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 __ne__(self, other):
  40         return not self.__eq__(other)
  41
  42     def __hash__(self):
  43         return self['uuid'].__hash__()
  44
  45     def __repr__(self):
  46         return "LazyUUIDTask: {0}".format(self._uuid)
  47
  48     def __copy__(self):
  49         return LazyUUIDTask(self._tw, self._uuid)
  50
  51     def __deepcopy__(self, memo):
  52         return LazyUUIDTask(self._tw, self._uuid)
  53
  54     @property
  55     def saved(self):
  56         """
  57         Implementation of the 'saved' property. Always returns True.
  58         """
  59         return True
  60
  61     @property
  62     def _modified_fields(self):
  63         return set()
  64
  65     @property
  66     def modified(self):
  67         return False
  68
  69     def replace(self):
  70         """
  71         Performs conversion to the regular Task object, referenced by the
  72         stored UUID.
  73         """
  74
  75         replacement = self._tw.tasks.get(uuid=self._uuid)
  76         self.__class__ = replacement.__class__
  77         self.__dict__ = replacement.__dict__
  78
  79
  80 class LazyUUIDTaskSet(object):
  81     """
  82     A lazy wrapper around TaskQuerySet object, for tasks referenced by UUID.
  83
  84     - Supports 'in' operator with LazyUUIDTask or Task objects
  85     - If iteration over the objects in the LazyUUIDTaskSet is requested, the
  86       LazyUUIDTaskSet will be converted to QuerySet and evaluated
  87     """
  88
  89     def __init__(self, tw, uuids):
  90         self._tw = tw
  91         self._uuids = set(uuids)
  92
  93     def __getattr__(self, name):
  94         # Getattr is called only if the attribute could not be found using
  95         # normal means
  96
  97         if name.startswith('__'):
  98             # If some internal method was being search, do not convert
  99             # to TaskQuerySet just because of that
 100             raise AttributeError
 101         else:
 102             self.replace()
 103             return getattr(self, name)
 104
 105     def __repr__(self):
 106         return "LazyUUIDTaskSet([{0}])".format(', '.join(self._uuids))
 107
 108     def __eq__(self, other):
 109         return set(t['uuid'] for t in other) == self._uuids
 110
 111     def __ne__(self, other):
 112         return not (self == other)
 113
 114     def __contains__(self, task):
 115         return task['uuid'] in self._uuids
 116
 117     def __len__(self):
 118         return len(self._uuids)
 119
 120     def __iter__(self):
 121         for uuid in self._uuids:
 122             yield LazyUUIDTask(self._tw, uuid)
 123
 124     def __sub__(self, other):
 125         return self.difference(other)
 126
 127     def __isub__(self, other):
 128         return self.difference_update(other)
 129
 130     def __rsub__(self, other):
 131         return LazyUUIDTaskSet(self._tw,
 132                                set(t['uuid'] for t in other) - self._uuids)
 133
 134     def __or__(self, other):
 135         return self.union(other)
 136
 137     def __ior__(self, other):
 138         return self.update(other)
 139
 140     def __ror__(self, other):
 141         return self.union(other)
 142
 143     def __xor__(self, other):
 144         return self.symmetric_difference(other)
 145
 146     def __ixor__(self, other):
 147         return self.symmetric_difference_update(other)
 148
 149     def __rxor__(self, other):
 150         return self.symmetric_difference(other)
 151
 152     def __and__(self, other):
 153         return self.intersection(other)
 154
 155     def __iand__(self, other):
 156         return self.intersection_update(other)
 157
 158     def __rand__(self, other):
 159         return self.intersection(other)
 160
 161     def __le__(self, other):
 162         return self.issubset(other)
 163
 164     def __ge__(self, other):
 165         return self.issuperset(other)
 166
 167     def issubset(self, other):
 168         return all([task in other for task in self])
 169
 170     def issuperset(self, other):
 171         return all([task in self for task in other])
 172
 173     def union(self, other):
 174         return LazyUUIDTaskSet(self._tw,
 175                                self._uuids | set(t['uuid'] for t in other))
 176
 177     def intersection(self, other):
 178         return LazyUUIDTaskSet(self._tw,
 179                                self._uuids & set(t['uuid'] for t in other))
 180
 181     def difference(self, other):
 182         return LazyUUIDTaskSet(self._tw,
 183                                self._uuids - set(t['uuid'] for t in other))
 184
 185     def symmetric_difference(self, other):
 186         return LazyUUIDTaskSet(self._tw,
 187                                self._uuids ^ set(t['uuid'] for t in other))
 188
 189     def update(self, other):
 190         self._uuids |= set(t['uuid'] for t in other)
 191         return self
 192
 193     def intersection_update(self, other):
 194         self._uuids &= set(t['uuid'] for t in other)
 195         return self
 196
 197     def difference_update(self, other):
 198         self._uuids -= set(t['uuid'] for t in other)
 199         return self
 200
 201     def symmetric_difference_update(self, other):
 202         self._uuids ^= set(t['uuid'] for t in other)
 203         return self
 204
 205     def add(self, task):
 206         self._uuids.add(task['uuid'])
 207
 208     def remove(self, task):
 209         self._uuids.remove(task['uuid'])
 210
 211     def pop(self):
 212         return self._uuids.pop()
 213
 214     def clear(self):
 215         self._uuids.clear()
 216
 217     def replace(self):
 218         """
 219         Performs conversion to the regular TaskQuerySet object, referenced by
 220         the stored UUIDs.
 221         """
 222
 223         replacement = self._tw.tasks.filter(' '.join(self._uuids))
 224         self.__class__ = replacement.__class__
 225         self.__dict__ = replacement.__dict__