#include "arch/memory/page_table.hpp"

#include "kapi/memory.hpp"

#include <algorithm>
#include <bit>
#include <cstddef>
#include <cstdint>
#include <optional>
#include <utility>

namespace arch::memory
{

  auto page_table::entry::clear() noexcept -> void
  {
    m_raw = 0;
  }

  auto page_table::entry::present() const noexcept -> bool
  {
    return (all_flags() & flags::present) != flags::empty;
  }

  auto page_table::entry::huge() const noexcept -> bool
  {
    return (all_flags() & flags::huge_page) != flags::empty;
  }

  auto page_table::entry::all_flags() const noexcept -> flags
  {
    return std::bit_cast<flags>(m_raw & ~frame_number_mask);
  }

  auto page_table::entry::all_flags(flags flags) noexcept -> void
  {
    m_raw = (m_raw & ~frame_number_mask) | std::to_underlying(flags);
  }

  auto page_table::entry::operator|=(flags rhs) noexcept -> page_table::entry &
  {
    auto raw_flags = std::to_underlying(rhs) & ~frame_number_mask;
    m_raw |= raw_flags;
    return *this;
  }

  auto page_table::entry::frame() const noexcept -> std::optional<kapi::memory::frame>
  {
    if (present())
    {
      return kapi::memory::frame::containing(kapi::memory::physical_address{m_raw & frame_number_mask});
    }
    return std::nullopt;
  }

  auto page_table::entry::frame(kapi::memory::frame frame, flags flags) noexcept -> void
  {
    m_raw = (frame.start_address().raw() | static_cast<std::uint64_t>(flags));
  };

  auto page_table::operator[](std::size_t index) -> entry &
  {
    return m_entries.at(index);
  }

  auto page_table::operator[](std::size_t index) const -> entry const &
  {
    return m_entries.at(index);
  }

  auto page_table::clear() noexcept -> void
  {
    std::ranges::for_each(m_entries, &page_table::entry::clear);
  }

  auto page_table::empty() const noexcept -> bool
  {
    return std::ranges::all_of(m_entries,
                               [](auto const & entry) -> auto { return entry.all_flags() == entry::flags::empty; });
  }

}  // namespace arch::memory