--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/bGrease/component/base.py	Mon Sep 05 15:00:34 2011 +0200
@@ -0,0 +1,74 @@
+class ComponentBase(object):
+	"""Component abstract base class
+
+	Strictly speaking you do not need to derive from this class to create your
+	own components, but it does serve to document the full interface that a
+	component implements and it provides some basic implementations for
+	certain methods
+	"""
+
+	## Optional attributes and methods ##
+
+	def set_manager(self, manager):
+		"""Set the manager of this component. If this method exists it will be
+		automatically called when the component is added to a manager.
+
+		This method stores the manager and allows the component to be added
+		only once to a single manager.
+		"""
+		assert getattr(self, 'manager', None) is None, 'Component cannot be added to multiple managers'
+		self.manager = manager
+
+	def __del__(self):
+		"""Break circrefs to allow faster collection"""
+		if hasattr(self, 'manager'):
+			del self.manager
+	
+	## Mandatory methods ##
+
+	def add(self, entity_id, data=None, **data_kw):
+		"""Add a data entry in the component for the given entity.  Additional
+		data (if any) for the entry can be provided in the data argument or as
+		keyword arguments. Additional data is optional and if omitted then
+		suitable defaults will be used. Return an entity data object
+		for the new entity entry.
+
+		The semantics of the data arguments is up to the component.
+
+		An entity_id is a unique key, thus multiple separate data entries for
+		a given entity are not allowed.  Components can indivdually decide
+		what to do if an entity_id is added multiple times to the component.
+		Potential options include, raising an exception, replacing the
+		existing data or coalescing it somehow.
+		"""
+	
+	def remove(self, entity_id):
+		"""Remove the entity data entry from the component. If the
+		entity is not in the component, raise KeyError
+		"""
+	
+	def __delitem_(self, entity_id):
+		"""Same as remove()"""
+
+	def __len__(self):
+		"""Return the number of entities in the component"""
+		raise NotImplementedError()
+	
+	def __iter__(self):
+		"""Return an iterator of entity data objects in this component
+
+		No order is defined for these data objects
+		"""
+		raise NotImplementedError()
+	
+	def __contains__(self, entity_id):
+		"""Return True if the entity is contained in the component"""
+		raise NotImplementedError()
+	
+	def __getitem__(self, entity_id):
+		"""Return the entity data object for the given entity. 
+		The entity data object returned may be mutable, immutable or a
+		mutable copy of the data at the discretion of the component
+		"""
+		raise NotImplementedError()
+