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# vi: ts=4 expandtab
#
# Copyright (C) 2012 Yahoo! Inc.
#
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 3, as
# published by the Free Software Foundation.
#
# 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, see <http://www.gnu.org/licenses/>.
import re
from cloudinit import importer
from cloudinit import log as logging
from cloudinit import util
NAME_MTCH = re.compile(r"(^[a-zA-Z_][A-Za-z0-9_]*)\((.*?)\)$")
LOG = logging.getLogger(__name__)
class UnknownMerger(object):
# Named differently so auto-method finding
# doesn't pick this up if there is ever a type
# named "unknown"
def _handle_unknown(self, meth_wanted, value, merge_with):
return value
def merge(self, source, merge_with):
type_name = util.obj_name(source)
type_name = type_name.lower()
method_name = "_on_%s" % (type_name)
meth = None
args = [source, merge_with]
if hasattr(self, method_name):
meth = getattr(self, method_name)
if not meth:
meth = self._handle_unknown
args.insert(0, method_name)
return meth(*args)
class LookupMerger(UnknownMerger):
def __init__(self, lookups=None):
UnknownMerger.__init__(self)
if lookups is None:
self._lookups = []
else:
self._lookups = lookups
def _handle_unknown(self, meth_wanted, value, merge_with):
meth = None
for merger in self._lookups:
if hasattr(merger, meth_wanted):
# First one that has that method/attr gets to be
# the one that will be called
meth = getattr(merger, meth_wanted)
break
if not meth:
return UnknownMerger._handle_unknown(self, meth_wanted,
value, merge_with)
return meth(value, merge_with)
def _extract_merger_names(merge_how):
names = []
for m_name in merge_how.split("+"):
# Canonicalize the name (so that it can be found
# even when users alter it in various ways)
m_name = m_name.lower().strip()
m_name = m_name.replace("-", "_")
if not m_name:
continue
names.append(m_name)
return names
def construct(merge_how):
mergers_to_be = []
for name in _extract_merger_names(merge_how):
match = NAME_MTCH.match(name)
if not match:
msg = "Matcher identifer '%s' is not in the right format" % (name)
raise ValueError(msg)
(m_name, m_ops) = match.groups()
m_ops = m_ops.strip().split(",")
m_ops = [m.strip().lower() for m in m_ops if m.strip()]
merger_locs = importer.find_module(m_name,
[__name__],
['Merger'])
if not merger_locs:
msg = "Could not find merger named '%s'" % (m_name)
raise ImportError(msg)
else:
mod = importer.import_module(merger_locs[0])
mod_attr = getattr(mod, 'Merger')
mergers_to_be.append((mod_attr, m_ops))
# Now form them...
mergers = []
root = LookupMerger(mergers)
for (attr, opts) in mergers_to_be:
mergers.append(attr(root, opts))
return root
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