gistfile1.txt

# model/order.rb
class Order
 def items_format_type
    items.group_by{ |order_item| order_item.item.format.type }.keys
  end
end

# lib/order_resource.rb
class OrderResource
 
  def self.create_on_external_service(order)
    order_external = ServiceExternal::Order.new(order, messagem: OrderResource.channer_text(order))
 
    if order_external.save
      order_external
    else
      raise InvalidOrderOnExternalService
    end
  end

 def self.channel_text order
    items_type = order.items_format_type.sort.join '_'

    if items_type.match /paper/
      I18n.t "order.final.message.#{items_type}", delivery_date: order.delivery_date.strftime("%d/%m/%Y")
    else
      I18n.t "order.final.message.#{items_type}"
    end
  end
end

# locales/pt.yml
pt:
  order:
    final:
      message:
        paper: "bla bla bla #{delivery_date}"
        pdf: etc etc etc
        epub: tititi tititi