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 and 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     def __copy__(self):
  46         return LazyUUIDTask(self._tw, self._uuid)
  47
  48     def __deepcopy__(self, memo):
  49         return LazyUUIDTask(self._tw, self._uuid)
  50
  51     @property
  52     def saved(self):
  53         """
  54         Implementation of the 'saved' property. Always returns True.
  55         """
  56         return True
  57
  58     @property
  59     def _modified_fields(self):
  60         return set()
  61
  62     @property
  63     def modified(self):
  64         return False
  65
  66     def replace(self):
  67         """
  68         Performs conversion to the regular Task object, referenced by the
  69         stored UUID.
  70         """
  71
  72         replacement = self._tw.tasks.get(uuid=self._uuid)
  73         self.__class__ = replacement.__class__
  74         self.__dict__ = replacement.__dict__
  75
  76
  77 class LazyUUIDTaskSet(object):
  78     """
  79     A lazy wrapper around TaskQuerySet object, for tasks referenced by UUID.
  80
  81     - Supports 'in' operator with LazyUUIDTask or Task objects
  82     - If iteration over the objects in the LazyUUIDTaskSet is requested, the
  83       LazyUUIDTaskSet will be converted to QuerySet and evaluated
  84     """
  85
  86     def __init__(self, tw, uuids):
  87         self._tw = tw
  88         self._uuids = set(uuids)
  89
  90     def __getattr__(self, name):
  91         # Getattr is called only if the attribute could not be found using
  92         # normal means
  93
  94         if name.startswith('__'):
  95             # If some internal method was being search, do not convert
  96             # to TaskQuerySet just because of that
  97             raise AttributeError
  98         else:
  99             self.replace()
 100             return getattr(self, name)
 101
 102     def __repr__(self):
 103         return 'LazyUUIDTaskSet([{0}])'.format(', '.join(self._uuids))
 104
 105     def __eq__(self, other):
 106         return set(t['uuid'] for t in other) == self._uuids
 107
 108     def __ne__(self, other):
 109         return not (self == other)
 110
 111     def __contains__(self, task):
 112         return task['uuid'] in self._uuids
 113
 114     def __len__(self):
 115         return len(self._uuids)
 116
 117     def __iter__(self):
 118         for uuid in self._uuids:
 119             yield LazyUUIDTask(self._tw, uuid)
 120
 121     def __sub__(self, other):
 122         return self.difference(other)
 123
 124     def __isub__(self, other):
 125         return self.difference_update(other)
 126
 127     def __rsub__(self, other):
 128         return LazyUUIDTaskSet(
 129             self._tw,
 130             set(t['uuid'] for t in other) - self._uuids,
 131         )
 132
 133     def __or__(self, other):
 134         return self.union(other)
 135
 136     def __ior__(self, other):
 137         return self.update(other)
 138
 139     def __ror__(self, other):
 140         return self.union(other)
 141
 142     def __xor__(self, other):
 143         return self.symmetric_difference(other)
 144
 145     def __ixor__(self, other):
 146         return self.symmetric_difference_update(other)
 147
 148     def __rxor__(self, other):
 149         return self.symmetric_difference(other)
 150
 151     def __and__(self, other):
 152         return self.intersection(other)
 153
 154     def __iand__(self, other):
 155         return self.intersection_update(other)
 156
 157     def __rand__(self, other):
 158         return self.intersection(other)
 159
 160     def __le__(self, other):
 161         return self.issubset(other)
 162
 163     def __ge__(self, other):
 164         return self.issuperset(other)
 165
 166     def issubset(self, other):
 167         return all([task in other for task in self])
 168
 169     def issuperset(self, other):
 170         return all([task in self for task in other])
 171
 172     def union(self, other):
 173         return LazyUUIDTaskSet(
 174             self._tw,
 175             self._uuids | set(t['uuid'] for t in other),
 176         )
 177
 178     def intersection(self, other):
 179         return LazyUUIDTaskSet(
 180             self._tw,
 181             self._uuids & set(t['uuid'] for t in other),
 182         )
 183
 184     def difference(self, other):
 185         return LazyUUIDTaskSet(
 186             self._tw,
 187             self._uuids - set(t['uuid'] for t in other),
 188         )
 189
 190     def symmetric_difference(self, other):
 191         return LazyUUIDTaskSet(
 192             self._tw,
 193             self._uuids ^ set(t['uuid'] for t in other),
 194         )
 195
 196     def update(self, other):
 197         self._uuids |= set(t['uuid'] for t in other)
 198         return self
 199
 200     def intersection_update(self, other):
 201         self._uuids &= set(t['uuid'] for t in other)
 202         return self
 203
 204     def difference_update(self, other):
 205         self._uuids -= set(t['uuid'] for t in other)
 206         return self
 207
 208     def symmetric_difference_update(self, other):
 209         self._uuids ^= set(t['uuid'] for t in other)
 210         return self
 211
 212     def add(self, task):
 213         self._uuids.add(task['uuid'])
 214
 215     def remove(self, task):
 216         self._uuids.remove(task['uuid'])
 217
 218     def pop(self):
 219         return self._uuids.pop()
 220
 221     def clear(self):
 222         self._uuids.clear()
 223
 224     def replace(self):
 225         """
 226         Performs conversion to the regular TaskQuerySet object, referenced by
 227         the stored UUIDs.
 228         """
 229
 230         replacement = self._tw.tasks.filter(' '.join(self._uuids))
 231         self.__class__ = replacement.__class__
 232         self.__dict__ = replacement.__dict__