defmodule Localizator.Translator do
  alias Localizator.Direction

  @typedoc """
  Locale
  """
  @type locale :: String.t()
  @type from :: locale
  @type from_may_be_nil :: from | nil
  @type to :: locale
  @type direction :: {from, to} | to | %{from: from, to: to} | %{to: to}
  @type direction_map :: %{to: to, from: from_may_be_nil}

  @typedoc """
  Translation service
  """
  @type translator :: Atom.t()

  @typedoc """
  Translation services list
  """
  @type translators :: [translator]

  @typedoc """
  Translation resource
  """
  @type resource :: String.t() | Map.t() | List.t()
  @type source :: resource
  @type result :: resource

  @typedoc """
  Error Message
  """
  @type message :: String.t()

  @spec list() :: translators
  def list(), do: Application.get_env(:localizator, :translators)

  @spec default() :: translator
  def default(), do: list() |> List.first()

  @spec translate(source, direction, translator) :: {:ok, result} | {:error, message}
  def translate(source, direction, translator \\ default()) do
    map = Direction.get(direction)
    translator.translate(source, map.to, map.from)
  end
end