namespace seafire::protocol
{

  template<typename H>
  bool
  has(message_t const& m)
  {
    // FIXME: Parse header as well, to make sure it is valid.
    return m.headers().contains(H::name);
  }

  template<typename H>
  bool
  has_quick(message_t const& m)
  {
    return m.headers().contains(H::name);
  }

  template<typename H>
  std::optional<traits::alias_type_t<H>>
  get(message_t const& m)
  {
    std::error_code ignored_ec;
    return get<H>(m, ignored_ec);
  }

  template<typename H>
  std::optional<traits::alias_type_t<H>>
  get(message_t const& m, std::error_code& ec)
  {
    return H::try_parse(m.headers().get(H::name), ec);
  }

  template<typename H, typename... Args>
  void
  set(message_t& m, Args&&... args)
  {
    using type = traits::alias_type_t<H>;

    if constexpr (traits::has_overridden_to_string_v<H>) {
      m.set_header(H::name, H::to_string(type{std::forward<Args>(args)...}));
    }
    else {
      using std::to_string;
      m.set_header(H::name, to_string(type{std::forward<Args>(args)...}));
    }
  }

  template<typename H, typename... Args>
  void
  set_if_not_set(message_t& m, Args&&... args)
  {
    if (has_quick<H>())
      return;

    set<H>(m, std::forward<Args>(args)...);
  }

  template<typename H>
  void
  erase(message_t& m)
  {
    m.erase_header(H::name);
  }

} // namespace seafire::protocol