LibWeb: Implement creation of fresh top-level traversables

Co-authored-by: Andreas Kling <kling@serenityos.org>

Userland/Libraries/LibWeb/HTML/TraversableNavigable.cpp

@@ -4,6 +4,10 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibWeb/Bindings/MainThreadVM.h>
+#include <LibWeb/DOM/Document.h>
+#include <LibWeb/HTML/BrowsingContextGroup.h>
+#include <LibWeb/HTML/DocumentState.h>
 #include <LibWeb/HTML/SessionHistoryEntry.h>
 #include <LibWeb/HTML/TraversableNavigable.h>
 
@@ -20,6 +24,92 @@ void TraversableNavigable::visit_edges(Cell::Visitor& visitor)
         visitor.visit(entry);
 }
 
+static OrderedHashTable<TraversableNavigable*>& user_agent_top_level_traversable_set()
+{
+    static OrderedHashTable<TraversableNavigable*> set;
+    return set;
+}
+
+struct BrowsingContextAndDocument {
+    JS::NonnullGCPtr<HTML::BrowsingContext> browsing_context;
+    JS::NonnullGCPtr<DOM::Document> document;
+};
+
+// https://html.spec.whatwg.org/multipage/document-sequences.html#creating-a-new-top-level-browsing-context
+static WebIDL::ExceptionOr<BrowsingContextAndDocument> create_a_new_top_level_browsing_context_and_document(Page& page)
+{
+    // 1. Let group and document be the result of creating a new browsing context group and document.
+    auto [group, document] = TRY(BrowsingContextGroup::create_a_new_browsing_context_group_and_document(page));
+
+    // 2. Return group's browsing context set[0] and document.
+    return BrowsingContextAndDocument { **group->browsing_context_set().begin(), document };
+}
+
+// https://html.spec.whatwg.org/multipage/document-sequences.html#creating-a-new-top-level-traversable
+WebIDL::ExceptionOr<JS::NonnullGCPtr<TraversableNavigable>> TraversableNavigable::create_a_new_top_level_traversable(Page& page, JS::GCPtr<HTML::BrowsingContext> opener, String target_name)
+{
+    auto& vm = Bindings::main_thread_vm();
+
+    // 1. Let document be null.
+    JS::GCPtr<DOM::Document> document = nullptr;
+
+    // 2. If opener is null, then set document to the second return value of creating a new top-level browsing context and document.
+    if (!opener) {
+        document = TRY(create_a_new_top_level_browsing_context_and_document(page)).document;
+    }
+
+    // 3. Otherwise, set document to the second return value of creating a new auxiliary browsing context and document given opener.
+    else {
+        document = TRY(BrowsingContext::create_a_new_auxiliary_browsing_context_and_document(page, *opener)).document;
+    }
+
+    // 4. Let documentState be a new document state, with
+    auto document_state = vm.heap().allocate_without_realm<DocumentState>();
+
+    // document: document
+    document_state->set_document(document);
+
+    // navigable target name: targetName
+    document_state->set_navigable_target_name(target_name);
+
+    // 5. Let traversable be a new traversable navigable.
+    auto traversable = vm.heap().allocate_without_realm<TraversableNavigable>();
+
+    // 6. Initialize the navigable traversable given documentState.
+    TRY_OR_THROW_OOM(vm, traversable->initialize_navigable(document_state, nullptr));
+
+    // 7. Let initialHistoryEntry be traversable's active session history entry.
+    auto initial_history_entry = traversable->active_session_history_entry();
+    VERIFY(initial_history_entry);
+
+    // 8. Set initialHistoryEntry's step to 0.
+    initial_history_entry->step = 0;
+
+    // 9. Append initialHistoryEntry to traversable's session history entries.
+    traversable->m_session_history_entries.append(*initial_history_entry);
+
+    // FIXME: 10. If opener is non-null, then legacy-clone a traversable storage shed given opener's top-level traversable and traversable. [STORAGE]
+
+    // 11. Append traversable to the user agent's top-level traversable set.
+    user_agent_top_level_traversable_set().set(traversable);
+
+    // 12. Return traversable.
+    return traversable;
+}
+
+// https://html.spec.whatwg.org/multipage/document-sequences.html#create-a-fresh-top-level-traversable
+WebIDL::ExceptionOr<JS::NonnullGCPtr<TraversableNavigable>> TraversableNavigable::create_a_fresh_top_level_traversable(Page& page, AK::URL const& initial_navigation_url, Variant<Empty, String, POSTResource> initial_navigation_post_resource)
+{
+    // 1. Let traversable be the result of creating a new top-level traversable given null and the empty string.
+    auto traversable = TRY(create_a_new_top_level_traversable(page, nullptr, {}));
+
+    // 2. Navigate traversable to initialNavigationURL using traversable's active document, with documentResource set to initialNavigationPostResource.
+    TRY(traversable->navigate(initial_navigation_url, *traversable->active_document(), initial_navigation_post_resource));
+
+    // 3. Return traversable.
+    return traversable;
+}
+
 // https://html.spec.whatwg.org/multipage/document-sequences.html#top-level-traversable
 bool TraversableNavigable::is_top_level_traversable() const
 {