defmodule EctoGettext do
  @moduledoc """
  EctoGettext - library for localization Ecto validation errors with using Gettext

  ### Example:

    import EctoGettext

    localize_validations(MyApp.Gettext, errors)
  """

  @doc """
  Get a list of errors and return a new list with translated errors
  """
  @spec localize_validations(module, list) :: list
  def localize_validations(module, errors) do
    errors
    |> Enum.map(fn elem -> localize(module, elem) end)
  end

  @spec localize(module, tuple) :: {String.t, String.t}
  defp localize(module, error) do
    {attr, message} = error
    {set_attr(module, attr), set_message(module, message)}
  end

  @spec numbers() :: list
  defp numbers, do: ~w(0 1 2 3 4 5 6 7 8 9)

  @spec set_attr(module, atom) :: String.t
  defp set_attr(module, attr) do
    attr =
      attr
      |> Atom.to_string
      |> String.replace("_", " ")

    Gettext.dgettext(module, "attributes", attr)
  end

  @spec set_message(module, String.t) :: String.t
  defp set_message(module, message) do
    message = String.downcase(message)

    cond do
      String.starts_with?(message, "should be") && parse_number(message) ->
        Gettext.dgettext(module, "errors", format_message(message), count: parse_number(message))
      true ->
        Gettext.dgettext(module, "errors", message)
    end
  end

  @spec format_message(String.t) :: String.t
  defp format_message(message) do
    message
    |> String.graphemes
    |> Enum.filter(fn elem -> !Enum.member?(numbers, elem) end)
    |> Enum.join
    |> String.split(" ", trim: true)
    |> List.insert_at(4, "%{count}")
    |> Enum.join(" ")
  end

  @spec parse_number(String.t) :: integer | nil
  defp parse_number(message) do
    message =
      message
      |> String.graphemes
      |> Enum.filter(fn elem -> Enum.member?(numbers, elem) end)
      |> Enum.join

    case message do
      "" ->
        nil
      _ ->
        String.to_integer(message)
    end
  end
end