get bought items by cart items
update main
update Pos class
fix BoughtItem Class
update handleBarcodes function
delete useless code
delete useless code
rename DiscountItem class to Promotion class
delete useless code
update main
update main
add getBarcode function
update calculatePromotion function
add get_promotion_type test
add getPromotionType function
success getPromotionType test
fix code
fix code
update code
add getPrice function