LoriCreditCard.rb

card_number = "342801633855673"

credit_card = card_number.chars.map(&:to_i).reverse

double_index = credit_card.select.with_index { |_,i| i.odd? }
products = double_index.map {|num| num * 2 }
doubled_sum = products.map {|digits| digits.to_s.split('')}.map{|pair| pair.reduce(0) {|sum, x| sum + x.to_i}}.reduce(:+)

product_sum = credit_card.select.with_index { |_,i| i.even? }.reduce(:+)

total_sum = doubled_sum + product_sum
if total_sum % 10 == 0
  puts "The card number #{card_number} is valid. Let's go shopping!"
else
  puts "The card number #{card_number} is invalid. Sorry!"
end