From 708263790a9da79af87dc2356060bc20d8b0fd91 Mon Sep 17 00:00:00 2001
From: Shannon Booth <shannon@serenityos.org>
Date: Fri, 25 Aug 2023 12:16:44 +1200
Subject: [PATCH] LibWeb: Implement LiveNodeList::first_matching

This function returns the first element which matches both the filter
for the LiveNodeList collection itself, and a further filter that is
supplied as an argument to this function.
---
 .../Libraries/LibWeb/DOM/LiveNodeList.cpp     | 23 +++++++++++++++++++
 Userland/Libraries/LibWeb/DOM/LiveNodeList.h  |  2 ++
 2 files changed, 25 insertions(+)

diff --git a/Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp b/Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp
index e3743ff454..677178d98a 100644
--- a/Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp
+++ b/Userland/Libraries/LibWeb/DOM/LiveNodeList.cpp
@@ -52,6 +52,29 @@ JS::MarkedVector<Node*> LiveNodeList::collection() const
     return nodes;
 }
 
+Node* LiveNodeList::first_matching(Function<bool(Node const&)> const& filter) const
+{
+    Node* matched_node = nullptr;
+    if (m_scope == Scope::Descendants) {
+        m_root->for_each_in_subtree([&](auto& node) {
+            if (m_filter(node) && filter(node)) {
+                matched_node = const_cast<Node*>(&node);
+                return IterationDecision::Break;
+            }
+            return IterationDecision::Continue;
+        });
+    } else {
+        m_root->for_each_child([&](auto& node) {
+            if (m_filter(node) && filter(node)) {
+                matched_node = const_cast<Node*>(&node);
+                return IterationDecision::Break;
+            }
+            return IterationDecision::Continue;
+        });
+    }
+    return matched_node;
+}
+
 // https://dom.spec.whatwg.org/#dom-nodelist-length
 u32 LiveNodeList::length() const
 {
diff --git a/Userland/Libraries/LibWeb/DOM/LiveNodeList.h b/Userland/Libraries/LibWeb/DOM/LiveNodeList.h
index 80b97d66b5..b99fcadde0 100644
--- a/Userland/Libraries/LibWeb/DOM/LiveNodeList.h
+++ b/Userland/Libraries/LibWeb/DOM/LiveNodeList.h
@@ -34,6 +34,8 @@ public:
 protected:
     LiveNodeList(JS::Realm&, Node& root, Scope, Function<bool(Node const&)> filter);
 
+    Node* first_matching(Function<bool(Node const&)> const& filter) const;
+
 private:
     virtual void visit_edges(Cell::Visitor&) override;