//
// Created by erki on 13.05.21.
//

#ifndef SKULLC_UTILITY_PIXELBUFFER_HPP
#define SKULLC_UTILITY_PIXELBUFFER_HPP

#include <array>
#include <cmath>
#include <cstdint>
#include <string_view>

namespace Utility
{

template<std::size_t W, std::size_t H>
class PixelBuffer
{
public:
  static constexpr std::size_t width = W;
  static constexpr std::size_t height = H;
  using value = std::uint8_t;
  using container = std::array<value, width * height>;
  using iterator = typename container::iterator;
  using const_iterator = typename container::const_iterator;
  using coordinates = std::pair<std::size_t, std::size_t>;

  PixelBuffer()
      : data_({0})
  {}

  explicit PixelBuffer(const value& fill_value)
      : data_()
  {
    fill(fill_value);
  }

  constexpr value& at(const std::size_t& x, const std::size_t& y)
  {
    return data_[x + ((y) *width)];
  }

  constexpr const value& at(const std::size_t& x, const std::size_t& y) const
  {
    return data_[x + ((y) *width)];
  }

  constexpr value& at(const coordinates& c)
  {
    return at(x_(c), y_(c));
  }

  constexpr const value& at(const coordinates& c) const
  {
    return at(x_(c), y_(c));
  }

  const container& data() const
  {
    return data_;
  }

  const value* ptr() const
  {
    return data_.data();
  }

  iterator begin()
  {
    return data_.begin();
  }

  iterator end()
  {
    return data_.end();
  }

  const_iterator cbegin() const
  {
    return data_.cbegin();
  }

  const_iterator cend() const
  {
    return data_.cend();
  }

  void fill(const value& color)
  {
    data_.fill(color);
  }

  /**
   * Draws the text in the font provided onto the pixel buffer.
   *
   * Currently only supports fonts which are 1 byte high at most.
   *
   * @todo: make the function work with multi-byte fonts.
   *
   * @tparam Font The font object to be used. Must have the following members:
   *  * height, indicating how many pixels tall the font is.
   *  * width, indicating how many pixels wide the font is.
   *  * getCharacterBytes(char) that returns start and stop iterators for a given character.
   */
  template<typename Font>
  void text(const std::string_view& text, const coordinates& start, const value& color, const value& background = 0x00)
  {
    std::uint32_t x = x_(start);
    const std::uint32_t y = y_(start);
    for (const char& c : text)
    {
      const auto [c_start, c_stop] = Font::getCharacterBytes(c);

      for (auto it = c_start; it != c_stop; it++, x++)
      {
        const std::uint8_t& column_byte = *it;

        if (x >= width)
          return;

        for (std::uint32_t i = 0; i < Font::height && i + y < height; i++)
        {
          at(x, y + i) = column_byte & (1 << i) ? color : background;
        }
      }

      x++;
    }
  }

  void rectangle(const coordinates& top_left, const coordinates& size, const value& color)
  {
    for (auto i = x_(top_left); i < (x_(top_left) + x_(size)); i++)
    {
      at(i, y_(top_left)) = color;
      at(i, y_(top_left) + y_(size) - 1) = color;
    }

    for (auto i = y_(top_left); i < (y_(top_left) + y_(size)); i++)
    {
      at(x_(top_left), i) = color;
      at(x_(top_left) + x_(size) - 1, i) = color;
    }
  }

  void line(const coordinates& p1, const coordinates& p2, const value& color)
  {
    const coordinates start = {std::min(x_(p1), x_(p2)), std::min(y_(p1), y_(p2))};
    const coordinates stop = {std::max(x_(p1), x_(p2)), std::max(y_(p1), y_(p2))};

    const auto dx = std::int32_t(x_(stop)) - std::int32_t(x_(start));
    const auto dy = std::int32_t(y_(stop)) - std::int32_t(y_(start));

    auto x = std::int32_t(x_(start));
    auto y = std::int32_t(y_(start));

    // We shortcut the direct lines, as Bresenham's algorithm cannot handle them.
    if (dx == 0 && dy == 0)
    {
      at(start) = color;
    }
    else if (dx == 0)
    {
      for (; y < y_(stop); y++)
        at({x, y}) = color;
    }
    else if (dy == 0)
    {
      for (; x < x_(stop); x++)
        at({x, y}) = color;
    }
    else
    {
      // Bresenham's algorithm.
      std::int32_t p = 2 * dy - dx;

      while (x < x_(stop))
      {
        at({x, y}) = color;

        if (p >= 0)
        {
          y++;
          p = p + 2 * dy - 2 * dx;
        }
        else
        {
          p = p + 2 * dy;
        }

        x++;
      }
    }
  }

  void circle(const coordinates& center, const std::size_t radius, const value& color)
  {
    auto draw_pixels = [this, color, center](const std::size_t& x, const std::size_t& y) {
      at(x_(center) + x, y_(center) + y) = color;
      at(x_(center) - x, y_(center) + y) = color;
      at(x_(center) + x, y_(center) - y) = color;
      at(x_(center) - x, y_(center) - y) = color;

      at(x_(center) + y, y_(center) + x) = color;
      at(x_(center) - y, y_(center) + x) = color;
      at(x_(center) + y, y_(center) - x) = color;
      at(x_(center) - y, y_(center) - x) = color;
    };

    auto x = std::int32_t(0);
    auto y = std::int32_t(radius);

    auto d = 3 - 2 * std::int32_t(radius);

    draw_pixels(x, y);
    while (y >= x)
    {
      x++;

      if (d > 0)
      {
        y--;
        d = d + 4 * (x - y) + 10;
      }
      else
      {
        d = d + 4 * x + 6;
      }

      draw_pixels(x, y);
    }
  }

  template<std::size_t VW, std::size_t VH, typename TP>
  struct View
  {
    constexpr static std::size_t width = VW;
    constexpr static std::size_t height = VH;
    using parent_type = std::decay_t<TP>;
    using value = typename parent_type::value;
    using coordinates = typename parent_type::coordinates;

    static_assert(width <= parent_type::width, "Parent type width is smaller than view's width.");
    static_assert(height <= parent_type::height, "Parent type height is smaller than view's height.");

    coordinates offset;
    parent_type& parent;

    View() = delete;
    explicit View(const coordinates& offset, parent_type& buffer)
        : offset(offset), parent(buffer)
    {}

    constexpr value& at(const std::size_t& x, const std::size_t& y)
    {
      return parent.at(parent.x_(offset) + x, parent.y_(offset) + y);
    }

    constexpr const value& at(const std::size_t& x, const std::size_t& y) const
    {
      return parent.at(parent.x_(offset) + x, parent.y_(offset) + y);
    }

    constexpr value& at(const coordinates& c)
    {
      return parent.at(parent.x_(offset) + parent.x_(c), parent.y_(offset) + parent.y_(c));
    }

    constexpr const value& at(const coordinates& c) const
    {
      return parent.at(parent.x_(offset) + parent.x_(c), parent.y_(offset) + parent.y_(c));
    }

    template<std::size_t VW_, std::size_t VH_>
    auto view(const coordinates& offset)
    {
      return View<VW_, VH_, parent_type>(offset, parent);
    }
  };

  template<std::size_t VW, std::size_t VH, typename TP>
  friend struct View;

  template<std::size_t VW, std::size_t VH>
  auto view(const coordinates& offset) -> View<VW, VH, decltype(*this)>
  {
    using rtype = View<VW, VH, decltype(*this)>;
    return rtype(offset, *this);
  }

private:
  container data_;

  constexpr const std::size_t& x_(const coordinates& c) const
  {
    return c.first;
  }

  constexpr const std::size_t& y_(const coordinates& c) const
  {
    return c.second;
  }
};

}// namespace Utility

#endif//SKULLC_UTILITY_PIXELBUFFER_HPP