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Questions

When we send emails to users, should we download the body of the email and send it in the email body? Or should we tell them to visit the portal?
- At the moment, files are assumed to be stored as plain text
Should notifications of this nature be implemented now or later?
- Proposed implementation:
  - On create/update of ACL, fetch the original ACL
  - Compare the original with the new ACL and send a message to all users that have changed permissions
  - Message will contain the ID/alias of the person who made the change and the entity ID. It may also contain the set of permissions.
How should we tie Entities to users in terms of notifications?
- Ownership? << It might be this.
- Favorites? << It might be this.
- Permissions? << I don't think it's this.
- Something else? << It could be a completely new set of services, allowing users to enable/disable notification. (Could be initialized from Favorites and Owners.)

Objects

Name	DBO	Migration	DTO
MessageContent (Immutable after creation)	Primary key: ID Foreign key: CreatedBy (UserGroup) Foreign key: MessageBody (S3 File Handle ID) Etag CreatedOn	Backup via ID Note: Etag is required because MessageStatus is mutable.	Interface ID CreatedBy (principal ID) S3 File Handle ID CreatedOn
MessageToUser (Immutable after creation)	Foreign key: ID (MessageContent) Subject (nullable) Self foreign key: InReplyTo (ID) (nullable) Foreign key: InReplyToRootId Recursive foreign key to primary key	Secondary to MessageContent	Implements MessageContent Subject (string, optional) Set of recipient IDs inReplyTo (optional) inReplyToRoot (optional)
MessageRecipient (Immutable after creation)	Foreign key: ID (MessageContent) Foreign key: Recipient ID (UserGroup)	Secondary to MessageContent
MessageStatus	Foreign key: ID (MessageContent) Foreign key: Recipient ID (UserGroup) States: UNREAD, READ, ARCHIVED	Secondary to MessageContent	ID Recipient State
Comment (Immutable after creation)	Foreign key: ID (MessageContent) Target type (Enum ObjectType) Target ID TBD: references to other Comments in the conversation*	Secondary to MessageContent	Implements MessageContent Target type Target ID
MessagingSettings	Part of UserProfile Use existing services to support this	Secondary to UserGroup	Should email be sent? Should emailed messages be READ automatically? Other options (as necessary) Blacklist of blocked users
CommentVotes	Primary key: Message ID Up votes Down votes Is-comment-inappropriate votes	TBD	ID Up Down
MessageBundle			Bundles the MessageToUser and Message Status
MessageRecipientSet			Set of recipient IDs

'* per Marcel, Comments may have a more complex set of references/relationships than Messages to Users have. Rather than just 'inReplyTo', it might be that one Comment is an 'answer' to another comment which is a question. Further, the multiple answers to a question may have 'previous' references which order them.

Other TODOs

Throttle message input
- Max 10 creations per minute
- Max 50 recipients
When adding a new person to a conversation, the new person should get the whole history of the conversation
- Might be implemented by forwarding ALL the previous messages
- OR by concatenating all previous into one new message
Configure Amazon SES
- Automated proposal:
  - Reroute bounce and complaints to SNS
  - Have a worker subscribe to the topic via SQS
  - Have a worker disable emails to hard-bounced recipients
  - The worker may email a Google Group to notify us of anything it cannot handle
  - Also flip flags in settings for complaints
  - Store the bounce/complaint in a blob
Should users be notified of bounces? <<< Yes, and (1) this is a special case of 'notification', i.e. a Message triggered by a Synapse event, (2) perhaps user can configure email receipt to avoid excessive email from notifications (or other sources)
Add methods to send messages according to templates
- Each individual Message should be stored in its final form.
- This design choice would change for very very large notification message volumes.
- Templates:
  - Password reset
  - Welcome
  - Entity shared
  - Entity changed
  - TBD

Message sender (worker)

Extend ObjectType to include a "MESSAGE" type
Have DBOMessage extend ObservableEntity
Send a change message when a message is created
Subscribe worker to the repo-changes topic
Look for MESSAGE-CREATED changes to process
The worker should always check to see if a message has already been sent, so that messages do not get resent every time the stack changes.
A message has been sent if there is a recipient. The worker is in charge of making sure all sent messages have at least one recipient. In the case where a user sends a message to multiple recipients, all of which are not visible to the user, then the worker should bounce the message back to the user, along with a bounce message. This ensures the message has a row in the MessageStatus table.
Process change of other ObjectTypes (i.e. ENTITY) for notifications
- Needs additional state: either a link between ObjectID/Type and messageContent or ObjectID/Type and UserID

Services

Sorting & Pagination
- Sort by creation date
- Sort by subject
- Sort by recipient name

Method	URI	Body	Parameters	Return	Description	Permission
POST	/message	MessageToUser		MessageToUser	Sends a message. Note, message delivery permission is on a recipient-by-recipient basis, asynchronous to the message creation. Unauthorized delivery may result in silent failure or a bounce message (TBD).	Authenticated User Must be admin to send to AUTH_USERS Must have SEND_MESSAGE permission on team to send to team
GET	/message/inbox		Sorting + pagination	Paginated results<MessageBundle>	Gets all messages the authenticated user has received	Authenticated User
GET	/message/outbox		Sorting + pagination	Paginated results<MessageToUser>	Gets all messages the authenticated user has sent	Authenticated User
GET	/message/{id}			MessageToUser	Gets a specific message	Sender or Receiver
POST	/message/{id}/forward	MessageRecipientSet		MessageToUser	Forwards a message to other recipients. This is equivalent to getting a (visible) message and POST-ing it to /message	Sender or Receiver
GET	/message/{id}/conversation		Sorting + pagination	Paginated results<MessageToUser>	Gets messages belonging in the same thread as the message ID. The list is filtered according to the user's ID.	Sender or Receiver
PUT	/message/status	MessageStatus			Marks a message as: READ UNREAD ARCHIVED	Receiver
POST	/entity/{id}/message	MessageToUser		MessageToUser	Sends a message to the creator or administrator of the given entity. This allows users to ask for permission to see restricted entities. Added per	Authenticated user
POST	/entity/{id}/comment	Comment		Comment	Method for commenting on an entity.	Authenticated user with SEND_MESSAGE permission on entity
GET	/entity/{id}/comment		Sorting + pagination	Paginated results<Comment>	Gets messages belonging to the thread tied to the entity.	Authenticated user with READ permission on entity