Add filter that filters todos with uncompleted child todos.

Filter.py

 class Filter(object):
-    # def __init__(self):
-    #     pass
-
     def filter(self, p_todos, p_limit=None):
         """
         Filters a list of todos. Truncates the list after p_limit todo
@@ -56,3 +53,23 @@ class RelevanceFilter(Filter):
         is_due |= p_todo.priority() == 'C' and p_todo.days_till_due() <= 14
 
         return p_todo.is_active() and is_due
+
+class DependencyFilter(Filter):
+    """ Matches when a todo has no unfinished child tasks.  """
+    def __init__(self, p_todolist):
+        """
+        Constructor.
+
+        Pass on a TodoList instance such that the dependencies can be
+        looked up.
+        """
+        self.todolist = p_todolist
+
+    def match(self, p_todo):
+        """
+        Returns True when there are no children that are uncompleted yet.
+        """
+        children = self.todolist.children(p_todo.number)
+        uncompleted = [todo for todo in children if not todo.is_completed()]
+
+        return not uncompleted

test/FilterTest.py

@@ -4,14 +4,11 @@ import datetime
 import unittest
 
 import Filter
-from TestFacilities import load_file, todolist_to_string
+from TestFacilities import load_file, load_file_to_raw_list, todolist_to_string
 import Todo
+import TodoList
 
 class FilterTest(unittest.TestCase):
-    def setUp(self):
-        # self.today = datetime.date.today()
-        pass
-
     def test_filter1(self):
         todo = Todo.Todo("(C) Relevant")
         relevance = Filter.RelevanceFilter()
@@ -65,3 +62,17 @@ class FilterTest(unittest.TestCase):
 
         self.assertEquals(todolist_to_string(filtered_todos), \
             todolist_to_string(reference))
+
+    def test_filter7(self):
+        """ Tests the dependency filter. """
+        todos_raw = load_file_to_raw_list('data/FilterTest2.txt')
+        todos = load_file('data/FilterTest2.txt')
+
+        todolist = TodoList.TodoList(todos_raw)
+        depfilter = Filter.DependencyFilter(todolist)
+
+        filtered_todos = depfilter.filter(todos)
+        reference = load_file('data/FilterTest2-result.txt')
+
+        self.assertEquals(todolist_to_string(filtered_todos), \
+            todolist_to_string(reference))

test/data/FilterTest2-result.txt

+Baz p:2
+Buzz id:5
+x 2014-07-20 Blob p:5
+Task 2 p:6
+x 2014-07-20 Task 3 p:6

test/data/FilterTest2.txt

+Foo id:1
+Bar p:1 id:2
+Baz p:2
+Buzz id:5
+x 2014-07-20 Blob p:5
+Task 1 id:6
+Task 2 p:6
+x 2014-07-20 Task 3 p:6