#include <cmath>

#include <basic_widgets/core/math.hpp>
#include <basic_widgets/w/button_impl.hpp>
#include <basic_widgets/w/widget_factory.hpp>

using namespace bwidgets;

ButtonImpl::ButtonImpl(Widget* parent) noexcept
  : WidgetImpl {parent}, _caption {create_caption(this)}
{
    enable_mouse_handler(_widget_area, _viewport);

    _caption->alignment = Caption::Alignment::CENTER;
    _caption->render_mode(Font::RenderMode::BLENDED);

    border_gradient = [this](const int len, const int pos,
                             const float divider) -> Color {
        const auto& end_color = hovered() ? color_bg_hover : color_bg;
        return lerp(end_color / divider, end_color, linear(pos, 0, len));
    };
}

auto ButtonImpl::size() const noexcept -> Size
{
    return _caption->size() + border_size * 2;
}

auto ButtonImpl::text() const noexcept -> std::string_view
{
    return _caption->text();
}

void ButtonImpl::text(std::string txt)
{
    _caption->text(std::move(txt));
    _handle_geometry_change(_viewport);
}

void ButtonImpl::_handle_font_change(const std::shared_ptr<Font>& f)
{
    _caption->font(f);
    _handle_geometry_change(_viewport);
}

void ButtonImpl::_handle_font_color_change(const Color fg, Color)
{
    _caption->font_color_fg(fg);
}

void ButtonImpl::_handle_geometry_change(const SDL_Rect& vp)
{
    const auto h = _caption->size().h + 2 * border_size.h;
    _widget_area = {0, center_line(vp.h, _caption->size().h) - border_size.h, vp.w, h};

    const auto txt_size = _caption->size();
    _caption_area       = {center_line(vp.w, txt_size.w), center_line(vp.h, txt_size.h),
                     txt_size.w, txt_size.h};

    _caption->viewport(rect_offset(_caption_area, vp));
}

void ButtonImpl::_handle_renderer_change(const std::shared_ptr<Renderer>& r)
{
    _caption->renderer(r);
}

void ButtonImpl::_handle_rendering()
{
    const Color& c       = hovered() ? color_bg_hover : color_bg;
    const auto   divider = pushed() ? 1.5F : 2.F;
    auto         x       = 0;
    auto         y       = 0;
    const auto   biggest_dimension =
      border_size.w > border_size.h ? border_size.w : border_size.h;
    const auto& max_xy = border_size.w > border_size.h ? x : y;

    // Render button borders.
    while (x < border_size.w || y < border_size.h) {
        _renderer->draw_color(border_gradient(biggest_dimension, max_xy, divider))
          ->draw_rect(rect_margin(_widget_area, {x, y}));
        if (x < border_size.w) x++;
        if (y < border_size.h) y++;
    }

    _renderer->draw_color(c)->fill_rect(rect_margin(_widget_area, border_size));
    _caption->font_color_bg(c);
    _caption->render();
}

void ButtonImpl::_on_push(const bool state)
{
    // Move slightly the caption position to give a push effect.
    const auto offset = [state, this]() -> SDL_Point {
        if (state) {
            return {_viewport.x + 1, _viewport.y + 1};
        }
        return {_viewport.x, _viewport.y};
    }();

    _caption->viewport(rect_offset(_caption_area, offset));
}