# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1454970279 -3600
# Node ID 068aa85f0c454af278c5b0c484c3dab422b6f89c
# Parent  5abe3fb608d67ccdc38fcb68c508ccf13f5ef8d1
Made the retraction operation a complete transaction.
Tidied up the locking and unlocking function application.

diff -r 5abe3fb608d6 -r 068aa85f0c45 imiptools/handlers/scheduling/__init__.py
--- a/imiptools/handlers/scheduling/__init__.py	Mon Feb 08 23:24:09 2016 +0100
+++ b/imiptools/handlers/scheduling/__init__.py	Mon Feb 08 23:24:39 2016 +0100
@@ -32,23 +32,17 @@
 
     """
     Apply the given scheduling 'functions' in the current object of the given
-    'handler'.
+    'handler'. This function starts a transaction that should be finalised using
+    the 'finish_scheduling' function.
     """
 
-    # Obtain the actual scheduling functions with arguments.
-    # Also obtain functions to lock resources.
-
-    schedulers = get_function_calls(functions, scheduling_functions)
-    locks = get_function_calls(functions, locking_functions)
-
     # First, lock the resources to be used.
 
-    for fn, args in locks:
+    start_scheduling(functions, handler)
 
-        # Not all scheduling functions require compound locking.
+    # Obtain the actual scheduling functions with arguments.
 
-        if fn:
-            fn(handler, args)
+    schedulers = get_function_calls(functions, scheduling_functions)
 
     # Then, invoke the scheduling functions.
 
@@ -84,7 +78,8 @@
 
     """
     Confirm scheduling using the given listener 'functions' for the current
-    object of the given 'handler'.
+    object of the given 'handler'. This function continues a transaction that
+    should be finalised using the 'finish_scheduling' function.
     """
 
     # Obtain the actual listener functions with arguments.
@@ -92,6 +87,39 @@
     functions = get_function_calls(functions, confirmation_functions)
     apply_functions(functions, handler)
 
+def retract_scheduling(functions, handler):
+
+    """
+    Retract scheduling using the given listener 'functions' for the current
+    object of the given 'handler'. This function is a complete transaction in
+    itself.
+    """
+
+    # First, lock the resources to be used.
+
+    start_scheduling(functions, handler)
+
+    # Obtain the actual listener functions with arguments.
+
+    retractors = get_function_calls(functions, retraction_functions)
+    apply_functions(retractors, handler)
+
+    # Finally, unlock the resources.
+
+    finish_scheduling(functions, handler)
+
+def start_scheduling(functions, handler):
+
+    """
+    Apply locking functions for the given scheduling 'functions' and for the
+    current object of the given 'handler'.
+    """
+
+    # Obtain functions to lock resources.
+
+    locks = get_function_calls(functions, locking_functions)
+    apply_functions(locks, handler)
+
 def finish_scheduling(functions, handler):
 
     """
@@ -102,27 +130,7 @@
     # Obtain functions to unlock resources.
 
     locks = get_function_calls(functions, unlocking_functions)
-
-    # Unlock the resources that were used.
-
-    for fn, args in locks:
-
-        # Not all scheduling functions require compound locking.
-
-        if fn:
-            fn(handler, args)
-
-def retract_scheduling(functions, handler):
-
-    """
-    Retract scheduling using the given listener 'functions' for the current
-    object of the given 'handler'.
-    """
-
-    # Obtain the actual listener functions with arguments.
-
-    functions = get_function_calls(functions, retraction_functions)
-    apply_functions(functions, handler)
+    apply_functions(locks, handler)
 
 def apply_functions(functions, handler):