#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 & f) -> int
  {
    auto it = std::ranges::find(m_open_files, nullptr);
    if (it != m_open_files.end())
    {
      *it = &f;
      return static_cast<int>(it - m_open_files.begin());
    }

    return -1;
  }

  auto file_descriptor_table::get_file(int fd) -> open_file_description &
  {
    if (fd < 0)
    {
      kapi::system::panic("[FILESYSTEM] get_file called with negative descriptor.");
    }

    auto const index = static_cast<size_t>(fd);
    if (index >= m_open_files.size() || m_open_files[index] == nullptr)
    {
      kapi::system::panic("[FILESYSTEM] get_file called with invalid descriptor.");
    }

    return *m_open_files[index];
  }

  auto file_descriptor_table::remove_file(int fd) -> void
  {
    if (fd < 0)
    {
      kapi::system::panic("[FILESYSTEM] remove_file called with negative descriptor.");
    }

    auto const index = static_cast<size_t>(fd);
    if (index >= m_open_files.size())
    {
      kapi::system::panic("[FILESYSTEM] remove_file called with out-of-range descriptor.");
    }

    m_open_files[index] = nullptr;
  }
}  // namespace filesystem