/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * Copyright (c) 2021, Sam Atkins <atkinssj@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <LibGfx/Painter.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/HTML/HTMLBodyElement.h>
#include <LibWeb/HTML/HTMLHtmlElement.h>
#include <LibWeb/Layout/BlockBox.h>
#include <LibWeb/Layout/Box.h>
#include <LibWeb/Layout/FormattingContext.h>
#include <LibWeb/Page/BrowsingContext.h>
#include <LibWeb/Painting/BackgroundPainting.h>
#include <LibWeb/Painting/BorderPainting.h>
#include <LibWeb/Painting/ShadowPainting.h>

namespace Web::Layout {

void Box::paint(PaintContext& context, PaintPhase phase)
{
    if (!is_visible())
        return;

    Gfx::PainterStateSaver saver(context.painter());
    if (is_fixed_position())
        context.painter().translate(context.scroll_offset());

    if (phase == PaintPhase::Background) {
        paint_background(context);
        paint_box_shadow(context);
    }

    if (phase == PaintPhase::Border) {
        paint_border(context);
    }

    if (phase == PaintPhase::Overlay && dom_node() && document().inspected_node() == dom_node()) {
        auto content_rect = absolute_rect();

        auto margin_box = box_model().margin_box();
        Gfx::FloatRect margin_rect;
        margin_rect.set_x(absolute_x() - margin_box.left);
        margin_rect.set_width(width() + margin_box.left + margin_box.right);
        margin_rect.set_y(absolute_y() - margin_box.top);
        margin_rect.set_height(height() + margin_box.top + margin_box.bottom);

        context.painter().draw_rect(enclosing_int_rect(margin_rect), Color::Yellow);
        context.painter().draw_rect(enclosing_int_rect(padded_rect()), Color::Cyan);
        context.painter().draw_rect(enclosing_int_rect(content_rect), Color::Magenta);
    }

    if (phase == PaintPhase::FocusOutline && dom_node() && dom_node()->is_element() && verify_cast<DOM::Element>(*dom_node()).is_focused()) {
        context.painter().draw_rect(enclosing_int_rect(absolute_rect()), context.palette().focus_outline());
    }
}

void Box::paint_border(PaintContext& context)
{
    auto const bordered_rect = this->bordered_rect();
    auto const border_rect = bordered_rect;

    auto const border_radius_data = normalized_border_radius_data();
    auto const top_left_radius = border_radius_data.top_left;
    auto const top_right_radius = border_radius_data.top_right;
    auto const bottom_right_radius = border_radius_data.bottom_right;
    auto const bottom_left_radius = border_radius_data.bottom_left;

    // FIXME: Support elliptical border radii.

    Gfx::FloatRect top_border_rect = {
        border_rect.x() + top_left_radius,
        border_rect.y(),
        border_rect.width() - top_left_radius - top_right_radius,
        border_rect.height()
    };
    Gfx::FloatRect right_border_rect = {
        border_rect.x(),
        border_rect.y() + top_right_radius,
        border_rect.width(),
        border_rect.height() - top_right_radius - bottom_right_radius
    };
    Gfx::FloatRect bottom_border_rect = {
        border_rect.x() + bottom_left_radius,
        border_rect.y(),
        border_rect.width() - bottom_left_radius - bottom_right_radius,
        border_rect.height()
    };
    Gfx::FloatRect left_border_rect = {
        border_rect.x(),
        border_rect.y() + top_left_radius,
        border_rect.width(),
        border_rect.height() - top_left_radius - bottom_left_radius
    };

    Painting::paint_border(context, Painting::BorderEdge::Top, top_border_rect, computed_values());
    Painting::paint_border(context, Painting::BorderEdge::Right, right_border_rect, computed_values());
    Painting::paint_border(context, Painting::BorderEdge::Bottom, bottom_border_rect, computed_values());
    Painting::paint_border(context, Painting::BorderEdge::Left, left_border_rect, computed_values());

    // Draws a quarter cirle clockwise
    auto draw_quarter_circle = [&](Gfx::FloatPoint const& from, Gfx::FloatPoint const& to, Gfx::Color color, int thickness) {
        Gfx::FloatPoint center = { 0, 0 };
        Gfx::FloatPoint offset = { 0, 0 };
        Gfx::FloatPoint circle_position = { 0, 0 };

        auto radius = fabsf(from.x() - to.x());

        if (from.x() < to.x() && from.y() > to.y()) {
            // top-left
            center.set_x(radius);
            center.set_y(radius);
            offset.set_y(1);
        } else if (from.x() < to.x() && from.y() < to.y()) {
            // top-right
            circle_position.set_x(from.x());
            center.set_y(radius);
            offset.set_x(-1);
            offset.set_y(1);
        } else if (from.x() > to.x() && from.y() < to.y()) {
            // bottom-right
            circle_position.set_x(to.x());
            circle_position.set_y(from.y());
            offset.set_x(-1);
        } else if (from.x() > to.x() && from.y() > to.y()) {
            // bottom-left
            circle_position.set_y(to.y());
            center.set_x(radius);
        } else {
            // You are lying about your intentions of drawing a quarter circle, your coordinates are (partly) the same!
            return;
        }

        Gfx::FloatRect circle_rect = {
            border_rect.x() + circle_position.x(),
            border_rect.y() + circle_position.y(),
            radius,
            radius
        };

        context.painter().draw_circle_arc_intersecting(
            Gfx::enclosing_int_rect(circle_rect),
            (center + offset).to_rounded<int>(),
            radius,
            color,
            thickness);
    };

    // FIXME: Which color to use?
    if (top_left_radius != 0) {
        Gfx::FloatPoint arc_start = { 0, top_left_radius };
        Gfx::FloatPoint arc_end = { top_left_radius, 0 };
        draw_quarter_circle(arc_start, arc_end, computed_values().border_top().color, computed_values().border_top().width);
    }

    if (top_right_radius != 0) {
        Gfx::FloatPoint arc_start = { top_left_radius + top_border_rect.width(), 0 };
        Gfx::FloatPoint arc_end = { bordered_rect.width(), top_right_radius };
        draw_quarter_circle(arc_start, arc_end, computed_values().border_top().color, computed_values().border_top().width);
    }

    if (bottom_right_radius != 0) {
        Gfx::FloatPoint arc_start = { bordered_rect.width(), top_right_radius + right_border_rect.height() };
        Gfx::FloatPoint arc_end = { bottom_border_rect.width() + bottom_left_radius, bordered_rect.height() };
        draw_quarter_circle(arc_start, arc_end, computed_values().border_bottom().color, computed_values().border_bottom().width);
    }

    if (bottom_left_radius != 0) {
        Gfx::FloatPoint arc_start = { bottom_left_radius, bordered_rect.height() };
        Gfx::FloatPoint arc_end = { 0, bordered_rect.height() - bottom_left_radius };
        draw_quarter_circle(arc_start, arc_end, computed_values().border_bottom().color, computed_values().border_bottom().width);
    }
}

void Box::paint_background(PaintContext& context)
{
    // If the body's background properties were propagated to the root element, do no re-paint the body's background.
    if (is_body() && document().html_element()->should_use_body_background_properties())
        return;

    Gfx::IntRect background_rect;
    Color background_color = computed_values().background_color();
    const Gfx::Bitmap* background_image = this->background_image() ? this->background_image()->bitmap() : nullptr;
    CSS::Repeat background_repeat_x = computed_values().background_repeat_x();
    CSS::Repeat background_repeat_y = computed_values().background_repeat_y();

    if (is_root_element()) {
        // CSS 2.1 Appendix E.2: If the element is a root element, paint the background over the entire canvas.
        background_rect = context.viewport_rect();

        // Section 2.11.2: If the computed value of background-image on the root element is none and its background-color is transparent,
        // user agents must instead propagate the computed values of the background properties from that element’s first HTML BODY child element.
        if (document().html_element()->should_use_body_background_properties()) {
            background_color = document().background_color(context.palette());
            background_image = document().background_image();
            background_repeat_x = document().background_repeat_x();
            background_repeat_y = document().background_repeat_y();
        }
    } else {
        background_rect = enclosing_int_rect(padded_rect());
    }

    // HACK: If the Box has a border, use the bordered_rect to paint the background.
    //       This way if we have a border-radius there will be no gap between the filling and actual border.
    if (computed_values().border_top().width || computed_values().border_right().width || computed_values().border_bottom().width || computed_values().border_left().width)
        background_rect = enclosing_int_rect(bordered_rect());

    auto background_data = Painting::BackgroundData {
        .color = background_color,
        .image = background_image,
        .repeat_x = background_repeat_x,
        .repeat_y = background_repeat_y
    };
    Painting::paint_background(context, background_rect, background_data, normalized_border_radius_data());
}

void Box::paint_box_shadow(PaintContext& context)
{
    auto box_shadow_data = computed_values().box_shadow();
    if (!box_shadow_data.has_value())
        return;

    auto resolved_box_shadow_data = Painting::BoxShadowData {
        .offset_x = (int)box_shadow_data->offset_x.resolved_or_zero(*this, width()).to_px(*this),
        .offset_y = (int)box_shadow_data->offset_y.resolved_or_zero(*this, width()).to_px(*this),
        .blur_radius = (int)box_shadow_data->blur_radius.resolved_or_zero(*this, width()).to_px(*this),
        .color = box_shadow_data->color
    };
    Painting::paint_box_shadow(context, enclosing_int_rect(bordered_rect()), resolved_box_shadow_data);
}

Painting::BorderRadiusData Box::normalized_border_radius_data()
{
    return Painting::normalized_border_radius_data(*this, bordered_rect(),
        computed_values().border_top_left_radius(),
        computed_values().border_top_right_radius(),
        computed_values().border_bottom_right_radius(),
        computed_values().border_bottom_left_radius());
}

// https://www.w3.org/TR/css-display-3/#out-of-flow
bool Box::is_out_of_flow(FormattingContext const& formatting_context) const
{
    // A box is out of flow if either:

    // 1. It is floated (which requires that floating is not inhibited).
    if (!formatting_context.inhibits_floating() && computed_values().float_() != CSS::Float::None)
        return true;

    // 2. It is "absolutely positioned".
    switch (computed_values().position()) {
    case CSS::Position::Absolute:
    case CSS::Position::Fixed:
        return true;
    case CSS::Position::Static:
    case CSS::Position::Relative:
    case CSS::Position::Sticky:
        break;
    }

    return false;
}

HitTestResult Box::hit_test(const Gfx::IntPoint& position, HitTestType type) const
{
    // FIXME: It would be nice if we could confidently skip over hit testing
    //        parts of the layout tree, but currently we can't just check
    //        m_rect.contains() since inline text rects can't be trusted..
    HitTestResult result { absolute_rect().contains(position.x(), position.y()) ? this : nullptr };
    for_each_child_in_paint_order([&](auto& child) {
        auto child_result = child.hit_test(position, type);
        if (child_result.layout_node)
            result = child_result;
    });
    return result;
}

void Box::set_needs_display()
{
    if (!is_inline()) {
        browsing_context().set_needs_display(enclosing_int_rect(absolute_rect()));
        return;
    }

    Node::set_needs_display();
}

bool Box::is_body() const
{
    return dom_node() && dom_node() == document().body();
}

void Box::set_offset(const Gfx::FloatPoint& offset)
{
    if (m_offset == offset)
        return;
    m_offset = offset;
    did_set_rect();
}

void Box::set_size(const Gfx::FloatSize& size)
{
    if (m_size == size)
        return;
    m_size = size;
    did_set_rect();
}

Gfx::FloatPoint Box::effective_offset() const
{
    if (m_containing_line_box_fragment)
        return m_containing_line_box_fragment->offset();
    return m_offset;
}

const Gfx::FloatRect Box::absolute_rect() const
{
    Gfx::FloatRect rect { effective_offset(), size() };
    for (auto* block = containing_block(); block; block = block->containing_block()) {
        rect.translate_by(block->effective_offset());
    }
    return rect;
}

void Box::set_containing_line_box_fragment(LineBoxFragment& fragment)
{
    m_containing_line_box_fragment = fragment.make_weak_ptr();
}

StackingContext* Box::enclosing_stacking_context()
{
    for (auto* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
        if (!is<Box>(ancestor))
            continue;
        auto& ancestor_box = verify_cast<Box>(*ancestor);
        if (!ancestor_box.establishes_stacking_context())
            continue;
        VERIFY(ancestor_box.stacking_context());
        return ancestor_box.stacking_context();
    }
    // We should always reach the Layout::InitialContainingBlock stacking context.
    VERIFY_NOT_REACHED();
}

LineBox& Box::ensure_last_line_box()
{
    if (m_line_boxes.is_empty())
        return add_line_box();
    return m_line_boxes.last();
}

LineBox& Box::add_line_box()
{
    m_line_boxes.append(LineBox());
    return m_line_boxes.last();
}

float Box::width_of_logical_containing_block() const
{
    auto* containing_block = this->containing_block();
    VERIFY(containing_block);
    return containing_block->width();
}

}