Friday challenge 2019-05-31

challenge.rb

#!/usr/bin/env ruby

class String
  def index
    ord > 96 ? ord - 96 : ord - 64
  end 

  def shift_by(other)
    caser = ord > 96 ? :downcase : :upcase
    i = self.index - other.index + 1 
    i +=26 if i < 0 
    ((i + 64).chr).send(caser)
  end 
end

message = 'DDaQuoKsukIhlwCzhySkmkosyTriVnjxzgNvysDMjDhFxzdhltbDTuoydmFnvozhtbh'

key = 'SALAD'.tr('[A-S]', '[D-V]') * 20

puts message.each_char.map.with_index { |l, i| l.shift_by(key[i]) }.join
~