LibWeb: Move QualifiedName.h into LibWeb/DOM/

Userland/Libraries/LibWeb/DOM/QualifiedName.h

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2020, the SerenityOS developers.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/FlyString.h>
+
+namespace Web {
+
+class QualifiedName {
+public:
+    QualifiedName(const FlyString& local_name, const FlyString& prefix, const FlyString& namespace_)
+        : m_local_name(local_name)
+        , m_prefix(prefix)
+        , m_namespace(namespace_)
+    {
+        make_internal_string();
+    }
+
+    const FlyString& local_name() const { return m_local_name; }
+    const FlyString& prefix() const { return m_prefix; }
+    const FlyString& namespace_() const { return m_namespace; }
+
+    const String& as_string() const { return m_as_string; }
+
+private:
+    FlyString m_local_name;
+    FlyString m_prefix;
+    FlyString m_namespace;
+    String m_as_string;
+
+    // https://dom.spec.whatwg.org/#concept-attribute-qualified-name
+    // https://dom.spec.whatwg.org/#concept-element-qualified-name
+    void make_internal_string()
+    {
+        // This is possible to do according to the spec: "User agents could have this as an internal slot as an optimization."
+        if (m_prefix.is_null()) {
+            m_as_string = m_local_name;
+            return;
+        }
+
+        m_as_string = String::formatted("{}:{}", m_prefix, m_local_name);
+    }
+};
+
+}