nickname.rb

class Nickname
  def initialize
    @dict = File.readlines('enable1.txt').map(&:strip)
  end

  def generate(name)
    name = name.downcase.gsub(/\W+/, '')
    substrings(name).reduce([]) do |names, substring|
      return names.map(&:capitalize).join(', ') if names.any? && substring.size < names.last.size
      (@dict.include? substring) ? names.push(substring) : names
    end
  end

  def substrings(str)
    Array.new(Array.new(str.size, 1).join.to_i(2)) do |n|
      binary = "%0#{str.size}b" % (n + 1)
      binary.chars.each_with_index.map { |e, i| e == '1' ? str.chars[i] : nil }.compact.join
    end.uniq.select { |sub| sub[0] == str[0] }.sort_by(&:size).reverse
  end
end