fix up some TODOs in replica.rs

docs/src/data-model.md

@@ -0,0 +1,42 @@
+# Data Model
+
+A client manages a single offline instance of a single user's task list.
+The data model is only seen from the clients' perspective.
+
+## Task Database
+
+The task database is composed of an un-ordered collection of tasks, each keyed by a UUID.
+Each task in the database has an arbitrary-sized set of key/value properties, with string values.
+
+Tasks are only created and modified; "deleted" tasks continue to stick around and can be modified and even un-deleted.
+Tasks have an expiration time, after which they may be purged from the database.
+
+## Task Fields
+
+Each task can have any of the following fields.
+Timestamps are stored as UNIX epoch timestamps, in the form of an integer expressed in decimal notation.
+Note that it is possible for any field to be omitted.
+
+NOTE: This structure is based on https://taskwarrior.org/docs/design/task.html, but will diverge from that
+model over time.
+
+* `status` - one of `Pending`, `Completed`, `Deleted`, `Recurring`, or `Waiting`
+* `entry` (timestamp) - time that the task was created
+* `description` - the one-line summary of the task
+* `start` (timestamp) - if set, the task is active and this field gives the time the task was started
+* `end` (timestamp) - the time at which the task was deleted or completed
+* `due` (timestamp) - the time at which the task is due
+* `until` (timestamp) - the time after which recurrent child tasks should not be created
+* `wait` (timestamp) - the time before which this task is considered waiting and should not be shown
+* `modified` (timestamp) - time that the task was last modified
+* `scheduled` (timestamp) - time that the task is available to start
+* `recur` - recurrence frequency
+* `mask` - recurrence history
+* `imask` - for children of recurring tasks, the index into the `mask` property on the parent
+* `parent` - for children of recurring tasks, the uuid of the parent task
+* `project` - the task's project (usually a short identifier)
+* `priority` - the task's priority, one of `L`, `M`, or `H`.
+* `depends` - a comma (`,`) separated list of uuids of tasks on which this task depends
+* `tags` - a comma (`,`) separated list of tags for this task
+* `annotation_<timestamp>` - an annotation for this task, with the timestamp as part of the key
+* `udas` - user-defined attributes