From 32a7ce3f361c7ae00d950b42921790eb36de69d5 Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Wed, 27 Sep 2023 18:27:52 -0400
Subject: [PATCH] Implement a macro for iterators with multiple fields.

---
 src/iter/ast_node_iter.rs | 11 +++++++++++
 src/iter/macros.rs        | 40 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)

diff --git a/src/iter/ast_node_iter.rs b/src/iter/ast_node_iter.rs
index aa7adcd..1c08490 100644
--- a/src/iter/ast_node_iter.rs
+++ b/src/iter/ast_node_iter.rs
@@ -3,6 +3,7 @@ use std::marker::PhantomData;
 use super::ast_node::AstNode;
 use super::macros::children_iter;
 use super::macros::empty_iter;
+use super::macros::multi_field_iter;
 use crate::types::Bold;
 use crate::types::Code;
 use crate::types::Document;
@@ -35,6 +36,7 @@ pub enum AstNodeIter<'r, 's> {
     // Elements
     Paragraph(ParagraphIter<'r, 's>),
     PlainList(PlainListIter<'r, 's>),
+    PlainListItem(PlainListItemIter<'r, 's>),
     // GreaterBlock(GreaterBlockIter<'r, 's>),
     // DynamicBlock(DynamicBlockIter<'r, 's>),
     // FootnoteDefinition(FootnoteDefinitionIter<'r, 's>),
@@ -154,6 +156,15 @@ children_iter!(
     PlainListIter,
     std::slice::Iter<'r, PlainListItem<'s>>
 );
+
+multi_field_iter!(
+    PlainListItem<'s>,
+    PlainListItemIter,
+    tag,
+    std::slice::Iter<'r, Object<'s>>,
+    children,
+    std::slice::Iter<'r, Element<'s>>
+);
 children_iter!(Bold<'s>, BoldIter, std::slice::Iter<'r, Object<'s>>);
 children_iter!(Italic<'s>, ItalicIter, std::slice::Iter<'r, Object<'s>>);
 children_iter!(
diff --git a/src/iter/macros.rs b/src/iter/macros.rs
index c6f1901..3834d1b 100644
--- a/src/iter/macros.rs
+++ b/src/iter/macros.rs
@@ -72,3 +72,43 @@ macro_rules! empty_iter {
 }
 
 pub(crate) use empty_iter;
+
+/// Create iterators for ast nodes where it has to iterate over multiple child lists.
+macro_rules! multi_field_iter {
+    ($astnodetype:ty, $itertype:ident, $firstfieldname: ident, $firstinnertype:ty, $($fieldname: ident, $innertype:ty),*) => {
+        pub struct $itertype<'r, 's> {
+            $firstfieldname: $firstinnertype,
+            $(
+$fieldname: $innertype,
+),*
+        }
+
+        impl<'r, 's> Iterator for $itertype<'r, 's> {
+            type Item = AstNode<'r, 's>;
+
+            fn next(&mut self) -> Option<Self::Item> {
+                self.$firstfieldname.next().map(Into::<AstNode>::into)
+                $(
+.or_else(|| self.$fieldname.next().map(Into::<AstNode>::into))
+),*
+            }
+        }
+
+        impl<'r, 's> IntoIterator for &'r $astnodetype {
+            type Item = AstNode<'r, 's>;
+
+            type IntoIter = $itertype<'r, 's>;
+
+            fn into_iter(self) -> Self::IntoIter {
+                $itertype {
+            $firstfieldname: self.$firstfieldname.iter(),
+            $(
+$fieldname: self.$fieldname.iter(),
+),*
+                }
+            }
+        }
+    };
+}
+
+pub(crate) use multi_field_iter;