Add dep subcommand to handle dependencies.

Main.py

@@ -10,6 +10,7 @@ from PrettyPrinter import pretty_print
 import Sorter
 import TodoFile
 import TodoList
+import View
 
 def print_iterable(p_iter):
     """ Prints an iterable to the standard output, one item per line. """
@@ -74,6 +75,58 @@ class Application(object):
 
         self.dirty = True
 
+    def dep(self):
+        """ Handles dependencies between todos. """
+        def handle_add_rm(operation):
+            """ Handles the add and rm subsubcommands. """
+            from_todonumber = convert_number(argument(3))
+            to_todonumber = argument(4)
+
+            if to_todonumber == 'to':
+                to_todonumber = convert_number(argument(5))
+            else:
+                to_todonumber = convert_number(to_todonumber)
+
+            if operation == 'add':
+                self.todolist.add_dependency(from_todonumber, to_todonumber)
+            else:
+                self.todolist.remove_dependency(from_todonumber, to_todonumber)
+
+            self.dirty = True
+
+        def handle_ls():
+            """ Handles the ls subsubcommand. """
+            arg1 = argument(3)
+            arg2 = argument(4)
+
+            todos = []
+            if arg2 == 'to':
+                # dep ls 1 to ...
+                todos = self.todolist.children(convert_number(arg1))
+            elif arg1 == 'to':
+                # dep ls ... to 1
+                todos = self.todolist.parents(convert_number(arg2))
+            else:
+                usage()
+
+            if todos:
+                sorter = Sorter.Sorter(Config.SORT_STRING)
+                view = View.View(sorter, [], todos)
+                print view.pretty_print()
+
+        subsubcommand = argument(2)
+        if subsubcommand == 'add' or \
+            subsubcommand == 'rm' or subsubcommand == 'del':
+
+            handle_add_rm(subsubcommand)
+        elif subsubcommand == 'clean' or subsubcommand == 'gc':
+            self.todolist.clean_dependencies()
+            self.dirty = True
+        elif subsubcommand == 'ls':
+            handle_ls()
+        else:
+            usage()
+
     def do(self):
         number = convert_number(argument(2))
         todo = self.todolist.todo(number)
@@ -127,6 +180,8 @@ class Application(object):
             self.add()
         elif subcommand == 'app' or subcommand == 'append':
             self.append()
+        elif subcommand == 'dep':
+            self.dep()
         elif subcommand == 'do':
             self.do()
         elif subcommand == 'ls':