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     @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__