ladybird/Userland/Libraries/LibWeb/HTML/Navigable.cpp

/*
 * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
 * Copyright (c) 2023, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/Crypto/Crypto.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/DocumentLoading.h>
#include <LibWeb/Fetch/Fetching/Fetching.h>
#include <LibWeb/Fetch/Infrastructure/FetchAlgorithms.h>
#include <LibWeb/Fetch/Infrastructure/FetchController.h>
#include <LibWeb/Fetch/Infrastructure/URL.h>
#include <LibWeb/HTML/BrowsingContext.h>
#include <LibWeb/HTML/DocumentState.h>
#include <LibWeb/HTML/HTMLIFrameElement.h>
#include <LibWeb/HTML/HistoryHandlingBehavior.h>
#include <LibWeb/HTML/Navigable.h>
#include <LibWeb/HTML/Navigation.h>
#include <LibWeb/HTML/NavigationParams.h>
#include <LibWeb/HTML/POSTResource.h>
#include <LibWeb/HTML/Parser/HTMLParser.h>
#include <LibWeb/HTML/SandboxingFlagSet.h>
#include <LibWeb/HTML/Scripting/ClassicScript.h>
#include <LibWeb/HTML/SessionHistoryEntry.h>
#include <LibWeb/HTML/StructuredSerialize.h>
#include <LibWeb/HTML/TraversableNavigable.h>
#include <LibWeb/HTML/Window.h>
#include <LibWeb/Infra/Strings.h>
#include <LibWeb/Layout/Node.h>
#include <LibWeb/Loader/GeneratedPagesLoader.h>
#include <LibWeb/Page/Page.h>
#include <LibWeb/Painting/Paintable.h>
#include <LibWeb/Painting/ViewportPaintable.h>
#include <LibWeb/Platform/EventLoopPlugin.h>
#include <LibWeb/XHR/FormData.h>

namespace Web::HTML {

JS_DEFINE_ALLOCATOR(Navigable);

class ResponseHolder : public JS::Cell {
    JS_CELL(ResponseHolder, JS::Cell);
    JS_DECLARE_ALLOCATOR(ResponseHolder);

public:
    [[nodiscard]] static JS::NonnullGCPtr<ResponseHolder> create(JS::VM& vm)
    {
        return vm.heap().allocate_without_realm<ResponseHolder>();
    }

    [[nodiscard]] JS::GCPtr<Fetch::Infrastructure::Response> response() const { return m_response; }
    void set_response(JS::GCPtr<Fetch::Infrastructure::Response> response) { m_response = response; }

    virtual void visit_edges(Cell::Visitor& visitor) override
    {
        visitor.visit(m_response);
    }

private:
    JS::GCPtr<Fetch::Infrastructure::Response> m_response;
};

JS_DEFINE_ALLOCATOR(ResponseHolder);

HashTable<Navigable*>& all_navigables()
{
    static HashTable<Navigable*> set;
    return set;
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#child-navigable
Vector<JS::Handle<Navigable>> Navigable::child_navigables() const
{
    Vector<JS::Handle<Navigable>> results;
    for (auto& entry : all_navigables()) {
        if (entry->current_session_history_entry()->step == SessionHistoryEntry::Pending::Tag)
            continue;
        if (entry->parent() == this)
            results.append(entry);
    }

    return results;
}

bool Navigable::is_traversable() const
{
    return is<TraversableNavigable>(*this);
}

Navigable::Navigable()
{
    all_navigables().set(this);
}

Navigable::~Navigable()
{
    all_navigables().remove(this);
}

void Navigable::visit_edges(Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_parent);
    visitor.visit(m_current_session_history_entry);
    visitor.visit(m_active_session_history_entry);
    visitor.visit(m_container);
}

void Navigable::set_delaying_load_events(bool value)
{
    if (value) {
        auto document = container_document();
        VERIFY(document);
        m_delaying_the_load_event.emplace(*document);
    } else {
        m_delaying_the_load_event.clear();
    }
}

JS::GCPtr<Navigable> Navigable::navigable_with_active_document(JS::NonnullGCPtr<DOM::Document> document)
{
    for (auto* navigable : all_navigables()) {
        if (navigable->active_document() == document)
            return navigable;
    }
    return nullptr;
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#initialize-the-navigable
ErrorOr<void> Navigable::initialize_navigable(JS::NonnullGCPtr<DocumentState> document_state, JS::GCPtr<Navigable> parent)
{
    static int next_id = 0;
    m_id = TRY(String::number(next_id++));

    // 1. Let entry be a new session history entry, with
    JS::NonnullGCPtr<SessionHistoryEntry> entry = *heap().allocate_without_realm<SessionHistoryEntry>();

    // URL: document's URL
    entry->url = document_state->document()->url();

    // document state: documentState
    entry->document_state = document_state;

    // 2. Set navigable's current session history entry to entry.
    m_current_session_history_entry = entry;

    // 3. Set navigable's active session history entry to entry.
    m_active_session_history_entry = entry;

    // 4. Set navigable's parent to parent.
    m_parent = parent;

    return {};
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#getting-the-target-history-entry
JS::GCPtr<SessionHistoryEntry> Navigable::get_the_target_history_entry(int target_step) const
{
    // 1. Let entries be the result of getting session history entries for navigable.
    auto& entries = get_session_history_entries();

    // 2. Return the item in entries that has the greatest step less than or equal to step.
    JS::GCPtr<SessionHistoryEntry> result = nullptr;
    for (auto& entry : entries) {
        auto entry_step = entry->step.get<int>();
        if (entry_step <= target_step) {
            if (!result || result->step.get<int>() < entry_step) {
                result = entry;
            }
        }
    }

    return result;
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#activate-history-entry
void Navigable::activate_history_entry(JS::GCPtr<SessionHistoryEntry> entry)
{
    // FIXME: 1. Save persisted state to the navigable's active session history entry.

    // 2. Let newDocument be entry's document.
    JS::GCPtr<DOM::Document> new_document = entry->document_state->document().ptr();

    // 3. Assert: newDocument's is initial about:blank is false, i.e., we never traverse
    //    back to the initial about:blank Document because it always gets replaced when we
    //    navigate away from it.
    VERIFY(!new_document->is_initial_about_blank());

    // 4. Set navigable's active session history entry to entry.
    m_active_session_history_entry = entry;

    // 5. Make active newDocument.
    new_document->make_active();

    // Not in the spec:
    VERIFY(active_browsing_context());
    active_browsing_context()->page().client().page_did_create_new_document(*new_document);
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-document
JS::GCPtr<DOM::Document> Navigable::active_document()
{
    // A navigable's active document is its active session history entry's document.
    return m_active_session_history_entry->document_state->document();
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-bc
JS::GCPtr<BrowsingContext> Navigable::active_browsing_context()
{
    // A navigable's active browsing context is its active document's browsing context.
    // If this navigable is a traversable navigable, then its active browsing context will be a top-level browsing context.
    if (auto document = active_document())
        return document->browsing_context();
    return nullptr;
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-wp
JS::GCPtr<HTML::WindowProxy> Navigable::active_window_proxy()
{
    // A navigable's active WindowProxy is its active browsing context's associated WindowProxy.
    if (auto browsing_context = active_browsing_context())
        return browsing_context->window_proxy();
    return nullptr;
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-window
JS::GCPtr<HTML::Window> Navigable::active_window()
{
    // A navigable's active window is its active WindowProxy's [[Window]].
    if (auto window_proxy = active_window_proxy())
        return window_proxy->window();
    return nullptr;
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-target
String Navigable::target_name() const
{
    // A navigable's target name is its active session history entry's document state's navigable target name.
    return active_session_history_entry()->document_state->navigable_target_name();
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-container
JS::GCPtr<NavigableContainer> Navigable::container() const
{
    // The container of a navigable navigable is the navigable container whose nested navigable is navigable, or null if there is no such element.
    return NavigableContainer::navigable_container_with_content_navigable(const_cast<Navigable&>(*this));
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-container-document
JS::GCPtr<DOM::Document> Navigable::container_document() const
{
    auto container = this->container();

    // 1. If navigable's container is null, then return null.
    if (!container)
        return nullptr;

    // 2. Return navigable's container's node document.
    return container->document();
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-traversable
JS::GCPtr<TraversableNavigable> Navigable::traversable_navigable() const
{
    // 1. Let navigable be inputNavigable.
    auto navigable = const_cast<Navigable*>(this);

    // 2. While navigable is not a traversable navigable, set navigable to navigable's parent.
    while (navigable && !is<TraversableNavigable>(*navigable))
        navigable = navigable->parent();

    // 3. Return navigable.
    return static_cast<TraversableNavigable*>(navigable);
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#nav-top
JS::GCPtr<TraversableNavigable> Navigable::top_level_traversable()
{
    // 1. Let navigable be inputNavigable.
    auto navigable = this;

    // 2. While navigable's parent is not null, set navigable to navigable's parent.
    while (navigable->parent())
        navigable = navigable->parent();

    // 3. Return navigable.
    return verify_cast<TraversableNavigable>(navigable);
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#set-the-ongoing-navigation
void Navigable::set_ongoing_navigation(Variant<Empty, Traversal, String> ongoing_navigation)
{
    // 1. If navigable's ongoing navigation is equal to newValue, then return.
    if (m_ongoing_navigation == ongoing_navigation)
        return;

    // 2. Inform the navigation API about aborting navigation given navigable.
    inform_the_navigation_api_about_aborting_navigation();

    // 3. Set navigable's ongoing navigation to newValue.
    m_ongoing_navigation = ongoing_navigation;
}

// https://html.spec.whatwg.org/multipage/document-sequences.html#the-rules-for-choosing-a-navigable
Navigable::ChosenNavigable Navigable::choose_a_navigable(StringView name, TokenizedFeature::NoOpener no_opener, ActivateTab)
{
    // NOTE: Implementation for step 7 here.
    JS::GCPtr<Navigable> same_name_navigable = nullptr;
    if (!Infra::is_ascii_case_insensitive_match(name, "_blank"sv)) {
        for (auto& n : all_navigables()) {
            if (n->target_name() == name) {
                same_name_navigable = n;
            }
        }
    }

    // 1. Let chosen be null.
    JS::GCPtr<Navigable> chosen = nullptr;

    // 2. Let windowType be "existing or none".
    auto window_type = WindowType::ExistingOrNone;

    // 3. Let sandboxingFlagSet be current's active document's active sandboxing flag set.
    auto sandboxing_flag_set = active_document()->active_sandboxing_flag_set();

    // 4. If name is the empty string or an ASCII case-insensitive match for "_self", then set chosen to currentNavigable.
    if (name.is_empty() || Infra::is_ascii_case_insensitive_match(name, "_self"sv)) {
        chosen = this;
    }

    // 5. Otherwise, if name is an ASCII case-insensitive match for "_parent",
    //    set chosen to currentNavigable's parent, if any, and currentNavigable otherwise.
    else if (Infra::is_ascii_case_insensitive_match(name, "_parent"sv)) {
        if (auto parent = this->parent())
            chosen = parent;
        else
            chosen = this;
    }

    // 6. Otherwise, if name is an ASCII case-insensitive match for "_top",
    //    set chosen to currentNavigable's traversable navigable.
    else if (Infra::is_ascii_case_insensitive_match(name, "_top"sv)) {
        chosen = traversable_navigable();
    }

    //  7. Otherwise, if name is not an ASCII case-insensitive match for "_blank",
    //     there exists a navigable whose target name is the same as name, currentNavigable's
    //     active browsing context is familiar with that navigable's active browsing context,
    //     and the user agent determines that the two browsing contexts are related enough that
    //     it is ok if they reach each other, set chosen to that navigable. If there are multiple
    //     matching navigables, the user agent should pick one in some arbitrary consistent manner,
    //     such as the most recently opened, most recently focused, or more closely related, and set
    //     chosen to it.
    else if (same_name_navigable != nullptr && (active_browsing_context()->is_familiar_with(*same_name_navigable->active_browsing_context()))) {
        // FIXME: Handle multiple name-match case
        // FIXME: When are these contexts 'not related enough' ?
        chosen = same_name_navigable;
    }

    // 8. Otherwise, a new top-level traversable is being requested, and what happens depends on the
    // user agent's configuration and abilities — it is determined by the rules given for the first
    // applicable option from the following list:
    else {
        // --> If current's active window does not have transient activation and the user agent has been configured to
        //     not show popups (i.e., the user agent has a "popup blocker" enabled)
        if (!active_window()->has_transient_activation() && traversable_navigable()->page().should_block_pop_ups()) {
            // FIXME: The user agent may inform the user that a popup has been blocked.
            dbgln("Pop-up blocked!");
        }

        // --> If sandboxingFlagSet has the sandboxed auxiliary navigation browsing context flag set
        else if (has_flag(sandboxing_flag_set, SandboxingFlagSet::SandboxedAuxiliaryNavigation)) {
            // FIXME: The user agent may report to a developer console that a popup has been blocked.
            dbgln("Pop-up blocked!");
        }

        // --> If the user agent has been configured such that in this instance it will create a new top-level traversable
        else if (true) { // FIXME: When is this the case?
            // 1. Set windowType to "new and unrestricted".
            window_type = WindowType::NewAndUnrestricted;

            // 2. Let currentDocument be currentNavigable's active document.
            auto current_document = active_document();

            // 3. If currentDocument's cross-origin opener policy's value is "same-origin" or "same-origin-plus-COEP",
            //    and currentDocument's origin is not same origin with currentDocument's relevant settings object's top-level origin, then:
            if ((current_document->cross_origin_opener_policy().value == CrossOriginOpenerPolicyValue::SameOrigin || current_document->cross_origin_opener_policy().value == CrossOriginOpenerPolicyValue::SameOriginPlusCOEP)
                && !current_document->origin().is_same_origin(relevant_settings_object(*current_document).top_level_origin)) {

                // 1. Set noopener to true.
                no_opener = TokenizedFeature::NoOpener::Yes;

                // 2. Set name to "_blank".
                name = "_blank"sv;

                // 3. Set windowType to "new with no opener".
                window_type = WindowType::NewWithNoOpener;
            }
            // NOTE: In the presence of a cross-origin opener policy,
            //       nested documents that are cross-origin with their top-level browsing context's active document always set noopener to true.

            // 4. Let chosen be null.
            chosen = nullptr;

            // 5. Let targetName be the empty string.
            String target_name;

            // 6. If name is not an ASCII case-insensitive match for "_blank", then set targetName to name.
            if (!Infra::is_ascii_case_insensitive_match(name, "_blank"sv))
                target_name = MUST(String::from_utf8(name));

            // 7. If noopener is true, then set chosen to the result of creating a new top-level traversable given null and targetName.
            if (no_opener == TokenizedFeature::NoOpener::Yes) {
                // FIXME: This should do something similar to RemoteBrowsingContext -- but RemoteTraversableNavigable instead
                TODO();
            }

            // 8. Otherwise:
            else {
                // 1. Set chosen to the result of creating a new top-level traversable given currentNavigable's active browsing context and targetName.
                // FIXME: Make this method return WebIDL::ExceptionOr<ChosenNavigable>
                chosen = TraversableNavigable::create_a_new_top_level_traversable(traversable_navigable()->page(), active_browsing_context(), target_name).release_value_but_fixme_should_propagate_errors();

                // FIXME: 2. If sandboxingFlagSet's sandboxed navigation browsing context flag is set,
                //    then set chosen's active browsing context's one permitted sandboxed navigator to currentNavigable's active browsing context.
            }

            // FIXME: 5. If sandboxingFlagSet's sandbox propagates to auxiliary browsing contexts flag is set,
            //    then all the flags that are set in sandboxingFlagSet must be set in chosen's active browsing context's popup sandboxing flag set.
            // Our BrowsingContexts do not have SandboxingFlagSets yet, only documents do
        }

        // --> If the user agent has been configured such that in this instance t will reuse current
        else if (false) { // FIXME: When is this the case?
            // Set chosen to current.
            chosen = *this;
        }

        // --> If the user agent has been configured such that in this instance it will not find a browsing context
        else if (false) { // FIXME: When is this the case?
            // Do nothing.
        }
    }

    return { chosen.ptr(), window_type };
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#getting-session-history-entries
Vector<JS::NonnullGCPtr<SessionHistoryEntry>>& Navigable::get_session_history_entries() const
{
    // 1. Let traversable be navigable's traversable navigable.
    auto traversable = traversable_navigable();

    // FIXME 2. Assert: this is running within traversable's session history traversal queue.

    // 3. If navigable is traversable, return traversable's session history entries.
    if (this == traversable)
        return traversable->session_history_entries();

    // 4. Let docStates be an empty ordered set of document states.
    Vector<JS::GCPtr<DocumentState>> doc_states;

    // 5. For each entry of traversable's session history entries, append entry's document state to docStates.
    for (auto& entry : traversable->session_history_entries())
        doc_states.append(entry->document_state);

    // 6. For each docState of docStates:
    while (!doc_states.is_empty()) {
        auto doc_state = doc_states.take_first();

        // 1. For each nestedHistory of docState's nested histories:
        for (auto& nested_history : doc_state->nested_histories()) {
            // 1. If nestedHistory's id equals navigable's id, return nestedHistory's entries.
            if (nested_history.id == id())
                return nested_history.entries;

            // 2. For each entry of nestedHistory's entries, append entry's document state to docStates.
            for (auto& entry : nested_history.entries)
                doc_states.append(entry->document_state);
        }
    }

    VERIFY_NOT_REACHED();
}

// https://html.spec.whatwg.org/multipage/browsers.html#determining-navigation-params-policy-container
static PolicyContainer determine_navigation_params_policy_container(AK::URL const& response_url,
    Optional<PolicyContainer> history_policy_container,
    Optional<PolicyContainer> initiator_policy_container,
    Optional<PolicyContainer> parent_policy_container,
    Optional<PolicyContainer> response_policy_container)
{
    // NOTE: The clone a policy container AO is just a C++ copy

    // 1. If historyPolicyContainer is not null, then:
    if (history_policy_container.has_value()) {
        // FIXME: 1. Assert: responseURL requires storing the policy container in history.

        // 2. Return a clone of historyPolicyContainer.
        return *history_policy_container;
    }

    // 2. If responseURL is about:srcdoc, then:
    if (response_url == "about:srcdoc"sv) {
        // 1. Assert: parentPolicyContainer is not null.
        VERIFY(parent_policy_container.has_value());

        // 2. Return a clone of parentPolicyContainer.
        return *parent_policy_container;
    }

    // 3. If responseURL is local and initiatorPolicyContainer is not null, then return a clone of initiatorPolicyContainer.
    if (Fetch::Infrastructure::is_local_url(response_url) && initiator_policy_container.has_value())
        return *initiator_policy_container;

    // 4. If responsePolicyContainer is not null, then return responsePolicyContainer.
    // FIXME: File a spec issue to say "a clone of" here for consistency
    if (response_policy_container.has_value())
        return *response_policy_container;

    // 5. Return a new policy container.
    return {};
}

// https://html.spec.whatwg.org/multipage/browsers.html#obtain-coop
static CrossOriginOpenerPolicy obtain_a_cross_origin_opener_policy(JS::NonnullGCPtr<Fetch::Infrastructure::Response>, Fetch::Infrastructure::Request::ReservedClientType const& reserved_client)
{

    // 1. Let policy be a new cross-origin opener policy.
    CrossOriginOpenerPolicy policy = {};

    // AD-HOC: We don't yet setup environments in all cases
    if (reserved_client.has<Empty>())
        return policy;

    auto& reserved_environment = reserved_client.visit(
        [](Empty const&) -> Environment& { VERIFY_NOT_REACHED(); },
        [](Environment* env) -> Environment& { return *env; },
        [](JS::GCPtr<EnvironmentSettingsObject> eso) -> Environment& { return *eso; });

    // 2. If reservedEnvironment is a non-secure context, then return policy.
    if (is_non_secure_context(reserved_environment))
        return policy;

    // FIXME: We don't yet have the technology to extract structured data from Fetch headers
    // FIXME: 3. Let parsedItem be the result of getting a structured field value given `Cross-Origin-Opener-Policy` and "item" from response's header list.
    // FIXME: 4. If parsedItem is not null, then:
    //     FIXME: nested steps...
    // FIXME: 5. Set parsedItem to the result of getting a structured field value given `Cross-Origin-Opener-Policy-Report-Only` and "item" from response's header list.
    // FIXME: 6. If parsedItem is not null, then:
    //     FIXME: nested steps...

    // 7. Return policy.
    return policy;
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#attempt-to-create-a-non-fetch-scheme-document
static JS::GCPtr<DOM::Document> attempt_to_create_a_non_fetch_scheme_document(NonFetchSchemeNavigationParams const& params)
{
    // FIXME: Implement this algorithm to hand off to external software or display inline content
    dbgln("(FIXME) Don't know how to navigate to {}", params.url);
    return nullptr;
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#create-navigation-params-from-a-srcdoc-resource
static WebIDL::ExceptionOr<NavigationParams> create_navigation_params_from_a_srcdoc_resource(JS::GCPtr<SessionHistoryEntry> entry, JS::GCPtr<Navigable> navigable, TargetSnapshotParams const& target_snapshot_params, Optional<String> navigation_id)
{
    auto& vm = navigable->vm();
    auto& realm = navigable->active_window()->realm();

    // 1. Let documentResource be entry's document state's resource.
    auto document_resource = entry->document_state->resource();
    VERIFY(document_resource.has<String>());

    // 2. Let response be a new response with
    //    URL: about:srcdoc
    //    header list: (`Content-Type`, `text/html`)
    //    body: the UTF-8 encoding of documentResource, as a body
    auto response = Fetch::Infrastructure::Response::create(vm);
    response->url_list().append(AK::URL("about:srcdoc"));
    auto header = TRY_OR_THROW_OOM(vm, Fetch::Infrastructure::Header::from_string_pair("Content-Type"sv, "text/html"sv));
    TRY_OR_THROW_OOM(vm, response->header_list()->append(move(header)));
    response->set_body(TRY(Fetch::Infrastructure::byte_sequence_as_body(realm, document_resource.get<String>().bytes())));

    // 3. Let responseOrigin be the result of determining the origin given response's URL, targetSnapshotParams's sandboxing flags, and entry's document state's origin.
    auto response_origin = determine_the_origin(*response->url(), target_snapshot_params.sandboxing_flags, entry->document_state->origin());

    // 4. Let coop be a new cross-origin opener policy.
    CrossOriginOpenerPolicy coop = {};

    // 5. Let coopEnforcementResult be a new cross-origin opener policy enforcement result with
    //    url: response's URL
    //    origin: responseOrigin
    //    cross-origin opener policy: coop
    CrossOriginOpenerPolicyEnforcementResult coop_enforcement_result {
        .url = *response->url(),
        .origin = response_origin,
        .cross_origin_opener_policy = coop
    };

    // 6. Let policyContainer be the result of determining navigation params policy container given response's URL,
    //    entry's document state's history policy container, null, navigable's container document's policy container, and null.
    Optional<PolicyContainer> history_policy_container = entry->document_state->history_policy_container().visit(
        [](PolicyContainer const& c) -> Optional<PolicyContainer> { return c; },
        [](DocumentState::Client) -> Optional<PolicyContainer> { return {}; });
    PolicyContainer policy_container;
    if (navigable->container()) {
        // NOTE: Specification assumes that only navigables corresponding to iframes can be navigated to about:srcdoc.
        //       We also use srcdoc to implement load_html() for top level navigables so we need to null check container
        //       because it might be null.
        policy_container = determine_navigation_params_policy_container(*response->url(), history_policy_container, {}, navigable->container_document()->policy_container(), {});
    }

    // 7. Return a new navigation params, with
    //    id: navigationId
    //    navigable: navigable
    //    request: null
    //    response: response
    //    fetch controller: null
    //    commit early hints: null
    //    COOP enforcement result: coopEnforcementResult
    //    reserved environment: null
    //    origin: responseOrigin
    //    policy container: policyContainer
    //    final sandboxing flag set: targetSnapshotParams's sandboxing flags
    //    cross-origin opener policy: coop
    //    FIXME: navigation timing type: navTimingType
    //    about base URL: entry's document state's about base URL
    return NavigationParams {
        .id = move(navigation_id),
        .navigable = navigable,
        .request = nullptr,
        .response = *response,
        .fetch_controller = nullptr,
        .commit_early_hints = nullptr,
        .coop_enforcement_result = move(coop_enforcement_result),
        .reserved_environment = {},
        .origin = move(response_origin),
        .policy_container = policy_container,
        .final_sandboxing_flag_set = target_snapshot_params.sandboxing_flags,
        .cross_origin_opener_policy = move(coop),
        .about_base_url = entry->document_state->about_base_url(),
    };
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#create-navigation-params-by-fetching
static WebIDL::ExceptionOr<Variant<Empty, NavigationParams, NonFetchSchemeNavigationParams>> create_navigation_params_by_fetching(JS::GCPtr<SessionHistoryEntry> entry, JS::GCPtr<Navigable> navigable, SourceSnapshotParams const& source_snapshot_params, TargetSnapshotParams const& target_snapshot_params, CSPNavigationType csp_navigation_type, Optional<String> navigation_id)
{
    auto& vm = navigable->vm();
    auto& realm = navigable->active_window()->realm();
    auto& active_document = *navigable->active_document();

    (void)csp_navigation_type;

    // FIXME: 1. Assert: this is running in parallel.

    // 2. Let documentResource be entry's document state's resource.
    auto document_resource = entry->document_state->resource();

    // 3. Let request be a new request, with
    //    url: entry's URL
    //    client: sourceSnapshotParams's fetch client
    //    destination: "document"
    //    credentials mode: "include"
    //    use-URL-credentials flag: set
    //    redirect mode: "manual"
    //    replaces client id: navigable's active document's relevant settings object's id
    //    mode: "navigate"
    //    referrer: entry's document state's request referrer
    //    referrer policy: entry's document state's request referrer policy
    auto request = Fetch::Infrastructure::Request::create(vm);
    request->set_url(entry->url);
    request->set_client(source_snapshot_params.fetch_client);
    request->set_destination(Fetch::Infrastructure::Request::Destination::Document);
    request->set_credentials_mode(Fetch::Infrastructure::Request::CredentialsMode::Include);
    request->set_use_url_credentials(true);
    request->set_redirect_mode(Fetch::Infrastructure::Request::RedirectMode::Manual);
    request->set_replaces_client_id(active_document.relevant_settings_object().id);
    request->set_mode(Fetch::Infrastructure::Request::Mode::Navigate);
    request->set_referrer(entry->document_state->request_referrer());

    // 4. If documentResource is a POST resource, then:
    if (document_resource.has<POSTResource>()) {
        // 1. Set request's method to `POST`.
        request->set_method(TRY_OR_THROW_OOM(vm, ByteBuffer::copy("POST"sv.bytes())));

        // 2. Set request's body to documentResource's request body.
        request->set_body(document_resource.get<POSTResource>().request_body.value());

        // 3. Set `Content-Type` to documentResource's request content-type in request's header list.
        auto request_content_type = document_resource.get<POSTResource>().request_content_type;
        auto request_content_type_string = [request_content_type]() {
            switch (request_content_type) {
            case POSTResource::RequestContentType::ApplicationXWWWFormUrlencoded:
                return "application/x-www-form-urlencoded"sv;
            case POSTResource::RequestContentType::MultipartFormData:
                return "multipart/form-data"sv;
            case POSTResource::RequestContentType::TextPlain:
                return "text/plain"sv;
            default:
                VERIFY_NOT_REACHED();
            }
        }();
        auto header = TRY_OR_THROW_OOM(vm, Fetch::Infrastructure::Header::from_string_pair("Content-Type"sv, request_content_type_string));
        TRY_OR_THROW_OOM(vm, request->header_list()->append(move(header)));
    }

    // 5. If entry's document state's reload pending is true, then set request's reload-navigation flag.
    if (entry->document_state->reload_pending())
        request->set_reload_navigation(true);

    // 6. Otherwise, if entry's document state's ever populated is true, then set request's history-navigation flag.
    if (entry->document_state->ever_populated())
        request->set_history_navigation(true);

    // 7. If sourceSnapshotParams's has transient activation is true, then set request's user-activation to true.
    if (source_snapshot_params.has_transient_activation)
        request->set_user_activation(true);

    // 8. If navigable's container is non-null:
    if (navigable->container() != nullptr) {
        // 1. If the navigable's container has a browsing context scope origin, then set request's origin to that browsing context scope origin.
        // FIXME: From "browsing context scope origin": This definition is broken and needs investigation to see what it was intended to express: see issue #4703.
        //        The referenced issue suggests that it is a no-op to retrieve the browsing context scope origin.

        // 2. Set request's destination to navigable's container's local name.
        // FIXME: Are there other container types? If so, we need a helper here
        Web::Fetch::Infrastructure::Request::Destination destination = is<HTMLIFrameElement>(*navigable->container()) ? Web::Fetch::Infrastructure::Request::Destination::IFrame
                                                                                                                      : Web::Fetch::Infrastructure::Request::Destination::Object;
        request->set_destination(destination);

        // 3. If sourceSnapshotParams's fetch client is navigable's container document's relevant settings object,
        //    then set request's initiator type to navigable's container's local name.
        // NOTE: This ensure that only container-initiated navigations are reported to resource timing.
        if (source_snapshot_params.fetch_client == &navigable->container_document()->relevant_settings_object()) {
            // FIXME: Are there other container types? If so, we need a helper here
            Web::Fetch::Infrastructure::Request::InitiatorType initiator_type = is<HTMLIFrameElement>(*navigable->container()) ? Web::Fetch::Infrastructure::Request::InitiatorType::IFrame
                                                                                                                               : Web::Fetch::Infrastructure::Request::InitiatorType::Object;
            request->set_initiator_type(initiator_type);
        }
    }

    // 9. Let response be null.
    // NOTE: We use a heap-allocated cell to hold the response pointer because the processResponse callback below
    //       might use it after this stack is freed.
    auto response_holder = ResponseHolder::create(vm);

    // 10. Let responseOrigin be null.
    Optional<HTML::Origin> response_origin;

    // 11. Let fetchController be null.
    JS::GCPtr<Fetch::Infrastructure::FetchController> fetch_controller = nullptr;

    // 12. Let coopEnforcementResult be a new cross-origin opener policy enforcement result, with
    // - url: navigable's active document's URL
    // - origin: navigable's active document's origin
    // - cross-origin opener policy: navigable's active document's cross-origin opener policy
    // - current context is navigation source: true if navigable's active document's origin is same origin with
    //                                         entry's document state's initiator origin otherwise false
    CrossOriginOpenerPolicyEnforcementResult coop_enforcement_result = {
        .url = active_document.url(),
        .origin = active_document.origin(),
        .cross_origin_opener_policy = active_document.cross_origin_opener_policy(),
        .current_context_is_navigation_source = entry->document_state->initiator_origin().has_value() && active_document.origin().is_same_origin(*entry->document_state->initiator_origin())
    };

    // 13. Let finalSandboxFlags be an empty sandboxing flag set.
    SandboxingFlagSet final_sandbox_flags = {};

    // 14. Let responsePolicyContainer be null.
    Optional<PolicyContainer> response_policy_container = {};

    // 15. Let responseCOOP be a new cross-origin opener policy.
    CrossOriginOpenerPolicy response_coop = {};

    // 16. Let locationURL be null.
    ErrorOr<Optional<AK::URL>> location_url { OptionalNone {} };

    // 17. Let currentURL be request's current URL.
    AK::URL current_url = request->current_url();

    // 18. Let commitEarlyHints be null.
    Function<void(DOM::Document&)> commit_early_hints = nullptr;

    // 19. While true:
    while (true) {
        // FIXME: 1. If request's reserved client is not null and currentURL's origin is not the same as request's reserved client's creation URL's origin, then:
        // FIXME: 2. If request's reserved client is null, then:
        // FIXME: 3. If the result of should navigation request of type be blocked by Content Security Policy? given request and cspNavigationType is "Blocked", then set response to a network error and break. [CSP]

        // 4. Set response to null.
        response_holder->set_response(nullptr);

        // 5. If fetchController is null, then set fetchController to the result of fetching request,
        //    with processEarlyHintsResponse set to processEarlyHintsResponseas defined below, processResponse
        //    set to processResponse as defined below, and useParallelQueue set to true.
        if (!fetch_controller) {
            // FIXME: Let processEarlyHintsResponse be the following algorithm given a response earlyResponse:

            // Let processResponse be the following algorithm given a response fetchedResponse:
            auto process_response = [response_holder](JS::NonnullGCPtr<Fetch::Infrastructure::Response> fetch_response) {
                // 1. Set response to fetchedResponse.
                response_holder->set_response(fetch_response);
            };

            fetch_controller = TRY(Fetch::Fetching::fetch(
                realm,
                request,
                Fetch::Infrastructure::FetchAlgorithms::create(vm,
                    {
                        .process_request_body_chunk_length = {},
                        .process_request_end_of_body = {},
                        .process_early_hints_response = {},
                        .process_response = move(process_response),
                        .process_response_end_of_body = {},
                        .process_response_consume_body = {},
                    }),
                Fetch::Fetching::UseParallelQueue::Yes));
        }
        // 6. Otherwise, process the next manual redirect for fetchController.
        else {
            fetch_controller->process_next_manual_redirect();
        }

        // 7. Wait until either response is non-null, or navigable's ongoing navigation changes to no longer equal navigationId.
        Platform::EventLoopPlugin::the().spin_until([&]() {
            if (response_holder->response() != nullptr)
                return true;

            if (navigation_id.has_value() && (!navigable->ongoing_navigation().has<String>() || navigable->ongoing_navigation().get<String>() != *navigation_id))
                return true;

            return false;
        });
        // If the latter condition occurs, then abort fetchController, and return. Otherwise, proceed onward.
        if (navigation_id.has_value() && (!navigable->ongoing_navigation().has<String>() || navigable->ongoing_navigation().get<String>() != *navigation_id)) {
            fetch_controller->abort(realm, {});
            return Empty {};
        }

        // 8. If request's body is null, then set entry's document state's resource to null.
        if (!request->body().has<Empty>()) {
            entry->document_state->set_resource(Empty {});
        }

        // FIXME 9. Set responsePolicyContainer to the result of creating a policy container from a fetch response given response and request's reserved client.
        // FIXME 10. Set finalSandboxFlags to the union of targetSnapshotParams's sandboxing flags and responsePolicyContainer's CSP list's CSP-derived sandboxing flags.

        // 11. Set responseOrigin to the result of determining the origin given response's URL, finalSandboxFlags, and entry's document state's initiator origin.
        response_origin = determine_the_origin(*response_holder->response()->url(), final_sandbox_flags, entry->document_state->initiator_origin());

        // 12. If navigable is a top-level traversable, then:
        if (navigable->is_top_level_traversable()) {
            // 1. Set responseCOOP to the result of obtaining a cross-origin opener policy given response and request's reserved client.
            response_coop = obtain_a_cross_origin_opener_policy(*response_holder->response(), request->reserved_client());

            // FIXME: 2. Set coopEnforcementResult to the result of enforcing the response's cross-origin opener policy given navigable's active browsing context,
            //    response's URL, responseOrigin, responseCOOP, coopEnforcementResult and request's referrer.

            // FIXME: 3. If finalSandboxFlags is not empty and responseCOOP's value is not "unsafe-none", then set response to an appropriate network error and break.
            // NOTE: This results in a network error as one cannot simultaneously provide a clean slate to a response
            //       using cross-origin opener policy and sandbox the result of navigating to that response.
        }

        // 13. FIXME If response is not a network error, navigable is a child navigable, and the result of performing a cross-origin resource policy check
        //    with navigable's container document's origin, navigable's container document's relevant settings object, request's destination, response,
        //    and true is blocked, then set response to a network error and break.
        // NOTE: Here we're running the cross-origin resource policy check against the parent navigable rather than navigable itself
        //       This is because we care about the same-originness of the embedded content against the parent context, not the navigation source.

        // 14. Set locationURL to response's location URL given currentURL's fragment.
        location_url = response_holder->response()->location_url(current_url.fragment());

        VERIFY(!location_url.is_error());

        // 15. If locationURL is failure or null, then break.
        if (location_url.is_error() || !location_url.value().has_value()) {
            break;
        }

        // 16. Assert: locationURL is a URL.
        VERIFY(location_url.value()->is_valid());

        // 17. Set entry's classic history API state to StructuredSerializeForStorage(null).
        entry->classic_history_api_state = MUST(structured_serialize_for_storage(vm, JS::js_null()));

        // 18. Let oldDocState be entry's document state.
        auto old_doc_state = entry->document_state;

        // 19. Set entry's document state to a new document state, with
        // history policy container: a clone of the oldDocState's history policy container if it is non-null; null otherwise
        // request referrer: oldDocState's request referrer
        // request referrer policy: oldDocState's request referrer policy
        // origin: oldDocState's origin
        // resource: oldDocState's resource
        // ever populated: oldDocState's ever populated
        // navigable target name: oldDocState's navigable target name
        entry->document_state = navigable->heap().allocate_without_realm<DocumentState>();
        entry->document_state->set_history_policy_container(old_doc_state->history_policy_container());
        entry->document_state->set_request_referrer(old_doc_state->request_referrer());
        entry->document_state->set_request_referrer_policy(old_doc_state->request_referrer_policy());
        entry->document_state->set_origin(old_doc_state->origin());
        entry->document_state->set_resource(old_doc_state->resource());
        entry->document_state->set_ever_populated(old_doc_state->ever_populated());
        entry->document_state->set_navigable_target_name(old_doc_state->navigable_target_name());

        // 20. If locationURL's scheme is not an HTTP(S) scheme, then:
        if (!Fetch::Infrastructure::is_http_or_https_scheme(location_url.value()->scheme())) {
            // 1. Set entry's document state's resource to null.
            entry->document_state->set_resource(Empty {});

            // 2. Break.
            break;
        }

        // 21. Set currentURL to locationURL.
        current_url = location_url.value().value();

        // 22. Set entry's URL to currentURL.
        entry->url = current_url;
    }

    // 20. If locationURL is a URL whose scheme is not a fetch scheme, then return a new non-fetch scheme navigation params, with
    if (!location_url.is_error() && location_url.value().has_value() && !Fetch::Infrastructure::is_fetch_scheme(location_url.value().value().scheme())) {
        // - id: navigationId
        // - navigable: navigable
        // - URL: locationURL
        // - target snapshot sandboxing flags: targetSnapshotParams's sandboxing flags
        // - source snapshot has transient activation: sourceSnapshotParams's has transient activation
        // - initiator origin: responseOrigin
        // FIXME: - navigation timing type: navTimingType
        return NonFetchSchemeNavigationParams {
            .id = navigation_id,
            .navigable = navigable,
            .url = location_url.release_value().value(),
            .target_snapshot_sandboxing_flags = target_snapshot_params.sandboxing_flags,
            .source_snapshot_has_transient_activation = source_snapshot_params.has_transient_activation,
            .initiator_origin = move(*response_origin),
        };
    }

    // 21. If any of the following are true:
    //       - response is a network error;
    //       - locationURL is failure; or
    //       - locationURL is a URL whose scheme is a fetch scheme
    //     then return null.
    if (response_holder->response()->is_network_error() || location_url.is_error() || (location_url.value().has_value() && Fetch::Infrastructure::is_fetch_scheme(location_url.value().value().scheme()))) {
        return Empty {};
    }

    // 22. Assert: locationURL is null and response is not a network error.
    VERIFY(!location_url.value().has_value());
    VERIFY(!response_holder->response()->is_network_error());

    // 23. Let resultPolicyContainer be the result of determining navigation params policy container given response's URL,
    //     entry's document state's history policy container, sourceSnapshotParams's source policy container, null, and responsePolicyContainer.
    Optional<PolicyContainer> history_policy_container = entry->document_state->history_policy_container().visit(
        [](PolicyContainer const& c) -> Optional<PolicyContainer> { return c; },
        [](DocumentState::Client) -> Optional<PolicyContainer> { return {}; });
    auto result_policy_container = determine_navigation_params_policy_container(*response_holder->response()->url(), history_policy_container, source_snapshot_params.source_policy_container, {}, response_policy_container);

    // 24. If navigable's container is an iframe, and response's timing allow passed flag is set, then set container's pending resource-timing start time to null.
    if (navigable->container() && is<HTML::HTMLIFrameElement>(*navigable->container()) && response_holder->response()->timing_allow_passed())
        static_cast<HTML::HTMLIFrameElement&>(*navigable->container()).set_pending_resource_start_time({});

    // 25. Return a new navigation params, with
    //     id: navigationId
    //     navigable: navigable
    //     request: request
    //     response: response
    //     fetch controller: fetchController
    //     commit early hints: commitEarlyHints
    //     cross-origin opener policy: responseCOOP
    //     reserved environment: request's reserved client
    //     origin: responseOrigin
    //     policy container: resultPolicyContainer
    //     final sandboxing flag set: finalSandboxFlags
    //     COOP enforcement result: coopEnforcementResult
    //     FIXME: navigation timing type: navTimingType
    //     about base URL: entry's document state's about base URL
    HTML::NavigationParams navigation_params {
        .id = navigation_id,
        .navigable = navigable,
        .request = request,
        .response = *response_holder->response(),
        .fetch_controller = fetch_controller,
        .commit_early_hints = move(commit_early_hints),
        .coop_enforcement_result = coop_enforcement_result,
        .reserved_environment = request->reserved_client(),
        .origin = *response_origin,
        .policy_container = result_policy_container,
        .final_sandboxing_flag_set = final_sandbox_flags,
        .cross_origin_opener_policy = response_coop,
        .about_base_url = entry->document_state->about_base_url(),
    };

    return navigation_params;
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#attempt-to-populate-the-history-entry's-document
WebIDL::ExceptionOr<void> Navigable::populate_session_history_entry_document(
    JS::GCPtr<SessionHistoryEntry> entry,
    SourceSnapshotParams const& source_snapshot_params,
    TargetSnapshotParams const& target_snapshot_params,
    Optional<String> navigation_id,
    Variant<Empty, NavigationParams, NonFetchSchemeNavigationParams> navigation_params,
    CSPNavigationType csp_navigation_type,
    bool allow_POST,
    Function<void()> completion_steps)
{
    // FIXME: 1. Assert: this is running in parallel.

    // 2. Assert: if navigationParams is non-null, then navigationParams's response is non-null.
    // NavigationParams' response field is NonnullGCPtr
    if (!navigation_params.has<Empty>())
        VERIFY(navigation_params.has<NavigationParams>());

    // 3. Let currentBrowsingContext be navigable's active browsing context.
    [[maybe_unused]] auto current_browsing_context = active_browsing_context();

    // 4. Let documentResource be entry's document state's resource.
    auto document_resource = entry->document_state->resource();

    // 5. If navigationParams is null, then:
    if (navigation_params.has<Empty>()) {
        // 1. If documentResource is a string, then set navigationParams to the result
        //    of creating navigation params from a srcdoc resource given entry, navigable,
        //    targetSnapshotParams, navigationId, and navTimingType.
        if (document_resource.has<String>()) {
            navigation_params = TRY(create_navigation_params_from_a_srcdoc_resource(entry, this, target_snapshot_params, navigation_id));
        }
        // 2. Otherwise, if both of the following are true:
        //    - entry's URL's scheme is a fetch scheme; and
        //    - documentResource is null, or allowPOST is true and documentResource's request body is not failure (FIXME: check if request body is not failure)
        else if (Fetch::Infrastructure::is_fetch_scheme(entry->url.scheme()) && (document_resource.has<Empty>() || allow_POST)) {
            navigation_params = TRY(create_navigation_params_by_fetching(entry, this, source_snapshot_params, target_snapshot_params, csp_navigation_type, navigation_id));
        }
        // 3. Otherwise, if entry's URL's scheme is not a fetch scheme, then set navigationParams to a new non-fetch scheme navigation params, with:
        else if (!Fetch::Infrastructure::is_fetch_scheme(entry->url.scheme())) {
            // - id: navigationId
            // - navigable: navigable
            // - URL: entry's URL
            // - target snapshot sandboxing flags: targetSnapshotParams's sandboxing flags
            // - source snapshot has transient activation: sourceSnapshotParams's has transient activation
            // - initiator origin: entry's document state's initiator origin
            // FIXME: - navigation timing type: navTimingType
            navigation_params = NonFetchSchemeNavigationParams {
                .id = navigation_id,
                .navigable = this,
                .url = entry->url,
                .target_snapshot_sandboxing_flags = target_snapshot_params.sandboxing_flags,
                .source_snapshot_has_transient_activation = source_snapshot_params.has_transient_activation,
                .initiator_origin = *entry->document_state->initiator_origin(),
            };
        }
    }

    // NOTE: Not in the spec but queuing task on the next step will fail because active_window() does not exist for destroyed navigable.
    if (has_been_destroyed())
        return {};

    // 6. Queue a global task on the navigation and traversal task source, given navigable's active window, to run these steps:
    queue_global_task(Task::Source::NavigationAndTraversal, *active_window(), [this, entry, navigation_params = move(navigation_params), navigation_id, completion_steps = move(completion_steps)]() mutable {
        // NOTE: This check is not in the spec but we should not continue navigation if navigable has been destroyed.
        if (has_been_destroyed())
            return;

        // 1. If navigable's ongoing navigation no longer equals navigationId, then run completionSteps and return.
        if (navigation_id.has_value() && (!ongoing_navigation().has<String>() || ongoing_navigation().get<String>() != *navigation_id)) {
            completion_steps();
            return;
        }

        // 2. Let failure be false.
        auto failure = false;

        // 3. If navigationParams is a non-fetch scheme navigation params, then set entry's document state's document to the result of
        //    running attempt to create a non-fetch scheme document navigationParams
        if (navigation_params.has<NonFetchSchemeNavigationParams>()) {
            // FIXME: https://github.com/whatwg/html/issues/9767
            // We probably are expected to skip to steps 13 and 14 and return after doing this
            entry->document_state->set_document(attempt_to_create_a_non_fetch_scheme_document(navigation_params.get<NonFetchSchemeNavigationParams>()));
            if (entry->document_state->document()) {
                entry->document_state->set_ever_populated(true);
            }
            completion_steps();
            return;
        }

        // 4. Otherwise, if navigationParams is null, then set failure to true.
        if (navigation_params.has<Empty>()) {
            failure = true;
        }

        // FIXME: 5. Otherwise, if the result of should navigation response to navigation request of type in target be blocked by Content Security Policy? given navigationParams's request,
        //    navigationParams's response, navigationParams's policy container's CSP list, cspNavigationType, and navigable is "Blocked", then set failure to true.

        // FIXME: 6. Otherwise, if navigationParams's reserved environment is non-null and the result of checking a navigation response's adherence to its embedder policy given
        //    navigationParams's response, navigable, and navigationParams's policy container's embedder policy is false, then set failure to true.

        // FIXME: 7. Otherwise, if the result of checking a navigation response's adherence to `X-Frame-Options` given navigationParams's response, navigable,
        //    navigationParams's policy container's CSP list, and navigationParams's origin is false, then set failure to true.

        // 8. If failure is true, then:
        if (failure) {
            // 1. Set entry's document state's document to the result of creating a document for inline content that doesn't have a DOM, given navigable, null, and navTimingType.
            //    The inline content should indicate to the user the sort of error that occurred.
            // FIXME: Add error message to generated error page
            auto error_html = load_error_page(entry->url).release_value_but_fixme_should_propagate_errors();
            entry->document_state->set_document(create_document_for_inline_content(this, navigation_id, [error_html](auto& document) {
                auto parser = HTML::HTMLParser::create(document, error_html, "utf-8");
                document.set_url(AK::URL("about:error"));
                parser->run();
            }));

            // 2. Set entry's document state's document's salvageable to false.
            entry->document_state->document()->set_salvageable(false);

            // FIXME: 3. If navigationParams is not null, then:
            if (!navigation_params.has<Empty>()) {
                // 1. FIXME: Run the environment discarding steps for navigationParams's reserved environment.
                // 2. Invoke WebDriver BiDi navigation failed with currentBrowsingContext and a new WebDriver BiDi navigation status
                //    whose id is navigationId, status is "canceled", and url is navigationParams's response's URL.
            }
        }
        // FIXME: 9. Otherwise, if navigationParams's response's status is 204 or 205, then:
        else if (navigation_params.get<NavigationParams>().response->status() == 204 || navigation_params.get<NavigationParams>().response->status() == 205) {
            // 1. Run completionSteps.
            completion_steps();

            // 2. Return.
            return;
        }
        // FIXME: 10. Otherwise, if navigationParams's response has a `Content-Disposition`
        //            header specifying the attachment disposition type, then:
        // 11. Otherwise:
        else {
            // 1. Let document be the result of loading a document given navigationParams, sourceSnapshotParams,
            //    and entry's document state's initiator origin.
            auto document = load_document(move(navigation_params.get<NavigationParams>()));

            // 2. If document is null, then run completionSteps and return.
            if (!document) {
                completion_steps();
                return;
            }

            // 3. Set entry's document state's document to document.
            entry->document_state->set_document(document.ptr());

            // 4. Set entry's document state's origin to document's origin.
            entry->document_state->set_origin(document->origin());
        }

        // FIXME: 12. If entry's document state's request referrer is "client", then set it to request's referrer.
        //     https://github.com/whatwg/html/issues/9767
        //     What is "request" here?

        // 13. If entry's document state's document is not null, then set entry's document state's ever populated to true.
        if (entry->document_state->document()) {
            entry->document_state->set_ever_populated(true);
        }

        // 14. Run completionSteps.
        completion_steps();
    });

    return {};
}

// To navigate a navigable navigable to a URL url using a Document sourceDocument,
// with an optional POST resource, string, or null documentResource (default null),
// an optional response-or-null response (default null), an optional boolean exceptionsEnabled (default false),
// an optional NavigationHistoryBehavior historyHandling (default "auto"),
// an optional serialized state-or-null navigationAPIState (default null),
// an optional entry list or null formDataEntryList (default null),
// an optional referrer policy referrerPolicy (default the empty string),
// and an optional user navigation involvement userInvolvement (default "none"):

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigate
WebIDL::ExceptionOr<void> Navigable::navigate(NavigateParams params)
{
    auto const& url = params.url;
    auto source_document = params.source_document;
    auto const& document_resource = params.document_resource;
    auto response = params.response;
    auto exceptions_enabled = params.exceptions_enabled;
    auto history_handling = params.history_handling;
    auto const& navigation_api_state = params.navigation_api_state;
    auto const& form_data_entry_list = params.form_data_entry_list;
    auto referrer_policy = params.referrer_policy;
    auto user_involvement = params.user_involvement;
    auto& active_document = *this->active_document();
    auto& realm = active_document.realm();
    auto& vm = this->vm();

    // 1. Let cspNavigationType be "form-submission" if formDataEntryList is non-null; otherwise "other".
    auto csp_navigation_type = form_data_entry_list.has_value() ? CSPNavigationType::FormSubmission : CSPNavigationType::Other;

    // 2. Let sourceSnapshotParams be the result of snapshotting source snapshot params given sourceDocument.
    auto source_snapshot_params = source_document->snapshot_source_snapshot_params();

    // 3. Let initiatorOriginSnapshot be sourceDocument's origin.
    auto initiator_origin_snapshot = source_document->origin();

    // 4. Let initiatorBaseURLSnapshot be sourceDocument's document base URL.
    auto initiator_base_url_snapshot = source_document->base_url();

    // 5. If sourceDocument's node navigable is not allowed by sandboxing to navigate navigable given and sourceSnapshotParams, then:
    if (!source_document->navigable()->allowed_by_sandboxing_to_navigate(*this, source_snapshot_params)) {
        // 1. If exceptionsEnabled is true, then throw a "SecurityError" DOMException.
        if (exceptions_enabled) {
            return WebIDL::SecurityError::create(realm, "Source document's node navigable is not allowed to navigate"_fly_string);
        }

        // 2 Return.
        return {};
    }

    // 6. Let navigationId be the result of generating a random UUID.
    String navigation_id = TRY_OR_THROW_OOM(vm, Crypto::generate_random_uuid());

    // FIXME: 7. If the surrounding agent is equal to navigable's active document's relevant agent, then continue these steps.
    //           Otherwise, queue a global task on the navigation and traversal task source given navigable's active window to continue these steps.

    // 8. If navigable's active document's unload counter is greater than 0,
    //    then invoke WebDriver BiDi navigation failed with a WebDriver BiDi navigation status whose id is navigationId,
    //    status is "canceled", and url is url, and return.
    if (active_document.unload_counter() > 0) {
        // FIXME: invoke WebDriver BiDi navigation failed with a WebDriver BiDi navigation status whose id is navigationId,
        //        status is "canceled", and url is url
        return {};
    }

    // 9. If historyHandling is "auto", then:
    if (history_handling == Bindings::NavigationHistoryBehavior::Auto) {
        // FIXME: Fix spec typo targetNavigable --> navigable
        // 1. If url equals navigable's active document's URL,
        //     and initiatorOriginSnapshot is same origin with targetNavigable's active document's origin,
        //     then set historyHandling to "replace".
        if (url.equals(active_document.url(), AK::URL::ExcludeFragment::Yes) && initiator_origin_snapshot.is_same_origin(active_document.origin()))
            history_handling = Bindings::NavigationHistoryBehavior::Replace;

        // 2. Otherwise, set historyHandling to "push".
        else
            history_handling = Bindings::NavigationHistoryBehavior::Push;
    }

    // 10. If the navigation must be a replace given url and navigable's active document, then set historyHandling to "replace".
    if (navigation_must_be_a_replace(url, active_document))
        history_handling = Bindings::NavigationHistoryBehavior::Replace;

    // 11. If all of the following are true:
    //    - documentResource is null;
    //    - response is null;
    //    - url equals navigable's active session history entry's URL with exclude fragments set to true; and
    //    - url's fragment is non-null
    if (document_resource.has<Empty>()
        && !response
        && url.equals(active_session_history_entry()->url, AK::URL::ExcludeFragment::Yes)
        && url.fragment().has_value()) {
        // 1. Navigate to a fragment given navigable, url, historyHandling, and navigationId.
        TRY(navigate_to_a_fragment(url, to_history_handling_behavior(history_handling), navigation_id));

        traversable_navigable()->process_session_history_traversal_queue();

        // 2. Return.
        return {};
    }

    // 12. If navigable's parent is non-null, then set navigable's is delaying load events to true.
    if (parent() != nullptr)
        set_delaying_load_events(true);

    // 13. Let targetBrowsingContext be navigable's active browsing context.
    [[maybe_unused]] auto target_browsing_context = active_browsing_context();

    // 14. Let targetSnapshotParams be the result of snapshotting target snapshot params given navigable.
    auto target_snapshot_params = snapshot_target_snapshot_params();

    // FIXME: 15. Invoke WebDriver BiDi navigation started with targetBrowsingContext, and a new WebDriver BiDi navigation status whose id is navigationId, url is url, and status is "pending".

    // 16. If navigable's ongoing navigation is "traversal", then:
    if (ongoing_navigation().has<Traversal>()) {
        // FIXME: 1. Invoke WebDriver BiDi navigation failed with targetBrowsingContext and a new WebDriver BiDi navigation status whose id is navigationId, status is "canceled", and url is url.

        // 2. Return.
        return {};
    }

    // 17. Set navigable's ongoing navigation to navigationId.
    set_ongoing_navigation(navigation_id);

    // 18. If url's scheme is "javascript", then:
    if (url.scheme() == "javascript"sv) {
        // 1. Queue a global task on the navigation and traversal task source given navigable's active window to navigate to a javascript: URL given navigable, url, historyHandling, initiatorOriginSnapshot, and cspNavigationType.
        queue_global_task(Task::Source::NavigationAndTraversal, *active_window(), [this, url, history_handling, initiator_origin_snapshot, csp_navigation_type, navigation_id] {
            (void)navigate_to_a_javascript_url(url, to_history_handling_behavior(history_handling), initiator_origin_snapshot, csp_navigation_type, navigation_id);
        });

        // 2. Return.
        return {};
    }

    // 19. If all of the following are true:
    //     - userInvolvement is not "browser UI";
    //     - navigable's active document's origin is same origin-domain with sourceDocument's origin;
    //     - navigable's active document's is initial about:blank is false; and
    //     - url's scheme is a fetch scheme
    //     then:
    if (user_involvement != UserNavigationInvolvement::BrowserUI && active_document.origin().is_same_origin_domain(source_document->origin()) && !active_document.is_initial_about_blank() && Fetch::Infrastructure::is_fetch_scheme(url.scheme())) {
        // 1. Let navigation be navigable's active window's navigation API.
        auto navigation = active_window()->navigation();

        // 2. Let entryListForFiring be formDataEntryList if documentResource is a POST resource; otherwise, null.
        auto entry_list_for_firing = [&]() -> Optional<Vector<XHR::FormDataEntry>&> {
            if (document_resource.has<POSTResource>())
                return form_data_entry_list;
            return {};
        }();

        // 3. Let navigationAPIStateForFiring be navigationAPIState if navigationAPIState is not null;
        //    otherwise, StructuredSerializeForStorage(undefined).
        auto navigation_api_state_for_firing = navigation_api_state.value_or(MUST(structured_serialize_for_storage(vm, JS::js_undefined())));

        // FIXME: 4. Let continue be the result of firing a push/replace/reload navigate event at navigation
        //           with navigationType set to historyHandling, isSameDocument set to false, userInvolvement set to userInvolvement,
        //           formDataEntryList set to entryListForFiring, destinationURL set to url, and navigationAPIState set to navigationAPIStateForFiring.
        (void)navigation;
        (void)entry_list_for_firing;
        (void)navigation_api_state_for_firing;

        // FIXME: 5. If continue is false, then return.
    }

    if (is_top_level_traversable()) {
        active_browsing_context()->page().client().page_did_start_loading(url, false);
    }

    // 20. In parallel, run these steps:
    Platform::EventLoopPlugin::the().deferred_invoke([this, source_snapshot_params, target_snapshot_params, csp_navigation_type, document_resource, url, navigation_id, referrer_policy, initiator_origin_snapshot, response, history_handling, initiator_base_url_snapshot] {
        // NOTE: Not in the spec but subsequent steps will fail because destroyed navigable does not have active document.
        if (has_been_destroyed())
            return;

        // FIXME: 1. Let unloadPromptCanceled be the result of checking if unloading is user-canceled for navigable's active document's inclusive descendant navigables.

        // FIXME: 2. If unloadPromptCanceled is true, or navigable's ongoing navigation is no longer navigationId, then:
        if (!ongoing_navigation().has<String>() || ongoing_navigation().get<String>() != navigation_id) {
            // FIXME: 1. Invoke WebDriver BiDi navigation failed with targetBrowsingContext and a new WebDriver BiDi navigation status whose id is navigationId, status is "canceled", and url is url.

            // 2. Abort these steps.
            return;
        }

        // 3. Queue a global task on the navigation and traversal task source given navigable's active window to abort navigable's active document.
        queue_global_task(Task::Source::NavigationAndTraversal, *active_window(), [this] {
            VERIFY(this->active_document());
            this->active_document()->abort();
        });

        // 4. Let documentState be a new document state with
        //    request referrer policy: referrerPolicy
        //    initiator origin: initiatorOriginSnapshot
        //    resource: documentResource
        //    navigable target name: navigable's target name
        JS::NonnullGCPtr<DocumentState> document_state = *heap().allocate_without_realm<DocumentState>();
        document_state->set_request_referrer_policy(referrer_policy);
        document_state->set_initiator_origin(initiator_origin_snapshot);
        document_state->set_resource(document_resource);
        document_state->set_navigable_target_name(target_name());

        // 5. If url matches about:blank or is about:srcdoc, then set documentState's origin to documentState's initiator origin.
        //   FIXME: should this say "matches about:srcdoc"
        if (url_matches_about_blank(url) || url == "about:srcdoc"sv) {
            // 1. Set documentState's origin to initiatorOriginSnapshot.
            document_state->set_origin(document_state->initiator_origin());

            // 2. Set documentState's about base URL to initiatorBaseURLSnapshot.
            document_state->set_about_base_url(initiator_base_url_snapshot);
        }

        // 6. Let historyEntry be a new session history entry, with its URL set to url and its document state set to documentState.
        JS::NonnullGCPtr<SessionHistoryEntry> history_entry = *heap().allocate_without_realm<SessionHistoryEntry>();
        history_entry->url = url;
        history_entry->document_state = document_state;

        // 8. Let navigationParams be null.
        Variant<Empty, NavigationParams, NonFetchSchemeNavigationParams> navigation_params = Empty {};

        // FIXME: 9. If response is non-null:
        if (response) {
        }

        // 10. Attempt to populate the history entry's document
        //     for historyEntry, given navigable, "navigate", sourceSnapshotParams,
        //     targetSnapshotParams, navigationId, navigationParams, cspNavigationType, with allowPOST
        //     set to true and completionSteps set to the following step:
        populate_session_history_entry_document(history_entry, source_snapshot_params, target_snapshot_params, navigation_id, move(navigation_params), csp_navigation_type, true, [this, history_entry, history_handling, navigation_id] {
            // 1.     Append session history traversal steps to navigable's traversable to finalize a cross-document navigation given navigable, historyHandling, and historyEntry.
            traversable_navigable()->append_session_history_traversal_steps([this, history_entry, history_handling, navigation_id] {
                if (this->has_been_destroyed()) {
                    // NOTE: This check is not in the spec but we should not continue navigation if navigable has been destroyed.
                    return;
                }
                if (this->ongoing_navigation() != navigation_id) {
                    // NOTE: This check is not in the spec but we should not continue navigation if ongoing navigation id has changed.
                    return;
                }
                finalize_a_cross_document_navigation(*this, to_history_handling_behavior(history_handling), history_entry);
            });
        }).release_value_but_fixme_should_propagate_errors();
    });

    return {};
}

WebIDL::ExceptionOr<void> Navigable::navigate_to_a_fragment(AK::URL const& url, HistoryHandlingBehavior history_handling, String)
{
    // FIXME: 1. Let navigation be navigable's active window's navigation API.
    // FIXME: 2. Let destinationNavigationAPIState be navigable's active session history entry's navigation API state.
    // FIXME: 3. If navigationAPIState is not null, then set destinationNavigationAPIState to navigationAPIState.
    // FIXME: 4. Let continue be the result of firing a push/replace/reload navigate event at navigation with navigationType set to historyHandling, isSameDocument set to true,
    //           userInvolvement set to userInvolvement, and destinationURL set to url, and navigationAPIState set to destinationNavigationAPIState.
    // FIXME: 5. If continue is false, then return.

    // 6. Let historyEntry be a new session history entry, with
    //      URL: url
    //      document state: navigable's active session history entry's document state
    //      navigation API state: destinationNavigationAPIState
    //      scroll restoration mode: navigable's active session history entry's scroll restoration mode
    JS::NonnullGCPtr<SessionHistoryEntry> history_entry = heap().allocate_without_realm<SessionHistoryEntry>();
    history_entry->url = url;
    history_entry->document_state = active_session_history_entry()->document_state;
    history_entry->scroll_restoration_mode = active_session_history_entry()->scroll_restoration_mode;

    // 7. Let entryToReplace be navigable's active session history entry if historyHandling is "replace", otherwise null.
    auto entry_to_replace = history_handling == HistoryHandlingBehavior::Replace ? active_session_history_entry() : nullptr;

    // 8. Let history be navigable's active document's history object.
    auto history = active_document()->history();

    // 9. Let scriptHistoryIndex be history's index.
    auto script_history_index = history->m_index;

    // 10. Let scriptHistoryLength be history's length.
    auto script_history_length = history->m_length;

    // 11. If historyHandling is "push", then:
    if (history_handling == HistoryHandlingBehavior::Push) {
        // FIXME: 1. Set history's state to null.

        // 2. Increment scriptHistoryIndex.
        script_history_index++;

        // 3. Set scriptHistoryLength to scriptHistoryIndex + 1.
        script_history_length = script_history_index + 1;
    }

    // 12. Set navigable's active session history entry to historyEntry.
    m_active_session_history_entry = history_entry;

    // 13. Update document for history step application given navigable's active document, historyEntry, true, scriptHistoryIndex, and scriptHistoryLength.
    active_document()->update_for_history_step_application(*history_entry, true, script_history_length, script_history_index);

    // FIXME: 14. Update the navigation API entries for a same-document navigation given navigation, historyEntry, and historyHandling.

    // 15. Scroll to the fragment given navigable's active document.
    // FIXME: Specification doesn't say when document url needs to update during fragment navigation
    active_document()->set_url(url);
    active_document()->scroll_to_the_fragment();

    // 16. Let traversable be navigable's traversable navigable.
    auto traversable = traversable_navigable();

    // 17. Append the following session history synchronous navigation steps involving navigable to traversable:
    traversable->append_session_history_traversal_steps([this, traversable, history_entry, entry_to_replace] {
        // 1. Finalize a same-document navigation given traversable, navigable, historyEntry, and entryToReplace.
        finalize_a_same_document_navigation(*traversable, *this, history_entry, entry_to_replace);

        // FIXME: 2. Invoke WebDriver BiDi fragment navigated with navigable's active browsing context and a new WebDriver BiDi
        //            navigation status whose id is navigationId, url is url, and status is "complete".
    });

    return {};
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#evaluate-a-javascript:-url
WebIDL::ExceptionOr<JS::GCPtr<DOM::Document>> Navigable::evaluate_javascript_url(AK::URL const& url, Origin const& new_document_origin, String navigation_id)
{
    auto& vm = this->vm();
    auto& realm = active_window()->realm();

    // 1. Let urlString be the result of running the URL serializer on url.
    auto url_string = url.serialize();

    // 2. Let encodedScriptSource be the result of removing the leading "javascript:" from urlString.
    auto encoded_script_source = url_string.substring_view(11, url_string.length() - 11);

    // 3. Let scriptSource be the UTF-8 decoding of the percent-decoding of encodedScriptSource.
    auto script_source = AK::URL::percent_decode(encoded_script_source);

    // 4. Let settings be targetNavigable's active document's relevant settings object.
    auto& settings = active_document()->relevant_settings_object();

    // 5. Let baseURL be settings's API base URL.
    auto base_url = settings.api_base_url();

    // 6. Let script be the result of creating a classic script given scriptSource, settings, baseURL, and the default classic script fetch options.
    auto script = HTML::ClassicScript::create("(javascript url)", script_source, settings, base_url);

    // 7. Let evaluationStatus be the result of running the classic script script.
    auto evaluation_status = script->run();

    // 8. Let result be null.
    String result;

    // 9. If evaluationStatus is a normal completion, and evaluationStatus.[[Value]] is a String, then set result to evaluationStatus.[[Value]].
    if (evaluation_status.type() == JS::Completion::Type::Normal && evaluation_status.value()->is_string()) {
        result = evaluation_status.value()->as_string().utf8_string();
    } else {
        // 10. Otherwise, return null.
        return nullptr;
    }

    // 11. Let response be a new response with
    //     URL: targetNavigable's active document's URL
    //     header list: «(`Content-Type`, `text/html;charset=utf-8`)»
    //     body: the UTF-8 encoding of result, as a body
    auto response = Fetch::Infrastructure::Response::create(vm);
    response->url_list().append(active_document()->url());
    auto header = TRY_OR_THROW_OOM(vm, Fetch::Infrastructure::Header::from_string_pair("Content-Type"sv, "text/html"sv));
    TRY_OR_THROW_OOM(vm, response->header_list()->append(move(header)));
    response->set_body(TRY(Fetch::Infrastructure::byte_sequence_as_body(realm, result.bytes())));

    // 12. Let policyContainer be targetNavigable's active document's policy container.
    auto const& policy_container = active_document()->policy_container();

    // FIXME: 13. Let finalSandboxFlags be policyContainer's CSP list's CSP-derived sandboxing flags.
    auto final_sandbox_flags = SandboxingFlagSet {};

    // 14. Let coop be targetNavigable's active document's cross-origin opener policy.
    auto const& coop = active_document()->cross_origin_opener_policy();

    // 15. Let coopEnforcementResult be a new cross-origin opener policy enforcement result with
    //     url: url
    //     origin: newDocumentOrigin
    //     cross-origin opener policy: coop
    CrossOriginOpenerPolicyEnforcementResult coop_enforcement_result {
        .url = url,
        .origin = new_document_origin,
        .cross_origin_opener_policy = coop,
    };

    // 16. Let navigationParams be a new navigation params, with
    //     id: navigationId
    //     navigable: targetNavigable
    //     request: null
    //     response: response
    //     fetch controller: null
    //     commit early hints: null
    //     COOP enforcement result: coopEnforcementResult
    //     reserved environment: null
    //     origin: newDocumentOrigin
    //     policy container: policyContainer
    //     final sandboxing flag set: finalSandboxFlags
    //     cross-origin opener policy: coop
    // FIXME: navigation timing type: "navigate"
    //     about base URL: targetNavigable's active document's about base URL
    NavigationParams navigation_params {
        .id = navigation_id,
        .navigable = this,
        .request = {},
        .response = response,
        .fetch_controller = nullptr,
        .commit_early_hints = nullptr,
        .coop_enforcement_result = move(coop_enforcement_result),
        .reserved_environment = {},
        .origin = new_document_origin,
        .policy_container = policy_container,
        .final_sandboxing_flag_set = final_sandbox_flags,
        .cross_origin_opener_policy = coop,
        .about_base_url = active_document()->about_base_url(),
    };

    // 17. Return the result of loading an HTML document given navigationParams.
    return load_document(move(navigation_params));
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigate-to-a-javascript:-url
WebIDL::ExceptionOr<void> Navigable::navigate_to_a_javascript_url(AK::URL const& url, HistoryHandlingBehavior history_handling, Origin const& initiator_origin, CSPNavigationType csp_navigation_type, String navigation_id)
{
    // 1. Assert: historyHandling is "replace".
    VERIFY(history_handling == HistoryHandlingBehavior::Replace);

    // 2. Set the ongoing navigation for targetNavigable to null.
    set_ongoing_navigation({});

    // 3. If initiatorOrigin is not same origin-domain with targetNavigable's active document's origin, then return.
    if (!initiator_origin.is_same_origin_domain(active_document()->origin()))
        return {};

    // FIXME: 4. Let request be a new request whose URL is url.

    // FIXME: 5. If the result of should navigation request of type be blocked by Content Security Policy? given request and cspNavigationType is "Blocked", then return.
    (void)csp_navigation_type;

    // 6. Let newDocument be the result of evaluating a javascript: URL given targetNavigable, url, and initiatorOrigin.
    auto new_document = TRY(evaluate_javascript_url(url, initiator_origin, navigation_id));

    // 7. If newDocument is null, then return.
    if (!new_document) {
        // NOTE: In this case, some JavaScript code was executed, but no new Document was created, so we will not perform a navigation.
        return {};
    }

    // 8. Assert: initiatorOrigin is newDocument's origin.
    VERIFY(initiator_origin == new_document->origin());

    // 9. Let entryToReplace be targetNavigable's active session history entry.
    auto entry_to_replace = active_session_history_entry();

    // 10. Let oldDocState be entryToReplace's document state.
    auto old_doc_state = entry_to_replace->document_state;

    // 11. Let documentState be a new document state with
    //     document: newDocument
    //     history policy container: a clone of the oldDocState's history policy container if it is non-null; null otherwise
    //     request referrer: oldDocState's request referrer
    //     request referrer policy: oldDocState's request referrer policy
    //     initiator origin: initiatorOrigin
    //     origin: initiatorOrigin
    //     about base URL: oldDocState's about base URL
    //     resource: null
    //     ever populated: true
    //     navigable target name: oldDocState's navigable target name
    JS::NonnullGCPtr<DocumentState> document_state = *heap().allocate_without_realm<DocumentState>();
    document_state->set_document(new_document);
    document_state->set_history_policy_container(old_doc_state->history_policy_container());
    document_state->set_request_referrer(old_doc_state->request_referrer());
    document_state->set_request_referrer_policy(old_doc_state->request_referrer_policy());
    document_state->set_initiator_origin(initiator_origin);
    document_state->set_origin(initiator_origin);
    document_state->set_about_base_url(old_doc_state->about_base_url());
    document_state->set_ever_populated(true);
    document_state->set_navigable_target_name(old_doc_state->navigable_target_name());

    // 12. Let historyEntry be a new session history entry, with
    //     URL: entryToReplace's URL
    //     document state: documentState
    JS::NonnullGCPtr<SessionHistoryEntry> history_entry = *heap().allocate_without_realm<SessionHistoryEntry>();
    history_entry->url = entry_to_replace->url;
    history_entry->document_state = document_state;

    // 13. Append session history traversal steps to targetNavigable's traversable to finalize a cross-document navigation with targetNavigable, historyHandling, and historyEntry.
    traversable_navigable()->append_session_history_traversal_steps([this, history_entry, history_handling, navigation_id] {
        finalize_a_cross_document_navigation(*this, history_handling, history_entry);
    });

    return {};
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#reload
void Navigable::reload()
{
    // 1. Set navigable's active session history entry's document state's reload pending to true.
    active_session_history_entry()->document_state->set_reload_pending(true);

    // 2. Let traversable be navigable's traversable navigable.
    auto traversable = traversable_navigable();

    // 3. Append the following session history traversal steps to traversable:
    traversable->append_session_history_traversal_steps([traversable] {
        // 1. Apply the reload history step to traversable.
        traversable->apply_the_reload_history_step();
    });
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#the-navigation-must-be-a-replace
bool navigation_must_be_a_replace(AK::URL const& url, DOM::Document const& document)
{
    return url.scheme() == "javascript"sv || document.is_initial_about_blank();
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#allowed-to-navigate
bool Navigable::allowed_by_sandboxing_to_navigate(Navigable const& target, SourceSnapshotParams const& source_snapshot_params)
{
    auto& source = *this;

    auto is_ancestor_of = [](Navigable const& a, Navigable const& b) {
        for (auto parent = b.parent(); parent; parent = parent->parent()) {
            if (parent.ptr() == &a)
                return true;
        }
        return false;
    };

    // A navigable source is allowed by sandboxing to navigate a second navigable target,
    // given a source snapshot params sourceSnapshotParams, if the following steps return true:

    // 1. If source is target, then return true.
    if (&source == &target)
        return true;

    // 2. If source is an ancestor of target, then return true.
    if (is_ancestor_of(source, target))
        return true;

    // 3. If target is an ancestor of source, then:
    if (is_ancestor_of(target, source)) {

        // 1. If target is not a top-level traversable, then return true.
        if (!target.is_top_level_traversable())
            return true;

        // 2. If sourceSnapshotParams's has transient activation is true, and sourceSnapshotParams's sandboxing flags's
        //    sandboxed top-level navigation with user activation browsing context flag is set, then return false.
        if (source_snapshot_params.has_transient_activation && has_flag(source_snapshot_params.sandboxing_flags, SandboxingFlagSet::SandboxedTopLevelNavigationWithUserActivation))
            return false;

        // 3. If sourceSnapshotParams's has transient activation is false, and sourceSnapshotParams's sandboxing flags's
        //    sandboxed top-level navigation without user activation browsing context flag is set, then return false.
        if (!source_snapshot_params.has_transient_activation && has_flag(source_snapshot_params.sandboxing_flags, SandboxingFlagSet::SandboxedTopLevelNavigationWithoutUserActivation))
            return false;

        // 4. Return true.
        return true;
    }

    // 4. If target is a top-level traversable:
    if (target.is_top_level_traversable()) {
        // FIXME: 1. If source is the one permitted sandboxed navigator of target, then return true.

        // 2. If sourceSnapshotParams's sandboxing flags's sandboxed navigation browsing context flag is set, then return false.
        if (has_flag(source_snapshot_params.sandboxing_flags, SandboxingFlagSet::SandboxedNavigation))
            return false;

        // 3. Return true.
        return true;
    }

    // 5. If sourceSnapshotParams's sandboxing flags's sandboxed navigation browsing context flag is set, then return false.
    // 6. Return true.
    return !has_flag(source_snapshot_params.sandboxing_flags, SandboxingFlagSet::SandboxedNavigation);
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#snapshotting-target-snapshot-params
TargetSnapshotParams Navigable::snapshot_target_snapshot_params()
{
    // To snapshot target snapshot params given a navigable targetNavigable, return a new target snapshot params
    // with sandboxing flags set to the result of determining the creation sandboxing flags given targetNavigable's
    // active browsing context and targetNavigable's container.

    return { determine_the_creation_sandboxing_flags(*active_browsing_context(), container()) };
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#finalize-a-cross-document-navigation
void finalize_a_cross_document_navigation(JS::NonnullGCPtr<Navigable> navigable, HistoryHandlingBehavior history_handling, JS::NonnullGCPtr<SessionHistoryEntry> history_entry)
{
    // NOTE: This is not in the spec but we should not navigate destroyed navigable.
    if (navigable->has_been_destroyed())
        return;

    // 1. FIXME: Assert: this is running on navigable's traversable navigable's session history traversal queue.

    // 2. Set navigable's is delaying load events to false.
    navigable->set_delaying_load_events(false);

    // 3. If historyEntry's document is null, then return.
    if (!history_entry->document_state->document())
        return;

    // 4. If all of the following are true:
    //    - navigable's parent is null;
    //    - historyEntry's document's browsing context is not an auxiliary browsing context whose opener browsing context is non-null; and
    //    - historyEntry's document's origin is not navigable's active document's origin
    //    then set historyEntry's document state's navigable target name to the empty string.
    if (navigable->parent() == nullptr && history_entry->document_state->document()->browsing_context()->opener_browsing_context() != nullptr && history_entry->document_state->document()->origin() != navigable->active_document()->origin())
        history_entry->document_state->set_navigable_target_name(String {});

    // 5. Let entryToReplace be navigable's active session history entry if historyHandling is "replace", otherwise null.
    auto entry_to_replace = history_handling == HistoryHandlingBehavior::Replace ? navigable->active_session_history_entry() : nullptr;

    // 6. Let traversable be navigable's traversable navigable.
    auto traversable = navigable->traversable_navigable();

    // 7. Let targetStep be null.
    int target_step;

    // 8. Let targetEntries be the result of getting session history entries for navigable.
    auto& target_entries = navigable->get_session_history_entries();

    // 9. If entryToReplace is null, then:
    if (entry_to_replace == nullptr) {
        // 1. Clear the forward session history of traversable.
        traversable->clear_the_forward_session_history();

        // 2. Set targetStep to traversable's current session history step + 1.
        target_step = traversable->current_session_history_step() + 1;

        // 3. Set historyEntry's step to targetStep.
        history_entry->step = target_step;

        // 4. Append historyEntry to targetEntries.
        target_entries.append(history_entry);
    } else {
        // 1. Replace entryToReplace with historyEntry in targetEntries.
        *(target_entries.find(*entry_to_replace)) = history_entry;

        // 2. Set historyEntry's step to entryToReplace's step.
        history_entry->step = entry_to_replace->step;

        // 3. If historyEntry's document state's origin is same origin with entryToReplace's document state's origin,
        //    then set historyEntry's navigation API key to entryToReplace's navigation API key.
        if (history_entry->document_state->origin().has_value() && entry_to_replace->document_state->origin().has_value() && history_entry->document_state->origin()->is_same_origin(*entry_to_replace->document_state->origin())) {
            history_entry->navigation_api_key = entry_to_replace->navigation_api_key;
        }

        // 4. Set targetStep to traversable's current session history step.
        target_step = traversable->current_session_history_step();
    }

    // 10. Apply the push/replace history step targetStep to traversable.
    traversable->apply_the_push_or_replace_history_step(target_step);
}

// https://html.spec.whatwg.org/multipage/browsing-the-web.html#url-and-history-update-steps
void perform_url_and_history_update_steps(DOM::Document& document, AK::URL new_url, HistoryHandlingBehavior history_handling)
{
    // 1. Let navigable be document's node navigable.
    auto navigable = document.navigable();

    // 2. Let activeEntry be navigable's active session history entry.
    auto active_entry = navigable->active_session_history_entry();

    // 3. Let newEntry be a new session history entry, with
    //      URL: newURL
    //      serialized state: if serializedData is not null, serializedData; otherwise activeEntry's classic history API state
    //      document state: activeEntry's document state
    //      scroll restoration mode: activeEntry's scroll restoration mode
    //      persisted user state: activeEntry's persisted user state
    JS::NonnullGCPtr<SessionHistoryEntry> new_entry = document.heap().allocate_without_realm<SessionHistoryEntry>();
    new_entry->url = new_url;
    new_entry->document_state = active_entry->document_state;
    new_entry->scroll_restoration_mode = active_entry->scroll_restoration_mode;

    // 4. If document's is initial about:blank is true, then set historyHandling to "replace".
    if (document.is_initial_about_blank()) {
        history_handling = HistoryHandlingBehavior::Replace;
    }

    // 5. Let entryToReplace be activeEntry if historyHandling is "replace", otherwise null.
    auto entry_to_replace = history_handling == HistoryHandlingBehavior::Replace ? active_entry : nullptr;

    // 6. If historyHandling is "push", then:
    if (history_handling == HistoryHandlingBehavior::Push) {
        // 1. Increment document's history object's index.
        document.history()->m_index++;

        // 2. Set document's history object's length to its index + 1.
        document.history()->m_length = document.history()->m_index + 1;
    }

    // FIXME: 7. If serializedData is not null, then restore the history object state given document and newEntry.

    // 8. Set document's URL to newURL.
    document.set_url(new_url);

    // FIXME: 9. Set document's latest entry to newEntry.

    // 10. Set navigable's active session history entry to newEntry.
    navigable->set_active_session_history_entry(new_entry);

    // FIXME: 11. Update the navigation API entries for a same-document navigation given document's relevant global object's navigation API, newEntry, and historyHandling.

    // 12. Let traversable be navigable's traversable navigable.
    auto traversable = navigable->traversable_navigable();

    // 13. Append the following session history synchronous navigation steps involving navigable to traversable:
    traversable->append_session_history_traversal_steps([traversable, navigable, new_entry, entry_to_replace] {
        // 1. Finalize a same-document navigation given traversable, navigable, newEntry, and entryToReplace.
        finalize_a_same_document_navigation(*traversable, *navigable, new_entry, entry_to_replace);
    });

    // FIXME: Implement synchronous session history steps.
    traversable->process_session_history_traversal_queue();
}

void Navigable::scroll_offset_did_change()
{
    // https://w3c.github.io/csswg-drafts/cssom-view-1/#scrolling-events
    // Whenever a viewport gets scrolled (whether in response to user interaction or by an API), the user agent must run these steps:

    // 1. Let doc be the viewport’s associated Document.
    auto doc = active_document();
    VERIFY(doc);

    // 2. If doc is already in doc’s pending scroll event targets, abort these steps.
    for (auto& target : doc->pending_scroll_event_targets()) {
        if (target.ptr() == doc)
            return;
    }

    // 3. Append doc to doc’s pending scroll event targets.
    doc->pending_scroll_event_targets().append(*doc);
}

CSSPixelRect Navigable::to_top_level_rect(CSSPixelRect const& a_rect)
{
    auto rect = a_rect;
    rect.set_location(to_top_level_position(a_rect.location()));
    return rect;
}

CSSPixelPoint Navigable::to_top_level_position(CSSPixelPoint a_position)
{
    auto position = a_position;
    for (auto ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
        if (is<TraversableNavigable>(*ancestor))
            break;
        if (!ancestor->container())
            return {};
        if (!ancestor->container()->paintable())
            return {};
        position.translate_by(ancestor->container()->paintable()->box_type_agnostic_position());
    }
    return position;
}

void Navigable::set_viewport_rect(CSSPixelRect const& rect)
{
    bool did_change = false;

    if (m_size != rect.size()) {
        m_size = rect.size();
        if (auto document = active_document()) {
            // NOTE: Resizing the viewport changes the reference value for viewport-relative CSS lengths.
            document->invalidate_style();
            document->set_needs_layout();
        }
        did_change = true;
    }

    if (m_viewport_scroll_offset != rect.location()) {
        m_viewport_scroll_offset = rect.location();
        scroll_offset_did_change();
        did_change = true;
    }

    if (did_change && active_document()) {
        active_document()->inform_all_viewport_clients_about_the_current_viewport_rect();
    }

    // Schedule the HTML event loop to ensure that a `resize` event gets fired.
    HTML::main_thread_event_loop().schedule();
}

void Navigable::set_size(CSSPixelSize size)
{
    if (m_size == size)
        return;
    m_size = size;

    if (auto document = active_document()) {
        document->invalidate_style();
        document->set_needs_layout();
    }

    if (auto document = active_document()) {
        document->inform_all_viewport_clients_about_the_current_viewport_rect();
    }

    // Schedule the HTML event loop to ensure that a `resize` event gets fired.
    HTML::main_thread_event_loop().schedule();
}

void Navigable::set_needs_display()
{
    set_needs_display(viewport_rect());
}

void Navigable::set_needs_display(CSSPixelRect const& rect)
{
    // FIXME: Ignore updates outside the visible viewport rect.
    //        This requires accounting for fixed-position elements in the input rect, which we don't do yet.

    if (is<TraversableNavigable>(*this)) {
        static_cast<TraversableNavigable*>(this)->page().client().page_did_invalidate(to_top_level_rect(rect));
        return;
    }

    if (container() && container()->paintable())
        container()->paintable()->set_needs_display();
}

// https://html.spec.whatwg.org/#rendering-opportunity
bool Navigable::has_a_rendering_opportunity() const
{
    // A navigable has a rendering opportunity if the user agent is currently able to present
    // the contents of the navigable to the user,
    // accounting for hardware refresh rate constraints and user agent throttling for performance reasons,
    // but considering content presentable even if it's outside the viewport.

    // A navigable has no rendering opportunities if its active document is render-blocked
    // or if it is suppressed for view transitions;
    // otherwise, rendering opportunities are determined based on hardware constraints
    // such as display refresh rates and other factors such as page performance
    // or whether the document's visibility state is "visible".
    // Rendering opportunities typically occur at regular intervals.

    // FIXME: We should at the very least say `false` here if we're an inactive browser tab.
    return true;
}

// https://html.spec.whatwg.org/multipage/nav-history-apis.html#inform-the-navigation-api-about-aborting-navigation
void Navigable::inform_the_navigation_api_about_aborting_navigation()
{
    // FIXME: 1. If this algorithm is running on navigable's active window's relevant agent's event loop, then continue on to the following steps.
    // Otherwise, queue a global task on the navigation and traversal task source given navigable's active window to run the following steps.

    queue_global_task(Task::Source::NavigationAndTraversal, *active_window(), [this] {
        // 2. Let navigation be navigable's active window's navigation API.
        auto navigation = active_window()->navigation();

        // 3. If navigation's ongoing navigate event is null, then return.
        if (navigation->ongoing_navigate_event() == nullptr)
            return;

        // 4. Abort the ongoing navigation given navigation.
        navigation->abort_the_ongoing_navigation();
    });
}

void Navigable::paint(Painting::RecordingPainter& recording_painter, PaintConfig config)
{
    auto document = active_document();
    if (!document)
        return;

    auto const& page = traversable_navigable()->page();
    auto viewport_rect = page.css_to_device_rect(this->viewport_rect());
    Gfx::IntRect bitmap_rect { {}, viewport_rect.size().to_type<int>() };

    document->update_layout();
    auto background_color = document->background_color();

    recording_painter.fill_rect(bitmap_rect, background_color);
    if (!document->paintable())
        return;

    Web::PaintContext context(recording_painter, page.palette(), page.client().device_pixels_per_css_pixel());
    context.set_device_viewport_rect(viewport_rect);
    context.set_should_show_line_box_borders(config.should_show_line_box_borders);
    context.set_should_paint_overlay(config.paint_overlay);
    context.set_has_focus(config.has_focus);

    if (is_traversable()) {
        document->paintable()->collect_scroll_frames(context);
    }

    document->paintable()->paint_all_phases(context);

    // FIXME: Support scrollable frames inside iframes.
    if (is_traversable()) {
        Vector<Gfx::IntPoint> scroll_offsets_by_frame_id;
        scroll_offsets_by_frame_id.resize(context.scroll_frames().size());
        for (auto [_, scrollable_frame] : context.scroll_frames())
            scroll_offsets_by_frame_id[scrollable_frame.id] = context.rounded_device_point(
                                                                         scrollable_frame.offset)
                                                                  .to_type<int>();
        recording_painter.apply_scroll_offsets(scroll_offsets_by_frame_id);
    }
}

}