if Code.ensure_loaded?(Ecto) do
  defmodule EView.Changeset.Validators.PhoneNumber do
    @moduledoc """
    This helper validates phone numbers in international format (with `+:country_code`).
    """
    import Ecto.Changeset

    @phone_regex ~r/^\+[0-9]{9,16}$/

    def validate_phone_number(changeset, field, opts \\ []) do
      validate_change(changeset, field, {:phone_number, @phone_regex}, fn _, value ->
        if value =~ @phone_regex,
          do: [],
          else: [{field, {message(opts, "is not a valid phone number"), [validation: :phone_number]}}]
      end)
    end

    defp message(opts, key \\ :message, default) do
      Keyword.get(opts, key, default)
    end
  end
end