Added: CalendarServer/trunk/twistedcaldav/directory/resource.py (0 => 840)

--- CalendarServer/trunk/twistedcaldav/directory/resource.py	                        (rev 0)
+++ CalendarServer/trunk/twistedcaldav/directory/resource.py	2006-12-15 19:53:12 UTC (rev 840)
@@ -0,0 +1,55 @@
+##
+# Copyright (c) 2006 Apple Computer, Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# DRI: Wilfredo Sanchez, wsanchez@apple.com
+##
+
+"""
+Implements a directory-backed principal hierarchy.
+"""
+
+__all__ = ["AutoProvisioningResourceMixIn"]
+
+class AutoProvisioningResourceMixIn (object):
+    """
+    Adds auto-provisioning to a Resource implementation.
+    """
+    def provision(self):
+        """
+        Provision this resource by creating any required backing store, etc. that
+        must be set up before the resource can be accessed normally.
+        FIXME: More description of what that means would be helpful here.  Basically,
+        RenderMixIn methods should work (perhaps returning None) without having to
+        call this first, so that dirlist can happen, but it is expected that this will
+        have been called before anything that involves I/O happens.
+        This method may be called multiple times; provisioning code should ensure that
+        it handles this properly, typically by returning immediately if the resource is
+        already provisioned (eg. the backing store exists).
+        @return: a deferred or None.
+        """
+        return None
+
+    def locateChild(self, *args):
+        """
+        This implementation calls L{provision}, then super's L{locateChild}, thereby
+        ensuring that looked-up resources are provisioned.
+        """
+        super_method = super(AutoProvisioningResourceMixIn, self).locateChild
+        d = self.provision()
+        if d is None:
+            return super_method(*args)
+        else:
+            d.addCallback(lambda _: super_method(*args))
+            return d