+local_zone = tzlocal.get_localzone()
+
+
+class ReadOnlyDictView(object):
+ """
+ Provides simplified read-only view upon dict object.
+ """
+
+ def __init__(self, viewed_dict):
+ self.viewed_dict = viewed_dict
+
+ def __getitem__(self, key):
+ return copy.deepcopy(self.viewed_dict.__getitem__(key))
+
+ def __contains__(self, k):
+ return self.viewed_dict.__contains__(k)
+
+ def __iter__(self):
+ for value in self.viewed_dict:
+ yield copy.deepcopy(value)
+
+ def __len__(self):
+ return len(self.viewed_dict)
+
+ def get(self, key, default=None):
+ return copy.deepcopy(self.viewed_dict.get(key, default))
+
+ def items(self):
+ return [copy.deepcopy(v) for v in self.viewed_dict.items()]
+
+ def values(self):
+ return [copy.deepcopy(v) for v in self.viewed_dict.values()]
+
+
+class SerializingObject(object):
+ """
+ Common ancestor for TaskResource & TaskFilter, since they both
+ need to serialize arguments.
+
+ Serializing method should hold the following contract:
+ - any empty value (meaning removal of the attribute)
+ is deserialized into a empty string
+ - None denotes a empty value for any attribute
+
+ Deserializing method should hold the following contract:
+ - None denotes a empty value for any attribute (however,
+ this is here as a safeguard, TaskWarrior currently does
+ not export empty-valued attributes) if the attribute
+ is not iterable (e.g. list or set), in which case
+ a empty iterable should be used.
+
+ Normalizing methods should hold the following contract:
+ - They are used to validate and normalize the user input.
+ Any attribute value that comes from the user (during Task
+ initialization, assignign values to Task attributes, or
+ filtering by user-provided values of attributes) is first
+ validated and normalized using the normalize_{key} method.
+ - If validation or normalization fails, normalizer is expected
+ to raise ValueError.
+ """
+
+ def __init__(self, warrior):
+ self.warrior = warrior
+
+ def _deserialize(self, key, value):
+ hydrate_func = getattr(self, 'deserialize_{0}'.format(key),
+ lambda x: x if x != '' else None)
+ return hydrate_func(value)
+
+ def _serialize(self, key, value):
+ dehydrate_func = getattr(self, 'serialize_{0}'.format(key),
+ lambda x: x if x is not None else '')
+ return dehydrate_func(value)
+
+ def _normalize(self, key, value):
+ """
+ Use normalize_<key> methods to normalize user input. Any user
+ input will be normalized at the moment it is used as filter,
+ or entered as a value of Task attribute.
+ """
+
+ # None value should not be converted by normalizer
+ if value is None:
+ return None
+
+ normalize_func = getattr(self, 'normalize_{0}'.format(key),
+ lambda x: x)
+
+ return normalize_func(value)
+
+ def timestamp_serializer(self, date):
+ if not date:
+ return ''
+
+ # Any serialized timestamp should be localized, we need to
+ # convert to UTC before converting to string (DATE_FORMAT uses UTC)
+ date = date.astimezone(pytz.utc)
+
+ return date.strftime(DATE_FORMAT)
+
+ def timestamp_deserializer(self, date_str):
+ if not date_str:
+ return None
+
+ # Return timestamp localized in the local zone
+ naive_timestamp = datetime.datetime.strptime(date_str, DATE_FORMAT)
+ localized_timestamp = pytz.utc.localize(naive_timestamp)
+ return localized_timestamp.astimezone(local_zone)
+
+ def serialize_entry(self, value):
+ return self.timestamp_serializer(value)
+
+ def deserialize_entry(self, value):
+ return self.timestamp_deserializer(value)
+
+ def normalize_entry(self, value):
+ return self.datetime_normalizer(value)
+
+ def serialize_modified(self, value):
+ return self.timestamp_serializer(value)
+
+ def deserialize_modified(self, value):
+ return self.timestamp_deserializer(value)
+
+ def normalize_modified(self, value):
+ return self.datetime_normalizer(value)
+
+ def serialize_start(self, value):
+ return self.timestamp_serializer(value)
+
+ def deserialize_start(self, value):
+ return self.timestamp_deserializer(value)
+
+ def normalize_start(self, value):
+ return self.datetime_normalizer(value)
+
+ def serialize_end(self, value):
+ return self.timestamp_serializer(value)
+
+ def deserialize_end(self, value):
+ return self.timestamp_deserializer(value)
+
+ def normalize_end(self, value):
+ return self.datetime_normalizer(value)
+
+ def serialize_due(self, value):
+ return self.timestamp_serializer(value)