task: Add LazyUUIDTask object

[etc/taskwarrior.git] / tasklib / task.py

diff --git a/tasklib/task.py b/tasklib/task.py
index 8145e2e12701add3cc9dac608d462062993972cf..faf6604c7838db7614db3fe3ce7eebc8fbee25ae 100644 (file)
--- a/tasklib/task.py
+++ b/tasklib/task.py
@@ -1,6 +1,5 @@
 from __future__ import print_function
 import copy
-import datetime
 import importlib
 import json
 import logging
@@ -39,6 +38,11 @@ class ReadOnlyDictView(object):
     def __len__(self):
         return len(self.viewed_dict)
 
+    def __unicode__(self):
+        return six.u('ReadOnlyDictView: {0}'.format(repr(self.viewed_dict)))
+
+    __repr__ = __unicode__
+
     def get(self, key, default=None):
         return copy.deepcopy(self.viewed_dict.get(key, default))
 
@@ -76,7 +80,6 @@ class TaskResource(SerializingObject):
         if update_original:
             self._original_data = copy.deepcopy(self._data)
 
-
     def __getitem__(self, key):
         # This is a workaround to make TaskResource non-iterable
         # over simple index-based iteration
@@ -121,7 +124,7 @@ class TaskResource(SerializingObject):
         # to pass that to TaskWarrior.
         data_tuples = filter(lambda t: t[1] is not '', data_tuples)
         data = dict(data_tuples)
-        return json.dumps(data, separators=(',',':'))
+        return json.dumps(data, separators=(',', ':'))
 
     @property
     def _modified_fields(self):
@@ -165,6 +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']
 
@@ -274,7 +324,6 @@ class Task(TaskResource):
             # If the tasks are not saved, compare the actual instances
             return id(self) == id(other)
 
-
     def __hash__(self):
         if self['uuid']:
             # For saved Tasks, just define equality by equality of uuids
@@ -420,6 +469,7 @@ class Task(TaskResource):
         else:
             self._load_data(new_data)
 
+
 class TaskQuerySet(object):
     """
     Represents a lazy lookup for a task objects.