~bzr-pqm/bzr/bzr.dev

# Copyright (C) 2008 Canonical Ltd

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

"""Directory service registration and usage.

Directory services are utilities that provide a mapping from URL-like strings

to true URLs.  Examples include lp:urls and per-user location aliases.

"""

from bzrlib import registry

class DirectoryServiceRegistry(registry.Registry):

    """This object maintains and uses a list of directory services.

    Directory services may be registered via the standard Registry methods.

    They will be invoked if their key is a prefix of the supplied URL.

    Each item registered should be a factory of objects that provide a look_up

    method, as invoked by dereference.  Specifically, look_up should accept a

    name and URL, and return a URL.

    """

    def dereference(self, url):

        """Dereference a supplied URL if possible.

        URLs that match a registered directory service prefix are looked up in

        it.  Non-matching urls are returned verbatim.

        This is applied only once; the resulting URL must not be one that

        requires further dereferencing.

        :param url: The URL to dereference

        :return: The dereferenced URL if applicable, the input URL otherwise.

        """

        match = self.get_prefix(url)

        if match is None:

            return url

        service, name = match

        return service().look_up(name, url)

directories = DirectoryServiceRegistry()