1 files changed, 55 insertions, 0 deletions
diff --git a/nbb/nbblib/plugins.py b/nbb/nbblib/plugins.py
new file mode 100644
index 0000000..64633f6
--- /dev/null
+++ b/nbb/nbblib/plugins.py
@@ -0,0 +1,55 @@
+class DuplicatePluginName(Exception):
+    pass
+
+
+class PluginDict(object):
+    """Helper for GenericPluginMeta class
+
+    Behaves basically like a standard dict, but fails when asked
+    to update an existing value.
+    """
+    def __init__(self):
+        self.dict = {}
+    def __getitem__(self, *args):
+        return self.dict.__getitem__(*args)
+    def __setitem__(self, key, value):
+        if self.dict.has_key(key):
+            raise DuplicatePluginName()
+        else:
+            self.dict[key] = value
+    def items(self): return self.dict.items()
+    def keys(self): return self.dict.keys()
+    def values(self): return self.dict.values()
+    def __iter__(self): return self.dict.__iter__()
+    def __str__(self): return self.dict.__str__()
+    def __repr__(self): return self.dict.__repr__()
+    def __len__(self): return self.dict.__len__()
+    def has_key(self, key): return self.dict.has_key(key)
+
+
+########################################################################
+# Generic plugin system
+########################################################################
+# Plugin architecture (metaclass tricks) by Marty Alchin from
+# http://gulopine.gamemusic.org/2008/jan/10/simple-plugin-framework/
+# Slightly modified go store plugins as dict.
+########################################################################
+
+class GenericPluginMeta(type):
+    def __init__(cls, name, bases, attrs):
+        if not hasattr(cls, 'plugins'):
+            # This branch only executes when processing the mount point itself.
+            # So, since this is a new plugin type, not an implementation, this
+            # class shouldn't be registered as a plugin. Instead, it sets up a
+            # list where plugins can be registered later.
+            cls.plugins = PluginDict()
+        elif hasattr(cls, 'name'):
+            # This must be a plugin implementation, which should be registered.
+            # Simply appending it to the list is all that's needed to keep
+            # track of it later.
+            cls.plugins[cls.name] = cls
+        else:
+            # This must be an abstract subclass of plugins.
+            pass
+
+