/*

 * Copyright (c) 2020-2024, Andreas Kling <kling@serenityos.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#include <LibWeb/CSS/Length.h>

#include <LibWeb/DOM/Node.h>

#include <LibWeb/Dump.h>

#include <LibWeb/Layout/BlockContainer.h>

#include <LibWeb/Layout/BlockFormattingContext.h>

#include <LibWeb/Layout/Box.h>

#include <LibWeb/Layout/InlineFormattingContext.h>

#include <LibWeb/Layout/InlineLevelIterator.h>

#include <LibWeb/Layout/LineBuilder.h>

#include <LibWeb/Layout/ReplacedBox.h>

#include <LibWeb/Layout/SVGSVGBox.h>

namespace Web::Layout {

InlineFormattingContext::InlineFormattingContext(

    LayoutState& state,

    LayoutMode layout_mode,

    BlockContainer const& containing_block,

    LayoutState::UsedValues& containing_block_used_values,

    BlockFormattingContext& parent)

    : FormattingContext(Type::Inline, layout_mode, state, containing_block, &parent)

    , m_containing_block_used_values(containing_block_used_values)

{

}

InlineFormattingContext::~InlineFormattingContext() = default;

BlockFormattingContext& InlineFormattingContext::parent()

{

    return static_cast<BlockFormattingContext&>(*FormattingContext::parent());

}

BlockFormattingContext const& InlineFormattingContext::parent() const

{

    return static_cast<BlockFormattingContext const&>(*FormattingContext::parent());

}

CSSPixels InlineFormattingContext::leftmost_x_offset_at(CSSPixels y) const

{

    // NOTE: Floats are relative to the BFC root box, not necessarily the containing block of this IFC.

    auto box_in_root_rect = content_box_rect_in_ancestor_coordinate_space(m_containing_block_used_values, parent().root());

    CSSPixels y_in_root = box_in_root_rect.y() + y;

    auto space_and_containing_margin = parent().space_used_and_containing_margin_for_floats(y_in_root);

    auto left_side_floats_limit_to_right = space_and_containing_margin.left_total_containing_margin + space_and_containing_margin.left_used_space;

    if (box_in_root_rect.x() >= left_side_floats_limit_to_right) {

        // The left edge of the containing block is to the right of the rightmost left-side float.

        // We start placing inline content at the left edge of the containing block.

        return 0;

    }

    // The left edge of the containing block is to the left of the rightmost left-side float.

    // We adjust the inline content insertion point by the overlap between the containing block and the float.

    return left_side_floats_limit_to_right - max(CSSPixels(0), box_in_root_rect.x());

}

AvailableSize InlineFormattingContext::available_space_for_line(CSSPixels y) const

{

    auto intrusions = parent().intrusion_by_floats_into_box(m_containing_block_used_values, y);

    if (m_available_space->width.is_definite()) {

        return AvailableSize::make_definite(m_available_space->width.to_px_or_zero() - (intrusions.left + intrusions.right));

    } else {

        return m_available_space->width;

    }

}

CSSPixels InlineFormattingContext::automatic_content_width() const

{

    return m_automatic_content_width;

}

CSSPixels InlineFormattingContext::automatic_content_height() const

{

    return m_automatic_content_height;

}

void InlineFormattingContext::run(AvailableSpace const& available_space)

{

    VERIFY(containing_block().children_are_inline());

    m_available_space = available_space;

    generate_line_boxes();

    CSSPixels content_height = 0;

    for (auto& line_box : m_containing_block_used_values.line_boxes) {

        content_height += line_box.height();

    }

    // NOTE: We ask the parent BFC to calculate the automatic content width of this IFC.

    //       This ensures that any floated boxes are taken into account.

    m_automatic_content_width = parent().greatest_child_width(containing_block());

    m_automatic_content_height = content_height;

}

void InlineFormattingContext::dimension_box_on_line(Box const& box, LayoutMode layout_mode)

{

    auto width_of_containing_block = m_available_space->width.to_px_or_zero();

    auto& box_state = m_state.get_mutable(box);

    auto const& computed_values = box.computed_values();

    box_state.margin_left = computed_values.margin().left().to_px(box, width_of_containing_block);

    box_state.border_left = computed_values.border_left().width;

    box_state.padding_left = computed_values.padding().left().to_px(box, width_of_containing_block);

    box_state.margin_right = computed_values.margin().right().to_px(box, width_of_containing_block);

    box_state.border_right = computed_values.border_right().width;

    box_state.padding_right = computed_values.padding().right().to_px(box, width_of_containing_block);

    box_state.margin_top = computed_values.margin().top().to_px(box, width_of_containing_block);

    box_state.border_top = computed_values.border_top().width;

    box_state.padding_top = computed_values.padding().top().to_px(box, width_of_containing_block);

    box_state.padding_bottom = computed_values.padding().bottom().to_px(box, width_of_containing_block);

    box_state.border_bottom = computed_values.border_bottom().width;

    box_state.margin_bottom = computed_values.margin().bottom().to_px(box, width_of_containing_block);

    if (box_is_sized_as_replaced_element(box)) {

        box_state.set_content_width(compute_width_for_replaced_element(box, *m_available_space));

        box_state.set_content_height(compute_height_for_replaced_element(box, *m_available_space));

        auto independent_formatting_context = layout_inside(box, layout_mode, box_state.available_inner_space_or_constraints_from(*m_available_space));

        if (independent_formatting_context)

            independent_formatting_context->parent_context_did_dimension_child_root_box();

        return;

    }

    // Any box that has simple flow inside should have generated line box fragments already.

    if (box.display().is_flow_inside()) {

        dbgln("FIXME: InlineFormattingContext::dimension_box_on_line got unexpected box in inline context:");

        dump_tree(box);

        return;

    }

    auto const& width_value = box.computed_values().width();

    CSSPixels unconstrained_width = 0;

    if (should_treat_width_as_auto(box, *m_available_space)) {

        auto result = calculate_shrink_to_fit_widths(box);

        if (m_available_space->width.is_definite()) {

            auto available_width = m_available_space->width.to_px_or_zero()

                - box_state.margin_left

                - box_state.border_left

                - box_state.padding_left

                - box_state.padding_right

                - box_state.border_right

                - box_state.margin_right;

            unconstrained_width = min(max(result.preferred_minimum_width, available_width), result.preferred_width);

        } else if (m_available_space->width.is_min_content()) {

            unconstrained_width = result.preferred_minimum_width;

        } else {

            unconstrained_width = result.preferred_width;

        }

    } else {

        if (width_value.contains_percentage() && !m_available_space->width.is_definite()) {

            // NOTE: We can't resolve percentages yet. We'll have to wait until after inner layout.

        } else {

            auto inner_width = calculate_inner_width(box, m_available_space->width, width_value);

            unconstrained_width = inner_width;

        }

    }

    CSSPixels width = unconstrained_width;

    if (!should_treat_max_width_as_none(box, m_available_space->width)) {

        auto max_width = calculate_inner_width(box, m_available_space->width, box.computed_values().max_width());

        width = min(width, max_width);

    }

    auto computed_min_width = box.computed_values().min_width();

    if (!computed_min_width.is_auto()) {

        auto min_width = calculate_inner_width(box, m_available_space->width, computed_min_width);

        width = max(width, min_width);

    }

    box_state.set_content_width(width);

    parent().resolve_used_height_if_not_treated_as_auto(box, AvailableSpace(AvailableSize::make_definite(width), AvailableSize::make_indefinite()));

    // NOTE: Flex containers with `auto` height are treated as `max-content`, so we can compute their height early.

    if (box.display().is_flex_inside())

        parent().resolve_used_height_if_treated_as_auto(box, AvailableSpace(AvailableSize::make_definite(width), AvailableSize::make_indefinite()));

    auto independent_formatting_context = layout_inside(box, layout_mode, box_state.available_inner_space_or_constraints_from(*m_available_space));

    auto const& height_value = box.computed_values().height();

    if (should_treat_height_as_auto(box, *m_available_space)) {

        // FIXME: (10.6.6) If 'height' is 'auto', the height depends on the element's descendants per 10.6.7.

        parent().resolve_used_height_if_treated_as_auto(box, AvailableSpace(AvailableSize::make_indefinite(), AvailableSize::make_indefinite()));

    } else {

        auto inner_height = calculate_inner_height(box, AvailableSize::make_definite(m_containing_block_used_values.content_height()), height_value);

        box_state.set_content_height(inner_height);

    }

    if (independent_formatting_context)

        independent_formatting_context->parent_context_did_dimension_child_root_box();

}

void InlineFormattingContext::apply_justification_to_fragments(CSS::TextJustify text_justify, LineBox& line_box, bool is_last_line)

{

    switch (text_justify) {

    case CSS::TextJustify::None:

        return;

    // FIXME: These two cases currently fall back to auto, handle them as well.

    case CSS::TextJustify::InterCharacter:

    case CSS::TextJustify::InterWord:

    case CSS::TextJustify::Auto:

        break;

    }

    // https://www.w3.org/TR/css-text-3/#text-align-property

    // Unless otherwise specified by text-align-last, the last line before a forced break or the end of the block is start-aligned.

    // FIXME: Support text-align-last.

    if (is_last_line || line_box.m_has_forced_break)

        return;

    CSSPixels excess_horizontal_space = line_box.original_available_width().to_px_or_zero() - line_box.width();

    CSSPixels excess_horizontal_space_including_whitespace = excess_horizontal_space;

    size_t whitespace_count = 0;

    for (auto& fragment : line_box.fragments()) {

        if (fragment.is_justifiable_whitespace()) {

            ++whitespace_count;

            excess_horizontal_space_including_whitespace += fragment.width();

        }

    }

    CSSPixels justified_space_width = whitespace_count > 0 ? (excess_horizontal_space_including_whitespace / whitespace_count) : 0;

    // This is the amount that each fragment will be offset by. If a whitespace

    // fragment is shorter than the justified space width, it increases to push

    // subsequent fragments, and decreases to pull them back otherwise.

    CSSPixels running_diff = 0;

    for (size_t i = 0; i < line_box.fragments().size(); ++i) {

        auto& fragment = line_box.fragments()[i];

        auto offset = fragment.offset();

        offset.translate_by(running_diff, 0);

        fragment.set_offset(offset);

        if (fragment.is_justifiable_whitespace()

            && fragment.width() != justified_space_width) {

            running_diff += justified_space_width - fragment.width();

            fragment.set_width(justified_space_width);

        }

    }

}

void InlineFormattingContext::generate_line_boxes()

{

    auto& line_boxes = m_containing_block_used_values.line_boxes;

    line_boxes.clear_with_capacity();

    auto direction = m_context_box->computed_values().direction();

    InlineLevelIterator iterator(*this, m_state, containing_block(), m_containing_block_used_values, m_layout_mode);

    LineBuilder line_builder(*this, m_state, m_containing_block_used_values, direction);

    // NOTE: When we ignore collapsible whitespace chunks at the start of a line,

    //       we have to remember how much start margin that chunk had in the inline

    //       axis, so that we can add it to the first non-whitespace chunk.

    CSSPixels leading_margin_from_collapsible_whitespace = 0;

    for (;;) {

        auto item_opt = iterator.next();

        if (!item_opt.has_value())

            break;

        auto& item = item_opt.value();

        // Ignore collapsible whitespace chunks at the start of line, and if the last fragment already ends in whitespace.

        if (item.is_collapsible_whitespace && (line_boxes.is_empty() || line_boxes.last().is_empty_or_ends_in_whitespace())) {

            if (item.node->computed_values().white_space() != CSS::WhiteSpace::Nowrap) {

                auto next_width = iterator.next_non_whitespace_sequence_width();

                if (next_width > 0)

                    line_builder.break_if_needed(next_width);

            }

            leading_margin_from_collapsible_whitespace += item.margin_start;

            continue;

        }

        item.margin_start += leading_margin_from_collapsible_whitespace;

        leading_margin_from_collapsible_whitespace = 0;

        switch (item.type) {

        case InlineLevelIterator::Item::Type::ForcedBreak: {

            line_builder.break_line(LineBuilder::ForcedBreak::Yes);

            if (item.node) {

                auto introduce_clearance = parent().clear_floating_boxes(*item.node, *this);

                if (introduce_clearance == BlockFormattingContext::DidIntroduceClearance::Yes)

                    parent().reset_margin_state();

            }

            break;

        }

        case InlineLevelIterator::Item::Type::Element: {

            auto& box = verify_cast<Layout::Box>(*item.node);

            compute_inset(box);

            if (containing_block().computed_values().white_space() != CSS::WhiteSpace::Nowrap) {

                auto minimum_space_needed_on_line = item.border_box_width();

                if (item.margin_start < 0)

                    minimum_space_needed_on_line += item.margin_start;

                if (item.margin_end < 0)

                    minimum_space_needed_on_line += item.margin_end;

                line_builder.break_if_needed(minimum_space_needed_on_line);

            }

            line_builder.append_box(box, item.border_start + item.padding_start, item.padding_end + item.border_end, item.margin_start, item.margin_end);

            break;

        }

        case InlineLevelIterator::Item::Type::AbsolutelyPositionedElement:

            if (is<Box>(*item.node))

                parent().add_absolutely_positioned_box(static_cast<Layout::Box const&>(*item.node));

            break;

        case InlineLevelIterator::Item::Type::FloatingElement:

            if (is<Box>(*item.node)) {

                [[maybe_unused]] auto introduce_clearance = parent().clear_floating_boxes(*item.node, *this);

                // Even if this introduces clearance, we do NOT reset

                // the margin state, because that is clearance between

                // floats and does not contribute to the height of the

                // Inline Formatting Context.

                parent().layout_floating_box(static_cast<Layout::Box const&>(*item.node), containing_block(), *m_available_space, 0, &line_builder);

            }

            break;

        case InlineLevelIterator::Item::Type::Text: {

            auto& text_node = verify_cast<Layout::TextNode>(*item.node);

            if (text_node.computed_values().white_space() != CSS::WhiteSpace::Nowrap) {

                bool is_whitespace = false;

                CSSPixels next_width = 0;

                // If we're in a whitespace-collapsing context, we can simply check the flag.

                if (item.is_collapsible_whitespace) {

                    is_whitespace = true;

                    next_width = iterator.next_non_whitespace_sequence_width();

                } else {

                    // In whitespace-preserving contexts (white-space: pre*), we have to check manually.

                    auto view = text_node.text_for_rendering().bytes_as_string_view().substring_view(item.offset_in_node, item.length_in_node);

                    is_whitespace = view.is_whitespace();

                    if (is_whitespace)

                        next_width = iterator.next_non_whitespace_sequence_width();

                }

                // If whitespace caused us to break, we swallow the whitespace instead of

                // putting it on the next line.

                if (is_whitespace && next_width > 0 && line_builder.break_if_needed(item.border_box_width() + next_width))

                    break;

            } else if (text_node.computed_values().text_overflow() == CSS::TextOverflow::Ellipsis

                && text_node.computed_values().overflow_x() != CSS::Overflow::Visible) {

                // We may need to do an ellipsis if the text is too long for the container

                constexpr u32 ellipsis_codepoint = 0x2026;

                if (m_available_space.has_value()

                    && item.width.to_double() > m_available_space.value().width.to_px_or_zero().to_double()) {

                    // Do the ellipsis

                    auto& glyph_run = item.glyph_run;

                    auto available_width = m_available_space.value().width.to_px_or_zero().to_float();

                    auto ellipsis_width = glyph_run->font().glyph_width(ellipsis_codepoint);

                    auto max_text_width = available_width - ellipsis_width;

                    auto& glyphs = glyph_run->glyphs();

                    size_t last_glyph_index = 0;

                    auto last_glyph_position = Gfx::FloatPoint();

                    for (auto const& glyph_or_emoji : glyphs) {

                        auto this_position = Gfx::FloatPoint();

                        glyph_or_emoji.visit(

                            [&](Gfx::DrawGlyph glyph) {

                                this_position = glyph.position;

                            },

                            [&](Gfx::DrawEmoji emoji) {

                                this_position = emoji.position;

                            });

                        if (this_position.x() > max_text_width)

                            break;

                        last_glyph_index++;

                        last_glyph_position = this_position;

                    }

                    if (last_glyph_index > 1) {

                        auto remove_item_count = glyphs.size() - last_glyph_index;

                        glyphs.remove(last_glyph_index - 1, remove_item_count);

                        glyphs.append(Gfx::DrawGlyph {

                            .position = last_glyph_position,

                            .code_point = ellipsis_codepoint });

                    }

                }

            }

            line_builder.append_text_chunk(

                text_node,

                item.offset_in_node,

                item.length_in_node,

                item.border_start + item.padding_start,

                item.padding_end + item.border_end,

                item.margin_start,

                item.margin_end,

                item.width,

                text_node.computed_values().line_height(),

                move(item.glyph_run));

            break;

        }

        }

    }

    for (auto& line_box : line_boxes) {

        line_box.trim_trailing_whitespace();

    }

    line_builder.remove_last_line_if_empty();

    auto const& containing_block = this->containing_block();

    auto text_align = containing_block.computed_values().text_align();

    auto text_justify = containing_block.computed_values().text_justify();

    if (text_align == CSS::TextAlign::Justify) {

        for (size_t i = 0; i < line_boxes.size(); i++) {

            auto& line_box = line_boxes[i];

            auto is_last_line = i == line_boxes.size() - 1;

            apply_justification_to_fragments(text_justify, line_box, is_last_line);

        }

    }

}

bool InlineFormattingContext::any_floats_intrude_at_y(CSSPixels y) const

{

    auto box_in_root_rect = content_box_rect_in_ancestor_coordinate_space(m_containing_block_used_values, parent().root());

    CSSPixels y_in_root = box_in_root_rect.y() + y;

    auto space_and_containing_margin = parent().space_used_and_containing_margin_for_floats(y_in_root);

    return space_and_containing_margin.left_used_space > 0 || space_and_containing_margin.right_used_space > 0;

}

bool InlineFormattingContext::can_fit_new_line_at_y(CSSPixels y) const

{

    auto top_intrusions = parent().intrusion_by_floats_into_box(m_containing_block_used_values, y);

    auto bottom_intrusions = parent().intrusion_by_floats_into_box(m_containing_block_used_values, y + containing_block().computed_values().line_height() - 1);

    auto left_edge = [](auto& space) -> CSSPixels {

        return space.left;

    };

    auto right_edge = [this](auto& space) -> CSSPixels {

        return m_available_space->width.to_px_or_zero() - space.right;

    };

    auto top_left_edge = left_edge(top_intrusions);

    auto top_right_edge = right_edge(top_intrusions);

    auto bottom_left_edge = left_edge(bottom_intrusions);

    auto bottom_right_edge = right_edge(bottom_intrusions);

    if (top_left_edge > bottom_right_edge)

        return false;

    if (bottom_left_edge > top_right_edge)

        return false;

    return true;

}

CSSPixels InlineFormattingContext::vertical_float_clearance() const

{

    return m_vertical_float_clearance;

}

void InlineFormattingContext::set_vertical_float_clearance(CSSPixels vertical_float_clearance)

{

    m_vertical_float_clearance = vertical_float_clearance;

}

}