defmodule Plans do
  alias Plans.Transactions
  alias LineItems

  def change_plans(subscription, new_plan, user) do
    Sage.new()
    |> Sage.run(:validate, Transactions.authorize/2)
    |> Sage.run(:update_plan, Transactions.update_plan/2)
    |> Sage.run(:charge_plan, Transactions.charge/2, Transactions.refund/4)
    |> update_line_items(subscription, new_plan, user)
  end

  defp update_line_items(sage, subscription, new_plan, user) do
    line_items = LineItems.fetch_new_line_items(subscription, new_plan)

    sage = Enum.reduce(line_items, sage, fn line_item ->
      LineItems.Sagas.create_line_item(sage)
    end)

    Enum.reduce(subscriptions.line_items, sage, fn line_item ->
      LineItems.Sagas.remove_line_item(line_item)
    end)
  end
end