X-Git-Url: https://git.madduck.net/etc/taskwarrior.git/blobdiff_plain/5ba0e1105517f8b0e22b0bcf5c79f40a0fb644d9..52ee36a43f1ab4c46ab7c7c1fbaba7a1c374d5e3:/tasklib/filters.py

diff --git a/tasklib/filters.py b/tasklib/filters.py
index 1899d1d..b85a882 100644
--- a/tasklib/filters.py
+++ b/tasklib/filters.py
@@ -1,7 +1,36 @@
-from tasklib.serializing import SerializingObject
+import abc
+import six
+from .serializing import SerializingObject
 
 
-class TaskFilter(SerializingObject):
+class TaskFilter(object):
+    """
+    Abstract base class that defines interface of a TaskFilter.
+    """
+
+    @abc.abstractmethod
+    def add_filter(self, arg):
+        """
+        Processes an non-keyword filter.
+        """
+        pass
+
+    @abc.abstractmethod
+    def add_filter_param(self, key, value):
+        """
+        Processes a keyword filter.
+        """
+        pass
+
+    @abc.abstractmethod
+    def clone(self):
+        """
+        Returns a new deep copy of itself.
+        """
+        pass
+
+
+class TaskWarriorFilter(TaskFilter, SerializingObject):
     """
     A set of parameters to filter the task list with.
     """
@@ -35,7 +64,7 @@ class TaskFilter(SerializingObject):
             # We enforce equality match by using 'is' (or 'none') modifier
             # Without using this syntax, filter fails due to TW-1479
             # which is, however, fixed in 2.4.5
-            if self.warrior.version < VERSION_2_4_5:
+            if self.warrior.version < warrior.VERSION_2_4_5:
                 modifier = '.is' if value else '.none'
                 key = key + modifier if '.' not in key else key