/*
 * Copyright (c) 2024, Andreas Kling <andreas@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibWeb/CSS/CSSStyleDeclaration.h>
#include <LibWeb/CSS/CascadedProperties.h>
#include <LibWeb/CSS/PropertyID.h>
#include <LibWeb/DOM/Element.h>
#include <LibWeb/DOM/ShadowRoot.h>

namespace Web::CSS {

GC_DEFINE_ALLOCATOR(CascadedProperties);

CascadedProperties::CascadedProperties() = default;

CascadedProperties::~CascadedProperties() = default;

void CascadedProperties::visit_edges(Visitor& visitor)
{
    Base::visit_edges(visitor);
    for (auto const& [property_id, entries] : m_properties) {
        for (auto const& entry : entries) {
            visitor.visit(entry.source);
            visitor.visit(entry.source_shadow_root);
        }
    }
}

void CascadedProperties::revert_property(PropertyID property_id, Important important, CascadeOrigin cascade_origin)
{
    auto it = m_properties.find(property_id);
    if (it == m_properties.end())
        return;
    auto& entries = it->value;
    entries.remove_all_matching([&](auto& entry) {
        // https://drafts.csswg.org/css-cascade-5/#author-presentational-hint-origin
        // For the purpose of cascading this author presentational hint origin is treated as an independent origin, but
        // for the purpose of the revert keyword it is considered part of the author origin.
        auto origin_matches = entry.origin == cascade_origin
            || (cascade_origin == CascadeOrigin::Author && entry.origin == CascadeOrigin::AuthorPresentationalHint);
        return entry.property.property_id == property_id
            && entry.property.important == important
            && origin_matches;
    });
    if (entries.is_empty()) {
        m_contained_properties_cache.set(to_underlying(property_id), false);
        m_properties.remove(it);
    }
}

void CascadedProperties::revert_layer_property(PropertyID property_id, Important important, Optional<FlyString> layer_name)
{
    auto it = m_properties.find(property_id);
    if (it == m_properties.end())
        return;
    auto& entries = it->value;
    entries.remove_all_matching([&](auto& entry) {
        return entry.property.property_id == property_id
            && entry.property.important == important
            && layer_name == entry.layer_name;
    });
    if (entries.is_empty()) {
        m_contained_properties_cache.set(to_underlying(property_id), false);
        m_properties.remove(it);
    }
}

void CascadedProperties::set_property(PropertyID property_id, NonnullRefPtr<StyleValue const> value, Important important, CascadeOrigin origin, Optional<FlyString> layer_name, GC::Ptr<CSS::CSSStyleDeclaration const> source, GC::Ptr<DOM::ShadowRoot const> source_shadow_root)
{
    m_contained_properties_cache.set(to_underlying(property_id), true);

    auto& entries = m_properties.ensure(property_id);

    for (auto& entry : entries.in_reverse()) {
        if (entry.origin == origin && entry.layer_name == layer_name) {
            if (entry.property.important == Important::Yes && important == Important::No)
                return;
            entry.property = StyleProperty {
                .important = important,
                .property_id = property_id,
                .value = value,
            };
            entry.cascade_index = m_next_cascade_index++;
            entry.source = source;
            entry.source_shadow_root = source_shadow_root;
            return;
        }
    }

    entries.append(Entry {
        .property = StyleProperty {
            .important = important,
            .property_id = property_id,
            .value = value,
        },
        .cascade_index = m_next_cascade_index++,
        .origin = origin,
        .layer_name = move(layer_name),
        .source = source,
        .source_shadow_root = source_shadow_root,
    });
}

RefPtr<StyleValue const> CascadedProperties::property(PropertyID property_id) const
{
    if (!m_contained_properties_cache.get(to_underlying(property_id)))
        return nullptr;

    return m_properties.get(property_id)->last().property.value;
}

PropertyID CascadedProperties::property_with_higher_priority(PropertyID first_property_id, PropertyID second_property_id) const
{
    if (!m_contained_properties_cache.get(to_underlying(first_property_id)))
        return second_property_id;

    if (!m_contained_properties_cache.get(to_underlying(second_property_id)))
        return first_property_id;

    if (m_properties.get(first_property_id)->last().cascade_index >= m_properties.get(second_property_id)->last().cascade_index)
        return first_property_id;

    return second_property_id;
}

GC::Ptr<CSSStyleDeclaration const> CascadedProperties::property_source(PropertyID property_id) const
{
    if (!m_contained_properties_cache.get(to_underlying(property_id)))
        return nullptr;

    return m_properties.get(property_id)->last().source;
}

GC::Ptr<DOM::ShadowRoot const> CascadedProperties::property_source_shadow_root(PropertyID property_id) const
{
    if (!m_contained_properties_cache.get(to_underlying(property_id)))
        return nullptr;

    return m_properties.get(property_id)->last().source_shadow_root;
}

Optional<StyleProperty> CascadedProperties::style_property(PropertyID property_id) const
{
    if (!m_contained_properties_cache.get(to_underlying(property_id)))
        return {};

    return m_properties.get(property_id)->last().property;
}

}