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

Userland/Libraries/LibWeb/Fetch/Headers.h

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/HashMap.h>
+#include <AK/NonnullRefPtr.h>
+#include <AK/String.h>
+#include <AK/Variant.h>
+#include <AK/Vector.h>
+#include <LibWeb/Bindings/Wrappable.h>
+#include <LibWeb/DOM/ExceptionOr.h>
+#include <LibWeb/Fetch/Infrastructure/HTTP/Headers.h>
+
+namespace Web::Fetch {
+
+using HeadersInit = Variant<Vector<Vector<String>>, OrderedHashMap<String, String>>;
+
+// https://fetch.spec.whatwg.org/#headers-class
+class Headers
+    : public Bindings::Wrappable
+    , public RefCounted<Headers> {
+public:
+    using WrapperType = Bindings::HeadersWrapper;
+
+    enum class Guard {
+        Immutable,
+        Request,
+        RequestNoCORS,
+        Response,
+        None,
+    };
+
+    static DOM::ExceptionOr<NonnullRefPtr<Headers>> create(Optional<HeadersInit> const&);
+
+    static DOM::ExceptionOr<NonnullRefPtr<Headers>> create_with_global_object(Bindings::WindowObject&, Optional<HeadersInit> const& init)
+    {
+        return create(init);
+    }
+
+    DOM::ExceptionOr<void> append(Infrastructure::Header);
+    DOM::ExceptionOr<void> append(String const& name, String const& value);
+    DOM::ExceptionOr<void> delete_(String const& name);
+    DOM::ExceptionOr<String> get(String const& name);
+    DOM::ExceptionOr<bool> has(String const& name);
+    DOM::ExceptionOr<void> set(String const& name, String const& value);
+
+    using ForEachCallback = Function<JS::ThrowCompletionOr<void>(String const&, String const&)>;
+    JS::ThrowCompletionOr<void> for_each(ForEachCallback);
+
+private:
+    friend class HeadersIterator;
+
+    Headers() = default;
+
+    DOM::ExceptionOr<void> fill(HeadersInit const&);
+    void remove_privileged_no_cors_headers();
+
+    // https://fetch.spec.whatwg.org/#concept-headers-header-list
+    // A Headers object has an associated header list (a header list), which is initially empty.
+    Infrastructure::HeaderList m_header_list;
+
+    // https://fetch.spec.whatwg.org/#concept-headers-guard
+    // A Headers object also has an associated guard, which is a headers guard. A headers guard is "immutable", "request", "request-no-cors", "response" or "none".
+    Guard m_guard { Guard::None };
+};
+
+}
+
+namespace Web::Bindings {
+
+HeadersWrapper* wrap(JS::GlobalObject&, Fetch::Headers&);
+
+}