class ROTP::Base32

def decode(str)
  buffer = 0
  idx = 0
  bits_left = 0
  str = str.tr('=', '').upcase
  result = []
  str.split('').each do |char|
    buffer = buffer << SHIFT
    buffer = buffer | (decode_quint(char) & MASK)
    bits_left = bits_left + SHIFT
    if bits_left >= 8
      result[idx] = (buffer >> (bits_left - 8)) & 255
      idx = idx + 1
      bits_left = bits_left - 8
    end
  end
  result.pack('c*')
end

def decode_quint(q)
  CHARS.index(q) || raise(Base32Error, "Invalid Base32 Character - '#{q}'")
end

def encode(b)
  data = b.unpack('c*')
  out = String.new
  buffer = data[0]
  idx = 1
  bits_left = 8
  while bits_left > 0 || idx < data.length
    if bits_left < SHIFT
      if idx < data.length
        buffer = buffer << 8
        buffer = buffer | (data[idx] & 255)
        bits_left = bits_left + 8
        idx = idx + 1
      else
        pad = SHIFT - bits_left
        buffer = buffer << pad
        bits_left = bits_left + pad
      end
    end
    val = MASK & (buffer >> (bits_left - SHIFT))
    bits_left = bits_left - SHIFT
    out.concat(CHARS[val])
  end
  return out
end

def random(byte_length = 20)
 rand_bytes = SecureRandom.random_bytes(byte_length)
 self.encode(rand_bytes)
end

def random_base32(str_len = 32)
  byte_length = str_len * 5/8
  random(byte_length)
end