/*
 * Copyright (c) 2018-2024, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2021, Tobias Christiansen <tobyase@serenityos.org>
 * Copyright (c) 2021-2025, Sam Atkins <sam@ladybird.org>
 * Copyright (c) 2022-2023, MacDue <macdue@dueutil.tech>
 * Copyright (c) 2024, Steffen T. Larssen <dudedbz@gmail.com>
 * Copyright (c) 2024-2025, Bastiaan van der Plaat <bastiaan.v.d.plaat@gmail.com>
 * Copyright (c) 2025, Jelle Raaijmakers <jelle@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/StringBuilder.h>
#include <LibGfx/Matrix4x4.h>
#include <LibWeb/CSS/CSSMatrixComponent.h>
#include <LibWeb/CSS/CSSPerspective.h>
#include <LibWeb/CSS/CSSRotate.h>
#include <LibWeb/CSS/CSSScale.h>
#include <LibWeb/CSS/CSSSkew.h>
#include <LibWeb/CSS/CSSSkewX.h>
#include <LibWeb/CSS/CSSSkewY.h>
#include <LibWeb/CSS/CSSTransformComponent.h>
#include <LibWeb/CSS/CSSTranslate.h>
#include <LibWeb/CSS/CSSUnitValue.h>
#include <LibWeb/CSS/PropertyID.h>
#include <LibWeb/CSS/Serialize.h>
#include <LibWeb/CSS/StyleValues/AngleStyleValue.h>
#include <LibWeb/CSS/StyleValues/CalculatedStyleValue.h>
#include <LibWeb/CSS/StyleValues/KeywordStyleValue.h>
#include <LibWeb/CSS/StyleValues/LengthStyleValue.h>
#include <LibWeb/CSS/StyleValues/NumberStyleValue.h>
#include <LibWeb/CSS/StyleValues/PercentageStyleValue.h>
#include <LibWeb/CSS/StyleValues/TransformationStyleValue.h>
#include <LibWeb/Geometry/DOMMatrix.h>
#include <LibWeb/Painting/Paintable.h>

namespace Web::CSS {

ValueComparingNonnullRefPtr<TransformationStyleValue const> TransformationStyleValue::identity_transformation(
    TransformFunction transform_function)
{
    // https://drafts.csswg.org/css-transforms-1/#identity-transform-function
    // A transform function that is equivalent to a identity 4x4 matrix (see Mathematical Description of Transform
    // Functions). Examples for identity transform functions are translate(0), translateX(0), translateY(0), scale(1),
    // scaleX(1), scaleY(1), rotate(0), skew(0, 0), skewX(0), skewY(0) and matrix(1, 0, 0, 1, 0, 0).

    // https://drafts.csswg.org/css-transforms-2/#identity-transform-function
    // In addition to the identity transform function in CSS Transforms, examples for identity transform functions
    // include translate3d(0, 0, 0), translateZ(0), scaleZ(1), rotate3d(1, 1, 1, 0), rotateX(0), rotateY(0), rotateZ(0)
    // and matrix3d(1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1). A special case is perspective: perspective(none).
    // The value of m34 becomes infinitesimal small and the transform function is therefore assumed to be equal to the
    // identity matrix.

    auto identity_parameters = [&] -> StyleValueVector {
        auto const number_zero = NumberStyleValue::create(0.);
        auto const number_one = NumberStyleValue::create(1.);

        switch (transform_function) {
        case TransformFunction::Matrix:
            return { number_one, number_zero, number_zero, number_one, number_zero, number_zero };
        case TransformFunction::Matrix3d:
            return { number_one, number_zero, number_zero, number_zero,
                number_zero, number_one, number_zero, number_zero,
                number_zero, number_zero, number_one, number_zero,
                number_zero, number_zero, number_zero, number_one };
        case TransformFunction::Perspective:
            return { KeywordStyleValue::create(Keyword::None) };
        case TransformFunction::Rotate:
        case TransformFunction::RotateX:
        case TransformFunction::RotateY:
        case TransformFunction::RotateZ:
        case TransformFunction::Skew:
        case TransformFunction::SkewX:
        case TransformFunction::SkewY:
            return { AngleStyleValue::create(Angle::make_degrees(0.)) };
        case TransformFunction::Rotate3d:
            return { number_one, number_one, number_one, AngleStyleValue::create(Angle::make_degrees(0.)) };
        case TransformFunction::Translate:
        case TransformFunction::TranslateX:
        case TransformFunction::TranslateY:
        case TransformFunction::TranslateZ:
            return { LengthStyleValue::create(Length::make_px(0.)) };
        case TransformFunction::Translate3d:
            return {
                LengthStyleValue::create(Length::make_px(0.)),
                LengthStyleValue::create(Length::make_px(0.)),
                LengthStyleValue::create(Length::make_px(0.)),
            };
        case TransformFunction::Scale:
        case TransformFunction::ScaleX:
        case TransformFunction::ScaleY:
        case TransformFunction::ScaleZ:
            return { number_one };
        case TransformFunction::Scale3d:
            return { number_one, number_one, number_one };
        }
        VERIFY_NOT_REACHED();
    };
    return create(PropertyID::Transform, transform_function, identity_parameters());
}

bool TransformationStyleValue::can_be_converted_to_matrix_without_reference_box() const
{
    auto function_metadata = transform_function_metadata(m_properties.transform_function);

    for (size_t i = 0; i < m_properties.values.size(); i++) {
        auto const& value = m_properties.values[i];

        if (value->is_length() && !value->as_length().length().is_absolute())
            return false;

        // NB: At time of writing the only calculated values that can't be fully simplified are those which either
        //     contain relative lengths or length-percentage mixes, both of which are disallowed. This may change
        //     in the future if transform functions support other dimension percentage mixes (i.e. AnglePercentage).
        if (value->is_calculated() && !value->as_calculated().is_fully_simplified())
            return false;

        auto value_type = function_metadata.parameters[i].type;

        if (value_type == CSS::TransformFunctionParameterType::LengthPercentage) {
            if (value->is_percentage())
                return false;

            if (value->is_calculated() && value->as_calculated().contains_percentage())
                return false;
        }

        if (first_is_one_of(value_type, CSS::TransformFunctionParameterType::Number, CSS::TransformFunctionParameterType::NumberPercentage)) {
            if (value->is_tree_counting_function())
                return false;
        }
    }

    return true;
}

FloatMatrix4x4 TransformationStyleValue::to_matrix(Optional<Painting::Paintable const&> paintable_box) const
{
    auto count = m_properties.values.size();
    auto function_metadata = transform_function_metadata(m_properties.transform_function);

    auto get_value = [&](size_t argument_index, Optional<CSSPixels> reference_length = {}) -> float {
        auto const& transformation_value = *m_properties.values[argument_index];

        switch (function_metadata.parameters[argument_index].type) {
        case TransformFunctionParameterType::Angle:
            return Angle::from_style_value(transformation_value, {}).to_radians();
        case TransformFunctionParameterType::Length:
        case TransformFunctionParameterType::LengthNone:
        case TransformFunctionParameterType::LengthPercentage:
            return Length::from_style_value(transformation_value, reference_length.map([](CSSPixels px) { return Length::make_px(px); })).absolute_length_to_px().to_float();
        case TransformFunctionParameterType::Number:
        case TransformFunctionParameterType::NumberPercentage:
            return number_from_style_value(transformation_value, 1);
        }

        VERIFY_NOT_REACHED();
    };

    Optional<CSSPixels> width;
    Optional<CSSPixels> height;
    if (paintable_box.has_value()) {
        auto reference_box = paintable_box->transform_reference_box();
        width = reference_box.width();
        height = reference_box.height();
    }

    switch (m_properties.transform_function) {
    case TransformFunction::Perspective:
        // https://drafts.csswg.org/css-transforms-2/#perspective
        if (count == 1) {
            if (m_properties.values.first()->to_keyword() == Keyword::None)
                return FloatMatrix4x4::identity();

            // FIXME: Add support for the 'perspective-origin' CSS property.
            auto distance = get_value(0);
            // If the depth value is less than '1px', it must be treated as '1px' for the purpose of rendering, for
            // computing the resolved value of 'transform', and when used as the endpoint of interpolation.
            // Note: The intent of the above rules on values less than '1px' is that they cover the cases where
            // the 'perspective()' function needs to be converted into a matrix.
            return Gfx::perspective_matrix(max(distance, 1));
        }
        break;
    case TransformFunction::Matrix:
        if (count == 6)
            return FloatMatrix4x4(get_value(0), get_value(2), 0, get_value(4),
                get_value(1), get_value(3), 0, get_value(5),
                0, 0, 1, 0,
                0, 0, 0, 1);
        break;
    case TransformFunction::Matrix3d:
        if (count == 16)
            return FloatMatrix4x4(get_value(0), get_value(4), get_value(8), get_value(12),
                get_value(1), get_value(5), get_value(9), get_value(13),
                get_value(2), get_value(6), get_value(10), get_value(14),
                get_value(3), get_value(7), get_value(11), get_value(15));
        break;
    case TransformFunction::Translate:
        if (count == 1)
            return Gfx::translation_matrix(Vector3 { get_value(0, width), 0.f, 0.f });
        if (count == 2)
            return Gfx::translation_matrix(Vector3 { get_value(0, width), get_value(1, height), 0.f });
        break;
    case TransformFunction::Translate3d:
        return Gfx::translation_matrix(Vector3 { get_value(0, width), get_value(1, height), get_value(2) });
    case TransformFunction::TranslateX:
        if (count == 1)
            return Gfx::translation_matrix(Vector3 { get_value(0, width), 0.f, 0.f });
        break;
    case TransformFunction::TranslateY:
        if (count == 1)
            return Gfx::translation_matrix(Vector3 { 0.f, get_value(0, height), 0.f });
        break;
    case TransformFunction::TranslateZ:
        if (count == 1)
            return Gfx::translation_matrix(Vector3 { 0.f, 0.f, get_value(0) });
        break;
    case TransformFunction::Scale:
        if (count == 1) {
            auto scale = get_value(0);
            return Gfx::scale_matrix(Vector3 { scale, scale, 1.f });
        }
        if (count == 2)
            return Gfx::scale_matrix(Vector3 { get_value(0), get_value(1), 1.f });
        break;
    case TransformFunction::Scale3d:
        if (count == 3)
            return Gfx::scale_matrix(Vector3 { get_value(0), get_value(1), get_value(2) });
        break;
    case TransformFunction::ScaleX:
        if (count == 1)
            return Gfx::scale_matrix(Vector3 { get_value(0), 1.f, 1.f });
        break;
    case TransformFunction::ScaleY:
        if (count == 1)
            return Gfx::scale_matrix(Vector3 { 1.f, get_value(0), 1.f });
        break;
    case TransformFunction::ScaleZ:
        if (count == 1)
            return Gfx::scale_matrix(Vector3 { 1.f, 1.f, get_value(0) });
        break;
    case TransformFunction::Rotate3d:
        if (count == 4) {
            auto axis = FloatVector3 { get_value(0), get_value(1), get_value(2) };
            auto epsilon = 1e-5f;
            if (axis.length() < epsilon)
                return FloatMatrix4x4::identity();
            return Gfx::rotation_matrix(axis.normalized(), get_value(3));
        }
        break;
    case TransformFunction::RotateX:
        if (count == 1)
            return Gfx::rotation_matrix({ 1.f, 0.f, 0.f }, get_value(0));
        break;
    case TransformFunction::RotateY:
        if (count == 1)
            return Gfx::rotation_matrix({ 0.f, 1.f, 0.f }, get_value(0));
        break;
    case TransformFunction::Rotate:
    case TransformFunction::RotateZ:
        if (count == 1)
            return Gfx::rotation_matrix({ 0.f, 0.f, 1.f }, get_value(0));
        break;
    case TransformFunction::Skew:
        if (count == 1)
            return FloatMatrix4x4(1, tanf(get_value(0)), 0, 0,
                0, 1, 0, 0,
                0, 0, 1, 0,
                0, 0, 0, 1);
        if (count == 2)
            return FloatMatrix4x4(1, tanf(get_value(0)), 0, 0,
                tanf(get_value(1)), 1, 0, 0,
                0, 0, 1, 0,
                0, 0, 0, 1);
        break;
    case TransformFunction::SkewX:
        if (count == 1)
            return FloatMatrix4x4(1, tanf(get_value(0)), 0, 0,
                0, 1, 0, 0,
                0, 0, 1, 0,
                0, 0, 0, 1);
        break;
    case TransformFunction::SkewY:
        if (count == 1)
            return FloatMatrix4x4(1, 0, 0, 0,
                tanf(get_value(0)), 1, 0, 0,
                0, 0, 1, 0,
                0, 0, 0, 1);
        break;
    }
    dbgln_if(LIBWEB_CSS_DEBUG, "FIXME: Unhandled transformation function {} with {} arguments", CSS::to_string(m_properties.transform_function), m_properties.values.size());
    return FloatMatrix4x4::identity();
}

void TransformationStyleValue::serialize(StringBuilder& builder, SerializationMode mode) const
{
    // https://drafts.csswg.org/css-transforms-2/#individual-transform-serialization
    if (m_properties.property == PropertyID::Rotate) {
        auto resolve_to_number = [](ValueComparingNonnullRefPtr<StyleValue const> const& value) -> Optional<double> {
            if (value->is_number())
                return value->as_number().number();
            if (value->is_calculated() && value->as_calculated().resolves_to_number())
                return value->as_calculated().resolve_number({});

            VERIFY_NOT_REACHED();
        };

        // NOTE: Serialize simple rotations directly.
        switch (m_properties.transform_function) {
            // If the axis is parallel with the x or y axes, it must serialize as the appropriate keyword.
        case TransformFunction::RotateX:
            builder.append("x "sv);
            m_properties.values[0]->serialize(builder, mode);
            return;
        case TransformFunction::RotateY:
            builder.append("y "sv);
            m_properties.values[0]->serialize(builder, mode);
            return;

            // If a rotation about the z axis (that is, in 2D) is specified, the property must serialize as just an <angle>.
        case TransformFunction::Rotate:
        case TransformFunction::RotateZ:
            m_properties.values[0]->serialize(builder, mode);
            return;

        default:
            break;
        }

        auto& rotation_x = m_properties.values[0];
        auto& rotation_y = m_properties.values[1];
        auto& rotation_z = m_properties.values[2];
        auto& angle = m_properties.values[3];

        auto x_value = resolve_to_number(rotation_x).value_or(0);
        auto y_value = resolve_to_number(rotation_y).value_or(0);
        auto z_value = resolve_to_number(rotation_z).value_or(0);

        // If the axis is parallel with the x or y axes, it must serialize as the appropriate keyword.
        if (x_value > 0.0 && y_value == 0 && z_value == 0) {
            builder.append("x "sv);
            angle->serialize(builder, mode);
            return;
        }

        if (x_value == 0 && y_value > 0.0 && z_value == 0) {
            builder.append("y "sv);
            angle->serialize(builder, mode);
            return;
        }

        // If a rotation about the z axis (that is, in 2D) is specified, the property must serialize as just an <angle>.
        if (x_value == 0 && y_value == 0 && z_value > 0.0) {
            angle->serialize(builder, mode);
            return;
        }

        // It must serialize as the keyword none if and only if none was originally specified.
        // NOTE: This is handled by returning a keyword from the parser.

        // If any other rotation is specified, the property must serialize with an axis specified.
        rotation_x->serialize(builder, mode);
        builder.append(' ');
        rotation_y->serialize(builder, mode);
        builder.append(' ');
        rotation_z->serialize(builder, mode);
        builder.append(' ');
        angle->serialize(builder, mode);
        return;
    }
    if (m_properties.property == PropertyID::Scale) {
        auto resolve_to_string = [mode](StyleValue const& value) -> String {
            Optional<double> raw_value;

            if (value.is_number())
                raw_value = value.as_number().number();
            if (value.is_percentage())
                raw_value = value.as_percentage().percentage().as_fraction();
            if (value.is_calculated()) {
                if (value.as_calculated().resolves_to_number()) {
                    if (auto resolved = value.as_calculated().resolve_number({}); resolved.has_value())
                        raw_value = *resolved;
                }
                if (value.as_calculated().resolves_to_percentage()) {
                    if (auto resolved = value.as_calculated().resolve_percentage({}); resolved.has_value())
                        raw_value = resolved->as_fraction();
                }
            }

            if (!raw_value.has_value())
                return value.to_string(mode);

            return serialize_a_number(*raw_value);
        };

        auto x_value = resolve_to_string(m_properties.values[0]);
        auto y_value = resolve_to_string(m_properties.values[1]);
        Optional<String> z_value;
        if (m_properties.values.size() == 3 && (!m_properties.values[2]->is_number() || m_properties.values[2]->as_number().number() != 1))
            z_value = resolve_to_string(m_properties.values[2]);

        builder.append(x_value);
        if (x_value != y_value || (z_value.has_value() && *z_value != "1"sv)) {
            builder.append(" "sv);
            builder.append(y_value);
        }
        if (z_value.has_value() && *z_value != "1"sv) {
            builder.append(" "sv);
            builder.append(z_value.value());
        }
        return;
    }
    if (m_properties.property == PropertyID::Translate) {
        auto resolve_to_string = [mode](StyleValue const& value) -> Optional<String> {
            auto string_value = value.to_string(mode);

            if (string_value == "0px"_string)
                return {};

            return string_value;
        };

        auto x_value = resolve_to_string(m_properties.values[0]);
        auto y_value = resolve_to_string(m_properties.values[1]);
        Optional<String> z_value;
        if (m_properties.values.size() == 3 && (!m_properties.values[2]->is_length() || m_properties.values[2]->as_length().length() != Length::make_px(0)))
            z_value = resolve_to_string(m_properties.values[2]);

        builder.append(x_value.value_or("0px"_string));
        if (y_value.has_value() || z_value.has_value()) {
            builder.append(" "sv);
            builder.append(y_value.value_or("0px"_string));
        }
        if (z_value.has_value()) {
            builder.append(" "sv);
            builder.append(z_value.value());
        }
        return;
    }

    builder.append(CSS::to_string(m_properties.transform_function));
    builder.append('(');
    for (size_t i = 0; i < m_properties.values.size(); ++i) {
        auto const& value = m_properties.values[i];

        // https://www.w3.org/TR/css-transforms-2/#individual-transforms
        // A <percentage> is equivalent to a <number>, for example scale: 100% is equivalent to scale: 1.
        // Numbers are used during serialization of specified and computed values.
        if ((m_properties.transform_function == CSS::TransformFunction::Scale
                || m_properties.transform_function == CSS::TransformFunction::Scale3d
                || m_properties.transform_function == CSS::TransformFunction::ScaleX
                || m_properties.transform_function == CSS::TransformFunction::ScaleY
                || m_properties.transform_function == CSS::TransformFunction::ScaleZ)
            && value->is_percentage()) {
            builder.append(String::number(value->as_percentage().percentage().as_fraction()));
        } else {
            value->serialize(builder, mode);
        }

        if (i != m_properties.values.size() - 1)
            builder.append(", "sv);
    }
    builder.append(')');
}

// https://drafts.css-houdini.org/css-typed-om-1/#reify-a-transform-function
GC::Ptr<CSSTransformComponent> TransformationStyleValue::reify_a_transform_function(JS::Realm& realm) const
{
    auto reify_numeric_argument = [&](size_t index) {
        return GC::Ref { as<CSSNumericValue>(*m_properties.values[index]->reify(realm, {})) };
    };
    auto reify_0 = [&] { return CSSUnitValue::create(realm, 0, "number"_utf16_fly_string); };
    auto reify_1 = [&] { return CSSUnitValue::create(realm, 1, "number"_utf16_fly_string); };
    auto reify_0px = [&] { return CSSUnitValue::create(realm, 0, "px"_utf16_fly_string); };
    auto reify_0deg = [&] { return CSSUnitValue::create(realm, 0, "deg"_utf16_fly_string); };

    // To reify a <transform-function> func, perform the appropriate set of steps below, based on func:
    switch (m_properties.transform_function) {
    // -> matrix()
    // -> matrix3d()
    //    1. Return a new CSSMatrixComponent object, whose matrix internal slot is set to a 4x4 matrix representing the
    //       same information as func, and whose is2D internal slot is true if func is matrix(), and false otherwise.
    case TransformFunction::Matrix:
    case TransformFunction::Matrix3d: {
        if (!can_be_converted_to_matrix_without_reference_box())
            return nullptr;

        auto transform_as_matrix = to_matrix({});
        auto matrix = Geometry::DOMMatrix::create(realm);
        matrix->set_m11(transform_as_matrix[0, 0]);
        matrix->set_m12(transform_as_matrix[1, 0]);
        matrix->set_m13(transform_as_matrix[2, 0]);
        matrix->set_m14(transform_as_matrix[3, 0]);
        matrix->set_m21(transform_as_matrix[0, 1]);
        matrix->set_m22(transform_as_matrix[1, 1]);
        matrix->set_m23(transform_as_matrix[2, 1]);
        matrix->set_m24(transform_as_matrix[3, 1]);
        matrix->set_m31(transform_as_matrix[0, 2]);
        matrix->set_m32(transform_as_matrix[1, 2]);
        matrix->set_m33(transform_as_matrix[2, 2]);
        matrix->set_m34(transform_as_matrix[3, 2]);
        matrix->set_m41(transform_as_matrix[0, 3]);
        matrix->set_m42(transform_as_matrix[1, 3]);
        matrix->set_m43(transform_as_matrix[2, 3]);
        matrix->set_m44(transform_as_matrix[3, 3]);

        auto is_2d = m_properties.transform_function == TransformFunction::Matrix ? CSSTransformComponent::Is2D::Yes : CSSTransformComponent::Is2D::No;
        return CSSMatrixComponent::create(realm, is_2d, matrix);
    }

    // -> translate()
    // -> translateX()
    // -> translateY()
    // -> translate3d()
    // -> translateZ()
    //    1. Return a new CSSTranslate object, whose x, y, and z internal slots are set to the reification of the
    //       specified x/y/z offsets, or the reification of 0px if not specified in func, and whose is2D internal slot
    //       is true if func is translate(), translateX(), or translateY(), and false otherwise.
    case TransformFunction::Translate: {
        // NB: Default y to 0px if it's not specified.
        auto y = m_properties.values.size() > 1 ? reify_numeric_argument(1) : reify_0px();
        return CSSTranslate::create(realm, CSSTransformComponent::Is2D::Yes, reify_numeric_argument(0), y, reify_0px());
    }
    case TransformFunction::TranslateX:
        return CSSTranslate::create(realm, CSSTransformComponent::Is2D::Yes, reify_numeric_argument(0), reify_0px(), reify_0px());
    case TransformFunction::TranslateY:
        return CSSTranslate::create(realm, CSSTransformComponent::Is2D::Yes, reify_0px(), reify_numeric_argument(0), reify_0px());
    case TransformFunction::Translate3d:
        return CSSTranslate::create(realm, CSSTransformComponent::Is2D::No, reify_numeric_argument(0), reify_numeric_argument(1), reify_numeric_argument(2));
    case TransformFunction::TranslateZ:
        return CSSTranslate::create(realm, CSSTransformComponent::Is2D::No, reify_0px(), reify_0px(), reify_numeric_argument(0));

    // -> scale()
    // -> scaleX()
    // -> scaleY()
    // -> scale3d()
    // -> scaleZ()
    //    1. Return a new CSSScale object, whose x, y, and z internal slots are set to the specified x/y/z scales, or
    //       to 1 if not specified in func and whose is2D internal slot is true if func is scale(), scaleX(), or
    //       scaleY(), and false otherwise.
    case TransformFunction::Scale: {
        // NB: Default y to a copy of x if it's not specified.
        auto y = m_properties.values.size() > 1 ? reify_numeric_argument(1) : reify_numeric_argument(0);
        return CSSScale::create(realm, CSSTransformComponent::Is2D::Yes, reify_numeric_argument(0), y, reify_1());
    }
    case TransformFunction::ScaleX:
        return CSSScale::create(realm, CSSTransformComponent::Is2D::Yes, reify_numeric_argument(0), reify_1(), reify_1());
    case TransformFunction::ScaleY:
        return CSSScale::create(realm, CSSTransformComponent::Is2D::Yes, reify_1(), reify_numeric_argument(0), reify_1());
    case TransformFunction::Scale3d:
        return CSSScale::create(realm, CSSTransformComponent::Is2D::No, reify_numeric_argument(0), reify_numeric_argument(1), reify_numeric_argument(2));
    case TransformFunction::ScaleZ:
        return CSSScale::create(realm, CSSTransformComponent::Is2D::No, reify_1(), reify_1(), reify_numeric_argument(0));

    // -> rotate()
    // -> rotate3d()
    // -> rotateX()
    // -> rotateY()
    // -> rotateZ()
    //    1. Return a new CSSRotate object, whose angle internal slot is set to the reification of the specified angle,
    //       and whose x, y, and z internal slots are set to the specified rotation axis coordinates, or the implicit
    //       axis coordinates if not specified in func and whose is2D internal slot is true if func is rotate(), and
    //       false otherwise.
    case TransformFunction::Rotate:
        return CSSRotate::create(realm, CSSTransformComponent::Is2D::Yes, reify_0(), reify_0(), reify_1(), reify_numeric_argument(0));
    case TransformFunction::Rotate3d:
        return CSSRotate::create(realm, CSSTransformComponent::Is2D::No, reify_numeric_argument(0), reify_numeric_argument(1), reify_numeric_argument(2), reify_numeric_argument(3));
    case TransformFunction::RotateX:
        return CSSRotate::create(realm, CSSTransformComponent::Is2D::No, reify_1(), reify_0(), reify_0(), reify_numeric_argument(0));
    case TransformFunction::RotateY:
        return CSSRotate::create(realm, CSSTransformComponent::Is2D::No, reify_0(), reify_1(), reify_0(), reify_numeric_argument(0));
    case TransformFunction::RotateZ:
        return CSSRotate::create(realm, CSSTransformComponent::Is2D::No, reify_0(), reify_0(), reify_1(), reify_numeric_argument(0));

    // -> skew()
    //    1. Return a new CSSSkew object, whose ax and ay internal slots are set to the reification of the specified x
    //       and y angles, or the reification of 0deg if not specified in func, and whose is2D internal slot is true.
    case TransformFunction::Skew: {
        // NB: Default y to 0deg if it's not specified.
        auto y = m_properties.values.size() > 1 ? reify_numeric_argument(1) : reify_0deg();
        return CSSSkew::create(realm, reify_numeric_argument(0), y);
    }

    // -> skewX()
    //    1. Return a new CSSSkewX object, whose ax internal slot is set to the reification of the specified x angle,
    //       or the reification of 0deg if not specified in func, and whose is2D internal slot is true.
    case TransformFunction::SkewX:
        return CSSSkewX::create(realm, reify_numeric_argument(0));

    // -> skewY()
    //    1. Return a new CSSSkewY object, whose ay internal slot is set to the reification of the specified y angle,
    //       or the reification of 0deg if not specified in func, and whose is2D internal slot is true.
    case TransformFunction::SkewY:
        return CSSSkewY::create(realm, reify_numeric_argument(0));

    // -> perspective()
    //    1. Return a new CSSPerspective object, whose length internal slot is set to the reification of the specified
    //       length (see reify a numeric value if it is a length, and reify an identifier if it is the keyword none)
    //       and whose is2D internal slot is false.
    case TransformFunction::Perspective: {
        CSSPerspectiveValueInternal length = [&]() -> CSSPerspectiveValueInternal {
            auto reified = m_properties.values[0]->reify(realm, {});
            if (auto* keyword = as_if<CSSKeywordValue>(*reified))
                return GC::Ref { *keyword };
            if (auto* numeric = as_if<CSSNumericValue>(*reified))
                return GC::Ref { *numeric };
            VERIFY_NOT_REACHED();
        }();
        return CSSPerspective::create(realm, length);
    }
    }
    VERIFY_NOT_REACHED();
}

ValueComparingNonnullRefPtr<StyleValue const> TransformationStyleValue::absolutized(ComputationContext const& computation_context) const
{
    StyleValueVector absolutized_values;

    bool absolutized_values_different = false;

    for (auto const& value : m_properties.values) {
        auto const& absolutized_value = value->absolutized(computation_context);

        if (absolutized_value != value)
            absolutized_values_different = true;

        absolutized_values.append(absolutized_value);
    }

    if (!absolutized_values_different)
        return *this;

    return TransformationStyleValue::create(m_properties.property, m_properties.transform_function, move(absolutized_values));
}

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

}