~launchpad-pqm/launchpad/devel

# Copyright 2009 Canonical Ltd.  This software is licensed under the

# GNU Affero General Public License version 3 (see the file LICENSE).

"""Utility methods for random token generation."""

__metaclass__ = type

__all__ = [

    'create_token',

    'create_unique_token_for_table',

    ]

import random

from zope.component import getUtility

from lp.services.database.lpstorm import IMasterStore

def create_token(token_length):

    """Create a random token string.

    :param token_length: Specifies how long you want the token.

    """

    # Since tokens are, in general, user-visible, vowels are not included

    # below to prevent them from having curse/offensive words.

    characters = '0123456789bcdfghjklmnpqrstvwxzBCDFGHJKLMNPQRSTVWXZ'

    token = ''.join(

        random.choice(characters) for count in range(token_length))

    return unicode(token)

def create_unique_token_for_table(token_length, column):

    """Create a new unique token in a table.

    Generates a token and makes sure it does not already exist in

    the table and column specified.

    :param token_length: The length for the token string

    :param column: Database column where the token will be stored.

    :return: A new token string

    """

    # Use the master Store to ensure no race conditions. 

    store = IMasterStore(column.cls)

    token = create_token(token_length)

    while store.find(column.cls, column==token).one() is not None:

        token = create_token(token_length)

    return token