstNode<'r, 's>;
+
+            type IntoIter = $itertype<'r, 's>;
+
+            fn into_iter(self) -> Self::IntoIter {
+                $itertype {
+                    phantom: PhantomData,
+                }
+            }
+        }
+    };
+}
+
+pub(crate) use empty_iter;