#include <kernel/filesystem/open_file_table.hpp>

#include <kernel/filesystem/open_file_descriptor.hpp>

#include <kapi/system.hpp>

#include <kstd/memory>

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

namespace
{
  constinit auto static global_open_file_table = std::optional<kernel::filesystem::open_file_table>{};
}  // namespace

namespace kernel::filesystem
{
  auto open_file_table::init() -> void
  {
    if (global_open_file_table)
    {
      kapi::system::panic("[FILESYSTEM] Open file table has already been initialized.");
    }

    global_open_file_table.emplace(open_file_table{});
  }

  auto open_file_table::get() -> open_file_table &
  {
    if (!global_open_file_table)
    {
      kapi::system::panic("[FILESYSTEM] Open file table has not been initialized.");
    }

    return *global_open_file_table;
  }

  auto open_file_table::add_file(kstd::shared_ptr<open_file_descriptor> const & file_descriptor) -> int
  {
    if (!file_descriptor)
    {
      return -1;
    }

    auto it = std::ranges::find_if(m_open_files, [](auto const & open_file) { return open_file == nullptr; });
    if (it != m_open_files.end())
    {
      *it = file_descriptor;
      return static_cast<int>(it - m_open_files.begin());
    }

    m_open_files.push_back(file_descriptor);
    return static_cast<int>(m_open_files.size() - 1);
  }

  auto open_file_table::get_file(int fd) const -> kstd::shared_ptr<open_file_descriptor>
  {
    if (fd < 0)
    {
      return nullptr;
    }

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

    return m_open_files.at(index);
  }

  auto open_file_table::remove_file(int fd) -> int
  {
    if (fd < 0)
    {
      return -1;
    }

    auto const index = static_cast<size_t>(fd);
    if (index >= m_open_files.size())
    {
      return -1;
    }

    m_open_files.at(index) = nullptr;
    return 0;
  }
}  // namespace kernel::filesystem

namespace kernel::tests::filesystem::open_file_table
{
  auto deinit() -> void
  {
    global_open_file_table.reset();
  }
}  // namespace kernel::tests::filesystem::open_file_table