ladybird/Userland/Libraries/LibWeb/CSS/StyleValue.cpp

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * Copyright (c) 2021-2023, Sam Atkins <atkinssj@serenityos.org>
 * Copyright (c) 2021, Tobias Christiansen <tobyase@serenityos.org>
 * Copyright (c) 2022-2023, MacDue <macdue@dueutil.tech>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/ByteBuffer.h>
#include <LibGfx/Palette.h>
#include <LibWeb/CSS/Serialize.h>
#include <LibWeb/CSS/StyleValue.h>
#include <LibWeb/CSS/StyleValues/AngleStyleValue.h>
#include <LibWeb/CSS/StyleValues/BackgroundRepeatStyleValue.h>
#include <LibWeb/CSS/StyleValues/BackgroundSizeStyleValue.h>
#include <LibWeb/CSS/StyleValues/BackgroundStyleValue.h>
#include <LibWeb/CSS/StyleValues/BorderRadiusShorthandStyleValue.h>
#include <LibWeb/CSS/StyleValues/BorderRadiusStyleValue.h>
#include <LibWeb/CSS/StyleValues/BorderStyleValue.h>
#include <LibWeb/CSS/StyleValues/ColorStyleValue.h>
#include <LibWeb/CSS/StyleValues/ContentStyleValue.h>
#include <LibWeb/CSS/StyleValues/FilterValueListStyleValue.h>
#include <LibWeb/CSS/StyleValues/FlexFlowStyleValue.h>
#include <LibWeb/CSS/StyleValues/FlexStyleValue.h>
#include <LibWeb/CSS/StyleValues/FontStyleValue.h>
#include <LibWeb/CSS/StyleValues/FrequencyStyleValue.h>
#include <LibWeb/CSS/StyleValues/GridAreaShorthandStyleValue.h>
#include <LibWeb/CSS/StyleValues/GridTemplateAreaStyleValue.h>
#include <LibWeb/CSS/StyleValues/GridTrackPlacementShorthandStyleValue.h>
#include <LibWeb/CSS/StyleValues/GridTrackPlacementStyleValue.h>
#include <LibWeb/CSS/StyleValues/GridTrackSizeStyleValue.h>
#include <LibWeb/CSS/StyleValues/IdentifierStyleValue.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/HTML/BrowsingContext.h>
#include <LibWeb/Loader/LoadRequest.h>
#include <LibWeb/Loader/ResourceLoader.h>
#include <LibWeb/Page/Page.h>
#include <LibWeb/Painting/GradientPainting.h>
#include <LibWeb/Platform/Timer.h>

namespace Web::CSS {

StyleValue::StyleValue(Type type)
    : m_type(type)
{
}

AbstractImageStyleValue const& StyleValue::as_abstract_image() const
{
    VERIFY(is_abstract_image());
    return static_cast<AbstractImageStyleValue const&>(*this);
}

AngleStyleValue const& StyleValue::as_angle() const
{
    VERIFY(is_angle());
    return static_cast<AngleStyleValue const&>(*this);
}

BackgroundStyleValue const& StyleValue::as_background() const
{
    VERIFY(is_background());
    return static_cast<BackgroundStyleValue const&>(*this);
}

BackgroundRepeatStyleValue const& StyleValue::as_background_repeat() const
{
    VERIFY(is_background_repeat());
    return static_cast<BackgroundRepeatStyleValue const&>(*this);
}

BackgroundSizeStyleValue const& StyleValue::as_background_size() const
{
    VERIFY(is_background_size());
    return static_cast<BackgroundSizeStyleValue const&>(*this);
}

BorderStyleValue const& StyleValue::as_border() const
{
    VERIFY(is_border());
    return static_cast<BorderStyleValue const&>(*this);
}

BorderRadiusStyleValue const& StyleValue::as_border_radius() const
{
    VERIFY(is_border_radius());
    return static_cast<BorderRadiusStyleValue const&>(*this);
}

BorderRadiusShorthandStyleValue const& StyleValue::as_border_radius_shorthand() const
{
    VERIFY(is_border_radius_shorthand());
    return static_cast<BorderRadiusShorthandStyleValue const&>(*this);
}

ShadowStyleValue const& StyleValue::as_shadow() const
{
    VERIFY(is_shadow());
    return static_cast<ShadowStyleValue const&>(*this);
}

CalculatedStyleValue const& StyleValue::as_calculated() const
{
    VERIFY(is_calculated());
    return static_cast<CalculatedStyleValue const&>(*this);
}

ColorStyleValue const& StyleValue::as_color() const
{
    VERIFY(is_color());
    return static_cast<ColorStyleValue const&>(*this);
}

ConicGradientStyleValue const& StyleValue::as_conic_gradient() const
{
    VERIFY(is_conic_gradient());
    return static_cast<ConicGradientStyleValue const&>(*this);
}

ContentStyleValue const& StyleValue::as_content() const
{
    VERIFY(is_content());
    return static_cast<ContentStyleValue const&>(*this);
}

FilterValueListStyleValue const& StyleValue::as_filter_value_list() const
{
    VERIFY(is_filter_value_list());
    return static_cast<FilterValueListStyleValue const&>(*this);
}

FlexStyleValue const& StyleValue::as_flex() const
{
    VERIFY(is_flex());
    return static_cast<FlexStyleValue const&>(*this);
}

FlexFlowStyleValue const& StyleValue::as_flex_flow() const
{
    VERIFY(is_flex_flow());
    return static_cast<FlexFlowStyleValue const&>(*this);
}

FontStyleValue const& StyleValue::as_font() const
{
    VERIFY(is_font());
    return static_cast<FontStyleValue const&>(*this);
}

FrequencyStyleValue const& StyleValue::as_frequency() const
{
    VERIFY(is_frequency());
    return static_cast<FrequencyStyleValue const&>(*this);
}

GridTrackPlacementShorthandStyleValue const& StyleValue::as_grid_track_placement_shorthand() const
{
    VERIFY(is_grid_track_placement_shorthand());
    return static_cast<GridTrackPlacementShorthandStyleValue const&>(*this);
}

GridAreaShorthandStyleValue const& StyleValue::as_grid_area_shorthand() const
{
    VERIFY(is_grid_area_shorthand());
    return static_cast<GridAreaShorthandStyleValue const&>(*this);
}

GridTemplateAreaStyleValue const& StyleValue::as_grid_template_area() const
{
    VERIFY(is_grid_template_area());
    return static_cast<GridTemplateAreaStyleValue const&>(*this);
}

GridTrackPlacementStyleValue const& StyleValue::as_grid_track_placement() const
{
    VERIFY(is_grid_track_placement());
    return static_cast<GridTrackPlacementStyleValue const&>(*this);
}

IdentifierStyleValue const& StyleValue::as_identifier() const
{
    VERIFY(is_identifier());
    return static_cast<IdentifierStyleValue const&>(*this);
}

ImageStyleValue const& StyleValue::as_image() const
{
    VERIFY(is_image());
    return static_cast<ImageStyleValue const&>(*this);
}

InheritStyleValue const& StyleValue::as_inherit() const
{
    VERIFY(is_inherit());
    return static_cast<InheritStyleValue const&>(*this);
}

InitialStyleValue const& StyleValue::as_initial() const
{
    VERIFY(is_initial());
    return static_cast<InitialStyleValue const&>(*this);
}

LengthStyleValue const& StyleValue::as_length() const
{
    VERIFY(is_length());
    return static_cast<LengthStyleValue const&>(*this);
}

GridTrackSizeStyleValue const& StyleValue::as_grid_track_size_list() const
{
    VERIFY(is_grid_track_size_list());
    return static_cast<GridTrackSizeStyleValue const&>(*this);
}

LinearGradientStyleValue const& StyleValue::as_linear_gradient() const
{
    VERIFY(is_linear_gradient());
    return static_cast<LinearGradientStyleValue const&>(*this);
}

ListStyleStyleValue const& StyleValue::as_list_style() const
{
    VERIFY(is_list_style());
    return static_cast<ListStyleStyleValue const&>(*this);
}

NumericStyleValue const& StyleValue::as_numeric() const
{
    VERIFY(is_numeric());
    return static_cast<NumericStyleValue const&>(*this);
}

OverflowStyleValue const& StyleValue::as_overflow() const
{
    VERIFY(is_overflow());
    return static_cast<OverflowStyleValue const&>(*this);
}

PercentageStyleValue const& StyleValue::as_percentage() const
{
    VERIFY(is_percentage());
    return static_cast<PercentageStyleValue const&>(*this);
}

PositionStyleValue const& StyleValue::as_position() const
{
    VERIFY(is_position());
    return static_cast<PositionStyleValue const&>(*this);
}

RadialGradientStyleValue const& StyleValue::as_radial_gradient() const
{
    VERIFY(is_radial_gradient());
    return static_cast<RadialGradientStyleValue const&>(*this);
}

RectStyleValue const& StyleValue::as_rect() const
{
    VERIFY(is_rect());
    return static_cast<RectStyleValue const&>(*this);
}

ResolutionStyleValue const& StyleValue::as_resolution() const
{
    VERIFY(is_resolution());
    return static_cast<ResolutionStyleValue const&>(*this);
}

StringStyleValue const& StyleValue::as_string() const
{
    VERIFY(is_string());
    return static_cast<StringStyleValue const&>(*this);
}

TextDecorationStyleValue const& StyleValue::as_text_decoration() const
{
    VERIFY(is_text_decoration());
    return static_cast<TextDecorationStyleValue const&>(*this);
}

TimeStyleValue const& StyleValue::as_time() const
{
    VERIFY(is_time());
    return static_cast<TimeStyleValue const&>(*this);
}

TransformationStyleValue const& StyleValue::as_transformation() const
{
    VERIFY(is_transformation());
    return static_cast<TransformationStyleValue const&>(*this);
}

UnresolvedStyleValue const& StyleValue::as_unresolved() const
{
    VERIFY(is_unresolved());
    return static_cast<UnresolvedStyleValue const&>(*this);
}

UnsetStyleValue const& StyleValue::as_unset() const
{
    VERIFY(is_unset());
    return static_cast<UnsetStyleValue const&>(*this);
}

StyleValueList const& StyleValue::as_value_list() const
{
    VERIFY(is_value_list());
    return static_cast<StyleValueList const&>(*this);
}

void CalculatedStyleValue::CalculationResult::add(CalculationResult const& other, Layout::Node const* layout_node, PercentageBasis const& percentage_basis)
{
    add_or_subtract_internal(SumOperation::Add, other, layout_node, percentage_basis);
}

void CalculatedStyleValue::CalculationResult::subtract(CalculationResult const& other, Layout::Node const* layout_node, PercentageBasis const& percentage_basis)
{
    add_or_subtract_internal(SumOperation::Subtract, other, layout_node, percentage_basis);
}

void CalculatedStyleValue::CalculationResult::add_or_subtract_internal(SumOperation op, CalculationResult const& other, Layout::Node const* layout_node, PercentageBasis const& percentage_basis)
{
    // We know from validation when resolving the type, that "both sides have the same type, or that one side is a <number> and the other is an <integer>".
    // Though, having the same type may mean that one side is a <dimension> and the other a <percentage>.
    // Note: This is almost identical to ::add()

    m_value.visit(
        [&](Number const& number) {
            auto other_number = other.m_value.get<Number>();
            if (op == SumOperation::Add) {
                m_value = number + other_number;
            } else {
                m_value = number - other_number;
            }
        },
        [&](Angle const& angle) {
            auto this_degrees = angle.to_degrees();
            if (other.m_value.has<Angle>()) {
                auto other_degrees = other.m_value.get<Angle>().to_degrees();
                if (op == SumOperation::Add)
                    m_value = Angle::make_degrees(this_degrees + other_degrees);
                else
                    m_value = Angle::make_degrees(this_degrees - other_degrees);
            } else {
                VERIFY(percentage_basis.has<Angle>());

                auto other_degrees = percentage_basis.get<Angle>().percentage_of(other.m_value.get<Percentage>()).to_degrees();
                if (op == SumOperation::Add)
                    m_value = Angle::make_degrees(this_degrees + other_degrees);
                else
                    m_value = Angle::make_degrees(this_degrees - other_degrees);
            }
        },
        [&](Frequency const& frequency) {
            auto this_hertz = frequency.to_hertz();
            if (other.m_value.has<Frequency>()) {
                auto other_hertz = other.m_value.get<Frequency>().to_hertz();
                if (op == SumOperation::Add)
                    m_value = Frequency::make_hertz(this_hertz + other_hertz);
                else
                    m_value = Frequency::make_hertz(this_hertz - other_hertz);
            } else {
                VERIFY(percentage_basis.has<Frequency>());

                auto other_hertz = percentage_basis.get<Frequency>().percentage_of(other.m_value.get<Percentage>()).to_hertz();
                if (op == SumOperation::Add)
                    m_value = Frequency::make_hertz(this_hertz + other_hertz);
                else
                    m_value = Frequency::make_hertz(this_hertz - other_hertz);
            }
        },
        [&](Length const& length) {
            auto this_px = length.to_px(*layout_node);
            if (other.m_value.has<Length>()) {
                auto other_px = other.m_value.get<Length>().to_px(*layout_node);
                if (op == SumOperation::Add)
                    m_value = Length::make_px(this_px + other_px);
                else
                    m_value = Length::make_px(this_px - other_px);
            } else {
                VERIFY(percentage_basis.has<Length>());

                auto other_px = percentage_basis.get<Length>().percentage_of(other.m_value.get<Percentage>()).to_px(*layout_node);
                if (op == SumOperation::Add)
                    m_value = Length::make_px(this_px + other_px);
                else
                    m_value = Length::make_px(this_px - other_px);
            }
        },
        [&](Time const& time) {
            auto this_seconds = time.to_seconds();
            if (other.m_value.has<Time>()) {
                auto other_seconds = other.m_value.get<Time>().to_seconds();
                if (op == SumOperation::Add)
                    m_value = Time::make_seconds(this_seconds + other_seconds);
                else
                    m_value = Time::make_seconds(this_seconds - other_seconds);
            } else {
                VERIFY(percentage_basis.has<Time>());

                auto other_seconds = percentage_basis.get<Time>().percentage_of(other.m_value.get<Percentage>()).to_seconds();
                if (op == SumOperation::Add)
                    m_value = Time::make_seconds(this_seconds + other_seconds);
                else
                    m_value = Time::make_seconds(this_seconds - other_seconds);
            }
        },
        [&](Percentage const& percentage) {
            if (other.m_value.has<Percentage>()) {
                if (op == SumOperation::Add)
                    m_value = Percentage { percentage.value() + other.m_value.get<Percentage>().value() };
                else
                    m_value = Percentage { percentage.value() - other.m_value.get<Percentage>().value() };
                return;
            }

            // Other side isn't a percentage, so the easiest way to handle it without duplicating all the logic, is just to swap `this` and `other`.
            CalculationResult new_value = other;
            if (op == SumOperation::Add) {
                new_value.add(*this, layout_node, percentage_basis);
            } else {
                // Turn 'this - other' into '-other + this', as 'A + B == B + A', but 'A - B != B - A'
                new_value.multiply_by({ Number { Number::Type::Integer, -1.0f } }, layout_node);
                new_value.add(*this, layout_node, percentage_basis);
            }

            *this = new_value;
        });
}

void CalculatedStyleValue::CalculationResult::multiply_by(CalculationResult const& other, Layout::Node const* layout_node)
{
    // We know from validation when resolving the type, that at least one side must be a <number> or <integer>.
    // Both of these are represented as a float.
    VERIFY(m_value.has<Number>() || other.m_value.has<Number>());
    bool other_is_number = other.m_value.has<Number>();

    m_value.visit(
        [&](Number const& number) {
            if (other_is_number) {
                m_value = number * other.m_value.get<Number>();
            } else {
                // Avoid duplicating all the logic by swapping `this` and `other`.
                CalculationResult new_value = other;
                new_value.multiply_by(*this, layout_node);
                *this = new_value;
            }
        },
        [&](Angle const& angle) {
            m_value = Angle::make_degrees(angle.to_degrees() * other.m_value.get<Number>().value());
        },
        [&](Frequency const& frequency) {
            m_value = Frequency::make_hertz(frequency.to_hertz() * other.m_value.get<Number>().value());
        },
        [&](Length const& length) {
            VERIFY(layout_node);
            m_value = Length::make_px(length.to_px(*layout_node) * other.m_value.get<Number>().value());
        },
        [&](Time const& time) {
            m_value = Time::make_seconds(time.to_seconds() * other.m_value.get<Number>().value());
        },
        [&](Percentage const& percentage) {
            m_value = Percentage { percentage.value() * other.m_value.get<Number>().value() };
        });
}

void CalculatedStyleValue::CalculationResult::divide_by(CalculationResult const& other, Layout::Node const* layout_node)
{
    // We know from validation when resolving the type, that `other` must be a <number> or <integer>.
    // Both of these are represented as a Number.
    auto denominator = other.m_value.get<Number>().value();
    // FIXME: Dividing by 0 is invalid, and should be caught during parsing.
    VERIFY(denominator != 0.0f);

    m_value.visit(
        [&](Number const& number) {
            m_value = Number {
                Number::Type::Number,
                number.value() / denominator
            };
        },
        [&](Angle const& angle) {
            m_value = Angle::make_degrees(angle.to_degrees() / denominator);
        },
        [&](Frequency const& frequency) {
            m_value = Frequency::make_hertz(frequency.to_hertz() / denominator);
        },
        [&](Length const& length) {
            VERIFY(layout_node);
            m_value = Length::make_px(length.to_px(*layout_node) / denominator);
        },
        [&](Time const& time) {
            m_value = Time::make_seconds(time.to_seconds() / denominator);
        },
        [&](Percentage const& percentage) {
            m_value = Percentage { percentage.value() / denominator };
        });
}

ErrorOr<String> CalculatedStyleValue::to_string() const
{
    return String::formatted("calc({})", TRY(m_expression->to_string()));
}

bool CalculatedStyleValue::equals(StyleValue const& other) const
{
    if (type() != other.type())
        return false;
    // This is a case where comparing the strings actually makes sense.
    return to_string().release_value_but_fixme_should_propagate_errors() == other.to_string().release_value_but_fixme_should_propagate_errors();
}

ErrorOr<String> CalculatedStyleValue::CalcNumberValue::to_string() const
{
    return value.visit(
        [](Number const& number) -> ErrorOr<String> { return String::number(number.value()); },
        [](NonnullOwnPtr<CalcNumberSum> const& sum) -> ErrorOr<String> { return String::formatted("({})", TRY(sum->to_string())); });
}

ErrorOr<String> CalculatedStyleValue::CalcValue::to_string() const
{
    return value.visit(
        [](Number const& number) -> ErrorOr<String> { return String::number(number.value()); },
        [](NonnullOwnPtr<CalcSum> const& sum) -> ErrorOr<String> { return String::formatted("({})", TRY(sum->to_string())); },
        [](auto const& v) -> ErrorOr<String> { return v.to_string(); });
}

ErrorOr<String> CalculatedStyleValue::CalcSum::to_string() const
{
    StringBuilder builder;
    TRY(builder.try_append(TRY(first_calc_product->to_string())));
    for (auto const& item : zero_or_more_additional_calc_products)
        TRY(builder.try_append(TRY(item->to_string())));
    return builder.to_string();
}

ErrorOr<String> CalculatedStyleValue::CalcNumberSum::to_string() const
{
    StringBuilder builder;
    TRY(builder.try_append(TRY(first_calc_number_product->to_string())));
    for (auto const& item : zero_or_more_additional_calc_number_products)
        TRY(builder.try_append(TRY(item->to_string())));
    return builder.to_string();
}

ErrorOr<String> CalculatedStyleValue::CalcProduct::to_string() const
{
    StringBuilder builder;
    TRY(builder.try_append(TRY(first_calc_value.to_string())));
    for (auto const& item : zero_or_more_additional_calc_values)
        TRY(builder.try_append(TRY(item->to_string())));
    return builder.to_string();
}

ErrorOr<String> CalculatedStyleValue::CalcSumPartWithOperator::to_string() const
{
    return String::formatted(" {} {}", op == SumOperation::Add ? "+"sv : "-"sv, TRY(value->to_string()));
}

ErrorOr<String> CalculatedStyleValue::CalcProductPartWithOperator::to_string() const
{
    auto value_string = TRY(value.visit(
        [](CalcValue const& v) { return v.to_string(); },
        [](CalcNumberValue const& v) { return v.to_string(); }));
    return String::formatted(" {} {}", op == ProductOperation::Multiply ? "*"sv : "/"sv, value_string);
}

ErrorOr<String> CalculatedStyleValue::CalcNumberProduct::to_string() const
{
    StringBuilder builder;
    TRY(builder.try_append(TRY(first_calc_number_value.to_string())));
    for (auto const& item : zero_or_more_additional_calc_number_values)
        TRY(builder.try_append(TRY(item->to_string())));
    return builder.to_string();
}

ErrorOr<String> CalculatedStyleValue::CalcNumberProductPartWithOperator::to_string() const
{
    return String::formatted(" {} {}", op == ProductOperation::Multiply ? "*"sv : "/"sv, TRY(value.to_string()));
}

ErrorOr<String> CalculatedStyleValue::CalcNumberSumPartWithOperator::to_string() const
{
    return String::formatted(" {} {}", op == SumOperation::Add ? "+"sv : "-"sv, TRY(value->to_string()));
}

Optional<Angle> CalculatedStyleValue::resolve_angle() const
{
    auto result = m_expression->resolve(nullptr, {});

    if (result.value().has<Angle>())
        return result.value().get<Angle>();
    return {};
}

Optional<Angle> CalculatedStyleValue::resolve_angle_percentage(Angle const& percentage_basis) const
{
    auto result = m_expression->resolve(nullptr, percentage_basis);

    return result.value().visit(
        [&](Angle const& angle) -> Optional<Angle> {
            return angle;
        },
        [&](Percentage const& percentage) -> Optional<Angle> {
            return percentage_basis.percentage_of(percentage);
        },
        [&](auto const&) -> Optional<Angle> {
            return {};
        });
}

Optional<Frequency> CalculatedStyleValue::resolve_frequency() const
{
    auto result = m_expression->resolve(nullptr, {});

    if (result.value().has<Frequency>())
        return result.value().get<Frequency>();
    return {};
}

Optional<Frequency> CalculatedStyleValue::resolve_frequency_percentage(Frequency const& percentage_basis) const
{
    auto result = m_expression->resolve(nullptr, percentage_basis);

    return result.value().visit(
        [&](Frequency const& frequency) -> Optional<Frequency> {
            return frequency;
        },
        [&](Percentage const& percentage) -> Optional<Frequency> {
            return percentage_basis.percentage_of(percentage);
        },
        [&](auto const&) -> Optional<Frequency> {
            return {};
        });
}

Optional<Length> CalculatedStyleValue::resolve_length(Layout::Node const& layout_node) const
{
    auto result = m_expression->resolve(&layout_node, {});

    if (result.value().has<Length>())
        return result.value().get<Length>();
    return {};
}

Optional<Length> CalculatedStyleValue::resolve_length_percentage(Layout::Node const& layout_node, Length const& percentage_basis) const
{
    auto result = m_expression->resolve(&layout_node, percentage_basis);

    return result.value().visit(
        [&](Length const& length) -> Optional<Length> {
            return length;
        },
        [&](Percentage const& percentage) -> Optional<Length> {
            return percentage_basis.percentage_of(percentage);
        },
        [&](auto const&) -> Optional<Length> {
            return {};
        });
}

Optional<Percentage> CalculatedStyleValue::resolve_percentage() const
{
    auto result = m_expression->resolve(nullptr, {});
    if (result.value().has<Percentage>())
        return result.value().get<Percentage>();
    return {};
}

Optional<Time> CalculatedStyleValue::resolve_time() const
{
    auto result = m_expression->resolve(nullptr, {});

    if (result.value().has<Time>())
        return result.value().get<Time>();
    return {};
}

Optional<Time> CalculatedStyleValue::resolve_time_percentage(Time const& percentage_basis) const
{
    auto result = m_expression->resolve(nullptr, percentage_basis);

    return result.value().visit(
        [&](Time const& time) -> Optional<Time> {
            return time;
        },
        [&](auto const&) -> Optional<Time> {
            return {};
        });
}

Optional<float> CalculatedStyleValue::resolve_number()
{
    auto result = m_expression->resolve(nullptr, {});
    if (result.value().has<Number>())
        return result.value().get<Number>().value();
    return {};
}

Optional<i64> CalculatedStyleValue::resolve_integer()
{
    auto result = m_expression->resolve(nullptr, {});
    if (result.value().has<Number>())
        return result.value().get<Number>().integer_value();
    return {};
}

static bool is_number(CalculatedStyleValue::ResolvedType type)
{
    return type == CalculatedStyleValue::ResolvedType::Number || type == CalculatedStyleValue::ResolvedType::Integer;
}

static bool is_dimension(CalculatedStyleValue::ResolvedType type)
{
    return type != CalculatedStyleValue::ResolvedType::Number
        && type != CalculatedStyleValue::ResolvedType::Integer
        && type != CalculatedStyleValue::ResolvedType::Percentage;
}

template<typename SumWithOperator>
static Optional<CalculatedStyleValue::ResolvedType> resolve_sum_type(CalculatedStyleValue::ResolvedType first_type, Vector<NonnullOwnPtr<SumWithOperator>> const& zero_or_more_additional_products)
{
    auto type = first_type;

    for (auto const& product : zero_or_more_additional_products) {
        auto maybe_product_type = product->resolved_type();
        if (!maybe_product_type.has_value())
            return {};
        auto product_type = maybe_product_type.value();

        // At + or -, check that both sides have the same type, or that one side is a <number> and the other is an <integer>.
        // If both sides are the same type, resolve to that type.
        if (product_type == type)
            continue;

        // If one side is a <number> and the other is an <integer>, resolve to <number>.
        if (is_number(type) && is_number(product_type)) {
            type = CalculatedStyleValue::ResolvedType::Number;
            continue;
        }

        // FIXME: calc() handles <percentage> by allowing them to pretend to be whatever <dimension> type is allowed at this location.
        //        Since we can't easily check what that type is, we just allow <percentage> to combine with any other <dimension> type.
        if (type == CalculatedStyleValue::ResolvedType::Percentage && is_dimension(product_type)) {
            type = product_type;
            continue;
        }
        if (is_dimension(type) && product_type == CalculatedStyleValue::ResolvedType::Percentage)
            continue;

        return {};
    }
    return type;
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcSum::resolved_type() const
{
    auto maybe_type = first_calc_product->resolved_type();
    if (!maybe_type.has_value())
        return {};
    auto type = maybe_type.value();
    return resolve_sum_type(type, zero_or_more_additional_calc_products);
}

// https://www.w3.org/TR/CSS2/visufx.html#value-def-shape
Gfx::FloatRect EdgeRect::resolved(Layout::Node const& layout_node, Gfx::FloatRect border_box) const
{
    // In CSS 2.1, the only valid <shape> value is: rect(<top>, <right>, <bottom>, <left>) where
    // <top> and <bottom> specify offsets from the top border edge of the box, and <right>, and
    // <left> specify offsets from the left border edge of the box.

    // The value 'auto' means that a given edge of the clipping region will be the same as the edge
    // of the element's generated border box (i.e., 'auto' means the same as '0' for <top> and
    // <left>, the same as the used value of the height plus the sum of vertical padding and border
    // widths for <bottom>, and the same as the used value of the width plus the sum of the
    // horizontal padding and border widths for <right>, such that four 'auto' values result in the
    // clipping region being the same as the element's border box).
    auto left = border_box.left() + (left_edge.is_auto() ? 0 : left_edge.to_px(layout_node)).value();
    auto top = border_box.top() + (top_edge.is_auto() ? 0 : top_edge.to_px(layout_node)).value();
    auto right = border_box.left() + (right_edge.is_auto() ? border_box.width() : right_edge.to_px(layout_node)).value();
    auto bottom = border_box.top() + (bottom_edge.is_auto() ? border_box.height() : bottom_edge.to_px(layout_node)).value();
    return Gfx::FloatRect {
        left,
        top,
        right - left,
        bottom - top
    };
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcNumberSum::resolved_type() const
{
    auto maybe_type = first_calc_number_product->resolved_type();
    if (!maybe_type.has_value())
        return {};
    auto type = maybe_type.value();
    return resolve_sum_type(type, zero_or_more_additional_calc_number_products);
}

template<typename ProductWithOperator>
static Optional<CalculatedStyleValue::ResolvedType> resolve_product_type(CalculatedStyleValue::ResolvedType first_type, Vector<NonnullOwnPtr<ProductWithOperator>> const& zero_or_more_additional_values)
{
    auto type = first_type;

    for (auto const& value : zero_or_more_additional_values) {
        auto maybe_value_type = value->resolved_type();
        if (!maybe_value_type.has_value())
            return {};
        auto value_type = maybe_value_type.value();

        if (value->op == CalculatedStyleValue::ProductOperation::Multiply) {
            // At *, check that at least one side is <number>.
            if (!(is_number(type) || is_number(value_type)))
                return {};
            // If both sides are <integer>, resolve to <integer>.
            if (type == CalculatedStyleValue::ResolvedType::Integer && value_type == CalculatedStyleValue::ResolvedType::Integer) {
                type = CalculatedStyleValue::ResolvedType::Integer;
            } else {
                // Otherwise, resolve to the type of the other side.
                if (is_number(type))
                    type = value_type;
            }

            continue;
        } else {
            VERIFY(value->op == CalculatedStyleValue::ProductOperation::Divide);
            // At /, check that the right side is <number>.
            if (!is_number(value_type))
                return {};
            // If the left side is <integer>, resolve to <number>.
            if (type == CalculatedStyleValue::ResolvedType::Integer) {
                type = CalculatedStyleValue::ResolvedType::Number;
            } else {
                // Otherwise, resolve to the type of the left side.
            }

            // FIXME: Division by zero makes the whole calc() expression invalid.
        }
    }
    return type;
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcProduct::resolved_type() const
{
    auto maybe_type = first_calc_value.resolved_type();
    if (!maybe_type.has_value())
        return {};
    auto type = maybe_type.value();
    return resolve_product_type(type, zero_or_more_additional_calc_values);
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcSumPartWithOperator::resolved_type() const
{
    return value->resolved_type();
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcNumberProduct::resolved_type() const
{
    auto maybe_type = first_calc_number_value.resolved_type();
    if (!maybe_type.has_value())
        return {};
    auto type = maybe_type.value();
    return resolve_product_type(type, zero_or_more_additional_calc_number_values);
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcNumberProductPartWithOperator::resolved_type() const
{
    return value.resolved_type();
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcNumberSumPartWithOperator::resolved_type() const
{
    return value->resolved_type();
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcProductPartWithOperator::resolved_type() const
{
    return value.visit(
        [](CalcValue const& calc_value) {
            return calc_value.resolved_type();
        },
        [](CalcNumberValue const& calc_number_value) {
            return calc_number_value.resolved_type();
        });
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcValue::resolved_type() const
{
    return value.visit(
        [](Number const& number) -> Optional<CalculatedStyleValue::ResolvedType> {
            return { number.is_integer() ? ResolvedType::Integer : ResolvedType::Number };
        },
        [](Angle const&) -> Optional<CalculatedStyleValue::ResolvedType> { return { ResolvedType::Angle }; },
        [](Frequency const&) -> Optional<CalculatedStyleValue::ResolvedType> { return { ResolvedType::Frequency }; },
        [](Length const&) -> Optional<CalculatedStyleValue::ResolvedType> { return { ResolvedType::Length }; },
        [](Percentage const&) -> Optional<CalculatedStyleValue::ResolvedType> { return { ResolvedType::Percentage }; },
        [](Time const&) -> Optional<CalculatedStyleValue::ResolvedType> { return { ResolvedType::Time }; },
        [](NonnullOwnPtr<CalcSum> const& sum) { return sum->resolved_type(); });
}

Optional<CalculatedStyleValue::ResolvedType> CalculatedStyleValue::CalcNumberValue::resolved_type() const
{
    return value.visit(
        [](Number const& number) -> Optional<CalculatedStyleValue::ResolvedType> {
            return { number.is_integer() ? ResolvedType::Integer : ResolvedType::Number };
        },
        [](NonnullOwnPtr<CalcNumberSum> const& sum) { return sum->resolved_type(); });
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcNumberValue::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    return value.visit(
        [&](Number const& number) -> CalculatedStyleValue::CalculationResult {
            return CalculatedStyleValue::CalculationResult { number };
        },
        [&](NonnullOwnPtr<CalcNumberSum> const& sum) -> CalculatedStyleValue::CalculationResult {
            return sum->resolve(layout_node, percentage_basis);
        });
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcValue::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    return value.visit(
        [&](NonnullOwnPtr<CalcSum> const& sum) -> CalculatedStyleValue::CalculationResult {
            return sum->resolve(layout_node, percentage_basis);
        },
        [&](auto const& v) -> CalculatedStyleValue::CalculationResult {
            return CalculatedStyleValue::CalculationResult { v };
        });
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcSum::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    auto value = first_calc_product->resolve(layout_node, percentage_basis);

    for (auto& additional_product : zero_or_more_additional_calc_products) {
        auto additional_value = additional_product->resolve(layout_node, percentage_basis);

        if (additional_product->op == CalculatedStyleValue::SumOperation::Add)
            value.add(additional_value, layout_node, percentage_basis);
        else if (additional_product->op == CalculatedStyleValue::SumOperation::Subtract)
            value.subtract(additional_value, layout_node, percentage_basis);
        else
            VERIFY_NOT_REACHED();
    }

    return value;
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcNumberSum::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    auto value = first_calc_number_product->resolve(layout_node, percentage_basis);

    for (auto& additional_product : zero_or_more_additional_calc_number_products) {
        auto additional_value = additional_product->resolve(layout_node, percentage_basis);

        if (additional_product->op == CSS::CalculatedStyleValue::SumOperation::Add)
            value.add(additional_value, layout_node, percentage_basis);
        else if (additional_product->op == CalculatedStyleValue::SumOperation::Subtract)
            value.subtract(additional_value, layout_node, percentage_basis);
        else
            VERIFY_NOT_REACHED();
    }

    return value;
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcProduct::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    auto value = first_calc_value.resolve(layout_node, percentage_basis);

    for (auto& additional_value : zero_or_more_additional_calc_values) {
        additional_value->value.visit(
            [&](CalculatedStyleValue::CalcValue const& calc_value) {
                VERIFY(additional_value->op == CalculatedStyleValue::ProductOperation::Multiply);
                auto resolved_value = calc_value.resolve(layout_node, percentage_basis);
                value.multiply_by(resolved_value, layout_node);
            },
            [&](CalculatedStyleValue::CalcNumberValue const& calc_number_value) {
                VERIFY(additional_value->op == CalculatedStyleValue::ProductOperation::Divide);
                auto resolved_calc_number_value = calc_number_value.resolve(layout_node, percentage_basis);
                // FIXME: Checking for division by 0 should happen during parsing.
                VERIFY(resolved_calc_number_value.value().get<Number>().value() != 0.0f);
                value.divide_by(resolved_calc_number_value, layout_node);
            });
    }

    return value;
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcNumberProduct::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    auto value = first_calc_number_value.resolve(layout_node, percentage_basis);

    for (auto& additional_number_value : zero_or_more_additional_calc_number_values) {
        auto additional_value = additional_number_value->resolve(layout_node, percentage_basis);

        if (additional_number_value->op == CalculatedStyleValue::ProductOperation::Multiply)
            value.multiply_by(additional_value, layout_node);
        else if (additional_number_value->op == CalculatedStyleValue::ProductOperation::Divide)
            value.divide_by(additional_value, layout_node);
        else
            VERIFY_NOT_REACHED();
    }

    return value;
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcProductPartWithOperator::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    return value.visit(
        [&](CalcValue const& calc_value) {
            return calc_value.resolve(layout_node, percentage_basis);
        },
        [&](CalcNumberValue const& calc_number_value) {
            return calc_number_value.resolve(layout_node, percentage_basis);
        });
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcSumPartWithOperator::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    return value->resolve(layout_node, percentage_basis);
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcNumberProductPartWithOperator::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    return value.resolve(layout_node, percentage_basis);
}

CalculatedStyleValue::CalculationResult CalculatedStyleValue::CalcNumberSumPartWithOperator::resolve(Layout::Node const* layout_node, PercentageBasis const& percentage_basis) const
{
    return value->resolve(layout_node, percentage_basis);
}

ImageStyleValue::ImageStyleValue(AK::URL const& url)
    : AbstractImageStyleValue(Type::Image)
    , m_url(url)
{
}

void ImageStyleValue::load_any_resources(DOM::Document& document)
{
    if (resource())
        return;

    m_document = &document;
    auto request = LoadRequest::create_for_url_on_page(m_url, document.page());
    set_resource(ResourceLoader::the().load_resource(Resource::Type::Image, request));
}

void ImageStyleValue::resource_did_load()
{
    if (!m_document)
        return;
    // FIXME: Do less than a full repaint if possible?
    if (m_document && m_document->browsing_context())
        m_document->browsing_context()->set_needs_display();

    if (resource()->is_animated() && resource()->frame_count() > 1) {
        m_timer = Platform::Timer::create();
        m_timer->set_interval(resource()->frame_duration(0));
        m_timer->on_timeout = [this] { animate(); };
        m_timer->start();
    }
}

void ImageStyleValue::animate()
{
    m_current_frame_index = (m_current_frame_index + 1) % resource()->frame_count();
    auto current_frame_duration = resource()->frame_duration(m_current_frame_index);

    if (current_frame_duration != m_timer->interval())
        m_timer->restart(current_frame_duration);

    if (m_current_frame_index == resource()->frame_count() - 1) {
        ++m_loops_completed;
        if (m_loops_completed > 0 && m_loops_completed == resource()->loop_count())
            m_timer->stop();
    }

    if (on_animate)
        on_animate();
}

Gfx::Bitmap const* ImageStyleValue::bitmap(size_t frame_index) const
{
    if (!resource())
        return nullptr;
    return resource()->bitmap(frame_index);
}

ErrorOr<String> ImageStyleValue::to_string() const
{
    return serialize_a_url(m_url.to_deprecated_string());
}

bool ImageStyleValue::equals(StyleValue const& other) const
{
    if (type() != other.type())
        return false;
    return m_url == other.as_image().m_url;
}

Optional<CSSPixels> ImageStyleValue::natural_width() const
{
    if (auto* b = bitmap(0); b != nullptr)
        return b->width();
    return {};
}

Optional<CSSPixels> ImageStyleValue::natural_height() const
{
    if (auto* b = bitmap(0); b != nullptr)
        return b->height();
    return {};
}

void ImageStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering image_rendering) const
{
    if (auto* b = bitmap(m_current_frame_index); b != nullptr)
        context.painter().draw_scaled_bitmap(dest_rect.to_type<int>(), *b, bitmap(0)->rect(), 1.0f, to_gfx_scaling_mode(image_rendering));
}

static ErrorOr<void> serialize_color_stop_list(StringBuilder& builder, auto const& color_stop_list)
{
    bool first = true;
    for (auto const& element : color_stop_list) {
        if (!first)
            TRY(builder.try_append(", "sv));

        if (element.transition_hint.has_value())
            TRY(builder.try_appendff("{}, "sv, TRY(element.transition_hint->value.to_string())));

        TRY(serialize_a_srgb_value(builder, element.color_stop.color));
        for (auto position : Array { &element.color_stop.position, &element.color_stop.second_position }) {
            if (position->has_value())
                TRY(builder.try_appendff(" {}"sv, TRY((*position)->to_string())));
        }
        first = false;
    }
    return {};
}

ErrorOr<String> LinearGradientStyleValue::to_string() const
{
    StringBuilder builder;
    auto side_or_corner_to_string = [](SideOrCorner value) {
        switch (value) {
        case SideOrCorner::Top:
            return "top"sv;
        case SideOrCorner::Bottom:
            return "bottom"sv;
        case SideOrCorner::Left:
            return "left"sv;
        case SideOrCorner::Right:
            return "right"sv;
        case SideOrCorner::TopLeft:
            return "top left"sv;
        case SideOrCorner::TopRight:
            return "top right"sv;
        case SideOrCorner::BottomLeft:
            return "bottom left"sv;
        case SideOrCorner::BottomRight:
            return "bottom right"sv;
        default:
            VERIFY_NOT_REACHED();
        }
    };

    if (m_properties.gradient_type == GradientType::WebKit)
        TRY(builder.try_append("-webkit-"sv));
    if (is_repeating())
        TRY(builder.try_append("repeating-"sv));
    TRY(builder.try_append("linear-gradient("sv));
    TRY(m_properties.direction.visit(
        [&](SideOrCorner side_or_corner) -> ErrorOr<void> {
            return builder.try_appendff("{}{}, "sv, m_properties.gradient_type == GradientType::Standard ? "to "sv : ""sv, side_or_corner_to_string(side_or_corner));
        },
        [&](Angle const& angle) -> ErrorOr<void> {
            return builder.try_appendff("{}, "sv, TRY(angle.to_string()));
        }));

    TRY(serialize_color_stop_list(builder, m_properties.color_stop_list));
    TRY(builder.try_append(")"sv));
    return builder.to_string();
}

bool LinearGradientStyleValue::equals(StyleValue const& other_) const
{
    if (type() != other_.type())
        return false;
    auto& other = other_.as_linear_gradient();
    return m_properties == other.m_properties;
}

float LinearGradientStyleValue::angle_degrees(CSSPixelSize gradient_size) const
{
    auto corner_angle_degrees = [&] {
        return static_cast<float>(atan2(gradient_size.height().value(), gradient_size.width().value())) * 180 / AK::Pi<float>;
    };
    return m_properties.direction.visit(
        [&](SideOrCorner side_or_corner) {
            auto angle = [&] {
                switch (side_or_corner) {
                case SideOrCorner::Top:
                    return 0.0f;
                case SideOrCorner::Bottom:
                    return 180.0f;
                case SideOrCorner::Left:
                    return 270.0f;
                case SideOrCorner::Right:
                    return 90.0f;
                case SideOrCorner::TopRight:
                    return corner_angle_degrees();
                case SideOrCorner::BottomLeft:
                    return corner_angle_degrees() + 180.0f;
                case SideOrCorner::TopLeft:
                    return -corner_angle_degrees();
                case SideOrCorner::BottomRight:
                    return -(corner_angle_degrees() + 180.0f);
                default:
                    VERIFY_NOT_REACHED();
                }
            }();
            // Note: For unknowable reasons the angles are opposite on the -webkit- version
            if (m_properties.gradient_type == GradientType::WebKit)
                return angle + 180.0f;
            return angle;
        },
        [&](Angle const& angle) {
            return angle.to_degrees();
        });
}

void LinearGradientStyleValue::resolve_for_size(Layout::Node const& node, CSSPixelSize size) const
{
    if (m_resolved.has_value() && m_resolved->size == size)
        return;
    m_resolved = ResolvedData { Painting::resolve_linear_gradient_data(node, size, *this), size };
}

void LinearGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering) const
{
    VERIFY(m_resolved.has_value());
    Painting::paint_linear_gradient(context, dest_rect, m_resolved->data);
}

CSSPixelPoint PositionValue::resolved(Layout::Node const& node, CSSPixelRect const& rect) const
{
    // Note: A preset + a none default x/y_relative_to is impossible in the syntax (and makes little sense)
    CSSPixels x = horizontal_position.visit(
        [&](HorizontalPreset preset) -> CSSPixels {
            return rect.width() * [&] {
                switch (preset) {
                case HorizontalPreset::Left:
                    return 0.0f;
                case HorizontalPreset::Center:
                    return 0.5f;
                case HorizontalPreset::Right:
                    return 1.0f;
                default:
                    VERIFY_NOT_REACHED();
                }
            }();
        },
        [&](LengthPercentage length_percentage) -> CSSPixels {
            return length_percentage.resolved(node, Length::make_px(rect.width())).to_px(node);
        });
    CSSPixels y = vertical_position.visit(
        [&](VerticalPreset preset) -> CSSPixels {
            return rect.height() * [&] {
                switch (preset) {
                case VerticalPreset::Top:
                    return 0.0f;
                case VerticalPreset::Center:
                    return 0.5f;
                case VerticalPreset::Bottom:
                    return 1.0f;
                default:
                    VERIFY_NOT_REACHED();
                }
            }();
        },
        [&](LengthPercentage length_percentage) -> CSSPixels {
            return length_percentage.resolved(node, Length::make_px(rect.height())).to_px(node);
        });
    if (x_relative_to == HorizontalEdge::Right)
        x = rect.width() - x;
    if (y_relative_to == VerticalEdge::Bottom)
        y = rect.height() - y;
    return CSSPixelPoint { rect.x() + x, rect.y() + y };
}

ErrorOr<void> PositionValue::serialize(StringBuilder& builder) const
{
    // Note: This means our serialization with simplify any with explicit edges that are just `top left`.
    bool has_relative_edges = x_relative_to == HorizontalEdge::Right || y_relative_to == VerticalEdge::Bottom;
    if (has_relative_edges)
        TRY(builder.try_append(x_relative_to == HorizontalEdge::Left ? "left "sv : "right "sv));
    TRY(horizontal_position.visit(
        [&](HorizontalPreset preset) -> ErrorOr<void> {
            return builder.try_append([&] {
                switch (preset) {
                case HorizontalPreset::Left:
                    return "left"sv;
                case HorizontalPreset::Center:
                    return "center"sv;
                case HorizontalPreset::Right:
                    return "right"sv;
                default:
                    VERIFY_NOT_REACHED();
                }
            }());
        },
        [&](LengthPercentage length_percentage) -> ErrorOr<void> {
            return builder.try_appendff(TRY(length_percentage.to_string()));
        }));
    TRY(builder.try_append(' '));
    if (has_relative_edges)
        TRY(builder.try_append(y_relative_to == VerticalEdge::Top ? "top "sv : "bottom "sv));
    TRY(vertical_position.visit(
        [&](VerticalPreset preset) -> ErrorOr<void> {
            return builder.try_append([&] {
                switch (preset) {
                case VerticalPreset::Top:
                    return "top"sv;
                case VerticalPreset::Center:
                    return "center"sv;
                case VerticalPreset::Bottom:
                    return "bottom"sv;
                default:
                    VERIFY_NOT_REACHED();
                }
            }());
        },
        [&](LengthPercentage length_percentage) -> ErrorOr<void> {
            return builder.try_append(TRY(length_percentage.to_string()));
        }));
    return {};
}

ErrorOr<String> RadialGradientStyleValue::to_string() const
{
    StringBuilder builder;
    if (is_repeating())
        TRY(builder.try_append("repeating-"sv));
    TRY(builder.try_appendff("radial-gradient({} "sv,
        m_properties.ending_shape == EndingShape::Circle ? "circle"sv : "ellipse"sv));

    TRY(m_properties.size.visit(
        [&](Extent extent) -> ErrorOr<void> {
            return builder.try_append([&] {
                switch (extent) {
                case Extent::ClosestCorner:
                    return "closest-corner"sv;
                case Extent::ClosestSide:
                    return "closest-side"sv;
                case Extent::FarthestCorner:
                    return "farthest-corner"sv;
                case Extent::FarthestSide:
                    return "farthest-side"sv;
                default:
                    VERIFY_NOT_REACHED();
                }
            }());
        },
        [&](CircleSize const& circle_size) -> ErrorOr<void> {
            return builder.try_append(TRY(circle_size.radius.to_string()));
        },
        [&](EllipseSize const& ellipse_size) -> ErrorOr<void> {
            return builder.try_appendff("{} {}", TRY(ellipse_size.radius_a.to_string()), TRY(ellipse_size.radius_b.to_string()));
        }));

    if (m_properties.position != PositionValue::center()) {
        TRY(builder.try_appendff(" at "sv));
        TRY(m_properties.position.serialize(builder));
    }

    TRY(builder.try_append(", "sv));
    TRY(serialize_color_stop_list(builder, m_properties.color_stop_list));
    TRY(builder.try_append(')'));
    return builder.to_string();
}

Gfx::FloatSize RadialGradientStyleValue::resolve_size(Layout::Node const& node, Gfx::FloatPoint center, Gfx::FloatRect const& size) const
{
    auto const side_shape = [&](auto distance_function) {
        auto const distance_from = [&](float v, float a, float b, auto distance_function) {
            return distance_function(fabs(a - v), fabs(b - v));
        };
        auto x_dist = distance_from(center.x(), size.left(), size.right(), distance_function);
        auto y_dist = distance_from(center.y(), size.top(), size.bottom(), distance_function);
        if (m_properties.ending_shape == EndingShape::Circle) {
            auto dist = distance_function(x_dist, y_dist);
            return Gfx::FloatSize { dist, dist };
        } else {
            return Gfx::FloatSize { x_dist, y_dist };
        }
    };

    auto const closest_side_shape = [&] {
        return side_shape(AK::min<float>);
    };

    auto const farthest_side_shape = [&] {
        return side_shape(AK::max<float>);
    };

    auto const corner_distance = [&](auto distance_compare, Gfx::FloatPoint& corner) {
        auto top_left_distance = size.top_left().distance_from(center);
        auto top_right_distance = size.top_right().distance_from(center);
        auto bottom_right_distance = size.bottom_right().distance_from(center);
        auto bottom_left_distance = size.bottom_left().distance_from(center);
        auto distance = top_left_distance;
        if (distance_compare(top_right_distance, distance)) {
            corner = size.top_right();
            distance = top_right_distance;
        }
        if (distance_compare(bottom_right_distance, distance)) {
            corner = size.top_right();
            distance = bottom_right_distance;
        }
        if (distance_compare(bottom_left_distance, distance)) {
            corner = size.top_right();
            distance = bottom_left_distance;
        }
        return distance;
    };

    auto const closest_corner_distance = [&](Gfx::FloatPoint& corner) {
        return corner_distance([](float a, float b) { return a < b; }, corner);
    };

    auto const farthest_corner_distance = [&](Gfx::FloatPoint& corner) {
        return corner_distance([](float a, float b) { return a > b; }, corner);
    };

    auto const corner_shape = [&](auto corner_distance, auto get_shape) {
        Gfx::FloatPoint corner {};
        auto distance = corner_distance(corner);
        if (m_properties.ending_shape == EndingShape::Ellipse) {
            auto shape = get_shape();
            auto aspect_ratio = shape.width() / shape.height();
            auto p = corner - center;
            auto radius_a = AK::sqrt(p.y() * p.y() * aspect_ratio * aspect_ratio + p.x() * p.x());
            auto radius_b = radius_a / aspect_ratio;
            return Gfx::FloatSize { radius_a, radius_b };
        }
        return Gfx::FloatSize { distance, distance };
    };

    // https://w3c.github.io/csswg-drafts/css-images/#radial-gradient-syntax
    auto resolved_size = m_properties.size.visit(
        [&](Extent extent) {
            switch (extent) {
            case Extent::ClosestSide:
                // The ending shape is sized so that it exactly meets the side of the gradient box closest to the gradient’s center.
                // If the shape is an ellipse, it exactly meets the closest side in each dimension.
                return closest_side_shape();
            case Extent::ClosestCorner:
                // The ending shape is sized so that it passes through the corner of the gradient box closest to the gradient’s center.
                // If the shape is an ellipse, the ending shape is given the same aspect-ratio it would have if closest-side were specified
                return corner_shape(closest_corner_distance, closest_side_shape);
            case Extent::FarthestCorner:
                // Same as closest-corner, except the ending shape is sized based on the farthest corner.
                // If the shape is an ellipse, the ending shape is given the same aspect ratio it would have if farthest-side were specified.
                return corner_shape(farthest_corner_distance, farthest_side_shape);
            case Extent::FarthestSide:
                // Same as closest-side, except the ending shape is sized based on the farthest side(s).
                return farthest_side_shape();
            default:
                VERIFY_NOT_REACHED();
            }
        },
        [&](CircleSize const& circle_size) {
            auto radius = circle_size.radius.to_px(node);
            return Gfx::FloatSize { radius, radius };
        },
        [&](EllipseSize const& ellipse_size) {
            auto radius_a = ellipse_size.radius_a.resolved(node, CSS::Length::make_px(size.width())).to_px(node);
            auto radius_b = ellipse_size.radius_b.resolved(node, CSS::Length::make_px(size.height())).to_px(node);
            return Gfx::FloatSize { radius_a, radius_b };
        });

    // Handle degenerate cases
    // https://w3c.github.io/csswg-drafts/css-images/#degenerate-radials

    constexpr auto arbitrary_small_number = 1e-10;
    constexpr auto arbitrary_large_number = 1e10;

    // If the ending shape is a circle with zero radius:
    if (m_properties.ending_shape == EndingShape::Circle && resolved_size.is_empty()) {
        // Render as if the ending shape was a circle whose radius was an arbitrary very small number greater than zero.
        // This will make the gradient continue to look like a circle.
        return Gfx::FloatSize { arbitrary_small_number, arbitrary_small_number };
    }
    // If the ending shape has zero width (regardless of the height):
    if (resolved_size.width() <= 0) {
        // Render as if the ending shape was an ellipse whose height was an arbitrary very large number
        // and whose width was an arbitrary very small number greater than zero.
        // This will make the gradient look similar to a horizontal linear gradient that is mirrored across the center of the ellipse.
        // It also means that all color-stop positions specified with a percentage resolve to 0px.
        return Gfx::FloatSize { arbitrary_small_number, arbitrary_large_number };
    }
    // Otherwise, if the ending shape has zero height:
    if (resolved_size.height() <= 0) {
        // Render as if the ending shape was an ellipse whose width was an arbitrary very large number and whose height
        // was an arbitrary very small number greater than zero. This will make the gradient look like a solid-color image equal
        // to the color of the last color-stop, or equal to the average color of the gradient if it’s repeating.
        return Gfx::FloatSize { arbitrary_large_number, arbitrary_small_number };
    }
    return resolved_size;
}

void RadialGradientStyleValue::resolve_for_size(Layout::Node const& node, CSSPixelSize paint_size) const
{
    CSSPixelRect gradient_box { { 0, 0 }, paint_size };
    auto center = m_properties.position.resolved(node, gradient_box).to_type<float>();
    auto gradient_size = resolve_size(node, center, gradient_box.to_type<float>());
    if (m_resolved.has_value() && m_resolved->gradient_size == gradient_size)
        return;
    m_resolved = ResolvedData {
        Painting::resolve_radial_gradient_data(node, gradient_size.to_type<CSSPixels>(), *this),
        gradient_size,
        center,
    };
}

bool RadialGradientStyleValue::equals(StyleValue const& other) const
{
    if (type() != other.type())
        return false;
    auto& other_gradient = other.as_radial_gradient();
    return m_properties == other_gradient.m_properties;
}

void RadialGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering) const
{
    VERIFY(m_resolved.has_value());
    Painting::paint_radial_gradient(context, dest_rect, m_resolved->data,
        context.rounded_device_point(m_resolved->center.to_type<CSSPixels>()),
        context.rounded_device_size(m_resolved->gradient_size.to_type<CSSPixels>()));
}

ErrorOr<String> ConicGradientStyleValue::to_string() const
{
    StringBuilder builder;
    if (is_repeating())
        TRY(builder.try_append("repeating-"sv));
    TRY(builder.try_append("conic-gradient("sv));
    bool has_from_angle = false;
    bool has_at_position = false;
    if ((has_from_angle = m_properties.from_angle.to_degrees() != 0))
        TRY(builder.try_appendff("from {}", TRY(m_properties.from_angle.to_string())));
    if ((has_at_position = m_properties.position != PositionValue::center())) {
        if (has_from_angle)
            TRY(builder.try_append(' '));
        TRY(builder.try_appendff("at "sv));
        TRY(m_properties.position.serialize(builder));
    }
    if (has_from_angle || has_at_position)
        TRY(builder.try_append(", "sv));
    TRY(serialize_color_stop_list(builder, m_properties.color_stop_list));
    TRY(builder.try_append(')'));
    return builder.to_string();
}

void ConicGradientStyleValue::resolve_for_size(Layout::Node const& node, CSSPixelSize size) const
{
    if (!m_resolved.has_value())
        m_resolved = ResolvedData { Painting::resolve_conic_gradient_data(node, *this), {} };
    m_resolved->position = m_properties.position.resolved(node, CSSPixelRect { { 0, 0 }, size });
}

void ConicGradientStyleValue::paint(PaintContext& context, DevicePixelRect const& dest_rect, CSS::ImageRendering) const
{
    VERIFY(m_resolved.has_value());
    Painting::paint_conic_gradient(context, dest_rect, m_resolved->data, context.rounded_device_point(m_resolved->position));
}

bool ConicGradientStyleValue::equals(StyleValue const& other) const
{
    if (type() != other.type())
        return false;
    auto& other_gradient = other.as_conic_gradient();
    return m_properties == other_gradient.m_properties;
}

float ConicGradientStyleValue::angle_degrees() const
{
    return m_properties.from_angle.to_degrees();
}

ErrorOr<String> ListStyleStyleValue::to_string() const
{
    return String::formatted("{} {} {}", TRY(m_properties.position->to_string()), TRY(m_properties.image->to_string()), TRY(m_properties.style_type->to_string()));
}

ErrorOr<String> NumericStyleValue::to_string() const
{
    return m_value.visit(
        [](auto value) {
            return String::formatted("{}", value);
        });
}

ErrorOr<String> OverflowStyleValue::to_string() const
{
    return String::formatted("{} {}", TRY(m_properties.overflow_x->to_string()), TRY(m_properties.overflow_y->to_string()));
}

ErrorOr<String> PercentageStyleValue::to_string() const
{
    return m_percentage.to_string();
}

ErrorOr<String> PositionStyleValue::to_string() const
{
    auto to_string = [](PositionEdge edge) {
        switch (edge) {
        case PositionEdge::Left:
            return "left";
        case PositionEdge::Right:
            return "right";
        case PositionEdge::Top:
            return "top";
        case PositionEdge::Bottom:
            return "bottom";
        }
        VERIFY_NOT_REACHED();
    };

    return String::formatted("{} {} {} {}", to_string(m_properties.edge_x), TRY(m_properties.offset_x.to_string()), to_string(m_properties.edge_y), TRY(m_properties.offset_y.to_string()));
}

ErrorOr<String> RectStyleValue::to_string() const
{
    return String::formatted("rect({} {} {} {})", m_rect.top_edge, m_rect.right_edge, m_rect.bottom_edge, m_rect.left_edge);
}

ErrorOr<String> ShadowStyleValue::to_string() const
{
    StringBuilder builder;
    TRY(builder.try_appendff("{} {} {} {} {}", m_properties.color.to_deprecated_string(), TRY(m_properties.offset_x.to_string()), TRY(m_properties.offset_y.to_string()), TRY(m_properties.blur_radius.to_string()), TRY(m_properties.spread_distance.to_string())));
    if (m_properties.placement == ShadowPlacement::Inner)
        TRY(builder.try_append(" inset"sv));
    return builder.to_string();
}

ErrorOr<String> TextDecorationStyleValue::to_string() const
{
    return String::formatted("{} {} {} {}", TRY(m_properties.line->to_string()), TRY(m_properties.thickness->to_string()), TRY(m_properties.style->to_string()), TRY(m_properties.color->to_string()));
}

ErrorOr<String> TransformationStyleValue::to_string() const
{
    StringBuilder builder;
    TRY(builder.try_append(CSS::to_string(m_properties.transform_function)));
    TRY(builder.try_append('('));
    for (size_t i = 0; i < m_properties.values.size(); ++i) {
        TRY(builder.try_append(TRY(m_properties.values[i]->to_string())));
        if (i != m_properties.values.size() - 1)
            TRY(builder.try_append(", "sv));
    }
    TRY(builder.try_append(')'));

    return builder.to_string();
}

bool TransformationStyleValue::Properties::operator==(Properties const& other) const
{
    return transform_function == other.transform_function && values.span() == other.values.span();
}

ErrorOr<String> UnresolvedStyleValue::to_string() const
{
    StringBuilder builder;
    for (auto& value : m_values)
        TRY(builder.try_append(TRY(value.to_string())));
    return builder.to_string();
}

bool UnresolvedStyleValue::equals(StyleValue const& other) const
{
    if (type() != other.type())
        return false;
    // This is a case where comparing the strings actually makes sense.
    return to_string().release_value_but_fixme_should_propagate_errors() == other.to_string().release_value_but_fixme_should_propagate_errors();
}

bool StyleValueList::Properties::operator==(Properties const& other) const
{
    return separator == other.separator && values.span() == other.values.span();
}

ErrorOr<String> StyleValueList::to_string() const
{
    auto separator = ""sv;
    switch (m_properties.separator) {
    case Separator::Space:
        separator = " "sv;
        break;
    case Separator::Comma:
        separator = ", "sv;
        break;
    default:
        VERIFY_NOT_REACHED();
    }

    StringBuilder builder;
    for (size_t i = 0; i < m_properties.values.size(); ++i) {
        TRY(builder.try_append(TRY(m_properties.values[i]->to_string())));
        if (i != m_properties.values.size() - 1)
            TRY(builder.try_append(separator));
    }
    return builder.to_string();
}


ValueComparingNonnullRefPtr<RectStyleValue> RectStyleValue::create(EdgeRect rect)
{
    return adopt_ref(*new RectStyleValue(rect));
}

ValueComparingNonnullRefPtr<LengthStyleValue> LengthStyleValue::create(Length const& length)
{
    if (length.is_auto()) {
        static auto value = adopt_ref(*new LengthStyleValue(CSS::Length::make_auto()));
        return value;
    }
    if (length.is_px()) {
        if (length.raw_value() == 0) {
            static auto value = adopt_ref(*new LengthStyleValue(CSS::Length::make_px(0)));
            return value;
        }
        if (length.raw_value() == 1) {
            static auto value = adopt_ref(*new LengthStyleValue(CSS::Length::make_px(1)));
            return value;
        }
    }
    return adopt_ref(*new LengthStyleValue(length));
}

Optional<CSS::Length> absolutized_length(CSS::Length const& length, CSSPixelRect const& viewport_rect, Gfx::FontPixelMetrics const& font_metrics, CSSPixels font_size, CSSPixels root_font_size, CSSPixels line_height, CSSPixels root_line_height)
{
    if (length.is_px())
        return {};
    if (length.is_absolute() || length.is_relative()) {
        auto px = length.to_px(viewport_rect, font_metrics, font_size, root_font_size, line_height, root_line_height);
        return CSS::Length::make_px(px);
    }
    return {};
}

ValueComparingNonnullRefPtr<StyleValue const> StyleValue::absolutized(CSSPixelRect const&, Gfx::FontPixelMetrics const&, CSSPixels, CSSPixels, CSSPixels, CSSPixels) const
{
    return *this;
}

ValueComparingNonnullRefPtr<StyleValue const> LengthStyleValue::absolutized(CSSPixelRect const& viewport_rect, Gfx::FontPixelMetrics const& font_metrics, CSSPixels font_size, CSSPixels root_font_size, CSSPixels line_height, CSSPixels root_line_height) const
{
    if (auto length = absolutized_length(m_length, viewport_rect, font_metrics, font_size, root_font_size, line_height, root_line_height); length.has_value())
        return LengthStyleValue::create(length.release_value());
    return *this;
}

ValueComparingNonnullRefPtr<StyleValue const> ShadowStyleValue::absolutized(CSSPixelRect const& viewport_rect, Gfx::FontPixelMetrics const& font_metrics, CSSPixels font_size, CSSPixels root_font_size, CSSPixels line_height, CSSPixels root_line_height) const
{
    auto absolutized_offset_x = absolutized_length(m_properties.offset_x, viewport_rect, font_metrics, font_size, root_font_size, line_height, root_line_height).value_or(m_properties.offset_x);
    auto absolutized_offset_y = absolutized_length(m_properties.offset_y, viewport_rect, font_metrics, font_size, root_font_size, line_height, root_line_height).value_or(m_properties.offset_y);
    auto absolutized_blur_radius = absolutized_length(m_properties.blur_radius, viewport_rect, font_metrics, font_size, root_font_size, line_height, root_line_height).value_or(m_properties.blur_radius);
    auto absolutized_spread_distance = absolutized_length(m_properties.spread_distance, viewport_rect, font_metrics, font_size, root_font_size, line_height, root_line_height).value_or(m_properties.spread_distance);
    return ShadowStyleValue::create(m_properties.color, absolutized_offset_x, absolutized_offset_y, absolutized_blur_radius, absolutized_spread_distance, m_properties.placement);
}

bool CalculatedStyleValue::contains_percentage() const
{
    return m_expression->contains_percentage();
}

bool CalculatedStyleValue::CalcSum::contains_percentage() const
{
    if (first_calc_product->contains_percentage())
        return true;
    for (auto& part : zero_or_more_additional_calc_products) {
        if (part->contains_percentage())
            return true;
    }
    return false;
}

bool CalculatedStyleValue::CalcSumPartWithOperator::contains_percentage() const
{
    return value->contains_percentage();
}

bool CalculatedStyleValue::CalcProduct::contains_percentage() const
{
    if (first_calc_value.contains_percentage())
        return true;
    for (auto& part : zero_or_more_additional_calc_values) {
        if (part->contains_percentage())
            return true;
    }
    return false;
}

bool CalculatedStyleValue::CalcProductPartWithOperator::contains_percentage() const
{
    return value.visit(
        [](CalcValue const& value) { return value.contains_percentage(); },
        [](CalcNumberValue const&) { return false; });
}

bool CalculatedStyleValue::CalcValue::contains_percentage() const
{
    return value.visit(
        [](Percentage const&) { return true; },
        [](NonnullOwnPtr<CalcSum> const& sum) { return sum->contains_percentage(); },
        [](auto const&) { return false; });
}

bool calculated_style_value_contains_percentage(CalculatedStyleValue const& value)
{
    return value.contains_percentage();
}

}