module RandomString

  HUMAN = %w{2 3 4 6 7 9 a c d e f g h j k m n p q r t v w x y}
  LOWER = [*'a'..'z']
  PARAM = [*'a'..'z', *0..9]
  FULL  = [*'a'..'z', *'A'..'Z', *0..9]
  MIXED = [*'a'..'z', *'A'..'Z']

  def self.by_rand(length = 8, set = :full)
    chars = get_chars(set)
    set_length = chars.length
    (0...length).map { chars[SecureRandom.random_number(set_length)] }.join
  end

  def self.by_sample(length = 8, set = :full)
    chars = get_chars(set)
    [].fill(0, length) { chars.sample }.join
  end

  def self.by_shuffle(length = 8, set = :full)
    get_chars(set).shuffle[0, length].join
  end

  def self.token(length = 28)
    by_rand(length, :param)
  end

  private

    def self.get_chars(set)
      return set if set.kind_of? Array
      const_get(set.to_s.upcase)
    end

end