/*
 * Copyright (c) 2024, Aliaksandr Kalenik <kalenik.aliaksandr@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/StdLibExtras.h>
#include <LibWeb/Forward.h>

namespace Web::CSS {

// Ordered by increasing severity. A higher level always implies all lower levels.
enum class InvalidationLevel : u8 {
    None,
    Repaint,
    Relayout,
    RebuildLayoutTree,
};

// Ordered by increasing severity: Rebuild subsumes UpdateValues.
enum class AccumulatedVisualContextInvalidation : u8 {
    None,
    UpdateValues,
    Rebuild,
};

struct RequiredInvalidationAfterStyleChange {
    void ensure_at_least(InvalidationLevel level) { m_level = max(m_level, level); }
    void ensure_at_least(AccumulatedVisualContextInvalidation invalidation) { m_accumulated_visual_contexts = max(m_accumulated_visual_contexts, invalidation); }

    void set_needs_stacking_context_tree_rebuild()
    {
        m_rebuild_stacking_context_tree = true;
        ensure_at_least(InvalidationLevel::Repaint);
    }

    [[nodiscard]] bool needs_repaint() const { return m_level >= InvalidationLevel::Repaint; }
    [[nodiscard]] bool needs_relayout() const { return m_level >= InvalidationLevel::Relayout; }
    [[nodiscard]] bool needs_layout_tree_rebuild() const { return m_level >= InvalidationLevel::RebuildLayoutTree; }
    [[nodiscard]] bool needs_stacking_context_tree_rebuild() const { return m_rebuild_stacking_context_tree; }
    [[nodiscard]] AccumulatedVisualContextInvalidation accumulated_visual_contexts() const { return m_accumulated_visual_contexts; }

    // The element's change affects rule matching for descendants, without necessarily changing inherited style.
    bool recompute_descendant_styles : 1 { false };
    // At least one inherited longhand changed, so shadow-tree descendants may need inherited style recomputation.
    bool inherited_style_changed : 1 { false };

    void operator|=(RequiredInvalidationAfterStyleChange const& other)
    {
        m_level = max(m_level, other.m_level);
        m_accumulated_visual_contexts = max(m_accumulated_visual_contexts, other.m_accumulated_visual_contexts);
        m_rebuild_stacking_context_tree |= other.m_rebuild_stacking_context_tree;
        recompute_descendant_styles |= other.recompute_descendant_styles;
        inherited_style_changed |= other.inherited_style_changed;
    }

    [[nodiscard]] bool is_none() const
    {
        return m_level == InvalidationLevel::None
            && m_accumulated_visual_contexts == AccumulatedVisualContextInvalidation::None
            && !recompute_descendant_styles
            && !inherited_style_changed;
    }

    static RequiredInvalidationAfterStyleChange full()
    {
        RequiredInvalidationAfterStyleChange invalidation;
        invalidation.ensure_at_least(InvalidationLevel::RebuildLayoutTree);
        invalidation.set_needs_stacking_context_tree_rebuild();
        return invalidation;
    }

private:
    InvalidationLevel m_level { InvalidationLevel::None };
    AccumulatedVisualContextInvalidation m_accumulated_visual_contexts { AccumulatedVisualContextInvalidation::None };
    bool m_rebuild_stacking_context_tree : 1 { false };
};

RequiredInvalidationAfterStyleChange compute_property_invalidation(CSS::PropertyID property_id, StyleValue const* old_value, StyleValue const* new_value);

}