from collections import namedtuple

import base64

DELIMITER = ':'
DecodedToken = namedtuple('DecodedToken', ['public_code', 'private_token'])

def encode_public_private_token(public_code, private_token, allow_public_only=False):
  # NOTE: This is for legacy tokens where the private token part is None. We should remove this
  # once older installations have been fully converted over (if at all possible).
  if private_token is None:
    assert allow_public_only
    return public_code

  assert isinstance(private_token, basestring)
  return base64.b64encode('%s%s%s' % (public_code, DELIMITER, private_token))


def decode_public_private_token(encoded, allow_public_only=False):
  try:
    decoded = base64.b64decode(encoded)
  except (ValueError, TypeError):
    if not allow_public_only:
      return None

    return DecodedToken(encoded, None)

  parts = decoded.split(DELIMITER, 2)
  if len(parts) != 2:
    return None

  return DecodedToken(*parts)