#include "arch/vga/text/buffer.hpp"

#include "arch/vga/text/attribute.hpp"

#include <algorithm>
#include <bit>
#include <cstddef>
#include <span>
#include <string_view>
#include <utility>

namespace arch::vga::text
{
  buffer::buffer(std::size_t width, std::size_t height, cell * start, std::size_t position)
      : m_width{width}
      , m_height{height}
      , m_buffer{start, m_width * m_height}
      , m_position{position}
  {}

  auto buffer::clear() -> void
  {
    m_position = 0;
    std::ranges::fill(m_buffer, std::pair{'\0', static_cast<std::byte>(0x00)});
  }

  auto buffer::write(std::string_view code_points, attribute attribute) -> void
  {
    std::ranges::for_each(code_points, [&](auto code_point) -> void { write(code_point, attribute); });
  }

  auto buffer::write(char code_point, attribute attribute) -> void
  {
    if (m_position + 1 > m_height * m_width)
    {
      scroll();
    }

    if (!handle_special_code_point(code_point, attribute))
    {
      do_write(code_point, attribute);
    }
  };

  auto buffer::newline() -> void
  {
    auto free_glyphs_in_line = m_width - column();
    m_position += free_glyphs_in_line;
  }

  auto buffer::scroll(std::size_t nof_lines) -> void
  {
    auto scroll_count = std::min(nof_lines, m_height);

    auto scroll_start = m_buffer.begin() + (scroll_count * m_width);
    std::ranges::move(scroll_start, m_buffer.end(), m_buffer.begin());

    auto clear_start = m_buffer.begin() + (m_height - scroll_count) * m_width;
    std::ranges::fill(clear_start, m_buffer.end(), cell{});

    m_position = (line() - scroll_count) * m_width;
  }

  auto buffer::column() const noexcept -> std::ptrdiff_t
  {
    return m_position % m_width;
  }

  auto buffer::line() const noexcept -> std::ptrdiff_t
  {
    return m_position / m_width;
  }
  auto buffer::handle_special_code_point(char code_point, attribute attribute) -> bool
  {
    switch (code_point)
    {
      case '\n':
        newline();
        return true;
      case '\r':
        m_position -= column();
        return true;
      case '\t':
        do_write("  ", attribute);
        return true;
      default:
        return false;
    }
  }

  auto buffer::do_write(std::string_view code_points, attribute attribute) -> void
  {
    std::ranges::for_each(code_points, [&](auto code_point) -> void { do_write(code_point, attribute); });
  }

  auto buffer::do_write(char code_point, attribute attribute) -> void
  {
    m_buffer[m_position++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
  }

}  // namespace arch::vga::text