168 lines
6.7 KiB
Plaintext
168 lines
6.7 KiB
Plaintext
============
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Design Notes
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============
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This document contains design notes for plone.app.discussion.
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Storage and traversal
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---------------------
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For each content item, there is a Conversation object stored in annotations.
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This can be traversed to via the ++conversation++ namespace, but also fetched
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via an adapter lookup to IConversation.
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The conversation stores all comments related to a content object. Each
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comment has an integer id (also representable as a string, to act as an OFS
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id and allow traversal). Hence, traversing to obj/++conversation++/123 retrieves
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the comment with id 123.
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Comments ids are assigned in order, so a comment with id N was posted before
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a comment with id N + 1. However, it is not guaranteed that ids will be
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incremental. Ids must be positive integers - 0 or negative numbers are not
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allowed.
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Threading information is stored in the conversation: we keep track of the
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set of children and the parent if any comment. Top-level comments have a
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parent id of 0. This information is managed by the conversation class when
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comments are manipulated using a dict-like API.
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Note that the __parent__/acquisition parent of an IComment is the
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IConversation, and the __parent__/acquisition parent of an IConversation is
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the content object.
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Events
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------
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Manipulating the IConversation object should fire the usual IObjectAddedEvent
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and IObjectRemovedEvent events. The UI may further fire IObjectCreatedEvent
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and IObjectModifiedEvent for comments.
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Factories
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---------
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Comments should always be created via the 'Discussion Item' IFactory utility.
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Conversations should always be obtained via the IConversation adapter (even
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the ++conversation++ namespace should use this). This makes it possible to
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replace conversations and comments transparently.
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The Comment class
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-----------------
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The inheritance tree for DiscussionItem is shown below. Classes we want to
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mix in and interface we want to implement in the Comment class are marked
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with [x].
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[ ] DiscussionItem
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[ ] Document
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[ ] PortalContent = [ ] IContentish
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[ ] DynamicType = [ ] IDynamicType
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[ ] CMFCatalogAware = [ ] <no interface>
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[ ] SimpleItem = [ ] ISimpleItem
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[ ] Item [ ]
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[?] Base = [ ] <no interface>
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[ ] Resource = [ ] <no interface>
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[ ] CopySource = [ ] ICopySource
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[ ] Tabs = [ ] <no interface>
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[x] Traversable = [ ] ITraversable
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[ ] Element = [ ] <no interface>
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[x] Owned = [ ] IOwned
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[ ] UndoSupport = [ ] IUndoSupport
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[ ] Persistent [ ]
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[ ] Implicit [ ]
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[x] RoleManager = [ ] IRoleManager
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[ ] RoleManager = [ ] IPermissionMappingSupport
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[ ] DefaultDublinCoreImpl = [ ] IDublinCore
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[ ] ICatalogableDublinCore
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[ ] IMutableDublinCore
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[ ] PropertyManager = [ ] IPropertyManager
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Thus, we want:
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* Traversable, to get absolute_url() and friends
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- this requires a good acquisition chain at all times
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* Acquisition.Explicit, to support acquisition
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- we do not want implicit acquisition
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* Owned, to be able to track ownership
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* RoleManager, to support permissions and local roles
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We also want to use a number of custom indexers for most of the standard
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metadata such as creator, effective date etc.
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Finally, we'll need event handlers to perform the actual indexing.
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Discussion settings
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-------------------
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Discussion can be enabled per-type and per-instance, via values in the FTI
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(allow_discussion) and on the object. These will remain unchanged. The
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IConversation object's 'enabled' property should consult these.
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Global settings should be managed using plone.registry. A control panel
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can be generated from this as well, using the helper class in
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plone.app.registry.
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Note that some settings, notably those to do with permissions and workflow,
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will need to be wired up as custom form fields with custom data mangers
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or similar.
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Workflow and permissions
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------------------------
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Where possible, we should use existing permissions:
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* View
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* Reply to Item
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* Modify Portal Content
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* Request Review
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In addition, we'll need a 'Moderator' role and a moderation permission,
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* Moderate comment
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* Bypass moderation
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To control whether Anonymous can post comments, we manage the 'Reply to Item'
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permission. To control whether moderation is required for various roles, we
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could manage the 'Bypass moderation' permission.
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These could work in a workflow like this:
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* --> [posted] -- {publish} --> [published]--> *
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| ^
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+----- {auto-publish} -----+
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+----- {auto-moderate} ----+
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The 'posted' state is the initial state. 'published' is the state where the
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comment is visible to non-reviewers.
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The 'publish' transition would be protected by the 'Moderate comment'
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permission. We could have states and transition for 'rejected', etc, but it
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is probably just as good to delete comments that are rejected.
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The 'auto-publish' transition would be an automatic transition protected by
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the 'Bypass moderation' permission.
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The 'auto-moderate' transition would be another automatic transition protected
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by an expression (e.g. calling a view) that returns True if the user is on
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an auto-moderation 'white-list', e.g. by email address or username.
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Forms and UI
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------------
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The basic commenting display/reply form is placed in a viewlet.
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The reply form is dynamically created right under the comment when the user hits
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the reply button. To do so, we copy the standard comment form with a jQuery
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function. This function sets the form's hidden in_reply_to field to the id of
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the comment the user wants to reply to. This also makes is possible to use
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z3c.form validation for the reply forms, because we can uniquely identify the
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a reply form request and return the reply form with validation errors.
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Since we rely on JavaScript for the reply form creation, the reply button is
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removed for nonJavaScript enabled browsers.
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The comment form uses z3c.form and plone.z3cform's ExtensibleForm support. This
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makes it possible to plug in additional fields declaratively, e.g. to include
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SPAM protection.
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