module LuhnPro

# File lib/luhn_pro.rb, line 14
def self.get_check_num(number)
        #get check number for 'number' with Luhn method
        #nil if number is empty string
        return nil if number.empty?
        a=(number.gsub(/[^\d]/, "").split("").map {|i| i.to_i}).reverse
        #gsub - clean up number, delete not number characters
        #split - split to characters
        #map - make an array
        #to_i - convert each element to integer
        #reverse - reverse array for right order
        #...otherwise wrong result if numbers size is odd
        a.each_index {|i| a[i]= i%2==0 ? (a[i]*2>9?a[i]*2-10+1:a[i]*2):a[i]}
        #even indexes = same value
        #odds indexes = doubble value, more then 9 => e.g. ´12=1+2=>3´
        a.inject(:+)%10==0 ? 0.to_s : (10-a.inject(:+)%10).to_s
        #summarize values and mod 10, 0 if mod10 = 0, otherwise 10-mod10
end

# File lib/luhn_pro.rb, line 2
def self.getnum(number)
        #get number with checknumber
        return nil if number.empty?
        number+get_check_num(number)
end

# File lib/luhn_pro.rb, line 8
def self.isvalid?(number)
        #true if number has correct checknumber
        return nil if number.empty?
        get_check_num(number[0..-2]) == number[-1] ? true : false
end