#include "x86_64/vga/text.hpp"

#include "kapi/boot.hpp"

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

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

namespace teachos::vga::x86_64::text
{
  namespace
  {
    constexpr auto BUFFER_BASE_ADDRESS = std::uintptr_t{0xb8000};
    constexpr auto DEFAULT_TEXT_BUFFER_WIDTH = 80U;
    constexpr auto DEFAULT_TEXT_BUFFER_HEIGHT = 25U;
    constexpr auto CURSOR_ENABLED_BIT = 5U;
  }  // namespace

  std::span<device::glyph> const device::buffer =
      std::span{std::bit_cast<device::glyph *>(BUFFER_BASE_ADDRESS +
                                               std::bit_cast<std::uintptr_t>(&teachos::boot::x86_64::TEACHOS_VMA)),
                DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT};

  device::device()
      : m_position{boot::bootstrap_information.vga_buffer_index}
  {}

  auto device::clear(attribute attribute) -> void
  {
    m_position = 0;
    std::ranges::fill(buffer, 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 = m_position / DEFAULT_TEXT_BUFFER_WIDTH;
    auto next_line = current_line + 1;

    if (std::cmp_greater_equal(next_line, DEFAULT_TEXT_BUFFER_HEIGHT))
    {
      auto begin = buffer.begin() + DEFAULT_TEXT_BUFFER_WIDTH;
      auto end = buffer.begin() + DEFAULT_TEXT_BUFFER_WIDTH * DEFAULT_TEXT_BUFFER_HEIGHT;
      std::ranges::move(begin, end, buffer.begin());
      m_position = current_line * DEFAULT_TEXT_BUFFER_WIDTH;
    }
    else
    {
      m_position = 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) -> void { write(code_point, attribute); });
  }

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

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

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