class Tins::Token

def initialize(options = {})
  bits     = options[:bits] || 128
  length   = options[:length]
  alphabet = options[:alphabet] || DEFAULT_ALPHABET
  alphabet.size > 1 or raise ArgumentError, 'need at least 2 symbols in alphabet'
  if length
    length > 0 or raise ArgumentError, 'length has to be positive'
  else
    bits > 0 or raise ArgumentError, 'bits has to be positive'
    length = (Math.log(1 << bits) / Math.log(alphabet.size)).ceil
  end
  self.bits = (Math.log(alphabet.size ** length) / Math.log(2)).floor
  token = ''
  length.times { token << alphabet[rand(alphabet.size)] }
  super token
end