Bump version for 0.11.0 release

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

diff --git a/tasklib/task.py b/tasklib/task.py
index 72e16af4d33d612938c0ffac314e5812ef97f87e..5eabc65178d2ae930835d6508a04ad45f0eafe0c 100644 (file)
--- a/tasklib/task.py
+++ b/tasklib/task.py
@@ -1,35 +1,20 @@
 from __future__ import print_function
 import copy
 from __future__ import print_function
 import copy

-import datetime
+import importlib

 import json
 import logging
 import os
 import json
 import logging
 import os

-import pytz

 import six
 import sys
 import six
 import sys

-import subprocess
-import tzlocal
+
+from .serializing import SerializingObject

 
 DATE_FORMAT = '%Y%m%dT%H%M%SZ'
 
 DATE_FORMAT = '%Y%m%dT%H%M%SZ'

-DATE_FORMAT_CALC = '%Y-%m-%dT%H:%M:%S'

 REPR_OUTPUT_SIZE = 10
 PENDING = 'pending'
 COMPLETED = 'completed'
 
 REPR_OUTPUT_SIZE = 10
 PENDING = 'pending'
 COMPLETED = 'completed'
 

-VERSION_2_1_0 = six.u('2.1.0')
-VERSION_2_2_0 = six.u('2.2.0')
-VERSION_2_3_0 = six.u('2.3.0')
-VERSION_2_4_0 = six.u('2.4.0')
-VERSION_2_4_1 = six.u('2.4.1')
-VERSION_2_4_2 = six.u('2.4.2')
-VERSION_2_4_3 = six.u('2.4.3')
-

 logger = logging.getLogger(__name__)
 logger = logging.getLogger(__name__)

-local_zone = tzlocal.get_localzone()
-
-
-class TaskWarriorException(Exception):
-    pass

 
 
 class ReadOnlyDictView(object):
 
 
 class ReadOnlyDictView(object):


@@ -53,6 +38,11 @@ class ReadOnlyDictView(object):
     def __len__(self):
         return len(self.viewed_dict)
 
     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))
 
     def get(self, key, default=None):
         return copy.deepcopy(self.viewed_dict.get(key, default))
 


@@ -63,230 +53,6 @@ class ReadOnlyDictView(object):
         return [copy.deepcopy(v) for v in self.viewed_dict.values()]
 
 
         return [copy.deepcopy(v) for v in self.viewed_dict.values()]
 
 

-class SerializingObject(object):
-    """
-    Common ancestor for TaskResource & TaskFilter, since they both
-    need to serialize arguments.
-
-    Serializing method should hold the following contract:
-      - any empty value (meaning removal of the attribute)
-        is deserialized into a empty string
-      - None denotes a empty value for any attribute
-
-    Deserializing method should hold the following contract:
-      - None denotes a empty value for any attribute (however,
-        this is here as a safeguard, TaskWarrior currently does
-        not export empty-valued attributes) if the attribute
-        is not iterable (e.g. list or set), in which case
-        a empty iterable should be used.
-
-    Normalizing methods should hold the following contract:
-      - They are used to validate and normalize the user input.
-        Any attribute value that comes from the user (during Task
-        initialization, assignign values to Task attributes, or
-        filtering by user-provided values of attributes) is first
-        validated and normalized using the normalize_{key} method.
-      - If validation or normalization fails, normalizer is expected
-        to raise ValueError.
-    """
-
-    def __init__(self, warrior):
-        self.warrior = warrior
-
-    def _deserialize(self, key, value):
-        hydrate_func = getattr(self, 'deserialize_{0}'.format(key),
-                               lambda x: x if x != '' else None)
-        return hydrate_func(value)
-
-    def _serialize(self, key, value):
-        dehydrate_func = getattr(self, 'serialize_{0}'.format(key),
-                                 lambda x: x if x is not None else '')
-        return dehydrate_func(value)
-
-    def _normalize(self, key, value):
-        """
-        Use normalize_<key> methods to normalize user input. Any user
-        input will be normalized at the moment it is used as filter,
-        or entered as a value of Task attribute.
-        """
-
-        # None value should not be converted by normalizer
-        if value is None:
-            return None
-
-        normalize_func = getattr(self, 'normalize_{0}'.format(key),
-                                 lambda x: x)
-
-        return normalize_func(value)
-
-    def timestamp_serializer(self, date):
-        if not date:
-            return ''
-
-        # Any serialized timestamp should be localized, we need to
-        # convert to UTC before converting to string (DATE_FORMAT uses UTC)
-        date = date.astimezone(pytz.utc)
-
-        return date.strftime(DATE_FORMAT)
-
-    def timestamp_deserializer(self, date_str):
-        if not date_str:
-            return None
-
-        # Return timestamp localized in the local zone
-        naive_timestamp = datetime.datetime.strptime(date_str, DATE_FORMAT)
-        localized_timestamp = pytz.utc.localize(naive_timestamp)
-        return localized_timestamp.astimezone(local_zone)
-
-    def serialize_entry(self, value):
-        return self.timestamp_serializer(value)
-
-    def deserialize_entry(self, value):
-        return self.timestamp_deserializer(value)
-
-    def normalize_entry(self, value):
-        return self.datetime_normalizer(value)
-
-    def serialize_modified(self, value):
-        return self.timestamp_serializer(value)
-
-    def deserialize_modified(self, value):
-        return self.timestamp_deserializer(value)
-
-    def normalize_modified(self, value):
-        return self.datetime_normalizer(value)
-
-    def serialize_start(self, value):
-        return self.timestamp_serializer(value)
-
-    def deserialize_start(self, value):
-        return self.timestamp_deserializer(value)
-
-    def normalize_start(self, value):
-        return self.datetime_normalizer(value)
-
-    def serialize_end(self, value):
-        return self.timestamp_serializer(value)
-
-    def deserialize_end(self, value):
-        return self.timestamp_deserializer(value)
-
-    def normalize_end(self, value):
-        return self.datetime_normalizer(value)
-
-    def serialize_due(self, value):
-        return self.timestamp_serializer(value)
-
-    def deserialize_due(self, value):
-        return self.timestamp_deserializer(value)
-
-    def normalize_due(self, value):
-        return self.datetime_normalizer(value)
-
-    def serialize_scheduled(self, value):
-        return self.timestamp_serializer(value)
-
-    def deserialize_scheduled(self, value):
-        return self.timestamp_deserializer(value)
-
-    def normalize_scheduled(self, value):
-        return self.datetime_normalizer(value)
-
-    def serialize_until(self, value):
-        return self.timestamp_serializer(value)
-
-    def deserialize_until(self, value):
-        return self.timestamp_deserializer(value)
-
-    def normalize_until(self, value):
-        return self.datetime_normalizer(value)
-
-    def serialize_wait(self, value):
-        return self.timestamp_serializer(value)
-
-    def deserialize_wait(self, value):
-        return self.timestamp_deserializer(value)
-
-    def normalize_wait(self, value):
-        return self.datetime_normalizer(value)
-
-    def serialize_annotations(self, value):
-        value = value if value is not None else []
-
-        # This may seem weird, but it's correct, we want to export
-        # a list of dicts as serialized value
-        serialized_annotations = [json.loads(annotation.export_data())
-                                  for annotation in value]
-        return serialized_annotations if serialized_annotations else ''
-
-    def deserialize_annotations(self, data):
-        return [TaskAnnotation(self, d) for d in data] if data else []
-
-    def serialize_tags(self, tags):
-        return ','.join(tags) if tags else ''
-
-    def deserialize_tags(self, tags):
-        if isinstance(tags, six.string_types):
-            return tags.split(',') if tags else []
-        return tags or []
-
-    def serialize_depends(self, value):
-        # Return the list of uuids
-        value = value if value is not None else set()
-        return ','.join(task['uuid'] for task in value)
-
-    def deserialize_depends(self, raw_uuids):
-        raw_uuids = raw_uuids or ''  # Convert None to empty string
-        uuids = raw_uuids.split(',')
-        return set(self.warrior.tasks.get(uuid=uuid) for uuid in uuids if uuid)
-
-    def datetime_normalizer(self, value):
-        """
-        Normalizes date/datetime value (considered to come from user input)
-        to localized datetime value. Following conversions happen:
-
-        naive date -> localized datetime with the same date, and time=midnight
-        naive datetime -> localized datetime with the same value
-        localized datetime -> localized datetime (no conversion)
-        """
-
-        if (isinstance(value, datetime.date)
-            and not isinstance(value, datetime.datetime)):
-            # Convert to local midnight
-            value_full = datetime.datetime.combine(value, datetime.time.min)
-            localized = local_zone.localize(value_full)
-        elif isinstance(value, datetime.datetime):
-            if value.tzinfo is None:
-                # Convert to localized datetime object
-                localized = local_zone.localize(value)
-            else:
-                # If the value is already localized, there is no need to change
-                # time zone at this point. Also None is a valid value too.
-                localized = value
-        elif (isinstance(value, six.string_types)
-                and self.warrior.version > VERSION_2_4_0):
-            # For strings, use 'task calc' to evaluate the string to datetime
-            # available since TW 2.4.0
-            args = value.split()
-            result = self.warrior.execute_command(['calc'] + args)
-            naive = datetime.datetime.strptime(result[0], DATE_FORMAT_CALC)
-            localized = local_zone.localize(naive)
-        else:
-            raise ValueError("Provided value could not be converted to "
-                             "datetime, its type is not supported: {}"
-                             .format(type(value)))
-
-        return localized
-
-    def normalize_uuid(self, value):
-        # Enforce sane UUID
-        if not isinstance(value, six.string_types) or value == '':
-            raise ValueError("UUID must be a valid non-empty string, "
-                             "not: {}".format(value))
-
-        return value
-
-

 class TaskResource(SerializingObject):
     read_only_fields = []
 
 class TaskResource(SerializingObject):
     read_only_fields = []
 


@@ -297,7 +63,7 @@ class TaskResource(SerializingObject):
         # are not propagated.
         self._original_data = copy.deepcopy(self._data)
 
         # are not propagated.
         self._original_data = copy.deepcopy(self._data)
 

-    def _update_data(self, data, update_original=False):
+    def _update_data(self, data, update_original=False, remove_missing=False):

         """
         Low level update of the internal _data dict. Data which are coming as
         updates should already be serialized. If update_original is True, the
         """
         Low level update of the internal _data dict. Data which are coming as
         updates should already be serialized. If update_original is True, the


@@ -306,10 +72,14 @@ class TaskResource(SerializingObject):
         self._data.update(dict((key, self._deserialize(key, value))
                                for key, value in data.items()))
 
         self._data.update(dict((key, self._deserialize(key, value))
                                for key, value in data.items()))
 

+        # In certain situations, we want to treat missing keys as removals
+        if remove_missing:
+            for key in set(self._data.keys()) - set(data.keys()):
+                self._data[key] = None
+

         if update_original:
             self._original_data = copy.deepcopy(self._data)
 
         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
     def __getitem__(self, key):
         # This is a workaround to make TaskResource non-iterable
         # over simple index-based iteration


@@ -354,7 +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)
         # 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):
 
     @property
     def _modified_fields(self):


@@ -379,10 +149,10 @@ class TaskResource(SerializingObject):
 class TaskAnnotation(TaskResource):
     read_only_fields = ['entry', 'description']
 
 class TaskAnnotation(TaskResource):
     read_only_fields = ['entry', 'description']
 

-    def __init__(self, task, data={}):
+    def __init__(self, task, data=None):

         self.task = task
         self.task = task

-        self._load_data(data)
-        super(TaskAnnotation, self).__init__(task.warrior)
+        self._load_data(data or dict())
+        super(TaskAnnotation, self).__init__(task.backend)

 
     def remove(self):
         self.task.remove_annotation(self)
 
     def remove(self):
         self.task.remove_annotation(self)


@@ -416,6 +186,18 @@ class Task(TaskResource):
         """
         pass
 
         """
         pass
 

+    class ActiveTask(Exception):
+        """
+        Raised when the operation cannot be performed on the active task.
+        """
+        pass
+
+    class InactiveTask(Exception):
+        """
+        Raised when the operation cannot be performed on an inactive task.
+        """
+        pass
+

     class NotSaved(Exception):
         """
         Raised when the operation cannot be performed on the task, because
     class NotSaved(Exception):
         """
         Raised when the operation cannot be performed on the task, because


@@ -424,7 +206,7 @@ class Task(TaskResource):
         pass
 
     @classmethod
         pass
 
     @classmethod

-    def from_input(cls, input_file=sys.stdin, modify=None, warrior=None):
+    def from_input(cls, input_file=sys.stdin, modify=None, backend=None):

         """
         Creates a Task object, directly from the stdin, by reading one line.
         If modify=True, two lines are used, first line interpreted as the
         """
         Creates a Task object, directly from the stdin, by reading one line.
         If modify=True, two lines are used, first line interpreted as the


@@ -445,12 +227,13 @@ class Task(TaskResource):
         modify = name.startswith('on-modify') if modify is None else modify
 
         # Create the TaskWarrior instance if none passed
         modify = name.startswith('on-modify') if modify is None else modify
 
         # Create the TaskWarrior instance if none passed

-        if warrior is None:
+        if backend is None:
+            backends = importlib.import_module('tasklib.backends')

             hook_parent_dir = os.path.dirname(os.path.dirname(sys.argv[0]))
             hook_parent_dir = os.path.dirname(os.path.dirname(sys.argv[0]))

-            warrior = TaskWarrior(data_location=hook_parent_dir)
+            backend = backends.TaskWarrior(data_location=hook_parent_dir)

 
         # TaskWarrior instance is set to None
 
         # TaskWarrior instance is set to None

-        task = cls(warrior)
+        task = cls(backend)

 
         # Load the data from the input
         task._load_data(json.loads(input_file.readline().strip()))
 
         # Load the data from the input
         task._load_data(json.loads(input_file.readline().strip()))


@@ -458,12 +241,13 @@ class Task(TaskResource):
         # If this is a on-modify event, we are provided with additional
         # line of input, which provides updated data
         if modify:
         # If this is a on-modify event, we are provided with additional
         # line of input, which provides updated data
         if modify:

-            task._update_data(json.loads(input_file.readline().strip()))
+            task._update_data(json.loads(input_file.readline().strip()),
+                              remove_missing=True)

 
         return task
 
 
         return task
 

-    def __init__(self, warrior, **kwargs):
-        super(Task, self).__init__(warrior)
+    def __init__(self, backend, **kwargs):
+        super(Task, self).__init__(backend)

 
         # Check that user is not able to set read-only value in __init__
         for key in kwargs.keys():
 
         # Check that user is not able to set read-only value in __init__
         for key in kwargs.keys():


@@ -493,7 +277,6 @@ class Task(TaskResource):
             # If the tasks are not saved, compare the actual instances
             return id(self) == id(other)
 
             # 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
     def __hash__(self):
         if self['uuid']:
             # For saved Tasks, just define equality by equality of uuids


@@ -518,6 +301,10 @@ class Task(TaskResource):
     def pending(self):
         return self['status'] == six.text_type('pending')
 
     def pending(self):
         return self['status'] == six.text_type('pending')
 

+    @property
+    def active(self):
+        return self['start'] is not None
+

     @property
     def saved(self):
         return self['uuid'] is not None or self['id'] is not None
     @property
     def saved(self):
         return self['uuid'] is not None or self['id'] is not None


@@ -531,33 +318,6 @@ class Task(TaskResource):
 
         return super(Task, self).serialize_depends(cur_dependencies)
 
 
         return super(Task, self).serialize_depends(cur_dependencies)
 

-    def format_depends(self):
-        # We need to generate added and removed dependencies list,
-        # since Taskwarrior does not accept redefining dependencies.
-
-        # This cannot be part of serialize_depends, since we need
-        # to keep a list of all depedencies in the _data dictionary,
-        # not just currently added/removed ones
-
-        old_dependencies = self._original_data.get('depends', set())
-
-        added = self['depends'] - old_dependencies
-        removed = old_dependencies - self['depends']
-
-        # Removed dependencies need to be prefixed with '-'
-        return 'depends:' + ','.join(
-                [t['uuid'] for t in added] +
-                ['-' + t['uuid'] for t in removed]
-            )
-
-    def format_description(self):
-        # Task version older than 2.4.0 ignores first word of the
-        # task description if description: prefix is used
-        if self.warrior.version < VERSION_2_4_0:
-            return self._data['description']
-        else:
-            return "description:'{0}'".format(self._data['description'] or '')
-

     def delete(self):
         if not self.saved:
             raise Task.NotSaved("Task needs to be saved before it can be deleted")
     def delete(self):
         if not self.saved:
             raise Task.NotSaved("Task needs to be saved before it can be deleted")


@@ -568,7 +328,7 @@ class Task(TaskResource):
         if self.deleted:
             raise Task.DeletedTask("Task was already deleted")
 
         if self.deleted:
             raise Task.DeletedTask("Task was already deleted")
 

-        self.warrior.execute_command([self['uuid'], 'delete'])
+        self.backend.delete_task(self)

 
         # Refresh the status again, so that we have updated info stored
         self.refresh(only_fields=['status', 'start', 'end'])
 
         # Refresh the status again, so that we have updated info stored
         self.refresh(only_fields=['status', 'start', 'end'])


@@ -584,8 +344,25 @@ class Task(TaskResource):
             raise Task.CompletedTask("Cannot start a completed task")
         elif self.deleted:
             raise Task.DeletedTask("Deleted task cannot be started")
             raise Task.CompletedTask("Cannot start a completed task")
         elif self.deleted:
             raise Task.DeletedTask("Deleted task cannot be started")

+        elif self.active:
+            raise Task.ActiveTask("Task is already active")
+
+        self.backend.start_task(self)
+
+        # Refresh the status again, so that we have updated info stored
+        self.refresh(only_fields=['status', 'start'])

 
 

-        self.warrior.execute_command([self['uuid'], 'start'])
+    def stop(self):
+        if not self.saved:
+            raise Task.NotSaved("Task needs to be saved before it can be stopped")
+
+        # Refresh, and raise exception if task is already completed/deleted
+        self.refresh(only_fields=['status'])
+
+        if not self.active:
+            raise Task.InactiveTask("Cannot stop an inactive task")
+
+        self.backend.stop_task(self)

 
         # Refresh the status again, so that we have updated info stored
         self.refresh(only_fields=['status', 'start'])
 
         # Refresh the status again, so that we have updated info stored
         self.refresh(only_fields=['status', 'start'])


@@ -602,7 +379,7 @@ class Task(TaskResource):
         elif self.deleted:
             raise Task.DeletedTask("Deleted task cannot be completed")
 
         elif self.deleted:
             raise Task.DeletedTask("Deleted task cannot be completed")
 

-        self.warrior.execute_command([self['uuid'], 'done'])
+        self.backend.complete_task(self)

 
         # Refresh the status again, so that we have updated info stored
         self.refresh(only_fields=['status', 'start', 'end'])
 
         # Refresh the status again, so that we have updated info stored
         self.refresh(only_fields=['status', 'start', 'end'])


@@ -611,34 +388,14 @@ class Task(TaskResource):
         if self.saved and not self.modified:
             return
 
         if self.saved and not self.modified:
             return
 

-        args = [self['uuid'], 'modify'] if self.saved else ['add']
-        args.extend(self._get_modified_fields_as_args())
-        output = self.warrior.execute_command(args)
-
-        # Parse out the new ID, if the task is being added for the first time
-        if not self.saved:
-            id_lines = [l for l in output if l.startswith('Created task ')]
-
-            # Complain loudly if it seems that more tasks were created
-            # Should not happen
-            if len(id_lines) != 1 or len(id_lines[0].split(' ')) != 3:
-                raise TaskWarriorException("Unexpected output when creating "
-                                           "task: %s" % '\n'.join(id_lines))
-
-            # Circumvent the ID storage, since ID is considered read-only
-            self._data['id'] = int(id_lines[0].split(' ')[2].rstrip('.'))
-
-        # Refreshing is very important here, as not only modification time
-        # is updated, but arbitrary attribute may have changed due hooks
-        # altering the data before saving
-        self.refresh()
+        # All the actual work is done by the backend
+        self.backend.save_task(self)

 
     def add_annotation(self, annotation):
         if not self.saved:
             raise Task.NotSaved("Task needs to be saved to add annotation")
 
 
     def add_annotation(self, annotation):
         if not self.saved:
             raise Task.NotSaved("Task needs to be saved to add annotation")
 

-        args = [self['uuid'], 'annotate', annotation]
-        self.warrior.execute_command(args)
+        self.backend.annotate_task(self, annotation)

         self.refresh(only_fields=['annotations'])
 
     def remove_annotation(self, annotation):
         self.refresh(only_fields=['annotations'])
 
     def remove_annotation(self, annotation):


@@ -647,56 +404,17 @@ class Task(TaskResource):
 
         if isinstance(annotation, TaskAnnotation):
             annotation = annotation['description']
 
         if isinstance(annotation, TaskAnnotation):
             annotation = annotation['description']

-        args = [self['uuid'], 'denotate', annotation]
-        self.warrior.execute_command(args)
-        self.refresh(only_fields=['annotations'])
-
-    def _get_modified_fields_as_args(self):
-        args = []
-
-        def add_field(field):
-            # Add the output of format_field method to args list (defaults to
-            # field:value)
-            serialized_value = self._serialize(field, self._data[field])
-
-            # Empty values should not be enclosed in quotation marks, see
-            # TW-1510
-            if serialized_value is '':
-                escaped_serialized_value = ''
-            else:
-                escaped_serialized_value = "'{0}'".format(serialized_value)
-
-            format_default = lambda: "{0}:{1}".format(field,
-                                                      escaped_serialized_value)

 
 

-            format_func = getattr(self, 'format_{0}'.format(field),
-                                  format_default)
-
-            args.append(format_func())
-
-        # If we're modifying saved task, simply pass on all modified fields
-        if self.saved:
-            for field in self._modified_fields:
-                add_field(field)
-        # For new tasks, pass all fields that make sense
-        else:
-            for field in self._data.keys():
-                if field in self.read_only_fields:
-                    continue
-                add_field(field)
-
-        return args
+        self.backend.denotate_task(self, annotation)
+        self.refresh(only_fields=['annotations'])

 
 

-    def refresh(self, only_fields=[]):
+    def refresh(self, only_fields=None, after_save=False):

         # Raise error when trying to refresh a task that has not been saved
         if not self.saved:
             raise Task.NotSaved("Task needs to be saved to be refreshed")
 
         # Raise error when trying to refresh a task that has not been saved
         if not self.saved:
             raise Task.NotSaved("Task needs to be saved to be refreshed")
 

-        # We need to use ID as backup for uuid here for the refreshes
-        # of newly saved tasks. Any other place in the code is fine
-        # with using UUID only.
-        args = [self['uuid'] or self['id'], 'export']
-        new_data = json.loads(self.warrior.execute_command(args)[0])
+        new_data = self.backend.refresh_task(self, after_save=after_save)
+

         if only_fields:
             to_update = dict(
                 [(k, new_data.get(k)) for k in only_fields])
         if only_fields:
             to_update = dict(
                 [(k, new_data.get(k)) for k in only_fields])


@@ -704,68 +422,22 @@ class Task(TaskResource):
         else:
             self._load_data(new_data)
 
         else:
             self._load_data(new_data)
 

-class TaskFilter(SerializingObject):
-    """
-    A set of parameters to filter the task list with.
-    """
-
-    def __init__(self, warrior, filter_params=[]):
-        self.filter_params = filter_params
-        super(TaskFilter, self).__init__(warrior)
-
-    def add_filter(self, filter_str):
-        self.filter_params.append(filter_str)
-
-    def add_filter_param(self, key, value):
-        key = key.replace('__', '.')
-
-        # Replace the value with empty string, since that is the
-        # convention in TW for empty values
-        attribute_key = key.split('.')[0]
-
-        # Since this is user input, we need to normalize before we serialize
-        value = self._normalize(attribute_key, value)
-        value = self._serialize(attribute_key, value)
-
-        # If we are filtering by uuid:, do not use uuid keyword
-        # due to TW-1452 bug
-        if key == 'uuid':
-            self.filter_params.insert(0, value)
-        else:
-            # Surround value with aphostrophes unless it's a empty string
-            value = "'%s'" % value if value else ''
-
-            # We enforce equality match by using 'is' (or 'none') modifier
-            # Without using this syntax, filter fails due to TW-1479
-            modifier = '.is' if value else '.none'
-            key = key + modifier if '.' not in key else key
-
-            self.filter_params.append("{0}:{1}".format(key, value))
-
-    def get_filter_params(self):
-        return [f for f in self.filter_params if f]
-
-    def clone(self):
-        c = self.__class__(self.warrior)
-        c.filter_params = list(self.filter_params)
-        return c
-

 
 class TaskQuerySet(object):
     """
     Represents a lazy lookup for a task objects.
     """
 
 
 class TaskQuerySet(object):
     """
     Represents a lazy lookup for a task objects.
     """
 

-    def __init__(self, warrior=None, filter_obj=None):
-        self.warrior = warrior
+    def __init__(self, backend, filter_obj=None):
+        self.backend = backend

         self._result_cache = None
         self._result_cache = None

-        self.filter_obj = filter_obj or TaskFilter(warrior)
+        self.filter_obj = filter_obj or self.backend.filter_class(backend)

 
     def __deepcopy__(self, memo):
         """
         Deep copy of a QuerySet doesn't populate the cache
         """
 
     def __deepcopy__(self, memo):
         """
         Deep copy of a QuerySet doesn't populate the cache
         """

-        obj = self.__class__()
+        obj = self.__class__(backend=self.backend)

         for k, v in self.__dict__.items():
             if k in ('_iter', '_result_cache'):
                 obj.__dict__[k] = None
         for k, v in self.__dict__.items():
             if k in ('_iter', '_result_cache'):
                 obj.__dict__[k] = None


@@ -810,7 +482,7 @@ class TaskQuerySet(object):
         if klass is None:
             klass = self.__class__
         filter_obj = self.filter_obj.clone()
         if klass is None:
             klass = self.__class__
         filter_obj = self.filter_obj.clone()

-        c = klass(warrior=self.warrior, filter_obj=filter_obj)
+        c = klass(backend=self.backend, filter_obj=filter_obj)

         c.__dict__.update(kwargs)
         return c
 
         c.__dict__.update(kwargs)
         return c
 


@@ -818,7 +490,7 @@ class TaskQuerySet(object):
         """
         Fetch the tasks which match the current filters.
         """
         """
         Fetch the tasks which match the current filters.
         """

-        return self.warrior.filter_tasks(self.filter_obj)
+        return self.backend.filter_tasks(self.filter_obj)

 
     def all(self):
         """
 
     def all(self):
         """


@@ -859,93 +531,3 @@ class TaskQuerySet(object):
         raise ValueError(
             'get() returned more than one Task -- it returned {0}! '
             'Lookup parameters were {1}'.format(num, kwargs))
         raise ValueError(
             'get() returned more than one Task -- it returned {0}! '
             'Lookup parameters were {1}'.format(num, kwargs))

-
-
-class TaskWarrior(object):
-    def __init__(self, data_location='~/.task', create=True, taskrc_location='~/.taskrc'):
-        data_location = os.path.expanduser(data_location)
-        self.taskrc_location = os.path.expanduser(taskrc_location)
-
-        # If taskrc does not exist, pass / to use defaults and avoid creating
-        # dummy .taskrc file by TaskWarrior
-        if not os.path.exists(self.taskrc_location):
-            self.taskrc_location = '/'
-
-        if create and not os.path.exists(data_location):
-            os.makedirs(data_location)
-
-        self.version = self._get_version()
-        self.config = {
-            'data.location': data_location,
-            'confirmation': 'no',
-            'dependency.confirmation': 'no',  # See TW-1483 or taskrc man page
-            'recurrence.confirmation': 'no',  # Necessary for modifying R tasks
-            # 2.4.3 onwards supports 0 as infite bulk, otherwise set just
-            # arbitrary big number which is likely to be large enough
-            'bulk': 0 if self.version > VERSION_2_4_3 else 100000,
-        }
-        self.tasks = TaskQuerySet(self)
-
-    def _get_command_args(self, args, config_override={}):
-        command_args = ['task', 'rc:{0}'.format(self.taskrc_location)]
-        config = self.config.copy()
-        config.update(config_override)
-        for item in config.items():
-            command_args.append('rc.{0}={1}'.format(*item))
-        command_args.extend(map(str, args))
-        return command_args
-
-    def _get_version(self):
-        p = subprocess.Popen(
-                ['task', '--version'],
-                stdout=subprocess.PIPE,
-                stderr=subprocess.PIPE)
-        stdout, stderr = [x.decode('utf-8') for x in p.communicate()]
-        return stdout.strip('\n')
-
-    def execute_command(self, args, config_override={}, allow_failure=True):
-        command_args = self._get_command_args(
-            args, config_override=config_override)
-        logger.debug(' '.join(command_args))
-        p = subprocess.Popen(command_args, stdout=subprocess.PIPE,
-                             stderr=subprocess.PIPE)
-        stdout, stderr = [x.decode('utf-8') for x in p.communicate()]
-        if p.returncode and allow_failure:
-            if stderr.strip():
-                error_msg = stderr.strip()
-            else:
-                error_msg = stdout.strip()
-            raise TaskWarriorException(error_msg)
-        return stdout.rstrip().split('\n')
-
-    def enforce_recurrence(self):
-        # Run arbitrary report command which will trigger generation
-        # of recurrent tasks.
-
-        # Only necessary for TW up to 2.4.1, fixed in 2.4.2.
-        if self.version < VERSION_2_4_2:
-            self.execute_command(['next'], allow_failure=False)
-
-    def filter_tasks(self, filter_obj):
-        self.enforce_recurrence()
-        args = ['export', '--'] + filter_obj.get_filter_params()
-        tasks = []
-        for line in self.execute_command(args):
-            if line:
-                data = line.strip(',')
-                try:
-                    filtered_task = Task(self)
-                    filtered_task._load_data(json.loads(data))
-                    tasks.append(filtered_task)
-                except ValueError:
-                    raise TaskWarriorException('Invalid JSON: %s' % data)
-        return tasks
-
-    def merge_with(self, path, push=False):
-        path = path.rstrip('/') + '/'
-        self.execute_command(['merge', path], config_override={
-            'merge.autopush': 'yes' if push else 'no',
-        })
-
-    def undo(self):
-        self.execute_command(['undo'])