#include "x86_64/vga/text.hpp"

#include "x86_64/boot/boot.hpp"
#include "x86_64/vga/crtc.hpp"

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

namespace teachos::vga::x86_64::text
{
  using boot::x86_64::vga_buffer_pointer;

  namespace
  {
    // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
    auto constinit buffer_offset = std::ptrdiff_t{};

    constexpr auto DEFAULT_TEXT_BUFFER_WIDTH = 80U;
    constexpr auto DEFAULT_TEXT_BUFFER_HEIGHT = 25U;
    constexpr auto CURSOR_ENABLED_BIT = 5U;

    auto write_char(char code_point, attribute attribute) -> void
    {
      vga_buffer_pointer[buffer_offset++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
    };
  }  // namespace

  auto device::clear(attribute attribute) -> void
  {
    buffer_offset = 0;
    std::ranges::fill_n(vga_buffer_pointer.get(), DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT,
                        std::pair{' ', std::bit_cast<std::byte>(attribute)});
  }

  auto device::cursor(bool enabled) -> void
  {
    auto cursor_disable_byte = std::byte{!enabled} << CURSOR_ENABLED_BIT;

    crtc::address::write(crtc::registers::cursor_start);
    crtc::data::write(crtc::data::read() | cursor_disable_byte);
  }

  auto device::newline() -> void
  {
    auto current_line = buffer_offset / DEFAULT_TEXT_BUFFER_WIDTH;
    auto next_line = current_line + 1;

    if (next_line >= DEFAULT_TEXT_BUFFER_HEIGHT)
    {
      auto begin = vga_buffer_pointer + DEFAULT_TEXT_BUFFER_WIDTH;
      auto end = vga_buffer_pointer + DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT;
      std::ranges::move(begin, end, vga_buffer_pointer.get());
      buffer_offset = current_line * DEFAULT_TEXT_BUFFER_WIDTH;
    }
    else
    {
      buffer_offset = next_line * DEFAULT_TEXT_BUFFER_WIDTH;
    }
  }

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

  auto device::writeln(std::string_view code_points, attribute attribute) -> void
  {
    std::ranges::for_each(code_points, [&](auto code_point) { write_char(code_point, attribute); });
    newline();
  }

}  // namespace teachos::vga::x86_64::text