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04ccdf5216f7bee3f3b5c83d24b304c3e095bc22
[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 getattr(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 __repr__(self):
43         return "LazyUUIDTask: {0}".format(self._uuid)
44
45     @property
46     def saved(self):
47         """
48         Implementation of the 'saved' property. Always returns True.
49         """
50         return True
51
52     def replace(self):
53         """
54         Performs conversion to the regular Task object, referenced by the
55         stored UUID.
56         """
57
58         replacement = self._tw.tasks.get(uuid=self._uuid)
59         self.__class__ = replacement.__class__
60         self.__dict__ = replacement.__dict__
61
62
63 class LazyUUIDTaskSet(object):
64     """
65     A lazy wrapper around TaskQuerySet object, for tasks referenced by UUID.
66
67     - Supports 'in' operator with LazyUUIDTask or Task objects
68     - If iteration over the objects in the LazyUUIDTaskSet is requested, the
69       LazyUUIDTaskSet will be converted to QuerySet and evaluated
70     """
71
72     def __init__(self, tw, uuids):
73         self._tw = tw
74         self._uuids = set(uuids)
75
76     def __getattr__(self, name):
77         # Getattr is called only if the attribute could not be found using
78         # normal means
79
80         if name.startswith('__'):
81             # If some internal method was being search, do not convert
82             # to TaskQuerySet just because of that
83             raise AttributeError
84         else:
85             self.replace()
86             return getattr(self, name)
87
88     def __repr__(self):
89         return "LazyUUIDTaskSet([{0}])".format(', '.join(self._uuids))
90
91     def __eq__(self, other):
92         return set(t['uuid'] for t in other) == self._uuids
93
94     def __ne__(self, other):
95         return not (self == other)
96
97     def __contains__(self, task):
98         return task['uuid'] in self._uuids
99
100     def __len__(self):
101         return len(self._uuids)
102
103     def __iter__(self):
104         for uuid in self._uuids:
105             yield LazyUUIDTask(self._tw, uuid)
106
107     def __sub__(self, other):
108         return LazyUUIDTaskSet(self._tw,
109                                self._uuids - set(t['uuid'] for t in other))
110
111     def __isub__(self, other):
112         self._uuids -= set(t['uuid'] for t in other)
113         return self
114
115     def __or__(self, other):
116         return LazyUUIDTaskSet(self._tw,
117                                self._uuids | set(t['uuid'] for t in other))
118
119     def __ior__(self, other):
120         self._uuids |= set(t['uuid'] for t in other)
121         return self
122
123     def replace(self):
124         """
125         Performs conversion to the regular TaskQuerySet object, referenced by
126         the stored UUIDs.
127         """
128
129         replacement = self._tw.tasks.filter(' '.join(self._uuids))
130         self.__class__ = replacement.__class__
131         self.__dict__ = replacement.__dict__