/*
 * Copyright (c) 2020, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
 * Copyright (c) 2024-2025, Tim Ledbetter <tim.ledbetter@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/SourceLocation.h>
#include <LibIPC/Decoder.h>
#include <LibIPC/Encoder.h>
#include <LibWeb/Bindings/ExceptionOrUtils.h>
#include <LibWeb/CSS/StyleComputer.h>
#include <LibWeb/Clipboard/SystemClipboard.h>
#include <LibWeb/Compositor/CompositorHost.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/DOM/Range.h>
#include <LibWeb/Fetch/Infrastructure/HTTP/Bodies.h>
#include <LibWeb/Fetch/Infrastructure/HTTP/Responses.h>
#include <LibWeb/HTML/BrowsingContext.h>
#include <LibWeb/HTML/EventLoop/EventLoop.h>
#include <LibWeb/HTML/EventNames.h>
#include <LibWeb/HTML/HTMLIFrameElement.h>
#include <LibWeb/HTML/HTMLInputElement.h>
#include <LibWeb/HTML/HTMLMediaElement.h>
#include <LibWeb/HTML/HTMLSelectElement.h>
#include <LibWeb/HTML/LocalTraversableNavigable.h>
#include <LibWeb/HTML/Scripting/Environments.h>
#include <LibWeb/HTML/Scripting/TemporaryExecutionContext.h>
#include <LibWeb/HTML/SelectedFile.h>
#include <LibWeb/HTML/Window.h>
#include <LibWeb/Loader/ContentBlocker.h>
#include <LibWeb/Page/Page.h>
#include <LibWeb/Platform/EventLoopPlugin.h>
#include <LibWeb/Selection/Selection.h>

namespace Web {

GC_DEFINE_ALLOCATOR(Page);

GC::Ref<Page> Page::create(JS::VM& vm, GC::Ref<PageClient> page_client)
{
    return vm.heap().allocate<Page>(page_client);
}

Page::Page(GC::Ref<PageClient> client)
    : m_client(client)
{
}

Page::~Page() = default;

void Page::acquire_screen_wake_lock()
{
    if (m_active_screen_wake_lock_count++ == 0)
        client().page_did_change_screen_wake_lock_state(ScreenWakeLockState::Acquired);
}

void Page::release_screen_wake_lock()
{
    VERIFY(m_active_screen_wake_lock_count > 0);
    if (--m_active_screen_wake_lock_count == 0)
        client().page_did_change_screen_wake_lock_state(ScreenWakeLockState::Released);
}

bool Page::has_compositor_host() const
{
    return m_client->compositor_host();
}

void Page::ensure_compositor_host()
{
    if (!m_client->supports_compositor())
        return;

    m_client->ensure_compositor_host();
}

Compositor::CompositorHost& Page::compositor_host()
{
    auto* compositor_host = m_client->compositor_host();
    VERIFY(compositor_host);
    return *compositor_host;
}

Compositor::CompositorHost const& Page::compositor_host() const
{
    auto const* compositor_host = m_client->compositor_host();
    VERIFY(compositor_host);
    return *compositor_host;
}

void Page::visit_edges(JS::Cell::Visitor& visitor)
{
    Base::visit_edges(visitor);
    visitor.visit(m_top_level_traversable);
    visitor.visit(m_client);
    visitor.visit(m_window_rect_observer);
    visitor.visit(m_on_pending_dialog_closed);
    visitor.visit(m_pending_clipboard_requests);
    m_pending_fullscreen_operations.for_each([&](auto const& operation) {
        operation.visit([&](PendingFullscreenEnter const& enter_operation) {
                visitor.visit(enter_operation.element);
                visitor.visit(enter_operation.pending_doc);
                visitor.visit(enter_operation.promise); },
            [&](PendingFullscreenExit const& exit_operation) {
                visitor.visit(exit_operation.doc);
                visitor.visit(exit_operation.promise);
            });
    });
}

HTML::LocalNavigable& Page::focused_navigable()
{
    if (m_focused_navigable)
        return *m_focused_navigable;
    return top_level_traversable();
}

void Page::set_focused_navigable(Badge<EventHandler>, HTML::LocalNavigable& navigable)
{
    m_focused_navigable = navigable;
}

void Page::navigable_document_destroyed(Badge<DOM::Document>, HTML::LocalNavigable& navigable)
{
    if (&navigable == m_focused_navigable.ptr())
        m_focused_navigable = nullptr;
}

void Page::load(URL::URL const& url, Bindings::NavigationHistoryBehavior history_handling)
{
    (void)top_level_traversable()->navigate({ .url = url, .source_document = *top_level_traversable()->active_document(), .history_handling = history_handling, .user_involvement = HTML::UserNavigationInvolvement::BrowserUI });
}

void Page::load(URL::URL const& url, Variant<Empty, String, HTML::POSTResource> document_resource,
    Bindings::NavigationHistoryBehavior history_handling)
{
    (void)top_level_traversable()->navigate({
        .url = url,
        .source_document = *top_level_traversable()->active_document(),
        .document_resource = move(document_resource),
        .history_handling = history_handling,
        .user_involvement = HTML::UserNavigationInvolvement::BrowserUI,
    });
}

void Page::load_html(StringView html)
{
    // FIXME: #23909 Figure out why GC threshold does not stay low when repeatedly loading html from the WebView
    heap().collect_garbage();

    (void)top_level_traversable()->navigate({ .url = URL::about_srcdoc(),
        .source_document = *top_level_traversable()->active_document(),
        .document_resource = String::from_utf8(html).release_value_but_fixme_should_propagate_errors(),
        .user_involvement = HTML::UserNavigationInvolvement::BrowserUI });
}

void Page::load_html(StringView html, URL::URL const& url)
{
    // FIXME: #23909 Figure out why GC threshold does not stay low when repeatedly loading html from the WebView
    heap().collect_garbage();

    auto document = top_level_traversable()->active_document();
    auto& realm = document->realm();
    auto html_string = String::from_utf8(html).release_value_but_fixme_should_propagate_errors();

    auto response = Fetch::Infrastructure::Response::create(realm.vm());
    response->url_list().append(url);
    response->header_list()->append({ "Content-Type"sv, "text/html"sv });
    response->set_body(Fetch::Infrastructure::byte_sequence_as_body(realm, html_string.bytes()));

    HTML::LocalNavigable::NavigateParams params { .url = url,
        .source_document = *document,
        .response = response,
        .user_involvement = HTML::UserNavigationInvolvement::BrowserUI };

    if (url == URL::about_srcdoc())
        params.document_resource = move(html_string);

    (void)top_level_traversable()->navigate(move(params));
}

void Page::reload()
{
    top_level_traversable()->reload();
}

void Page::traverse_the_history_by_delta(int delta)
{
    if (m_client->page_did_request_traverse_the_history_by_delta(delta, HistoryTraversalPrecheck::Needed))
        return;

    top_level_traversable()->traverse_the_history_by_delta(delta);
}

Gfx::Palette Page::palette() const
{
    return m_client->palette();
}

// https://drafts.csswg.org/cssom-view-1/#web-exposed-screen-area
CSSPixelRect Page::web_exposed_screen_area() const
{
    // FIXME: 1. Let target be this’s relevant global object’s browsing context.
    // FIXME: 2. Let emulated screen area be the WebDriver BiDi emulated total screen area of target.
    // FIXME: 3. If emulated screen area is not null, return emulated screen area.

    // 4. Otherwise, return one of the following:
    //    - The area of the output device, in CSS pixels.
    //    - The area of the viewport, in CSS pixels.
    // NB: This is the area of the output device, but in device pixels.
    // See: https://github.com/LadybirdBrowser/ladybird/pull/4084
    auto device_pixel_rect = m_client->screen_rect();
    return {
        device_pixel_rect.x().value(),
        device_pixel_rect.y().value(),
        device_pixel_rect.width().value(),
        device_pixel_rect.height().value()
    };
}

// https://drafts.csswg.org/cssom-view-1/#web-exposed-available-screen-area
CSSPixelRect Page::web_exposed_available_screen_area() const
{
    // FIXME: 1. Let target be this’s relevant global object’s browsing context.
    // FIXME: 2. Let emulated screen area be the WebDriver BiDi emulated total screen area of target.
    // FIXME: 3. If emulated screen area is not null, return emulated screen area.

    // 4. Otherwise, return one of the following:
    //    - The available area of the rendering surface of the output device, in CSS pixels.
    //    - The area of the output device, in CSS pixels.
    //    - The area of the viewport, in CSS pixels.
    // NB: This is the area of the output device, but in device pixels. See note in web_exposed_screen_area()
    auto device_pixel_rect = m_client->screen_rect();
    return {
        device_pixel_rect.x().value(),
        device_pixel_rect.y().value(),
        device_pixel_rect.width().value(),
        device_pixel_rect.height().value()
    };
}

CSS::PreferredColorScheme Page::preferred_color_scheme() const
{
    if (m_preferred_color_scheme_override_for_testing.has_value())
        return *m_preferred_color_scheme_override_for_testing;

    auto preferred_color_scheme = m_client->preferred_color_scheme();

    if (preferred_color_scheme == CSS::PreferredColorScheme::Auto)
        preferred_color_scheme = palette().is_dark() ? CSS::PreferredColorScheme::Dark : CSS::PreferredColorScheme::Light;

    return preferred_color_scheme;
}

CSS::PreferredContrast Page::preferred_contrast() const
{
    return m_client->preferred_contrast();
}

CSS::PreferredMotion Page::preferred_motion() const
{
    return m_client->preferred_motion();
}

CSSPixelPoint Page::device_to_css_point(DevicePixelPoint point) const
{
    return {
        point.x().value() / client().device_pixels_per_css_pixel(),
        point.y().value() / client().device_pixels_per_css_pixel(),
    };
}

DevicePixelPoint Page::css_to_device_point(CSSPixelPoint point) const
{
    return {
        point.x() * client().device_pixels_per_css_pixel(),
        point.y() * client().device_pixels_per_css_pixel(),
    };
}

DevicePixelRect Page::css_to_device_rect(CSSPixelRect rect) const
{
    return {
        rect.location().to_type<double>() * client().device_pixels_per_css_pixel(),
        rect.size().to_type<double>() * client().device_pixels_per_css_pixel(),
    };
}

CSSPixelRect Page::device_to_css_rect(DevicePixelRect rect) const
{
    auto scale = client().device_pixels_per_css_pixel();
    return {
        CSSPixels::nearest_value_for(rect.x().value() / scale),
        CSSPixels::nearest_value_for(rect.y().value() / scale),
        CSSPixels::floored_value_for(rect.width().value() / scale),
        CSSPixels::floored_value_for(rect.height().value() / scale),
    };
}

CSSPixelSize Page::device_to_css_size(DevicePixelSize size) const
{
    auto scale = client().device_pixels_per_css_pixel();
    return {
        CSSPixels::floored_value_for(size.width().value() / scale),
        CSSPixels::floored_value_for(size.height().value() / scale),
    };
}

DevicePixelRect Page::enclosing_device_rect(CSSPixelRect rect) const
{
    auto scale = client().device_pixels_per_css_pixel();
    return DevicePixelRect(
        floor(rect.x().to_double() * scale),
        floor(rect.y().to_double() * scale),
        ceil(rect.width().to_double() * scale),
        ceil(rect.height().to_double() * scale));
}

DevicePixelRect Page::rounded_device_rect(CSSPixelRect rect) const
{
    auto scale = client().device_pixels_per_css_pixel();
    return {
        roundf(rect.x().to_double() * scale),
        roundf(rect.y().to_double() * scale),
        roundf(rect.width().to_double() * scale),
        roundf(rect.height().to_double() * scale)
    };
}

ChromeMetrics Page::chrome_metrics() const
{
    return ChromeMetrics { m_client->zoom_level() };
}

EventResult Page::handle_mouseup(DevicePixelPoint position, DevicePixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers)
{
    return top_level_traversable()->event_handler().handle_mouseup(device_to_css_point(position), device_to_css_point(screen_position), button, buttons, modifiers);
}

EventResult Page::handle_mousedown(DevicePixelPoint position, DevicePixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers, int click_count)
{
    return top_level_traversable()->event_handler().handle_mousedown(device_to_css_point(position), device_to_css_point(screen_position), button, buttons, modifiers, click_count);
}

EventResult Page::handle_mousemove(DevicePixelPoint position, DevicePixelPoint screen_position, unsigned buttons, unsigned modifiers)
{
    return top_level_traversable()->event_handler().handle_mousemove(device_to_css_point(position), device_to_css_point(screen_position), buttons, modifiers);
}

EventResult Page::handle_mouseleave()
{
    return top_level_traversable()->event_handler().handle_mouseleave();
}

#if defined(AK_OS_MACOS)
bool Page::select_word_for_dictionary_lookup(DevicePixelPoint position)
{
    return top_level_traversable()->event_handler().select_word_for_dictionary_lookup(device_to_css_point(position));
}
#endif

UniqueNodeID Page::node_id_at_position(DevicePixelPoint position)
{
    auto node = top_level_traversable()->event_handler().target_node_for_mouse_position(device_to_css_point(position));
    if (!node)
        return 0;

    return node->unique_id();
}

EventResult Page::handle_mousewheel(DevicePixelPoint position, DevicePixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers, double wheel_delta_x, double wheel_delta_y, bool async_scroll_performed_default_action, Optional<AsyncScrollOperation>* async_scroll_operation)
{
    return top_level_traversable()->event_handler().handle_mousewheel(device_to_css_point(position), device_to_css_point(screen_position), button, buttons, modifiers, wheel_delta_x, wheel_delta_y, async_scroll_performed_default_action, async_scroll_operation);
}

EventResult Page::handle_drag_and_drop_event(DragEvent::Type type, DevicePixelPoint position, DevicePixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers, Vector<HTML::SelectedFile> files)
{
    return top_level_traversable()->event_handler().handle_drag_and_drop_event(type, device_to_css_point(position), device_to_css_point(screen_position), button, buttons, modifiers, move(files));
}

EventResult Page::handle_pinch_event(DevicePixelPoint position, unsigned modifiers, double scale)
{
    return top_level_traversable()->event_handler().handle_pinch_event(device_to_css_point(position), modifiers, scale);
}

EventResult Page::handle_keydown(UIEvents::KeyCode key, unsigned modifiers, u32 code_point, bool repeat, bool should_insert_text)
{
    return focused_navigable().event_handler().handle_keydown(key, modifiers, code_point, repeat, should_insert_text);
}

EventResult Page::handle_keyup(UIEvents::KeyCode key, unsigned modifiers, u32 code_point, bool repeat)
{
    return focused_navigable().event_handler().handle_keyup(key, modifiers, code_point, repeat);
}

void Page::handle_sdl_input_events()
{
    top_level_traversable()->event_handler().handle_sdl_input_events();
}

void Page::invalidate_compositor_wheel_event_listener_state()
{
    ++m_wheel_event_listener_state_generation;

    if (!m_async_scrolling_enabled || !top_level_traversable_is_initialized() || !top_level_traversable()->has_compositor_context())
        return;

    top_level_traversable()->compositor_context().invalidate_wheel_event_listener_state(m_wheel_event_listener_state_generation);
}

void Page::update_needs_beforeunload_check()
{
    auto needs_beforeunload_check = [&] {
        if (!top_level_traversable_is_initialized())
            return true;

        auto top_level_traversable = this->top_level_traversable();
        auto active_document = top_level_traversable->active_document();
        if (!active_document)
            return true;
        if (active_document->navigable() != top_level_traversable.ptr())
            return true;

        for (auto const& navigable : active_document->inclusive_descendant_navigables()) {
            auto window = navigable->active_window();
            if (window && window->has_event_listener(HTML::EventNames::beforeunload))
                return true;
        }

        return false;
    }();

    if (m_needs_beforeunload_check == needs_beforeunload_check)
        return;

    m_needs_beforeunload_check = needs_beforeunload_check;
    client().page_did_change_needs_beforeunload_check(m_needs_beforeunload_check);
}

void Page::set_top_level_traversable(GC::Ref<HTML::LocalTraversableNavigable> navigable)
{
    VERIFY(!m_top_level_traversable); // Replacement is not allowed!
    VERIFY(&navigable->page() == this);
    m_top_level_traversable = navigable;
    update_needs_beforeunload_check();
}

bool Page::top_level_traversable_is_initialized() const
{
    return m_top_level_traversable;
}

HTML::BrowsingContext& Page::top_level_browsing_context()
{
    return *m_top_level_traversable->active_browsing_context();
}

HTML::BrowsingContext const& Page::top_level_browsing_context() const
{
    return *m_top_level_traversable->active_browsing_context();
}

GC::Ref<HTML::LocalTraversableNavigable> Page::top_level_traversable() const
{
    return *m_top_level_traversable;
}

void Page::did_update_window_rect()
{
    if (m_window_rect_observer)
        m_window_rect_observer->function()({ window_position(), window_size() });
}

template<typename ResponseType>
static ResponseType spin_event_loop_until_dialog_closed(PageClient& client, Optional<ResponseType>& response, SourceLocation location = SourceLocation::current())
{
    auto& event_loop = Web::HTML::current_settings_object().responsible_event_loop();
    auto pause_handle = event_loop.pause();

    Web::Platform::EventLoopPlugin::the().spin_until(GC::create_function(event_loop.heap(), [&]() {
        return response.has_value() || !client.is_connection_open();
    }));

    if (!client.is_connection_open()) {
        dbgln("WebContent client disconnected during {}. Exiting peacefully.", location.function_name());
        exit(0);
    }

    return response.release_value();
}

void Page::did_request_alert(String const& message)
{
    m_pending_dialog = PendingDialog::Alert;
    m_client->page_did_request_alert(message);

    if (!message.is_empty())
        m_pending_dialog_text = message;

    spin_event_loop_until_dialog_closed(*m_client, m_pending_alert_response);
}

void Page::alert_closed()
{
    if (m_pending_dialog == PendingDialog::Alert) {
        m_pending_alert_response = Empty {};
        on_pending_dialog_closed();
    }
}

bool Page::did_request_confirm(String const& message)
{
    m_pending_dialog = PendingDialog::Confirm;
    m_client->page_did_request_confirm(message);

    if (!message.is_empty())
        m_pending_dialog_text = message;

    return spin_event_loop_until_dialog_closed(*m_client, m_pending_confirm_response);
}

void Page::confirm_closed(bool accepted)
{
    if (m_pending_dialog == PendingDialog::Confirm) {
        m_pending_confirm_response = accepted;
        on_pending_dialog_closed();
    }
}

Optional<String> Page::did_request_prompt(String const& message, String const& default_)
{
    m_pending_dialog = PendingDialog::Prompt;
    m_client->page_did_request_prompt(message, default_);

    if (!message.is_empty())
        m_pending_dialog_text = message;

    return spin_event_loop_until_dialog_closed(*m_client, m_pending_prompt_response);
}

void Page::prompt_closed(Optional<String> response)
{
    if (m_pending_dialog == PendingDialog::Prompt) {
        m_pending_prompt_response = move(response);
        on_pending_dialog_closed();
    }
}

void Page::dismiss_dialog(GC::Ref<GC::Function<void()>> on_dialog_closed)
{
    m_on_pending_dialog_closed = on_dialog_closed;

    switch (m_pending_dialog) {
    case PendingDialog::None:
        break;
    case PendingDialog::Alert:
        m_client->page_did_request_accept_dialog();
        break;
    case PendingDialog::Confirm:
    case PendingDialog::Prompt:
        m_client->page_did_request_dismiss_dialog();
        break;
    }
}

void Page::accept_dialog(GC::Ref<GC::Function<void()>> on_dialog_closed)
{
    m_on_pending_dialog_closed = on_dialog_closed;

    switch (m_pending_dialog) {
    case PendingDialog::None:
        break;
    case PendingDialog::Alert:
    case PendingDialog::Confirm:
    case PendingDialog::Prompt:
        m_client->page_did_request_accept_dialog();
        break;
    }
}

void Page::on_pending_dialog_closed()
{
    m_pending_dialog = PendingDialog::None;
    m_pending_dialog_text.clear();

    if (m_on_pending_dialog_closed) {
        m_on_pending_dialog_closed->function()();
        m_on_pending_dialog_closed = nullptr;
    }
}

void Page::did_request_color_picker(GC::Weak<HTML::HTMLInputElement> target, Color current_color)
{
    if (m_pending_non_blocking_dialog == PendingNonBlockingDialog::None) {
        m_pending_non_blocking_dialog = PendingNonBlockingDialog::ColorPicker;
        m_pending_non_blocking_dialog_target = move(target);

        m_client->page_did_request_color_picker(current_color);
    }
}

void Page::color_picker_update(Optional<Color> picked_color, HTML::ColorPickerUpdateState state)
{
    if (m_pending_non_blocking_dialog == PendingNonBlockingDialog::ColorPicker) {
        if (state == HTML::ColorPickerUpdateState::Closed)
            m_pending_non_blocking_dialog = PendingNonBlockingDialog::None;

        if (m_pending_non_blocking_dialog_target) {
            auto& input_element = as<HTML::HTMLInputElement>(*m_pending_non_blocking_dialog_target);
            input_element.did_pick_color(move(picked_color), state);
            if (state == HTML::ColorPickerUpdateState::Closed)
                m_pending_non_blocking_dialog_target = nullptr;
        }
    }
}

void Page::did_request_file_picker(GC::Weak<HTML::HTMLInputElement> target, HTML::FileFilter const& accepted_file_types, HTML::AllowMultipleFiles allow_multiple_files)
{
    if (m_pending_non_blocking_dialog == PendingNonBlockingDialog::None) {
        m_pending_non_blocking_dialog = PendingNonBlockingDialog::FilePicker;
        m_pending_non_blocking_dialog_target = move(target);

        m_client->page_did_request_file_picker(accepted_file_types, allow_multiple_files);
    }
}

void Page::file_picker_closed(Span<HTML::SelectedFile> selected_files)
{
    if (m_pending_non_blocking_dialog == PendingNonBlockingDialog::FilePicker) {
        m_pending_non_blocking_dialog = PendingNonBlockingDialog::None;

        if (m_pending_non_blocking_dialog_target) {
            auto& input_element = as<HTML::HTMLInputElement>(*m_pending_non_blocking_dialog_target);
            input_element.did_select_files(selected_files);

            m_pending_non_blocking_dialog_target = nullptr;
        }
    }
}

void Page::did_request_select_dropdown(GC::Weak<HTML::HTMLSelectElement> target, Web::CSSPixelPoint content_position, Web::CSSPixels minimum_width, Vector<Web::HTML::SelectItem> items)
{
    if (m_pending_non_blocking_dialog == PendingNonBlockingDialog::None) {
        m_pending_non_blocking_dialog = PendingNonBlockingDialog::Select;
        m_pending_non_blocking_dialog_target = move(target);
        m_client->page_did_request_select_dropdown(content_position, minimum_width, move(items));
    }
}

void Page::select_dropdown_closed(Optional<u32> const& selected_item_id)
{
    if (m_pending_non_blocking_dialog == PendingNonBlockingDialog::Select) {
        m_pending_non_blocking_dialog = PendingNonBlockingDialog::None;

        if (m_pending_non_blocking_dialog_target) {
            auto& select_element = as<HTML::HTMLSelectElement>(*m_pending_non_blocking_dialog_target);
            select_element.did_select_item(selected_item_id);
            m_pending_non_blocking_dialog_target = nullptr;
        }
    }
}

void Page::request_clipboard_entries(ClipboardRequest request)
{
    auto request_id = m_next_clipboard_request_id++;
    m_pending_clipboard_requests.set(request_id, request);

    client().page_did_request_clipboard_entries(request_id);
}

void Page::retrieved_clipboard_entries(u64 request_id, Vector<Clipboard::SystemClipboardItem> items)
{
    if (auto request = m_pending_clipboard_requests.take(request_id); request.has_value())
        (*request)->function()(move(items));
}

void Page::register_media_element(Badge<HTML::HTMLMediaElement>, UniqueNodeID media_id)
{
    m_media_elements.append(media_id);
}

void Page::unregister_media_element(Badge<HTML::HTMLMediaElement>, UniqueNodeID media_id)
{
    m_media_elements.remove_all_matching([&](auto candidate_id) {
        return candidate_id == media_id;
    });
}

template<typename Callback>
void Page::for_each_media_element(Callback&& callback)
{
    for (auto media_id : m_media_elements) {
        if (auto* node = DOM::Node::from_unique_id(media_id))
            callback(as<HTML::HTMLMediaElement>(*node));
    }
}

void Page::update_all_media_element_video_sinks()
{
    bool should_request_another_frame = false;
    for_each_media_element([&](auto& media_element) {
        media_element.update_video_frame_and_timeline();
        should_request_another_frame = true;
    });

    if (should_request_another_frame)
        client().request_frame();
}

void Page::register_canvas_element(Badge<HTML::HTMLCanvasElement>, UniqueNodeID canvas_id)
{
    m_canvas_elements.append(canvas_id);
}

void Page::unregister_canvas_element(Badge<HTML::HTMLCanvasElement>, UniqueNodeID canvas_id)
{
    m_canvas_elements.remove_all_matching([&](auto candidate_id) {
        return candidate_id == canvas_id;
    });
}

template<typename Callback>
void Page::for_each_canvas_element(Callback&& callback)
{
    for (auto canvas_id : m_canvas_elements) {
        if (auto* node = DOM::Node::from_unique_id(canvas_id))
            callback(as<HTML::HTMLCanvasElement>(*node));
    }
}

void Page::prepare_canvas_contexts_for_compositing()
{
    for_each_canvas_element([](auto& canvas_element) {
        canvas_element.prepare_for_compositing();
    });

    // Preparing only records commands and present markers into the shared
    // canvas command stream; flush it here so canvases reach the Compositor
    // even when nothing else repaints this rendering update.
    if (has_compositor_host())
        compositor_host().flush_canvas_2d_stream();
}

void Page::notify_all_canvas_elements_of_lost_backing_storage()
{
    for_each_canvas_element([](auto& canvas_element) {
        canvas_element.notify_compositor_backing_storage_lost();
    });
}

void Page::notify_all_webgl_contexts_lost()
{
    for_each_canvas_element([](auto& canvas_element) {
        canvas_element.notify_compositor_connection_lost();
    });
}

void Page::did_request_media_context_menu(UniqueNodeID media_id, CSSPixelPoint position, ByteString const& target, unsigned modifiers, MediaContextMenu const& menu)
{
    m_media_context_menu_element_id = media_id;
    client().page_did_request_media_context_menu(position, target, modifiers, menu);
}

void Page::toggle_media_play_state()
{
    auto media_element = media_context_menu_element();
    if (!media_element)
        return;

    // AD-HOC: An execution context is required for Promise creation hooks.
    HTML::TemporaryExecutionContext execution_context { media_element->realm() };

    if (media_element->potentially_playing())
        media_element->pause();
    else
        media_element->play();
}

void Page::toggle_media_mute_state()
{
    auto media_element = media_context_menu_element();
    if (!media_element)
        return;

    // AD-HOC: An execution context is required for Promise creation hooks.
    HTML::TemporaryExecutionContext execution_context { media_element->realm() };

    media_element->set_muted(!media_element->muted());
}

void Page::toggle_media_loop_state()
{
    auto media_element = media_context_menu_element();
    if (!media_element)
        return;

    // AD-HOC: An execution context is required for Promise creation hooks.
    HTML::TemporaryExecutionContext execution_context { media_element->realm() };

    if (media_element->has_attribute(HTML::AttributeNames::loop))
        media_element->remove_attribute(HTML::AttributeNames::loop);
    else
        media_element->set_attribute_value(HTML::AttributeNames::loop, Utf16String {});
}

void Page::toggle_media_fullscreen_state()
{
    auto media_element = media_context_menu_element();
    if (!media_element)
        return;

    HTML::TemporaryExecutionContext execution_context { media_element->realm() };
    media_element->toggle_fullscreen();
}

void Page::toggle_media_controls_state()
{
    auto media_element = media_context_menu_element();
    if (!media_element)
        return;

    HTML::TemporaryExecutionContext execution_context { media_element->realm() };

    if (media_element->has_attribute(HTML::AttributeNames::controls))
        media_element->remove_attribute(HTML::AttributeNames::controls);
    else
        media_element->set_attribute_value(HTML::AttributeNames::controls, Utf16String {});
}

void Page::set_page_mute_state(HTML::MuteState mute_state)
{
    if (m_mute_state == mute_state)
        return;

    m_mute_state = mute_state;

    for_each_media_element([&](auto& media_element) {
        media_element.page_mute_state_changed({});
    });
}

GC::Ptr<HTML::HTMLMediaElement> Page::media_context_menu_element()
{
    if (!m_media_context_menu_element_id.has_value())
        return nullptr;

    auto* dom_node = DOM::Node::from_unique_id(*m_media_context_menu_element_id);
    if (dom_node == nullptr)
        return nullptr;

    if (!is<HTML::HTMLMediaElement>(dom_node))
        return nullptr;

    return static_cast<HTML::HTMLMediaElement*>(dom_node);
}

void Page::set_user_style(String source)
{
    m_user_style_sheet_source = source;
    invalidate_user_style();
}

void Page::set_content_blocking_enabled(bool enabled)
{
    auto& blocker = ContentBlocker::the();
    if (blocker.filtering_enabled() == enabled)
        return;

    auto has_cosmetic_rules = blocker.has_cosmetic_rules();
    blocker.set_filtering_enabled(enabled);
    if (has_cosmetic_rules)
        invalidate_user_style();
}

void Page::invalidate_user_style()
{
    if (!top_level_traversable_is_initialized() || !top_level_traversable()->active_document())
        return;

    auto invalidate_document = [](DOM::Document& document) {
        document.invalidate_content_blocker_style_sheet();
        document.style_scope().invalidate_user_style_sheet();
        document.for_each_shadow_root([](auto& shadow_root) {
            shadow_root.invalidate_style(DOM::StyleInvalidationReason::StyleSheetReplace);
        });
        document.invalidate_style(DOM::StyleInvalidationReason::StyleSheetReplace);
    };

    auto& active_document = *top_level_traversable()->active_document();
    invalidate_document(active_document);

    for (auto& navigable : active_document.descendant_navigables()) {
        if (auto document = navigable->active_document())
            invalidate_document(*document);
    }
}

Vector<GC::Root<DOM::Document>> Page::documents_in_active_window() const
{
    if (!top_level_traversable_is_initialized())
        return {};

    auto documents = HTML::main_thread_event_loop().documents_in_this_event_loop_matching([&](auto& document) {
        return document.window() == top_level_traversable()->active_window();
    });

    return documents;
}

void Page::clear_selection()
{
    for (auto const& document : documents_in_active_window()) {
        auto selection = document->get_selection();
        if (!selection)
            continue;

        selection->remove_all_ranges();
    }
}

Page::FindInPageResult Page::perform_find_in_page_query(FindInPageQuery const& query, Optional<SearchDirection> direction)
{
    VERIFY(top_level_traversable_is_initialized());

    Vector<GC::Root<DOM::Range>> all_matches;

    auto active_range = [](auto& document) -> GC::Ptr<DOM::Range> {
        auto selection = document.get_selection();
        if (!selection || selection->is_collapsed())
            return {};

        return selection->range();
    };

    auto find_current_match_index = [this](DOM::Range& range, auto const& matches) -> Optional<size_t> {
        // Always return the first match if there is no active query.
        if (!m_last_find_in_page_query.has_value())
            return 0;

        for (size_t i = 0; i < matches.size(); ++i) {
            auto boundary_comparison_or_error = matches[i]->compare_boundary_points(DOM::Range::HowToCompareBoundaryPoints::START_TO_START, range);
            if (!boundary_comparison_or_error.is_error() && boundary_comparison_or_error.value() >= 0)
                return i;
        }

        return {};
    };

    auto should_update_match_index = false;
    for (auto const& document : documents_in_active_window()) {
        auto matches = document->find_matching_text(query.string, query.case_sensitivity);
        if (document == top_level_traversable()->active_document()) {
            if (auto range = active_range(*document)) {
                auto new_match_index = find_current_match_index(*range, matches);
                should_update_match_index = true;
                m_find_in_page_match_index = new_match_index.value_or(0) + all_matches.size();
            } else {
                m_find_in_page_match_index = all_matches.size();
            }
        }

        all_matches.extend(move(matches));
    }

    if (auto active_document = top_level_traversable()->active_document()) {
        if (m_last_find_in_page_url.serialize(URL::ExcludeFragment::Yes) != active_document->url().serialize(URL::ExcludeFragment::Yes)) {
            m_last_find_in_page_url = top_level_traversable()->active_document()->url();
            m_find_in_page_match_index = 0;
        }
    }

    if (direction.has_value() && should_update_match_index) {
        if (direction == SearchDirection::Forward) {
            if (m_find_in_page_match_index >= all_matches.size() - 1) {
                if (query.wrap_around == WrapAround::No)
                    return {};
                m_find_in_page_match_index = 0;
            } else {
                m_find_in_page_match_index++;
            }
        } else {
            if (m_find_in_page_match_index == 0) {
                if (query.wrap_around == WrapAround::No)
                    return {};
                m_find_in_page_match_index = all_matches.size() - 1;
            } else {
                m_find_in_page_match_index--;
            }
        }
    }

    update_find_in_page_selection(all_matches, query.clear_selection_on_no_match);

    return Page::FindInPageResult {
        .current_match_index = m_find_in_page_match_index,
        .total_match_count = all_matches.size(),
    };
}

Page::FindInPageResult Page::find_in_page(FindInPageQuery const& query)
{
    if (!top_level_traversable_is_initialized())
        return {};

    if (query.string.is_empty()) {
        m_last_find_in_page_query = {};
        clear_selection();
        return {};
    }

    auto result = perform_find_in_page_query(query);

    m_last_find_in_page_query = query;
    m_last_find_in_page_url = top_level_traversable()->active_document()->url();

    return result;
}

Page::FindInPageResult Page::find_in_page_next_match()
{
    if (!(m_last_find_in_page_query.has_value() && top_level_traversable_is_initialized()))
        return {};

    auto result = perform_find_in_page_query(*m_last_find_in_page_query, SearchDirection::Forward);
    return result;
}

Page::FindInPageResult Page::find_in_page_previous_match()
{
    if (!(m_last_find_in_page_query.has_value() && top_level_traversable_is_initialized()))
        return {};

    auto result = perform_find_in_page_query(*m_last_find_in_page_query, SearchDirection::Backward);
    return result;
}

void Page::update_find_in_page_selection(Vector<GC::Root<DOM::Range>> matches, ClearSelectionOnNoMatch clear_selection_on_no_match)
{
    if (matches.is_empty()) {
        if (clear_selection_on_no_match == ClearSelectionOnNoMatch::Yes)
            clear_selection();
        return;
    }

    clear_selection();

    auto current_range = matches[m_find_in_page_match_index];
    auto common_ancestor_container = current_range->common_ancestor_container();
    auto& document = common_ancestor_container->document();
    if (!document.window())
        return;

    auto selection = document.get_selection();
    if (!selection)
        return;

    selection->add_range(*current_range);

    if (auto element = common_ancestor_container->parent_element()) {
        Bindings::ScrollIntoViewOptions scroll_options;
        scroll_options.block = Bindings::ScrollLogicalPosition::Nearest;
        scroll_options.inline_ = Bindings::ScrollLogicalPosition::Nearest;
        scroll_options.behavior = Bindings::ScrollBehavior::Instant;
        (void)element->scroll_into_view(scroll_options);
    }
}

void Page::enqueue_fullscreen_enter(GC::Ref<DOM::Element> element, GC::Ref<DOM::Document> pending_doc, DOM::RequestFullscreenError error, GC::Ref<WebIDL::Promise> promise)
{
    m_pending_fullscreen_operations.enqueue(PendingFullscreenEnter { element, pending_doc, error, promise });
    // NOTE: Processing is deferred because the spec says "run the remaining steps in parallel",
    //       meaning the caller's synchronous JS should complete before we process the operation.
    Platform::EventLoopPlugin::the().deferred_invoke(GC::create_function(heap(), [this]() {
        process_pending_fullscreen_operations();
    }));
}

void Page::enqueue_fullscreen_exit(GC::Ref<DOM::Document> doc, bool resize, GC::Ref<WebIDL::Promise> promise)
{
    m_pending_fullscreen_operations.enqueue(PendingFullscreenExit { doc, resize, promise });
    // NOTE: Processing is deferred because the spec says "run the remaining steps in parallel",
    //       meaning the caller's synchronous JS should complete before we process the operation.
    Platform::EventLoopPlugin::the().deferred_invoke(GC::create_function(heap(), [this]() {
        process_pending_fullscreen_operations();
    }));
}

void Page::process_pending_fullscreen_operations()
{
    // FIXME: The Fullscreen API interacts with the top-level traversable's viewport. With site-isolation,
    //        an iframe's content process won't have direct access to this Page, so fullscreen operations
    //        will need to be routed through IPC to the top-level process.

    // NOTE: Resolving/rejecting promises during processing may trigger JS microtasks that re-enter
    //       this function (e.g., JS calls exitFullscreen() after a requestFullscreen() promise resolves).
    //       The outer call's while loop will pick up newly enqueued items.
    if (m_processing_fullscreen_operations)
        return;
    m_processing_fullscreen_operations = true;
    ScopeGuard guard = [this] { m_processing_fullscreen_operations = false; };

    while (!m_pending_fullscreen_operations.is_empty()) {
        auto& front = m_pending_fullscreen_operations.head();

        auto processed = front.visit(
            [&](PendingFullscreenEnter& enter) -> bool {
                // https://fullscreen.spec.whatwg.org/#dom-element-requestfullscreen

                // 8. If error is false, then resize pendingDoc's node navigable's top-level traversable's
                //    active document's viewport's dimensions, optionally taking into account
                //    options["navigationUI"]:
                if (enter.error == DOM::RequestFullscreenError::False) {
                    if (m_viewport_is_fullscreen == ViewportIsFullscreen::No) {
                        if (!m_fullscreen_ipc_sent_to_ui) {
                            m_client->page_did_request_fullscreen_window();
                            m_fullscreen_ipc_sent_to_ui = true;
                        }
                        // NB: Stop processing here and wait for a change in the fullscreen state if we aren't
                        //     in the desired state yet.
                        return false;
                    }

                    // 9. If any of the following conditions are false, then set error to true:
                    //    * This's node document is pendingDoc.
                    //    * The fullscreen element ready check for this returns true.
                    if (enter.element->owner_document() != enter.pending_doc.ptr())
                        enter.error = DOM::RequestFullscreenError::ElementNodeDocIsNotPendingDoc;
                    else if (!enter.element->is_element_ready_for_fullscreen())
                        enter.error = DOM::RequestFullscreenError::ElementReadyCheckFailed;
                }

                auto& realm = enter.element->realm();
                HTML::TemporaryExecutionContext context(realm, HTML::TemporaryExecutionContext::CallbacksEnabled::Yes);

                // 10. If error is true:
                if (enter.error != DOM::RequestFullscreenError::False) {
                    // 1. Append (fullscreenerror, this) to pendingDoc's list of pending fullscreen events.
                    enter.pending_doc->append_pending_fullscreen_change(DOM::PendingFullscreenEvent::Type::Error, enter.element);

                    // 2. Reject promise with a TypeError exception and terminate these steps.
                    WebIDL::reject_promise(realm, enter.promise, JS::TypeError::create(realm, DOM::request_fullscreen_error_to_string(enter.error)));
                    return true;
                }

                // 11. Let fullscreenElements be an ordered set initially consisting of this.
                auto fullscreen_elements = realm.heap().allocate<GC::HeapVector<GC::Ref<DOM::Element>>>();
                fullscreen_elements->elements().append(enter.element);

                // 12. While true:
                while (true) {
                    // 1. Let last be the last item of fullscreenElements.
                    auto last = fullscreen_elements->elements().last();

                    // 2. Let container be last's node navigable's container.
                    auto container = last->navigable()->container();

                    // 3. If container is null, then break.
                    if (!container)
                        break;

                    // 4. Append container to fullscreenElements.
                    fullscreen_elements->elements().append(*container);
                }

                // 13. For each element in fullscreenElements:
                for (auto& element : fullscreen_elements->elements()) {
                    // 1. Let doc be element's node document.
                    auto& doc = element->document();

                    // 2. If element is doc's fullscreen element, continue.
                    if (doc.fullscreen_element() == element)
                        continue;

                    // 3. If element is this and this is an iframe element, then set element's iframe fullscreen flag.
                    if (element == enter.element && is<HTML::HTMLIFrameElement>(*enter.element))
                        as<HTML::HTMLIFrameElement>(*element).set_iframe_fullscreen_flag(true);

                    // 4. Fullscreen element within doc.
                    doc.fullscreen_element_within_doc(element);

                    // 5. Append (fullscreenchange, element) to doc's list of pending fullscreen events.
                    doc.append_pending_fullscreen_change(DOM::PendingFullscreenEvent::Type::Change, element);
                }

                // 14. Resolve promise with undefined
                WebIDL::resolve_promise(realm, enter.promise, JS::js_undefined());
                return true;
            },
            [&](PendingFullscreenExit& exit) -> bool {
                auto& realm = exit.doc->realm();
                HTML::TemporaryExecutionContext context(realm, HTML::TemporaryExecutionContext::CallbacksEnabled::Yes);

                // https://fullscreen.spec.whatwg.org/#exit-fullscreen

                // FIXME: 9. Run the fully unlock the screen orientation steps with doc.

                // 10. If resize is true, resize doc's viewport to its "normal" dimensions.
                if (exit.resize && m_viewport_is_fullscreen == ViewportIsFullscreen::Yes) {
                    if (!m_fullscreen_ipc_sent_to_ui) {
                        m_client->page_did_request_exit_fullscreen();
                        m_fullscreen_ipc_sent_to_ui = true;
                    }
                    // NB: Stop processing here and wait for a change in the fullscreen state if we aren't
                    //     in the desired state yet.
                    return false;
                }

                // 11. If doc's fullscreen element is null, then resolve promise with undefined and terminate these
                //     steps.
                if (!exit.doc->fullscreen_element()) {
                    WebIDL::resolve_promise(realm, exit.promise, JS::js_undefined());
                    return true;
                }

                // 12. Let exitDocs be the result of collecting documents to unfullscreen given doc.
                auto exit_docs = exit.doc->collect_documents_to_unfullscreen();

                // 13. Let descendantDocs be an ordered set consisting of doc's descendant navigables' active documents
                //     whose fullscreen element is non-null, if any, in tree order.
                auto descendant_docs = realm.heap().allocate<GC::HeapVector<GC::Ref<DOM::Document>>>();
                for (auto& descendant : exit.doc->descendant_navigables()) {
                    if (descendant->active_document()->fullscreen_element())
                        descendant_docs->elements().append(*descendant->active_document());
                }

                // 14. For each exitDoc in exitDocs:
                for (auto& exit_doc : exit_docs->elements()) {
                    // 1. Append (fullscreenchange, exitDoc's fullscreen element) to exitDoc's list of pending
                    //    fullscreen events.
                    exit_doc->append_pending_fullscreen_change(DOM::PendingFullscreenEvent::Type::Change, *exit_doc->fullscreen_element());

                    // 2. If resize is true, unfullscreen exitDoc.
                    if (exit.resize)
                        exit_doc->unfullscreen();
                    // 3. Otherwise, unfullscreen exitDoc's fullscreen element.
                    else
                        exit_doc->unfullscreen_element(*exit_doc->fullscreen_element());
                }

                // 15. For each descendantDoc in descendantDocs:
                for (auto& descendant_doc : descendant_docs->elements()) {
                    // 1. Append (fullscreenchange, descendantDoc's fullscreen element) to descendantDoc's list of
                    //    pending fullscreen events.
                    descendant_doc->append_pending_fullscreen_change(DOM::PendingFullscreenEvent::Type::Change, *descendant_doc->fullscreen_element());

                    // 2. Unfullscreen descendantDoc.
                    descendant_doc->unfullscreen();
                }

                // 16. Resolve promise with undefined.
                WebIDL::resolve_promise(realm, exit.promise, JS::js_undefined());
                return true;
            });

        if (!processed)
            break;

        m_pending_fullscreen_operations.dequeue();
    }
}

void Page::set_viewport_is_fullscreen(ViewportIsFullscreen is_fullscreen)
{
    if (m_viewport_is_fullscreen == is_fullscreen)
        return;
    m_viewport_is_fullscreen = is_fullscreen;
    m_fullscreen_ipc_sent_to_ui = false;
    process_pending_fullscreen_operations();
}

}

template<>
ErrorOr<void> IPC::encode(Encoder& encoder, Web::Page::MediaContextMenu const& menu)
{
    TRY(encoder.encode(menu.media_url));
    TRY(encoder.encode(menu.is_video));
    TRY(encoder.encode(menu.is_playing));
    TRY(encoder.encode(menu.is_muted));
    TRY(encoder.encode(menu.has_user_agent_controls));
    TRY(encoder.encode(menu.is_looping));
    TRY(encoder.encode(menu.is_fullscreen));
    return {};
}

template<>
ErrorOr<Web::Page::MediaContextMenu> IPC::decode(Decoder& decoder)
{
    return Web::Page::MediaContextMenu {
        .media_url = TRY(decoder.decode<URL::URL>()),
        .is_video = TRY(decoder.decode<bool>()),
        .is_playing = TRY(decoder.decode<bool>()),
        .is_muted = TRY(decoder.decode<bool>()),
        .has_user_agent_controls = TRY(decoder.decode<bool>()),
        .is_looping = TRY(decoder.decode<bool>()),
        .is_fullscreen = TRY(decoder.decode<bool>()),
    };
}