TimelineEntry

Purpose

One place in a member's readable timeline. Because a member reads only their own inbox and receives only copies sealed for them, an entry is one of two shapes: readable, where the message opened and its writing is presented; or missing, where a message the member did hold names a parent MessageId no received message answers to — a message still travelling, withheld, or one from before the member's time that was never addressed to them. A missing entry is not yet an accusation, and there is no sealed placeholder for a message never delivered: an epoch you were not in is simply absent from your inbox, not a closed box on your timeline. There is no third shape: a message is readable whole or not at all.

Attributes

• kind: is one of "readable", "missing" that names the entry's shape

Readable attributes

• message id: the MessageId of the message presented
• sender: is Text that carries the sub of the member who wrote it, read from inside the seal
• writing: is Text that carries the readable text

Missing attributes

• awaited: is a MessageId that a received message follows while it has not itself arrived

Invariants

• A readable entry carries the writing and its sender; a missing entry carries only the awaited id.

Scenarios

A readable entry carries the writing

Given: kind "readable", the MessageId "m-8001", sender "anne.bruun", and writing "The hearing moved to Thursday." When: a TimelineEntry is created Then: it is accepted as a readable entry carrying that writing from "anne.bruun"

A missing entry names what it awaits

Given: kind "missing" and an awaited MessageId "m-8000" When: a TimelineEntry is created Then: it is accepted as a missing entry awaiting "m-8000"

An unknown shape is rejected

Given: kind "shouted", with no writing and no awaited id When: a TimelineEntry is created Then: the creation is rejected because the kind is not a recognised entry shape