#include "filesystem/file_descriptor_table.hpp"

#include "kapi/system.hpp"

#include "filesystem/open_file_description.hpp"

#include <algorithm>
#include <cstddef>
#include <optional>

namespace filesystem
{
  namespace
  {
    constinit auto static global_file_descriptor_table = std::optional<file_descriptor_table>{};
  }  // namespace

  auto file_descriptor_table::init() -> void
  {
    if (global_file_descriptor_table)
    {
      kapi::system::panic("[FILESYSTEM] File descriptor table has already been initialized.");
    }

    global_file_descriptor_table.emplace(file_descriptor_table{});
  }

  auto file_descriptor_table::get() -> file_descriptor_table &
  {
    if (!global_file_descriptor_table)
    {
      kapi::system::panic("[FILESYSTEM] File descriptor table has not been initialized.");
    }

    return *global_file_descriptor_table;
  }

  auto file_descriptor_table::add_file(open_file_description & file_description) -> int
  {
    auto it = std::ranges::find_if(m_open_files, [](auto & open_file) { return !open_file.has_value(); });
    if (it != m_open_files.end())
    {
      *it = file_description;
      return static_cast<int>(it - m_open_files.begin());
    }

    return -1;
  }

  auto file_descriptor_table::get_file(int fd) const -> std::optional<open_file_description>
  {
    if (fd < 0)
    {
      return std::nullopt;
    }

    auto const index = static_cast<size_t>(fd);
    if (index >= m_open_files.size() || !m_open_files[index].has_value())
    {
      return std::nullopt;
    }

    return *m_open_files[index];
  }

  auto file_descriptor_table::remove_file(int fd) -> void
  {
    if (fd < 0)
    {
      return;
    }

    auto const index = static_cast<size_t>(fd);
    if (index >= m_open_files.size())
    {
      return;
    }

    m_open_files[index].reset();
  }
}  // namespace filesystem