change-o-matic.rb

class NegativeAmountPaidError < ArgumentError; end
class NotEnoughPaidError < ArgumentError; end


def change_o_matic(price:, amount_paid:)
	if amount_paid <= 0
		raise NegativeAmountPaidError, "amount_paid (#{amount_paid}) must not be negative or zero"
	elsif price > amount_paid
		raise NotEnoughPaidError, "amount paid (#{amount_paid}) must not be less than price (#{price})"
	end

	change = {1000 => 0, 500 => 0, 200 => 0, 100 => 0, 50 => 0, 20 => 0, 10 => 0, 5 => 0, 2 => 0, 1 => 0 }
	denominations = change.keys.sort.reverse
	amount_due = amount_paid - price


	denominations.each do |den|
		while amount_due >= den do
			change[den] += 1
			amount_due -= den
		end
	end

	return change
end

def process_payment(price:)
	puts "That will be #{price}, thanks"
	change = change_o_matic(price: price, amount_paid: 500)
	puts "Att returnera"
	change.each_pair do |denomination, amount|
		if amount > 0
			puts "#{denomination}: #{amount}"
		end
	end
	puts "Thanks, have a nice day!"
end


process_payment(price: 123)