From 54e01824c7ad38b8cf289cbf4f153aca88073fb0 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 12 Dec 2022 12:17:46 +0100
Subject: [PATCH] LibWeb: Implement getting the top-level traversable of a
 navigable

---
 Userland/Libraries/LibWeb/HTML/Navigable.cpp | 14 ++++++++++++++
 Userland/Libraries/LibWeb/HTML/Navigable.h   |  1 +
 2 files changed, 15 insertions(+)

diff --git a/Userland/Libraries/LibWeb/HTML/Navigable.cpp b/Userland/Libraries/LibWeb/HTML/Navigable.cpp
index e1a464592e..5fab6968c6 100644
--- a/Userland/Libraries/LibWeb/HTML/Navigable.cpp
+++ b/Userland/Libraries/LibWeb/HTML/Navigable.cpp
@@ -95,4 +95,18 @@ JS::GCPtr<TraversableNavigable> Navigable::traversable_navigable()
     return static_cast<TraversableNavigable*>(navigable);
 }
 
+// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-top
+JS::GCPtr<TraversableNavigable> Navigable::top_level_traversable()
+{
+    // 1. Let navigable be inputNavigable.
+    auto navigable = this;
+
+    // 2. While navigable's parent is not null, set navigable to navigable's parent.
+    while (navigable->parent())
+        navigable = navigable->parent();
+
+    // 3. Return navigable.
+    return verify_cast<TraversableNavigable>(navigable);
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/HTML/Navigable.h b/Userland/Libraries/LibWeb/HTML/Navigable.h
index 553ae256e0..dc896e0d98 100644
--- a/Userland/Libraries/LibWeb/HTML/Navigable.h
+++ b/Userland/Libraries/LibWeb/HTML/Navigable.h
@@ -41,6 +41,7 @@ public:
     void set_container(JS::GCPtr<NavigableContainer>);
 
     JS::GCPtr<TraversableNavigable> traversable_navigable();
+    JS::GCPtr<TraversableNavigable> top_level_traversable();
 
 protected:
     Navigable();