LibJS: Add PrivateEnvironment

Userland/Libraries/LibJS/Runtime/PrivateEnvironment.cpp

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2021, David Tuin <davidot@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/PrivateEnvironment.h>
+
+namespace JS {
+
+PrivateEnvironment::PrivateEnvironment(PrivateEnvironment* parent)
+    : m_outer_environment(parent)
+    , m_unique_id(s_next_id++)
+{
+    // FIXME: We might want to delay getting the next unique id until required.
+    VERIFY(s_next_id != 0);
+}
+
+// Note: we start at one such that 0 can be invalid / default initialized.
+u64 PrivateEnvironment::s_next_id = 1u;
+
+PrivateName PrivateEnvironment::resolve_private_identifier(FlyString const& identifier) const
+{
+    auto name_or_end = find_private_name(identifier);
+
+    if (!name_or_end.is_end())
+        return *name_or_end;
+
+    // Note: This verify ensures that we must either have a private name with a matching description
+    //       or have an outer environment. Combined this means that we assert that we always return a PrivateName.
+    VERIFY(m_outer_environment);
+    return m_outer_environment->resolve_private_identifier(identifier);
+}
+
+void PrivateEnvironment::add_private_name(Badge<ClassExpression>, FlyString description)
+{
+    // FIXME: there is a exception for getter setter pairs.
+    VERIFY(find_private_name(description).is_end());
+    m_private_names.empend(m_unique_id, move(description));
+}
+
+bool PrivateName::operator==(PrivateName const& rhs) const
+{
+    return unique_id == rhs.unique_id && description == rhs.description;
+}
+
+}