task: Add LazyUUIDTask object

diff --git a/tasklib/task.py b/tasklib/task.py
index 5eabc65178d2ae930835d6508a04ad45f0eafe0c..faf6604c7838db7614db3fe3ce7eebc8fbee25ae 100644 (file)
--- a/tasklib/task.py
+++ b/tasklib/task.py
@@ -168,6 +168,53 @@ class TaskAnnotation(TaskResource):
     __repr__ = __unicode__
 
 
+class LazyUUIDTask(object):
+    """
+    A lazy wrapper around Task object, referenced by UUID.
+
+    - Supports comparison with LazyUUIDTask or Task objects (equality by UUIDs)
+    - If any attribute other than 'uuid' requested, a lookup in the
+      backend will be performed and this object will be replaced by a proper
+      Task object.
+    """
+
+    def __init__(self, tw, uuid):
+        self._tw = tw
+        self._uuid = uuid
+
+    def __getitem__(self, key):
+        # LazyUUIDTask does not provide anything else other than 'uuid'
+        if key is 'uuid':
+            return self._uuid
+        else:
+            self.replace()
+            return self[key]
+
+    def __getattr__(self, name):
+        # Getattr is called only if the attribute could not be found using
+        # normal means
+        self.replace()
+        return self.name
+
+    def __eq__(self, other):
+        if other['uuid']:
+            # For saved Tasks, just define equality by equality of uuids
+            return self['uuid'] == other['uuid']
+
+    def __hash__(self):
+        return self['uuid'].__hash__()
+
+    def replace(self):
+        """
+        Performs conversion to the regular Task object, referenced by the
+        stored UUID.
+        """
+
+        replacement = self._tw.tasks.get(uuid=self._uuid)
+        self.__class__ = replacement.__class__
+        self.__dict__ = replacement.__dict__
+
+
 class Task(TaskResource):
     read_only_fields = ['id', 'entry', 'urgency', 'uuid', 'modified']