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0bd93323762c7f8d265dd6ae455118d27f5b8f80
[etc/taskwarrior.git] / tasklib / lazy.py
1 """
2 Provides lazy implementations for Task and TaskQuerySet.
3 """
4
5
6 class LazyUUIDTask(object):
7     """
8     A lazy wrapper around Task object, referenced by UUID.
9
10     - Supports comparison with LazyUUIDTask or Task objects (equality by UUIDs)
11     - If any attribute other than 'uuid' requested, a lookup in the
12       backend will be performed and this object will be replaced by a proper
13       Task object.
14     """
15
16     def __init__(self, tw, uuid):
17         self._tw = tw
18         self._uuid = uuid
19
20     def __getitem__(self, key):
21         # LazyUUIDTask does not provide anything else other than 'uuid'
22         if key is 'uuid':
23             return self._uuid
24         else:
25             self.replace()
26             return self[key]
27
28     def __getattr__(self, name):
29         # Getattr is called only if the attribute could not be found using
30         # normal means
31         self.replace()
32         return self.name
33
34     def __eq__(self, other):
35         if other['uuid']:
36             # For saved Tasks, just define equality by equality of uuids
37             return self['uuid'] == other['uuid']
38
39     def __hash__(self):
40         return self['uuid'].__hash__()
41
42     def replace(self):
43         """
44         Performs conversion to the regular Task object, referenced by the
45         stored UUID.
46         """
47
48         replacement = self._tw.tasks.get(uuid=self._uuid)
49         self.__class__ = replacement.__class__
50         self.__dict__ = replacement.__dict__
51
52
53 class LazyUUIDTaskSet(object):
54     """
55     A lazy wrapper around TaskQuerySet object, for tasks referenced by UUID.
56
57     - Supports 'in' operator with LazyUUIDTask or Task objects
58     - If iteration over the objects in the LazyUUIDTaskSet is requested, the
59       LazyUUIDTaskSet will be converted to QuerySet and evaluated
60     """
61
62     def __init__(self, tw, uuids):
63         self._tw = tw
64         self._uuids = set(uuids)
65
66     def __getattr__(self, name):
67         # Getattr is called only if the attribute could not be found using
68         # normal means
69         self.replace()
70         return self.name
71
72     def __eq__(self, other):
73         return set(t['uuid'] for t in other) == self._uuids
74
75     def __contains__(self, task):
76         return task['uuid'] in self._uuids
77
78     def __len__(self):
79         return len(self._uuids)
80
81     def __iter__(self):
82         self.replace()
83         for task in self:
84             yield task
85
86     def replace(self):
87         """
88         Performs conversion to the regular TaskQuerySet object, referenced by
89         the stored UUIDs.
90         """
91
92         replacement = self._tw.tasks.filter(' '.join(self._uuids))
93         self.__class__ = replacement.__class__
94         self.__dict__ = replacement.__dict__