More notes/thoughts

svn path=/plone.app.discussion/trunk/; revision=26919

plone/app/discussion/NOTES.txt

@@ -4,6 +4,47 @@ plone.app.discussion design notes
 
 This document contains design notes for plone.app.discussion.
 
+Storage and traversal
+---------------------
+
+For each content item, there is a Conversation object stored in annotations.
+This can be traversed to via the ++comments++ namespace, but also fetched
+via an adapter lookup to IConversation.
+
+The conversation stores all comments related to a content object. Each
+comment has an integer id (also representable as a string, to act as an OFS
+id and allow traversal). Hence, traversing to obj/++comments++/123 retrieves
+the comment with id 123.
+
+Comments ids are assigned in order, so a comment with id N was posted before
+a comment with id N + 1. However, it is not guaranteed that ids will be 
+incremental. Ids must be positive integers - 0 or negative numbers are not
+allowed.
+
+Threading information is stored in the conversation: we keep track of the
+set of children and the parent if any comment. Top-level comments have a
+parent id of 0. This information is managed by the conversation class when
+comments are manipulated using a dict-like API.
+
+Note that the __parent__/acquisition parent of an IComment is the
+IConversation, and the __parent__/acquisition parent of an IConversation is
+the content object.
+
+Events
+------
+
+Manipulating the IConversation object should fire the usual IObjectAddedEvent
+and IObjectRemovedEvent events. The UI may further fire IObjectCreatedEvent
+and IObjectModifiedEvent for comments.
+
+Factories
+---------
+
+Comments should always be created via the 'Discussion Item' IFactory utility.
+Conversations should always be obtained via the IConversation adapter (even
+the ++comments++ namespace should use this). This makes it possible to replace
+conversations and comments transparently.
+
 The Comment class
 -----------------
 
@@ -49,53 +90,12 @@ metadata such as creator, effective date etc.
 
 Finally, we'll need event handlers to perform the actual indexing.
 
-The Discussable class
----------------------
-
-To obtain comments for a content item, we adapt the content to IDiscussable.
-This has a 'replies' BTree.
-
-To support __parent__ pointer integrity and stable URLs, we will implement
-IDiscussable as a persistent object stored in an annotation. Comments directly
-in reply to the content item have a __parent__ pointing to this, which in turn
-has a __parent__ pointing at the content item.
-
-The IDiscussable interface also maintains information about the total number
-of comments and the unique set of commenters' usernames. These are indexed in
-the catalog, allowing queries like "recently commented-upon content items",
-"my comments", or "all comments by user X". These values need to be stored and
-maintained by event handlers, not calculated on the fly.
-
-See collective.discussionplus for inspiration.
-
-Traversal and acquisition
---------------------------
-
-A comment may have a URL such as:
-
-    http://localhost:8080/site/content/++comments++/1/2/3
-    
-For this traversal to work, we have:
-
-    - a namespace traversal adapter for ++comments++ that looks up an
-      IDiscussable adapter on the context and returns this
-
-    - an IPublishTraverse adapter for IHasReplies (inherited by IDiscussable
-      and IComment), which looks up values in the 'replies' dictionary and
-      acquisition-wraps them.
-        
-    - the IDiscussable adapter needs to have an id of ++comment++
-
-XXX: unrestrictedTraverse() does not take IPublishTraverse adapters into
-account. This may mean we need to implement __getitem__ on comments instead
-of/in addition to using a custom IPublishTraverse for IHasReplies.
-
 Discussion settings
 -------------------
 
 Discussion can be enabled per-type and per-instance, via values in the FTI
 (allow_discussion) and on the object. These will remain unchanged. The
-IDiscussable object's 'enabled' property should consult these.
+IConversation object's 'enabled' property should consult these.
 
 Global settings should be managed using plone.registry. A control panel
 can be generated from this as well, using the helper class in

plone/app/discussion/comment.py

@@ -24,7 +24,8 @@ class Comment(Explicit, Traversable, RoleManager, Owned):
     meta_type = portal_type = 'Discussion Item'
     
     __parent__ = None
-    __name__ = None
+    
+    comment_id = None # int
 
     title = u""
     
@@ -40,8 +41,8 @@ class Comment(Explicit, Traversable, RoleManager, Owned):
     author_name = None
     author_email = None
     
-    def __init__(self, id=None, conversation=None, **kw):
-        self.__name__ = unicode(id)
+    def __init__(self, id=0, conversation=None, **kw):
+        self.comment_id = id
         self.__parent__ = conversation
         
         for k, v in kw:
@@ -49,9 +50,13 @@ class Comment(Explicit, Traversable, RoleManager, Owned):
     
     # convenience functions
     
+    @property
+    def __name__(self):
+        return unicode(self.comment_id)
+    
     @property
     def id(self):
-        return str(self.__name__)
+        return str(self.comment_id)
     
     def getId(self):
         """The id of the comment, as a string

plone/app/discussion/configure.zcml

@@ -1,12 +1,21 @@
 <configure xmlns="http://namespaces.zope.org/zope" i18n_domain="plone.app.discussion">
 
     <include file="permissions.zcml" />
+    <include package=".browser" />
 
-    <utility object=".comment.CommentFactory" name="Discussion Item" />
-
+    <!-- Comments -->
     <class class=".comment.Comment">
-        <require interface=".comment.Comment" permission="zope2.View" />
+        <require interface=".interfaces.IComment" permission="zope2.View" />
         <require attributes="Title Creator getId" permission="zope2.View" />
     </class>
+    
+    <utility object=".comment.CommentFactory" name="Discussion Item" />
+    
+    <!-- Conversations -->
+    <class class=".conversation.Conversation">
+        <require interface=".interfaces.IConversation" permission="zope2.View" />
+    </class>
+    
+    <adapter factory=".conversation.conversationAdapterFactory" />
 
 </configure>

plone/app/discussion/conversation.py

@@ -10,8 +10,12 @@ manipulating the comments directly in reply to a particular comment or at the
 top level of the conversation.
 """
 
-from zope.interface import implements
-from zope.component import adapts
+from persistence import Persistent
+
+from zope.interface import implements, implementer
+from zope.component import adapts, adapter
+
+from zope.annotation.interfaces import IAnnotatable
 
 from BTrees.OIBTree import OIBTree
 from BTrees.IOBTree import IOBTree
@@ -21,8 +25,11 @@ from Acquisition import Explicit
 
 from plone.app.discussion.interfaces import IConversation, IComment, IReplies
 
-class Conversation(Explicit):
+class Conversation(Persistent, Explicit):
     """A conversation is a container for all comments on a content object.
+    
+    It manages internal data structures for comment threading and efficient
+    comment lookup.
     """
     
     implements(IConversation)
@@ -79,17 +86,42 @@ class Conversation(Explicit):
     # Dict API
     
     # TODO: Update internal data structures when items added or removed
-    
-class ConversationReplies(object):
+
+@implementer(IConversation)
+@adapter(IAnnotatable)
+def conversationAdapterFactory(content):
+    """Adapter factory to fetch a conversation from annotations
     """
+    
+    # TODO
+    return None
+
+class ConversationReplies(object):
+    """An IReplies adapter for conversations.
+    
+    This makes it easy to work with top-level comments.
     """
     
     implements(IReplies)
     adapts(Conversation)
+    
+    def __init__(self, context):
+        self.conversation = context
+        self.root = 0
+    
+    # TODO: dict interface - generalise to work with any starting point, so
+    # that the subclassing below works
 
-class CommentReplies(object):
-    """
+class CommentReplies(ConversationReplies):
+    """An IReplies adapter for comments.
+    
+    This makes it easy to work with replies to specific comments.
     """
     
     implements(IReplies)
-    adapts(IComment)
+    adapts(IComment)
+    
+    def __init__(self, context):
+        self.conversation = context.__parent__
+        self.root = context.comment_id
+