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1e13fc3df3cff9156daf6663211ad27852c57d85
[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 issubset(self, other):
112         return all([task in other for task in self])
113
114     def issuperset(self, other):
115         return all([task in self for task in other])
116
117     def union(self, other):
118         return LazyUUIDTaskSet(self._tw,
119             self._uuids | set(t['uuid'] for t in other))
120
121     def intersection(self, other):
122         return LazyUUIDTaskSet(self._tw,
123             self._uuids & set(t['uuid'] for t in other))
124
125     def difference(self, other):
126         return LazyUUIDTaskSet(self._tw,
127             self._uuids - set(t['uuid'] for t in other))
128
129     def symmetric_difference(self, other):
130         return LazyUUIDTaskSet(self._tw,
131             self._uuids ^ set(t['uuid'] for t in other))
132
133     def update(self, other):
134         self._uuids |= set(t['uuid'] for t in other)
135         return self
136
137     def intersection_update(self, other):
138         self._uuids &= set(t['uuid'] for t in other)
139         return self
140
141     def difference_update(self, other):
142         self._uuids -= set(t['uuid'] for t in other)
143         return self
144
145     def symmetric_difference_update(self, other):
146         self._uuids ^= set(t['uuid'] for t in other)
147         return self
148
149     def add(self, task):
150         self._uuids.add(task['uuid'])
151
152     def remove(self, task):
153         self._uuids.remove(task['uuid'])
154
155     def pop(self):
156         return self._uuids.pop()
157
158     def clear(self):
159         self._uuids.clear()
160
161     def replace(self):
162         """
163         Performs conversion to the regular TaskQuerySet object, referenced by
164         the stored UUIDs.
165         """
166
167         replacement = self._tw.tasks.filter(' '.join(self._uuids))
168         self.__class__ = replacement.__class__
169         self.__dict__ = replacement.__dict__