Sage: Business Logic Getting Worse

sign_up_geeting_worse.ex

defmodule MyApp.Domain.User.SignUp do
  def create_and_subscribe_user(attrs) do
    Repo.transaction(fn ->
      with {:ok, user} <- create_user(attrs),
           {:ok, plans} <- fetch_subscription_plans(attrs),
           {:ok, charge} <- charge_card(user, subscription),
           {:ok, subscription} <- create_subscription(user, plan, attrs),
           {:ok, _delivery} <- schedule_delivery(user, subscription, attrs),
           {:ok, _receipt} <- send_email_receipt(user, subscription, attrs),
           {:ok, user} <- update_user(user, %{subscription: subscription}) do
        {:ok, user}
      else
        {:error, {:charge_failed, _reason} = error} ->
          # First problem: charge is not available here
          :ok = refund(charge)
          {:error, error}

        {:error, {:create_subscription, _reason} = error} ->
          # Second problem: growing list of compensations
          :ok = refund(charge)
          :ok = delete_subscription(subscription)
          {:error, error}

        # Third problem: how to decide when we should be sending another email or
        # at which stage we've failed?

        other ->
          # Will rollback transaction on all other errors
          :ok = ensure_deleted(fn -> refund(charge) end)
          :ok = ensure_deleted(fn -> delete_subscription(subscription) end)
          :ok = ensure_deleted(fn -> delete_delivery_from_schedule(delivery) end)
          other
      end
    end)
  end

  defp ensure_deleted(cb) do
    case cb.() do
      :ok -> :ok
      {:error, :not_found} -> :ok
    end
  end
end