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

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/TypeCasts.h>
#include <LibCore/DirIterator.h>
#include <LibGfx/FontDatabase.h>
#include <LibWeb/CSS/StyleProperties.h>
#include <LibWeb/FontCache.h>
#include <LibWeb/Layout/BlockBox.h>
#include <LibWeb/Layout/Node.h>

namespace Web::CSS {

StyleProperties::StyleProperties()
{
}

StyleProperties::StyleProperties(const StyleProperties& other)
    : m_property_values(other.m_property_values)
{
    if (other.m_font) {
        m_font = other.m_font->clone();
    } else {
        m_font = nullptr;
    }
}

NonnullRefPtr<StyleProperties> StyleProperties::clone() const
{
    return adopt_ref(*new StyleProperties(*this));
}

void StyleProperties::set_property(CSS::PropertyID id, NonnullRefPtr<StyleValue> value)
{
    m_property_values.set((unsigned)id, move(value));
}

void StyleProperties::set_property(CSS::PropertyID id, const StringView& value)
{
    m_property_values.set((unsigned)id, StringStyleValue::create(value));
}

Optional<NonnullRefPtr<StyleValue>> StyleProperties::property(CSS::PropertyID id) const
{
    auto fetch_initial = [](CSS::PropertyID id) -> Optional<NonnullRefPtr<StyleValue>> {
        auto initial_value = property_initial_value(id);
        if (initial_value)
            return initial_value.release_nonnull();
        return {};
    };
    auto fetch_inherited = [](CSS::PropertyID) -> Optional<NonnullRefPtr<StyleValue>> {
        // FIXME: Implement inheritance
        return {};
    };

    auto it = m_property_values.find((unsigned)id);
    if (it == m_property_values.end()) {
        if (is_inherited_property(id)) {
            return fetch_inherited(id);
        } else {
            // FIXME: This causes the Acid2 eyes to disappear for some reason
            return fetch_initial(id);
        }
    }

    auto& value = it->value;
    if (value->is_initial())
        return fetch_initial(id);
    if (value->is_inherit())
        return fetch_inherited(id);
    if (value->is_unset()) {
        if (is_inherited_property(id)) {
            return fetch_inherited(id);
        } else {
            return fetch_initial(id);
        }
    }

    return value;
}

Length StyleProperties::length_or_fallback(CSS::PropertyID id, const Length& fallback) const
{
    auto value = property(id);
    if (!value.has_value())
        return fallback;

    if (value.value()->is_calculated()) {
        Length length = Length(0, Length::Type::Calculated);
        length.set_calculated_style(verify_cast<CalculatedStyleValue>(value.value().ptr()));
        return length;
    }

    return value.value()->to_length();
}

LengthBox StyleProperties::length_box(CSS::PropertyID left_id, CSS::PropertyID top_id, CSS::PropertyID right_id, CSS::PropertyID bottom_id, const CSS::Length& default_value) const
{
    LengthBox box;
    box.left = length_or_fallback(left_id, default_value);
    box.top = length_or_fallback(top_id, default_value);
    box.right = length_or_fallback(right_id, default_value);
    box.bottom = length_or_fallback(bottom_id, default_value);
    return box;
}

Color StyleProperties::color_or_fallback(CSS::PropertyID id, const DOM::Document& document, Color fallback) const
{
    auto value = property(id);
    if (!value.has_value())
        return fallback;
    return value.value()->to_color(document);
}

void StyleProperties::load_font(Layout::Node const& node) const
{
    auto font_size = property(CSS::PropertyID::FontSize).value_or(IdentifierStyleValue::create(CSS::ValueID::Medium));
    auto font_weight = property(CSS::PropertyID::FontWeight).value_or(IdentifierStyleValue::create(CSS::ValueID::Normal));

    int weight = Gfx::FontWeight::Regular;
    if (font_weight->is_identifier()) {
        switch (static_cast<const IdentifierStyleValue&>(*font_weight).id()) {
        case CSS::ValueID::Normal:
            weight = Gfx::FontWeight::Regular;
            break;
        case CSS::ValueID::Bold:
            weight = Gfx::FontWeight::Bold;
            break;
        case CSS::ValueID::Lighter:
            // FIXME: This should be relative to the parent.
            weight = Gfx::FontWeight::Regular;
            break;
        case CSS::ValueID::Bolder:
            // FIXME: This should be relative to the parent.
            weight = Gfx::FontWeight::Bold;
            break;
        default:
            break;
        }
    } else if (font_weight->is_numeric()) {
        int font_weight_integer = roundf(static_cast<NumericStyleValue const&>(*font_weight).value());
        if (font_weight_integer <= Gfx::FontWeight::Regular)
            weight = Gfx::FontWeight::Regular;
        else if (font_weight_integer <= Gfx::FontWeight::Bold)
            weight = Gfx::FontWeight::Bold;
        else
            weight = Gfx::FontWeight::Black;
    }
    // FIXME: calc() for font-weight

    bool bold = weight > Gfx::FontWeight::Regular;

    int size = 10;
    auto parent_font_size = node.parent() == nullptr ? size : node.parent()->font_size();
    constexpr float font_size_ratio = 1.2f;

    if (font_size->is_identifier()) {
        switch (static_cast<const IdentifierStyleValue&>(*font_size).id()) {
        case CSS::ValueID::XxSmall:
        case CSS::ValueID::XSmall:
        case CSS::ValueID::Small:
        case CSS::ValueID::Medium:
            // FIXME: Should be based on "user's default font size"
            size = 10;
            break;
        case CSS::ValueID::Large:
        case CSS::ValueID::XLarge:
        case CSS::ValueID::XxLarge:
        case CSS::ValueID::XxxLarge:
            // FIXME: Should be based on "user's default font size"
            size = 12;
            break;
        case CSS::ValueID::Smaller:
            size = roundf(parent_font_size / font_size_ratio);
            break;
        case CSS::ValueID::Larger:
            size = roundf(parent_font_size * font_size_ratio);
            break;

        default:
            break;
        }
    } else {
        Optional<Length> maybe_length;
        if (font_size->is_length()) {
            maybe_length = font_size->to_length();
        } else if (font_size->is_calculated()) {
            Length length = Length(0, Length::Type::Calculated);
            length.set_calculated_style(verify_cast<CalculatedStyleValue>(font_size.ptr()));
            maybe_length = length;
        }
        if (maybe_length.has_value()) {
            // FIXME: em sizes return 0 here, for some reason
            auto calculated_size = maybe_length.value().resolved_or_zero(node, parent_font_size).to_px(node);
            if (calculated_size != 0)
                size = calculated_size;
        }
    }

    // FIXME: Implement the full font-matching algorithm: https://www.w3.org/TR/css-fonts-4/#font-matching-algorithm

    // Note: This is modified by the find_font() lambda
    FontSelector font_selector;
    bool monospace = false;

    auto find_font = [&](String const& family) -> RefPtr<Gfx::Font> {
        font_selector = { family, size, weight };

        if (auto found_font = FontCache::the().get(font_selector))
            return found_font;

        if (auto found_font = Gfx::FontDatabase::the().get(family, size, weight))
            return found_font;

        return {};
    };

    // FIXME: Replace hard-coded font names with a relevant call to FontDatabase.
    // Currently, we cannot request the default font's name, or request it at a specific size and weight.
    // So, hard-coded font names it is.
    auto find_generic_font = [&](ValueID font_id) -> RefPtr<Gfx::Font> {
        switch (font_id) {
        case ValueID::Monospace:
        case ValueID::UiMonospace:
            monospace = true;
            return find_font("Csilla");
        case ValueID::Serif:
        case ValueID::SansSerif:
        case ValueID::Cursive:
        case ValueID::Fantasy:
        case ValueID::UiSerif:
        case ValueID::UiSansSerif:
        case ValueID::UiRounded:
            return find_font("Katica");
        default:
            return {};
        }
    };

    RefPtr<Gfx::Font> found_font {};

    auto family_value = property(PropertyID::FontFamily).value_or(StringStyleValue::create("Katica"));
    if (family_value->is_value_list()) {
        auto& family_list = static_cast<StyleValueList const&>(*family_value).values();
        for (auto& family : family_list) {
            if (family.is_identifier()) {
                found_font = find_generic_font(family.to_identifier());
            } else if (family.is_string()) {
                found_font = find_font(family.to_string());
            }
            if (found_font)
                break;
        }
    } else if (family_value->is_identifier()) {
        found_font = find_generic_font(family_value->to_identifier());
    } else if (family_value->is_string()) {
        found_font = find_font(family_value->to_string());
    }

    if (!found_font) {
        dbgln("Font not found: '{}' {} {}", family_value->to_string(), size, weight);
        found_font = font_fallback(monospace, bold);
    }

    m_font = found_font;
    FontCache::the().set(font_selector, *m_font);
}

RefPtr<Gfx::Font> StyleProperties::font_fallback(bool monospace, bool bold) const
{
    if (monospace && bold)
        return Gfx::FontDatabase::default_fixed_width_font().bold_variant();

    if (monospace)
        return Gfx::FontDatabase::default_fixed_width_font();

    if (bold)
        return Gfx::FontDatabase::default_font().bold_variant();

    return Gfx::FontDatabase::default_font();
}

float StyleProperties::line_height(const Layout::Node& layout_node) const
{
    auto line_height_length = length_or_fallback(CSS::PropertyID::LineHeight, Length::make_auto());
    if (line_height_length.is_absolute())
        return (float)line_height_length.to_px(layout_node);
    return (float)font(layout_node).glyph_height() * 1.4f;
}

Optional<int> StyleProperties::z_index() const
{
    auto value = property(CSS::PropertyID::ZIndex);
    if (!value.has_value())
        return {};
    return static_cast<int>(value.value()->to_length().raw_value());
}

Optional<float> StyleProperties::opacity() const
{
    auto value = property(CSS::PropertyID::Opacity);
    if (!value.has_value())
        return {};

    if (auto length = value.value()->to_length(); length.is_percentage())
        return clamp(static_cast<float>(length.raw_value() / 100), 0.0f, 1.0f);
    else
        return clamp(static_cast<float>(length.raw_value()), 0.0f, 1.0f);
}

Optional<CSS::FlexDirection> StyleProperties::flex_direction() const
{
    auto value = property(CSS::PropertyID::FlexDirection);
    if (!value.has_value())
        return {};
    switch (value.value()->to_identifier()) {
    case CSS::ValueID::Row:
        return CSS::FlexDirection::Row;
    case CSS::ValueID::RowReverse:
        return CSS::FlexDirection::RowReverse;
    case CSS::ValueID::Column:
        return CSS::FlexDirection::Column;
    case CSS::ValueID::ColumnReverse:
        return CSS::FlexDirection::ColumnReverse;
    default:
        return {};
    }
}

Optional<CSS::FlexWrap> StyleProperties::flex_wrap() const
{
    auto value = property(CSS::PropertyID::FlexWrap);
    if (!value.has_value())
        return {};
    switch (value.value()->to_identifier()) {
    case CSS::ValueID::Wrap:
        return CSS::FlexWrap::Wrap;
    case CSS::ValueID::Nowrap:
        return CSS::FlexWrap::Nowrap;
    case CSS::ValueID::WrapReverse:
        return CSS::FlexWrap::WrapReverse;
    default:
        return {};
    }
}

Optional<CSS::FlexBasisData> StyleProperties::flex_basis() const
{
    auto value = property(CSS::PropertyID::FlexBasis);
    if (!value.has_value())
        return {};

    if (value.value()->is_identifier() && value.value()->to_identifier() == CSS::ValueID::Content)
        return { { CSS::FlexBasis::Content, {} } };

    if (value.value()->is_auto())
        return { { CSS::FlexBasis::Auto, {} } };

    if (value.value()->is_length())
        return { { CSS::FlexBasis::Length, value.value()->to_length() } };

    return {};
}

Optional<float> StyleProperties::flex_grow_factor() const
{
    auto value = property(CSS::PropertyID::FlexGrow);
    if (!value.has_value())
        return {};
    if (value.value()->is_numeric()) {
        auto numeric = verify_cast<CSS::NumericStyleValue>(value.value().ptr());
        return numeric->value();
    }
    if (value.value()->is_length() && value.value()->to_length().raw_value() == 0)
        return { 0 };
    return {};
}

Optional<float> StyleProperties::flex_shrink_factor() const
{
    auto value = property(CSS::PropertyID::FlexShrink);
    if (!value.has_value())
        return {};
    if (value.value()->is_numeric()) {
        auto numeric = verify_cast<CSS::NumericStyleValue>(value.value().ptr());
        return numeric->value();
    }
    if (value.value()->is_length() && value.value()->to_length().raw_value() == 0)
        return { 0 };
    return {};
}
Optional<CSS::JustifyContent> StyleProperties::justify_content() const
{
    auto value = property(CSS::PropertyID::JustifyContent);
    if (!value.has_value())
        return {};
    switch (value.value()->to_identifier()) {
    case CSS::ValueID::FlexStart:
        return CSS::JustifyContent::FlexStart;
    case CSS::ValueID::FlexEnd:
        return CSS::JustifyContent::FlexEnd;
    case CSS::ValueID::Center:
        return CSS::JustifyContent::Center;
    case CSS::ValueID::SpaceBetween:
        return CSS::JustifyContent::SpaceBetween;
    case CSS::ValueID::SpaceAround:
        return CSS::JustifyContent::SpaceAround;
    default:
        return {};
    }
}

Optional<CSS::Position> StyleProperties::position() const
{
    auto value = property(CSS::PropertyID::Position);
    if (!value.has_value() || !value.value()->is_identifier())
        return {};
    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::Static:
        return CSS::Position::Static;
    case CSS::ValueID::Relative:
        return CSS::Position::Relative;
    case CSS::ValueID::Absolute:
        return CSS::Position::Absolute;
    case CSS::ValueID::Fixed:
        return CSS::Position::Fixed;
    case CSS::ValueID::Sticky:
        return CSS::Position::Sticky;
    default:
        return {};
    }
}

bool StyleProperties::operator==(const StyleProperties& other) const
{
    if (m_property_values.size() != other.m_property_values.size())
        return false;

    for (auto& it : m_property_values) {
        auto jt = other.m_property_values.find(it.key);
        if (jt == other.m_property_values.end())
            return false;
        auto& my_value = *it.value;
        auto& other_value = *jt->value;
        if (my_value.type() != other_value.type())
            return false;
        if (my_value != other_value)
            return false;
    }

    return true;
}

Optional<CSS::TextAlign> StyleProperties::text_align() const
{
    auto value = property(CSS::PropertyID::TextAlign);
    if (!value.has_value() || !value.value()->is_identifier())
        return {};

    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::Left:
        return CSS::TextAlign::Left;
    case CSS::ValueID::Center:
        return CSS::TextAlign::Center;
    case CSS::ValueID::Right:
        return CSS::TextAlign::Right;
    case CSS::ValueID::Justify:
        return CSS::TextAlign::Justify;
    case CSS::ValueID::LibwebCenter:
        return CSS::TextAlign::LibwebCenter;
    default:
        return {};
    }
}

Optional<CSS::WhiteSpace> StyleProperties::white_space() const
{
    auto value = property(CSS::PropertyID::WhiteSpace);
    if (!value.has_value() || !value.value()->is_identifier())
        return {};
    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::Normal:
        return CSS::WhiteSpace::Normal;
    case CSS::ValueID::Nowrap:
        return CSS::WhiteSpace::Nowrap;
    case CSS::ValueID::Pre:
        return CSS::WhiteSpace::Pre;
    case CSS::ValueID::PreLine:
        return CSS::WhiteSpace::PreLine;
    case CSS::ValueID::PreWrap:
        return CSS::WhiteSpace::PreWrap;
    default:
        return {};
    }
}

Optional<CSS::LineStyle> StyleProperties::line_style(CSS::PropertyID property_id) const
{
    auto value = property(property_id);
    if (!value.has_value() || !value.value()->is_identifier())
        return {};
    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::None:
        return CSS::LineStyle::None;
    case CSS::ValueID::Hidden:
        return CSS::LineStyle::Hidden;
    case CSS::ValueID::Dotted:
        return CSS::LineStyle::Dotted;
    case CSS::ValueID::Dashed:
        return CSS::LineStyle::Dashed;
    case CSS::ValueID::Solid:
        return CSS::LineStyle::Solid;
    case CSS::ValueID::Double:
        return CSS::LineStyle::Double;
    case CSS::ValueID::Groove:
        return CSS::LineStyle::Groove;
    case CSS::ValueID::Ridge:
        return CSS::LineStyle::Ridge;
    case CSS::ValueID::Inset:
        return CSS::LineStyle::Inset;
    case CSS::ValueID::Outset:
        return CSS::LineStyle::Outset;
    default:
        return {};
    }
}

Optional<CSS::Float> StyleProperties::float_() const
{
    auto value = property(CSS::PropertyID::Float);
    if (!value.has_value() || !value.value()->is_identifier())
        return {};
    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::None:
        return CSS::Float::None;
    case CSS::ValueID::Left:
        return CSS::Float::Left;
    case CSS::ValueID::Right:
        return CSS::Float::Right;
    default:
        return {};
    }
}

Optional<CSS::Clear> StyleProperties::clear() const
{
    auto value = property(CSS::PropertyID::Clear);
    if (!value.has_value() || !value.value()->is_identifier())
        return {};
    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::None:
        return CSS::Clear::None;
    case CSS::ValueID::Left:
        return CSS::Clear::Left;
    case CSS::ValueID::Right:
        return CSS::Clear::Right;
    case CSS::ValueID::Both:
        return CSS::Clear::Both;
    default:
        return {};
    }
}

Optional<CSS::Cursor> StyleProperties::cursor() const
{
    auto value = property(CSS::PropertyID::Cursor);
    if (!value.has_value() || !value.value()->is_identifier())
        return {};
    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::Auto:
        return CSS::Cursor::Auto;
    case CSS::ValueID::Default:
        return CSS::Cursor::Default;
    case CSS::ValueID::None:
        return CSS::Cursor::None;
    case CSS::ValueID::ContextMenu:
        return CSS::Cursor::ContextMenu;
    case CSS::ValueID::Help:
        return CSS::Cursor::Help;
    case CSS::ValueID::Pointer:
        return CSS::Cursor::Pointer;
    case CSS::ValueID::Progress:
        return CSS::Cursor::Progress;
    case CSS::ValueID::Wait:
        return CSS::Cursor::Wait;
    case CSS::ValueID::Cell:
        return CSS::Cursor::Cell;
    case CSS::ValueID::Crosshair:
        return CSS::Cursor::Crosshair;
    case CSS::ValueID::Text:
        return CSS::Cursor::Text;
    case CSS::ValueID::VerticalText:
        return CSS::Cursor::VerticalText;
    case CSS::ValueID::Alias:
        return CSS::Cursor::Alias;
    case CSS::ValueID::Copy:
        return CSS::Cursor::Copy;
    case CSS::ValueID::Move:
        return CSS::Cursor::Move;
    case CSS::ValueID::NoDrop:
        return CSS::Cursor::NoDrop;
    case CSS::ValueID::NotAllowed:
        return CSS::Cursor::NotAllowed;
    case CSS::ValueID::Grab:
        return CSS::Cursor::Grab;
    case CSS::ValueID::Grabbing:
        return CSS::Cursor::Grabbing;
    case CSS::ValueID::EResize:
        return CSS::Cursor::EResize;
    case CSS::ValueID::NResize:
        return CSS::Cursor::NResize;
    case CSS::ValueID::NeResize:
        return CSS::Cursor::NeResize;
    case CSS::ValueID::NwResize:
        return CSS::Cursor::NwResize;
    case CSS::ValueID::SResize:
        return CSS::Cursor::SResize;
    case CSS::ValueID::SeResize:
        return CSS::Cursor::SeResize;
    case CSS::ValueID::SwResize:
        return CSS::Cursor::SwResize;
    case CSS::ValueID::WResize:
        return CSS::Cursor::WResize;
    case CSS::ValueID::EwResize:
        return CSS::Cursor::EwResize;
    case CSS::ValueID::NsResize:
        return CSS::Cursor::NsResize;
    case CSS::ValueID::NeswResize:
        return CSS::Cursor::NeswResize;
    case CSS::ValueID::NwseResize:
        return CSS::Cursor::NwseResize;
    case CSS::ValueID::ColResize:
        return CSS::Cursor::ColResize;
    case CSS::ValueID::RowResize:
        return CSS::Cursor::RowResize;
    case CSS::ValueID::AllScroll:
        return CSS::Cursor::AllScroll;
    case CSS::ValueID::ZoomIn:
        return CSS::Cursor::ZoomIn;
    case CSS::ValueID::ZoomOut:
        return CSS::Cursor::ZoomOut;
    default:
        return {};
    }
}

CSS::Display StyleProperties::display() const
{
    auto value = property(CSS::PropertyID::Display);
    if (!value.has_value() || !value.value()->is_identifier())
        return CSS::Display::Inline;
    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::None:
        return CSS::Display::None;
    case CSS::ValueID::Block:
        return CSS::Display::Block;
    case CSS::ValueID::Inline:
        return CSS::Display::Inline;
    case CSS::ValueID::InlineBlock:
        return CSS::Display::InlineBlock;
    case CSS::ValueID::ListItem:
        return CSS::Display::ListItem;
    case CSS::ValueID::Table:
        return CSS::Display::Table;
    case CSS::ValueID::TableRow:
        return CSS::Display::TableRow;
    case CSS::ValueID::TableCell:
        return CSS::Display::TableCell;
    case CSS::ValueID::TableColumn:
        return CSS::Display::TableColumn;
    case CSS::ValueID::TableColumnGroup:
        return CSS::Display::TableColumnGroup;
    case CSS::ValueID::TableCaption:
        return CSS::Display::TableCaption;
    case CSS::ValueID::TableRowGroup:
        return CSS::Display::TableRowGroup;
    case CSS::ValueID::TableHeaderGroup:
        return CSS::Display::TableHeaderGroup;
    case CSS::ValueID::TableFooterGroup:
        return CSS::Display::TableFooterGroup;
    case CSS::ValueID::Flex:
        return CSS::Display::Flex;
    default:
        return CSS::Display::Block;
    }
}

Optional<CSS::TextDecorationLine> StyleProperties::text_decoration_line() const
{
    auto value = property(CSS::PropertyID::TextDecorationLine);
    if (!value.has_value() || !value.value()->is_identifier())
        return {};
    switch (static_cast<const IdentifierStyleValue&>(*value.value()).id()) {
    case CSS::ValueID::None:
        return CSS::TextDecorationLine::None;
    case CSS::ValueID::Underline:
        return CSS::TextDecorationLine::Underline;
    case CSS::ValueID::Overline:
        return CSS::TextDecorationLine::Overline;
    case CSS::ValueID::LineThrough:
        return CSS::TextDecorationLine::LineThrough;
    case CSS::ValueID::Blink:
        return CSS::TextDecorationLine::Blink;
    default:
        return {};
    }
}

Optional<CSS::TextTransform> StyleProperties::text_transform() const
{
    auto value = property(CSS::PropertyID::TextTransform);
    if (!value.has_value())
        return {};
    switch (value.value()->to_identifier()) {
    case CSS::ValueID::None:
        return CSS::TextTransform::None;
    case CSS::ValueID::Lowercase:
        return CSS::TextTransform::Lowercase;
    case CSS::ValueID::Uppercase:
        return CSS::TextTransform::Uppercase;
    case CSS::ValueID::Capitalize:
        return CSS::TextTransform::Capitalize;
    case CSS::ValueID::FullWidth:
        return CSS::TextTransform::FullWidth;
    case CSS::ValueID::FullSizeKana:
        return CSS::TextTransform::FullSizeKana;
    default:
        return {};
    }
}

Optional<CSS::ListStyleType> StyleProperties::list_style_type() const
{
    auto value = property(CSS::PropertyID::ListStyleType);
    if (!value.has_value())
        return {};

    switch (value.value()->to_identifier()) {
    case CSS::ValueID::None:
        return CSS::ListStyleType::None;
    case CSS::ValueID::Disc:
        return CSS::ListStyleType::Disc;
    case CSS::ValueID::Circle:
        return CSS::ListStyleType::Circle;
    case CSS::ValueID::Square:
        return CSS::ListStyleType::Square;
    case CSS::ValueID::Decimal:
        return CSS::ListStyleType::Decimal;
    case CSS::ValueID::DecimalLeadingZero:
        return CSS::ListStyleType::DecimalLeadingZero;
    case CSS::ValueID::LowerAlpha:
        return CSS::ListStyleType::LowerAlpha;
    case CSS::ValueID::LowerLatin:
        return CSS::ListStyleType::LowerLatin;
    case CSS::ValueID::UpperAlpha:
        return CSS::ListStyleType::UpperAlpha;
    case CSS::ValueID::UpperLatin:
        return CSS::ListStyleType::UpperLatin;
    case CSS::ValueID::UpperRoman:
        return CSS::ListStyleType::UpperRoman;
    case CSS::ValueID::LowerRoman:
        return CSS::ListStyleType::LowerRoman;
    default:
        return {};
    }
}

Optional<CSS::Overflow> StyleProperties::overflow_x() const
{
    return overflow(CSS::PropertyID::OverflowX);
}

Optional<CSS::Overflow> StyleProperties::overflow_y() const
{
    return overflow(CSS::PropertyID::OverflowY);
}

Optional<CSS::Overflow> StyleProperties::overflow(CSS::PropertyID property_id) const
{
    auto value = property(property_id);
    if (!value.has_value())
        return {};

    switch (value.value()->to_identifier()) {
    case CSS::ValueID::Auto:
        return CSS::Overflow::Auto;
    case CSS::ValueID::Visible:
        return CSS::Overflow::Visible;
    case CSS::ValueID::Hidden:
        return CSS::Overflow::Hidden;
    case CSS::ValueID::Clip:
        return CSS::Overflow::Clip;
    case CSS::ValueID::Scroll:
        return CSS::Overflow::Scroll;
    default:
        return {};
    }
}

Optional<CSS::Repeat> StyleProperties::background_repeat_x() const
{
    auto value = property(CSS::PropertyID::BackgroundRepeatX);
    if (!value.has_value())
        return {};

    switch (value.value()->to_identifier()) {
    case CSS::ValueID::NoRepeat:
        return CSS::Repeat::NoRepeat;
    case CSS::ValueID::Repeat:
        return CSS::Repeat::Repeat;
    case CSS::ValueID::Round:
        return CSS::Repeat::Round;
    case CSS::ValueID::Space:
        return CSS::Repeat::Space;
    default:
        return {};
    }
}

Optional<CSS::Repeat> StyleProperties::background_repeat_y() const
{
    auto value = property(CSS::PropertyID::BackgroundRepeatY);
    if (!value.has_value())
        return {};

    switch (value.value()->to_identifier()) {
    case CSS::ValueID::NoRepeat:
        return CSS::Repeat::NoRepeat;
    case CSS::ValueID::Repeat:
        return CSS::Repeat::Repeat;
    case CSS::ValueID::Round:
        return CSS::Repeat::Round;
    case CSS::ValueID::Space:
        return CSS::Repeat::Space;
    default:
        return {};
    }
}

Optional<CSS::BoxShadowData> StyleProperties::box_shadow() const
{
    auto value_or_error = property(CSS::PropertyID::BoxShadow);
    if (!value_or_error.has_value())
        return {};

    auto value = value_or_error.value();
    if (!value->is_box_shadow())
        return {};

    auto box = verify_cast<CSS::BoxShadowStyleValue>(value.ptr());
    return { { box->offset_x(), box->offset_y(), box->blur_radius(), box->color() } };
}
}