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527a9955fc0a95360b378099a913ca5de4937779
[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     @property
53     def _modified_fields(self):
54         return set()
55
56     @property
57     def modified(self):
58         return False
59
60     def replace(self):
61         """
62         Performs conversion to the regular Task object, referenced by the
63         stored UUID.
64         """
65
66         replacement = self._tw.tasks.get(uuid=self._uuid)
67         self.__class__ = replacement.__class__
68         self.__dict__ = replacement.__dict__
69
70
71 class LazyUUIDTaskSet(object):
72     """
73     A lazy wrapper around TaskQuerySet object, for tasks referenced by UUID.
74
75     - Supports 'in' operator with LazyUUIDTask or Task objects
76     - If iteration over the objects in the LazyUUIDTaskSet is requested, the
77       LazyUUIDTaskSet will be converted to QuerySet and evaluated
78     """
79
80     def __init__(self, tw, uuids):
81         self._tw = tw
82         self._uuids = set(uuids)
83
84     def __getattr__(self, name):
85         # Getattr is called only if the attribute could not be found using
86         # normal means
87
88         if name.startswith('__'):
89             # If some internal method was being search, do not convert
90             # to TaskQuerySet just because of that
91             raise AttributeError
92         else:
93             self.replace()
94             return getattr(self, name)
95
96     def __repr__(self):
97         return "LazyUUIDTaskSet([{0}])".format(', '.join(self._uuids))
98
99     def __eq__(self, other):
100         return set(t['uuid'] for t in other) == self._uuids
101
102     def __ne__(self, other):
103         return not (self == other)
104
105     def __contains__(self, task):
106         return task['uuid'] in self._uuids
107
108     def __len__(self):
109         return len(self._uuids)
110
111     def __iter__(self):
112         for uuid in self._uuids:
113             yield LazyUUIDTask(self._tw, uuid)
114
115     def __sub__(self, other):
116         return self.difference(other)
117
118     def __isub__(self, other):
119         return self.difference_update(other)
120
121     def __rsub__(self, other):
122         return LazyUUIDTaskSet(self._tw,
123             set(t['uuid'] for t in other) - self._uuids)
124
125     def __or__(self, other):
126         return self.union(other)
127
128     def __ior__(self, other):
129         return self.update(other)
130
131     def __ror__(self, other):
132         return self.union(other)
133
134     def __xor__(self, other):
135         return self.symmetric_difference(other)
136
137     def __ixor__(self, other):
138         return self.symmetric_difference_update(other)
139
140     def __rxor__(self, other):
141         return self.symmetric_difference(other)
142
143     def __and__(self, other):
144         return self.intersection(other)
145
146     def __iand__(self, other):
147         return self.intersection_update(other)
148
149     def __rand__(self, other):
150         return self.intersection(other)
151
152     def __le__(self, other):
153         return self.issubset(other)
154
155     def __ge__(self, other):
156         return self.issuperset(other)
157
158     def issubset(self, other):
159         return all([task in other for task in self])
160
161     def issuperset(self, other):
162         return all([task in self for task in other])
163
164     def union(self, other):
165         return LazyUUIDTaskSet(self._tw,
166             self._uuids | set(t['uuid'] for t in other))
167
168     def intersection(self, other):
169         return LazyUUIDTaskSet(self._tw,
170             self._uuids & set(t['uuid'] for t in other))
171
172     def difference(self, other):
173         return LazyUUIDTaskSet(self._tw,
174             self._uuids - set(t['uuid'] for t in other))
175
176     def symmetric_difference(self, other):
177         return LazyUUIDTaskSet(self._tw,
178             self._uuids ^ set(t['uuid'] for t in other))
179
180     def update(self, other):
181         self._uuids |= set(t['uuid'] for t in other)
182         return self
183
184     def intersection_update(self, other):
185         self._uuids &= set(t['uuid'] for t in other)
186         return self
187
188     def difference_update(self, other):
189         self._uuids -= set(t['uuid'] for t in other)
190         return self
191
192     def symmetric_difference_update(self, other):
193         self._uuids ^= set(t['uuid'] for t in other)
194         return self
195
196     def add(self, task):
197         self._uuids.add(task['uuid'])
198
199     def remove(self, task):
200         self._uuids.remove(task['uuid'])
201
202     def pop(self):
203         return self._uuids.pop()
204
205     def clear(self):
206         self._uuids.clear()
207
208     def replace(self):
209         """
210         Performs conversion to the regular TaskQuerySet object, referenced by
211         the stored UUIDs.
212         """
213
214         replacement = self._tw.tasks.filter(' '.join(self._uuids))
215         self.__class__ = replacement.__class__
216         self.__dict__ = replacement.__dict__