LibWeb: Implement '5.1. Headers class' from the Fetch API :^)

Userland/Libraries/LibWeb/Fetch/HeadersIterator.cpp

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/Array.h>
+#include <LibJS/Runtime/IteratorOperations.h>
+#include <LibWeb/Bindings/HeadersIteratorWrapper.h>
+#include <LibWeb/Bindings/Wrapper.h>
+#include <LibWeb/Fetch/HeadersIterator.h>
+
+namespace Web::Fetch {
+
+// https://webidl.spec.whatwg.org/#es-iterable, Step 2
+JS::ThrowCompletionOr<JS::Object*> HeadersIterator::next()
+{
+    auto& global_object = wrapper()->global_object();
+    auto& vm = global_object.vm();
+
+    // The value pairs to iterate over are the return value of running sort and combine with this’s header list.
+    auto value_pairs_to_iterate_over = [&]() -> JS::ThrowCompletionOr<Vector<Fetch::Infrastructure::Header>> {
+        auto headers_or_error = m_headers.m_header_list.sort_and_combine();
+        if (headers_or_error.is_error())
+            return vm.throw_completion<JS::InternalError>(global_object, JS::ErrorType::NotEnoughMemoryToAllocate);
+        return headers_or_error.release_value();
+    };
+
+    auto pairs = TRY(value_pairs_to_iterate_over());
+
+    if (m_index >= pairs.size())
+        return create_iterator_result_object(global_object, JS::js_undefined(), true);
+
+    auto const& pair = pairs[m_index++];
+
+    switch (m_iteration_kind) {
+    case JS::Object::PropertyKind::Key:
+        return create_iterator_result_object(global_object, JS::js_string(vm, StringView { pair.name }), false);
+    case JS::Object::PropertyKind::Value:
+        return create_iterator_result_object(global_object, JS::js_string(vm, StringView { pair.value }), false);
+    case JS::Object::PropertyKind::KeyAndValue: {
+        auto* array = JS::Array::create_from(global_object, { JS::js_string(vm, StringView { pair.name }), JS::js_string(vm, StringView { pair.value }) });
+        return create_iterator_result_object(global_object, array, false);
+    }
+    default:
+        VERIFY_NOT_REACHED();
+    }
+}
+
+void HeadersIterator::visit_edges(JS::Cell::Visitor& visitor)
+{
+    visitor.visit(m_headers.wrapper());
+}
+
+}