LibWeb: Convert HTMLCollection to use IDL special operations

Author: https://github.com/Lubrsi
Commit: 37347cbcb6
Pull-request: https://github.com/SerenityOS/serenity/pull/10219

Userland/Libraries/LibWeb/DOM/HTMLCollection.cpp

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
@@ -7,6 +8,7 @@
 #include <LibWeb/DOM/Element.h>
 #include <LibWeb/DOM/HTMLCollection.h>
 #include <LibWeb/DOM/ParentNode.h>
+#include <LibWeb/Namespace.h>
 
 namespace Web::DOM {
 
@@ -20,7 +22,7 @@ HTMLCollection::~HTMLCollection()
 {
 }
 
-Vector<NonnullRefPtr<Element>> HTMLCollection::collect_matching_elements()
+Vector<NonnullRefPtr<Element>> HTMLCollection::collect_matching_elements() const
 {
     Vector<NonnullRefPtr<Element>> elements;
     m_root->for_each_in_inclusive_subtree_of_type<Element>([&](auto& element) {
@@ -31,31 +33,82 @@ Vector<NonnullRefPtr<Element>> HTMLCollection::collect_matching_elements()
     return elements;
 }
 
+// https://dom.spec.whatwg.org/#dom-htmlcollection-length
 size_t HTMLCollection::length()
 {
+    // The length getter steps are to return the number of nodes represented by the collection.
     return collect_matching_elements().size();
 }
 
-Element* HTMLCollection::item(size_t index)
+// https://dom.spec.whatwg.org/#dom-htmlcollection-item
+Element* HTMLCollection::item(size_t index) const
 {
+    // The item(index) method steps are to return the indexth element in the collection. If there is no indexth element in the collection, then the method must return null.
     auto elements = collect_matching_elements();
     if (index >= elements.size())
         return nullptr;
     return elements[index];
 }
 
-Element* HTMLCollection::named_item(FlyString const& name)
+// https://dom.spec.whatwg.org/#dom-htmlcollection-nameditem-key
+Element* HTMLCollection::named_item(FlyString const& name) const
 {
-    if (name.is_null())
+    // 1. If key is the empty string, return null.
+    if (name.is_empty())
         return nullptr;
     auto elements = collect_matching_elements();
-    // First look for an "id" attribute match
+    // 2. Return the first element in the collection for which at least one of the following is true:
+    //      - it has an ID which is key;
     if (auto it = elements.find_if([&](auto& entry) { return entry->attribute(HTML::AttributeNames::id) == name; }); it != elements.end())
         return *it;
-    // Then look for a "name" attribute match
-    if (auto it = elements.find_if([&](auto& entry) { return entry->name() == name; }); it != elements.end())
+    //      - it is in the HTML namespace and has a name attribute whose value is key;
+    if (auto it = elements.find_if([&](auto& entry) { return entry->namespace_() == Namespace::HTML && entry->name() == name; }); it != elements.end())
         return *it;
+    //    or null if there is no such element.
     return nullptr;
 }
 
+// https://dom.spec.whatwg.org/#ref-for-dfn-supported-property-names
+Vector<String> HTMLCollection::supported_property_names() const
+{
+    // 1. Let result be an empty list.
+    Vector<String> result;
+
+    // 2. For each element represented by the collection, in tree order:
+    auto elements = collect_matching_elements();
+
+    for (auto& element : elements) {
+        // 1. If element has an ID which is not in result, append element’s ID to result.
+        if (element->has_attribute(HTML::AttributeNames::id)) {
+            auto id = element->attribute(HTML::AttributeNames::id);
+
+            if (!result.contains_slow(id))
+                result.append(id);
+        }
+
+        // 2. If element is in the HTML namespace and has a name attribute whose value is neither the empty string nor is in result, append element’s name attribute value to result.
+        if (element->namespace_() == Namespace::HTML && element->has_attribute(HTML::AttributeNames::name)) {
+            auto name = element->attribute(HTML::AttributeNames::name);
+
+            if (!name.is_empty() && !result.contains_slow(name))
+                result.append(name);
+        }
+    }
+
+    // 3. Return result.
+    return result;
+}
+
+// https://dom.spec.whatwg.org/#ref-for-dfn-supported-property-indices%E2%91%A1
+bool HTMLCollection::is_supported_property_index(u32 index) const
+{
+    // The object’s supported property indices are the numbers in the range zero to one less than the number of elements represented by the collection.
+    // If there are no such elements, then there are no supported property indices.
+    auto elements = collect_matching_elements();
+    if (elements.is_empty())
+        return false;
+
+    return index < elements.size();
+}
+
 }