handlers: Rename Handler class to Action.

[matthijs/projects/backupninja.git] / src / lib / backupninja / handlers / __init__.py

diff --git a/src/lib/backupninja/handlers/__init__.py b/src/lib/backupninja/handlers/__init__.py
index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..72b30179a3a0017f9bfe3447b60d9e5d5365922a 100644 (file)
--- a/src/lib/backupninja/handlers/__init__.py
+++ b/src/lib/backupninja/handlers/__init__.py
@@ -0,0 +1,101 @@
+#
+#    Backupninja python reimplementation, based on original backupninja program
+#    by riseup.net.
+#    Copyright (C) 2010  Matthijs Kooijman <matthijs@stdin.nl>
+#
+#    This program is free software; you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation; either version 2 of the License, or
+#    (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License along
+#    with this program; if not, write to the Free Software Foundation, Inc.,
+#    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+""" Action superclass with common functionality """
+
+import sys
+import logging as log
+
+from backupninja import config
+
+class Action(object):
+    """
+    Subclasses of Action represent handlers for various action types.
+    This class is called Action instead of Handler, since even though the
+    classes could be referred to as handlers, the instances of this
+    class are really actions (i.e., it represents a specific action,
+    which is a combination of a action type and a specific action
+    configuration).
+    """
+    def __init__(self):
+        # Subclasses should overwrite this with their default config
+        # See backupninja.config.load_config for the structure of this
+        # value.
+        self.default_config = {}
+
+    def run(self, **kwargs):
+        """
+        Run this action for a single target. Override this method
+        in a subclass
+        """
+        pass
+
+    def finish(self, **kwargs):
+        """
+        Called when all targets have been processed. Can be overridden
+        in a subclass.
+        """
+        pass
+
+    def load_config(self, filename):
+        """
+        Load the configuration for this action from the given filename.
+        """
+        self.conf = config.load_config(filename, self.default_config)
+
+        
+
+def create_action(ty):
+    """
+    Create a new (subclass of) Action object for an action with the
+    given type.
+
+    If the handler class for this type cannot be loaded, an exception is
+    thrown.
+    """
+    modname = 'backupninja.handlers.%s' % ty
+    # Load the handler if it is not loaded yet
+    if not modname in sys.modules:
+        log.debug('Loading handler for type "%s"', ty)
+        try:
+            __import__(modname, globals(), locals(), [])
+        except ImportError, e:
+            # Add some extra info, since the default exception does not
+            # show the full module name.
+            raise ImportError('Cannot load module %s: %s' % (modname, e))
+        log.debug('Loaded handler for type "%s" from "%s"', ty, sys.modules[modname].__file__)
+    # Get the module from the module table
+    module = sys.modules[modname]
+
+    # Check that the module has a "handler" top level function, which
+    # should create a new Action object.
+    if not hasattr(module, 'handler'):
+        raise ImportError('%s is not valid: it '
+                          'does not have a "handler" top level function.' 
+                          % (module.__file__))
+
+    # Call the "handler" function to create the actual action
+    action = module.handler()
+   
+    # Check if the handler returned is really a subclass of Action
+    if not isinstance(action, Action):
+        raise TypeError('%s is not valid, %s.handler did not return a '
+                        'subclass of backupninja.handlers.Handler.'
+                        % (module.__file__, modname))
+    return action