class NextNumber < ActiveRecord::Base

  class << self
    VALID_CLASSES = [PurchaseOrder, SalesOrder]

    def get_next_number_for(object)
      throw Exception.new("Unsaved object not allowed") if object.new_record?
      throw Exception.new("Invalid object type for NextNumber#get_next_number_for") unless VALID_CLASSES.include?(object.class)

      begin
        next_number = NextNumber.find_by_sequential_type(object.class.to_s)
        next_number.sequential_id = object.id
        next_number.save
        next_number.lock_version
      rescue ActiveRecord::StaleObjectError => e
        retry
      end
    end
  end

end