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

9 files changed, 516 insertions, 0 deletions

diff --git a/Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h b/Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h
index c4e39a3433..de38e1c2a6 100644
--- a/Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h
+++ b/Userland/Libraries/LibWeb/Bindings/WindowObjectHelper.h
@@ -235,6 +235,8 @@
 #include <LibWeb/Bindings/HTMLUnknownElementPrototype.h>
 #include <LibWeb/Bindings/HTMLVideoElementConstructor.h>
 #include <LibWeb/Bindings/HTMLVideoElementPrototype.h>
+#include <LibWeb/Bindings/HeadersConstructor.h>
+#include <LibWeb/Bindings/HeadersPrototype.h>
 #include <LibWeb/Bindings/HistoryConstructor.h>
 #include <LibWeb/Bindings/HistoryPrototype.h>
 #include <LibWeb/Bindings/IdleDeadlineConstructor.h>
@@ -420,6 +422,7 @@
     ADD_WINDOW_OBJECT_INTERFACE(ErrorEvent)                                                         \
     ADD_WINDOW_OBJECT_INTERFACE(Event)                                                              \
     ADD_WINDOW_OBJECT_INTERFACE(EventTarget)                                                        \
+    ADD_WINDOW_OBJECT_INTERFACE(Headers)                                                            \
     ADD_WINDOW_OBJECT_INTERFACE(History)                                                            \
     ADD_WINDOW_OBJECT_INTERFACE(HTMLAnchorElement)                                                  \
     ADD_WINDOW_OBJECT_INTERFACE(HTMLAreaElement)                                                    \
diff --git a/Userland/Libraries/LibWeb/CMakeLists.txt b/Userland/Libraries/LibWeb/CMakeLists.txt
index e37e1ffc10..aaba562ed3 100644
--- a/Userland/Libraries/LibWeb/CMakeLists.txt
+++ b/Userland/Libraries/LibWeb/CMakeLists.txt
@@ -117,6 +117,8 @@ set(SOURCES
     Dump.cpp
     Encoding/TextDecoder.cpp
     Encoding/TextEncoder.cpp
+    Fetch/Headers.cpp
+    Fetch/HeadersIterator.cpp
     Fetch/Infrastructure/HTTP.cpp
     Fetch/Infrastructure/URL.cpp
     Fetch/Infrastructure/HTTP/Bodies.cpp
diff --git a/Userland/Libraries/LibWeb/Fetch/Headers.cpp b/Userland/Libraries/LibWeb/Fetch/Headers.cpp
new file mode 100644
index 0000000000..2d2bc9b16e
--- /dev/null
+++ b/Userland/Libraries/LibWeb/Fetch/Headers.cpp
@@ -0,0 +1,311 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Bindings/HeadersWrapper.h>
+#include <LibWeb/Fetch/Headers.h>
+
+namespace Web::Fetch {
+
+// https://fetch.spec.whatwg.org/#dom-headers
+DOM::ExceptionOr<NonnullRefPtr<Headers>> Headers::create(Optional<HeadersInit> const& init)
+{
+    // The new Headers(init) constructor steps are:
+
+    auto headers = adopt_ref(*new Headers());
+
+    // 1. Set this’s guard to "none".
+    headers->m_guard = Guard::None;
+
+    // 2. If init is given, then fill this with init.
+    if (init.has_value())
+        TRY(headers->fill(*init));
+
+    return headers;
+}
+
+// https://fetch.spec.whatwg.org/#dom-headers-append
+DOM::ExceptionOr<void> Headers::append(String const& name_string, String const& value_string)
+{
+    // The append(name, value) method steps are to append (name, value) to this.
+    auto header = Infrastructure::Header {
+        .name = TRY_OR_RETURN_OOM(ByteBuffer::copy(name_string.bytes())),
+        .value = TRY_OR_RETURN_OOM(ByteBuffer::copy(value_string.bytes())),
+    };
+    TRY(append(move(header)));
+    return {};
+}
+
+// https://fetch.spec.whatwg.org/#dom-headers-delete
+DOM::ExceptionOr<void> Headers::delete_(String const& name_string)
+{
+    // The delete(name) method steps are:
+    auto name = name_string.bytes();
+
+    // 1. If name is not a header name, then throw a TypeError.
+    if (!Infrastructure::is_header_name(name))
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+
+    // 2. If this’s guard is "immutable", then throw a TypeError.
+    if (m_guard == Guard::Immutable)
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Headers object is immutable" };
+
+    // 3. Otherwise, if this’s guard is "request" and name is a forbidden header name, return.
+    if (m_guard == Guard::Request && Infrastructure::is_forbidden_header_name(name))
+        return {};
+
+    // 4. Otherwise, if this’s guard is "request-no-cors", name is not a no-CORS-safelisted request-header name, and name is not a privileged no-CORS request-header name, return.
+    if (m_guard == Guard::RequestNoCORS && !Infrastructure::is_no_cors_safelisted_request_header_name(name) && !Infrastructure::is_privileged_no_cors_request_header_name(name))
+        return {};
+
+    // 5. Otherwise, if this’s guard is "response" and name is a forbidden response-header name, return.
+    if (m_guard == Guard::Response && Infrastructure::is_forbidden_response_header_name(name))
+        return {};
+
+    // 6. If this’s header list does not contain name, then return.
+    if (!m_header_list.contains(name))
+        return {};
+
+    // 7. Delete name from this’s header list.
+    m_header_list.delete_(name);
+
+    // 8. If this’s guard is "request-no-cors", then remove privileged no-CORS request headers from this.
+    if (m_guard == Guard::RequestNoCORS)
+        remove_privileged_no_cors_headers();
+
+    return {};
+}
+
+// https://fetch.spec.whatwg.org/#dom-headers-get
+DOM::ExceptionOr<String> Headers::get(String const& name_string)
+{
+    // The get(name) method steps are:
+    auto name = name_string.bytes();
+
+    // 1. If name is not a header name, then throw a TypeError.
+    if (!Infrastructure::is_header_name(name))
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+
+    // 2. Return the result of getting name from this’s header list.
+    auto byte_buffer = TRY_OR_RETURN_OOM(m_header_list.get(name));
+    // FIXME: Teach WrapperGenerator about Optional<String>
+    return byte_buffer.has_value() ? String { byte_buffer->span() } : String {};
+}
+
+// https://fetch.spec.whatwg.org/#dom-headers-has
+DOM::ExceptionOr<bool> Headers::has(String const& name_string)
+{
+    // The has(name) method steps are:
+    auto name = name_string.bytes();
+
+    // 1. If name is not a header name, then throw a TypeError.
+    if (!Infrastructure::is_header_name(name))
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+
+    // 2. Return true if this’s header list contains name; otherwise false.
+    return m_header_list.contains(name);
+}
+
+// https://fetch.spec.whatwg.org/#dom-headers-set
+DOM::ExceptionOr<void> Headers::set(String const& name_string, String const& value_string)
+{
+    // The set(name, value) method steps are:
+    auto name = name_string.bytes();
+    auto value = value_string.bytes();
+
+    // 1. Normalize value.
+    auto normalized_value = TRY_OR_RETURN_OOM(Infrastructure::normalize_header_value(value));
+
+    auto header = Infrastructure::Header {
+        .name = TRY_OR_RETURN_OOM(ByteBuffer::copy(name)),
+        .value = move(normalized_value),
+    };
+
+    // 2. If name is not a header name or value is not a header value, then throw a TypeError.
+    if (!Infrastructure::is_header_name(name))
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+    if (!Infrastructure::is_header_value(value))
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header value" };
+
+    // 3. If this’s guard is "immutable", then throw a TypeError.
+    if (m_guard == Guard::Immutable)
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Headers object is immutable" };
+
+    // 4. Otherwise, if this’s guard is "request" and name is a forbidden header name, return.
+    if (m_guard == Guard::Request && Infrastructure::is_forbidden_header_name(name))
+        return {};
+
+    // 5. Otherwise, if this’s guard is "request-no-cors" and name/value is not a no-CORS-safelisted request-header, return.
+    if (m_guard == Guard::RequestNoCORS && !Infrastructure::is_no_cors_safelisted_request_header(header))
+        return {};
+
+    // 6. Otherwise, if this’s guard is "response" and name is a forbidden response-header name, return.
+    if (m_guard == Guard::Response && Infrastructure::is_forbidden_response_header_name(name))
+        return {};
+
+    // 7. Set (name, value) in this’s header list.
+    TRY_OR_RETURN_OOM(m_header_list.set(move(header)));
+
+    // 8. If this’s guard is "request-no-cors", then remove privileged no-CORS request headers from this.
+    if (m_guard == Guard::RequestNoCORS)
+        remove_privileged_no_cors_headers();
+
+    return {};
+}
+
+// https://webidl.spec.whatwg.org/#es-iterable, Step 4
+JS::ThrowCompletionOr<void> Headers::for_each(ForEachCallback callback)
+{
+    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_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();
+    };
+
+    // 1-5. Are done in the generated wrapper code.
+
+    // 6. Let pairs be idlObject’s list of value pairs to iterate over.
+    auto pairs = TRY(value_pairs_to_iterate_over());
+
+    // 7. Let i be 0.
+    size_t i = 0;
+
+    // 8. While i < pairs’s size:
+    while (i < pairs.size()) {
+        // 1. Let pair be pairs[i].
+        auto const& pair = pairs[i];
+
+        // 2. Invoke idlCallback with « pair’s value, pair’s key, idlObject » and with thisArg as the callback this value.
+        TRY(callback(StringView { pair.name }, StringView { pair.value }));
+
+        // 3. Set pairs to idlObject’s current list of value pairs to iterate over. (It might have changed.)
+        pairs = TRY(value_pairs_to_iterate_over());
+
+        // 4. Set i to i + 1.
+        ++i;
+    }
+
+    return {};
+}
+
+// https://fetch.spec.whatwg.org/#concept-headers-append
+DOM::ExceptionOr<void> Headers::append(Infrastructure::Header header)
+{
+    // To append a header (name, value) to a Headers object headers, run these steps:
+    auto& [name, value] = header;
+
+    // 1. Normalize value.
+    value = TRY_OR_RETURN_OOM(Infrastructure::normalize_header_value(value));
+
+    // 2. If name is not a header name or value is not a header value, then throw a TypeError.
+    if (!Infrastructure::is_header_name(name))
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header name" };
+    if (!Infrastructure::is_header_value(value))
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Invalid header value" };
+
+    // 3. If headers’s guard is "immutable", then throw a TypeError.
+    if (m_guard == Guard::Immutable)
+        return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Headers object is immutable" };
+
+    // 4. Otherwise, if headers’s guard is "request" and name is a forbidden header name, return.
+    if (m_guard == Guard::Request && Infrastructure::is_forbidden_header_name(name))
+        return {};
+
+    // 5. Otherwise, if headers’s guard is "request-no-cors":
+    if (m_guard == Guard::RequestNoCORS) {
+        // 1. Let temporaryValue be the result of getting name from headers’s header list.
+        auto temporary_value = TRY_OR_RETURN_OOM(m_header_list.get(name));
+
+        // 2. If temporaryValue is null, then set temporaryValue to value.
+        if (!temporary_value.has_value()) {
+            temporary_value = TRY_OR_RETURN_OOM(ByteBuffer::copy(value));
+        }
+        // 3. Otherwise, set temporaryValue to temporaryValue, followed by 0x2C 0x20, followed by value.
+        else {
+            TRY_OR_RETURN_OOM(temporary_value->try_append(0x2c));
+            TRY_OR_RETURN_OOM(temporary_value->try_append(0x20));
+            TRY_OR_RETURN_OOM(temporary_value->try_append(value));
+        }
+
+        auto temporary_header = Infrastructure::Header {
+            .name = TRY_OR_RETURN_OOM(ByteBuffer::copy(name)),
+            .value = temporary_value.release_value(),
+        };
+
+        // 4. If name/temporaryValue is not a no-CORS-safelisted request-header, then return.
+        if (!Infrastructure::is_no_cors_safelisted_request_header(temporary_header))
+            return {};
+    }
+
+    // 6. Otherwise, if headers’s guard is "response" and name is a forbidden response-header name, return.
+    if (m_guard == Guard::Response && Infrastructure::is_forbidden_response_header_name(name))
+        return {};
+
+    // 7. Append (name, value) to headers’s header list.
+    TRY_OR_RETURN_OOM(m_header_list.append(move(header)));
+
+    // 8. If headers’s guard is "request-no-cors", then remove privileged no-CORS request headers from headers.
+    if (m_guard == Guard::RequestNoCORS)
+        remove_privileged_no_cors_headers();
+
+    return {};
+}
+
+// https://fetch.spec.whatwg.org/#concept-headers-fill
+DOM::ExceptionOr<void> Headers::fill(HeadersInit const& object)
+{
+    // To fill a Headers object headers with a given object object, run these steps:
+    return object.visit(
+        // 1. If object is a sequence, then for each header in object:
+        [this](Vector<Vector<String>> const& object) -> DOM::ExceptionOr<void> {
+            for (auto const& entry : object) {
+                // 1. If header does not contain exactly two items, then throw a TypeError.
+                if (entry.size() != 2)
+                    return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, "Array must contain header key/value pair" };
+
+                // 2. Append (header’s first item, header’s second item) to headers.
+                auto header = Fetch::Infrastructure::Header {
+                    .name = TRY_OR_RETURN_OOM(ByteBuffer::copy(entry[0].bytes())),
+                    .value = TRY_OR_RETURN_OOM(ByteBuffer::copy(entry[0].bytes())),
+                };
+                TRY(append(move(header)));
+            }
+            return {};
+        },
+        // 2. Otherwise, object is a record, then for each key → value in object, append (key, value) to headers.
+        [this](OrderedHashMap<String, String> const& object) -> DOM::ExceptionOr<void> {
+            for (auto const& entry : object) {
+                auto header = Fetch::Infrastructure::Header {
+                    .name = TRY_OR_RETURN_OOM(ByteBuffer::copy(entry.key.bytes())),
+                    .value = TRY_OR_RETURN_OOM(ByteBuffer::copy(entry.value.bytes())),
+                };
+                TRY(append(move(header)));
+            }
+            return {};
+        });
+}
+
+// https://fetch.spec.whatwg.org/#concept-headers-remove-privileged-no-cors-request-headers
+void Headers::remove_privileged_no_cors_headers()
+{
+    // To remove privileged no-CORS request headers from a Headers object (headers), run these steps:
+
+    static constexpr Array privileged_no_cors_request_header_names = {
+        "Range"sv,
+    };
+
+    // 1. For each headerName of privileged no-CORS request-header names:
+    for (auto const& header_name : privileged_no_cors_request_header_names) {
+        // 1. Delete headerName from headers’s header list.
+        m_header_list.delete_(header_name.bytes());
+    }
+}
+
+}
diff --git a/Userland/Libraries/LibWeb/Fetch/Headers.h b/Userland/Libraries/LibWeb/Fetch/Headers.h
new file mode 100644
index 0000000000..ef5a7d1fc5
--- /dev/null
+++ b/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&);
+
+}
diff --git a/Userland/Libraries/LibWeb/Fetch/Headers.idl b/Userland/Libraries/LibWeb/Fetch/Headers.idl
new file mode 100644
index 0000000000..f2dbd9e4c0
--- /dev/null
+++ b/Userland/Libraries/LibWeb/Fetch/Headers.idl
@@ -0,0 +1,13 @@
+typedef (sequence<sequence<ByteString>> or record<ByteString, ByteString>) HeadersInit;
+
+[Exposed=(Window,Worker)]
+interface Headers {
+    constructor(optional HeadersInit init);
+
+    undefined append(ByteString name, ByteString value);
+    undefined delete(ByteString name);
+    ByteString? get(ByteString name);
+    boolean has(ByteString name);
+    undefined set(ByteString name, ByteString value);
+    iterable<ByteString, ByteString>;
+};
diff --git a/Userland/Libraries/LibWeb/Fetch/HeadersIterator.cpp b/Userland/Libraries/LibWeb/Fetch/HeadersIterator.cpp
new file mode 100644
index 0000000000..f3163042d2
--- /dev/null
+++ b/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());
+}
+
+}
diff --git a/Userland/Libraries/LibWeb/Fetch/HeadersIterator.h b/Userland/Libraries/LibWeb/Fetch/HeadersIterator.h
new file mode 100644
index 0000000000..a678abacb0
--- /dev/null
+++ b/Userland/Libraries/LibWeb/Fetch/HeadersIterator.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/Bindings/Wrappable.h>
+#include <LibWeb/Fetch/Headers.h>
+
+namespace Web::Fetch {
+
+class HeadersIterator
+    : public Bindings::Wrappable
+    , public RefCounted<HeadersIterator> {
+public:
+    using WrapperType = Bindings::HeadersIteratorWrapper;
+
+    static NonnullRefPtr<HeadersIterator> create(Headers const& headers, JS::Object::PropertyKind iteration_kind)
+    {
+        return adopt_ref(*new HeadersIterator(headers, iteration_kind));
+    }
+
+    JS::ThrowCompletionOr<JS::Object*> next();
+
+    void visit_edges(JS::Cell::Visitor&);
+
+private:
+    HeadersIterator(Headers const& headers, JS::Object::PropertyKind iteration_kind)
+        : m_headers(headers)
+        , m_iteration_kind(iteration_kind)
+    {
+    }
+
+    Headers const& m_headers;
+    JS::Object::PropertyKind m_iteration_kind;
+    size_t m_index { 0 };
+};
+
+}
+
+namespace Web::Bindings {
+
+HeadersIteratorWrapper* wrap(JS::GlobalObject&, Fetch::HeadersIterator&);
+
+}
diff --git a/Userland/Libraries/LibWeb/Forward.h b/Userland/Libraries/LibWeb/Forward.h
index 219a57d8ac..3decec6049 100644
--- a/Userland/Libraries/LibWeb/Forward.h
+++ b/Userland/Libraries/LibWeb/Forward.h
@@ -170,6 +170,11 @@ namespace Web::Encoding {
 class TextEncoder;
 }
 
+namespace Web::Fetch {
+class Headers;
+class HeadersIterator;
+}
+
 namespace Web::Fetch::Infrastructure {
 class Body;
 struct Header;
@@ -470,6 +475,8 @@ class EventListenerWrapper;
 class EventTargetWrapper;
 class EventWrapper;
 class FocusEventWrapper;
+class HeadersWrapper;
+class HeadersIteratorWrapper;
 class HistoryWrapper;
 class HTMLAnchorElementWrapper;
 class HTMLAreaElementWrapper;
diff --git a/Userland/Libraries/LibWeb/idl_files.cmake b/Userland/Libraries/LibWeb/idl_files.cmake
index 3de3b944e4..8b0117ef5f 100644
--- a/Userland/Libraries/LibWeb/idl_files.cmake
+++ b/Userland/Libraries/LibWeb/idl_files.cmake
@@ -53,6 +53,7 @@ libweb_js_wrapper(DOM/TreeWalker)
 libweb_js_wrapper(DOMParsing/XMLSerializer)
 libweb_js_wrapper(Encoding/TextDecoder)
 libweb_js_wrapper(Encoding/TextEncoder)
+libweb_js_wrapper(Fetch/Headers ITERABLE)
 libweb_js_wrapper(FileAPI/Blob)
 libweb_js_wrapper(Geometry/DOMPoint)
 libweb_js_wrapper(Geometry/DOMPointReadOnly)