def export_orders_promo_info_csv(start_date, end_date)
  # start_date and end_date params should be Date objects
  rows = []
  rows << ["order_number", "status", "sub_total", "total", "discount", "promotion_code"]
  Order::History.where(order_number: /^WO/, finalized_at: start_date..end_date).each do |order|
    row = []
    row << order.order_number
    row << order.status
    row << order.final_sub_total
    row << order.final_total
    row << order.promotion_code_discount
    row << order.promotion_code
    rows << row
  end
  File.write("discount_orders_#{start_date}_#{end_date}.csv", rows.map(&:to_csv).join)
end