check number

check_number.rb

class CheckNumber
  ALPHABET = (2..9).to_a + ('a'..'z').to_a - %w[o i]
  # ALPHABET = (0..9).to_a + ('a'..'z').to_a + ('A'..'Z').to_a + %w[ @ & ]

  def initialize(uuid, size = 4, chunk_size = 4)
    @uuid = uuid
    @size = size
    @chunk_size = chunk_size
  end

  def run
    return chunks if size != chunk_size
    chars.join
  end

  private

  attr_reader :uuid, :size, :chunk_size

  def chars
    num = uuid.delete('-').to_i(16)
    Array.new(size).map.with_index do |elem, i|
      curr = ALPHABET.size
      ALPHABET[num % (curr).to_i].tap do
        num /= curr
      end
    end
  end

  def chunks
    chars
      .each_slice( chunk_size )
      .map(&:join)
      .join(' ')
  end

end