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# 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()
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