#include "x86_64/vga/text.hpp"

#include "kapi/boot.hpp"
#include "kapi/cio.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 = 80z;
    constexpr auto DEFAULT_TEXT_BUFFER_HEIGHT = 25z;
    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);
  }

  [[nodiscard]] auto device::column() const noexcept -> std::ptrdiff_t
  {
    return m_position % DEFAULT_TEXT_BUFFER_WIDTH;
  }

  [[nodiscard]] auto device::line() const noexcept -> std::ptrdiff_t
  {
    return m_position / DEFAULT_TEXT_BUFFER_WIDTH;
  }

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

  auto device::scroll(std::ptrdiff_t nof_lines) -> void
  {
    auto scroll_count = std::min(nof_lines, DEFAULT_TEXT_BUFFER_HEIGHT);

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

    auto clear_start = buffer.begin() + (DEFAULT_TEXT_BUFFER_HEIGHT - scroll_count) * DEFAULT_TEXT_BUFFER_WIDTH;
    std::ranges::fill(clear_start, buffer.end(), glyph{});

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

  auto device::write(cio::output_stream stream, std::string_view text) -> void
  {
    auto attributes = [&] -> attribute {
      switch (stream)
      {
        case cio::output_stream::stderr:
          return common_attributes::red_on_black;
        default:
          return common_attributes::green_on_black;
      }
    }();
    write(text, attributes);
  }

  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
  {
    if (m_position + 1 > DEFAULT_TEXT_BUFFER_HEIGHT * DEFAULT_TEXT_BUFFER_WIDTH)
    {
      scroll();
    }

    if (code_point == '\n')
    {
      if (column())
      {
        newline();
      }
      return;
    }

    buffer[m_position++] = std::pair{code_point, std::bit_cast<std::byte>(attribute)};
  };

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