defmodule Mercury.Types do
  @moduledoc false

  # Shared conversion helpers used by every resource's `from_json/1`.

  @doc false
  @spec datetime(value :: String.t() | nil) :: DateTime.t() | nil
  def datetime(nil), do: nil

  def datetime(value) when is_binary(value) do
    case DateTime.from_iso8601(value) do
      {:ok, datetime, _utc_offset} -> datetime
      {:error, _reason} -> nil
    end
  end

  def datetime(_other), do: nil

  @doc false
  @spec list_of(list :: list() | nil, from_json :: (map() -> struct())) :: [struct()]
  def list_of(nil, _from_json), do: []
  def list_of(list, from_json) when is_list(list), do: Enum.map(list, from_json)
end