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# Copyright (c) 2010 Mark Sandstrom
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
from declarations import OrderedDeclaration, SubFactory
ATTR_SPLITTER = '__'
class CyclicDefinitionError(Exception):
"""Raised when cyclic definition were found."""
class LazyStub(object):
"""A generic container that allows for getting but not setting of attributes.
Attributes are set at initialization time."""
initialized = False
def __init__(self, attrs):
self.__attrs = attrs
self.__values = {}
self.__pending = []
self.initialized = True
def __fill__(self):
res = {}
for attr in self.__attrs:
res[attr] = getattr(self, attr)
return res
def __getattr__(self, name):
if name in self.__pending:
raise CyclicDefinitionError(
"Cyclic lazy attribute definition for %s. Current cycle is %r." %
(name, self.__pending))
elif name in self.__values:
return self.__values[name]
elif name in self.__attrs:
val = self.__attrs[name]
if isinstance(val, LazyValue):
self.__pending.append(name)
val = val.evaluate(self)
assert name == self.__pending.pop()
self.__values[name] = val
return val
else:
raise AttributeError(
"The parameter %s is unknown. Evaluated attributes are %r, definitions are %r." % (name, self.__values, self.__attrs))
def __setattr__(self, name, value):
if not self.initialized:
return super(LazyStub, self).__setattr__(name, value)
else:
raise AttributeError('Setting of object attributes is not allowed')
class DeclarationDict(dict):
def update_with_public(self, d):
"""Updates the DeclarationDict from a class definition dict.
Takes into account all public attributes and OrderedDeclaration
instances; ignores all attributes starting with '_'.
Returns a dict containing all remaining elements.
"""
remaining = {}
for k, v in d.iteritems():
if k.startswith('_') and not isinstance(v, OrderedDeclaration):
remaining[k] = v
else:
self[k] = v
return remaining
def copy(self, extra=None):
new = DeclarationDict()
new.update(self)
if extra:
new.update(extra)
return new
class LazyValue(object):
def evaluate(self, obj):
raise NotImplementedError("This is an abstract method.")
class SubFactoryWrapper(LazyValue):
def __init__(self, subfactory, subfields, create):
self.subfactory = subfactory
self.subfields = subfields
self.create = create
def evaluate(self, obj):
return self.subfactory.evaluate(self.create, self.subfields)
class OrderedDeclarationWrapper(LazyValue):
def __init__(self, declaration, sequence):
self.declaration = declaration
self.sequence = sequence
def evaluate(self, obj):
return self.declaration.evaluate(self.sequence, obj)
class AttributeBuilder(object):
"""Builds attributes from a factory and extra data."""
def __init__(self, factory, extra=None):
if not extra:
extra = {}
self.factory = factory
self._attrs = factory.declarations(extra)
self._subfields = self._extract_subfields()
def _extract_subfields(self):
sub_fields = {}
for key in list(self._attrs):
if ATTR_SPLITTER in key:
cls_name, attr_name = key.split(ATTR_SPLITTER, 1)
if cls_name in self._attrs:
sub_fields.setdefault(cls_name, {})[attr_name] = self._attrs.pop(key)
return sub_fields
def build(self, create):
self.factory.sequence = self.factory._generate_next_sequence()
wrapped_attrs = {}
for k, v in self._attrs.iteritems():
if isinstance(v, SubFactory):
v = SubFactoryWrapper(v, self._subfields.get(k, {}), create)
elif isinstance(v, OrderedDeclaration):
v = OrderedDeclarationWrapper(v, self.factory.sequence)
wrapped_attrs[k] = v
stub = LazyStub(wrapped_attrs)
return stub.__fill__()
class StubObject(object):
"""A generic container."""
pass
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