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FabledScribe/src/scribe/services/rule_versions.py
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feat(rules): a preference is a rule that does not bind (#3849 step 1)
Adds `kind` to rules — `rule` binds, `preference` is how the operator wants
work done. One column, because the two differ in exactly one dimension and
everything else a preference needs already lives on `rules`: a trigger
column, a trigger-dominated embedding document, ownership-scoped search,
three retrieval arms with telemetry, typed relations, and versioning.

Defaults to `rule`, so nothing changes force on upgrade — 0088's argument
for `tier`, unchanged.

`rule_versions` gets the column too, and that half is not bookkeeping.
`record_if_changed` decides whether an edit deserves a snapshot by comparing
the fields a version carries, so a field absent from SNAPSHOT_FIELDS is a
field whose change records no history at all. Without it, turning a rule
into a preference — the moment something stops binding, and the single most
consequential edit either kind can undergo — would leave the history silent.

Backup carries it through all four seams. A missed one would have restored
every preference as a rule, quietly.

Guarded on real Postgres in three halves: a preference writes, a typo is
refused (without which every other assertion would pass against a table
whose CHECK had been dropped), and a row written with no kind reads back as
`rule` — the migration's whole safety claim, asserted rather than assumed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011cPyzNnegXHr5iRMzzy5KJ
2026-09-10 21:14:29 -04:00

83 lines
3.5 KiB
Python

"""A rule's edit history — the snapshot taken when an edit overwrites text.
Sibling of `note_versions`, and the differences are the whole design.
WHAT A VERSION IS FOR. It records what a rule USED TO SAY, because an update
overwrites that and nothing can recompute it. It is not a record of the rule's
lifecycle: a soft delete keeps the rule row whole and restorable, so there is
nothing to preserve at delete time, and anything that outlived a purge would be
data the operator explicitly asked to be gone.
WHAT IS DELIBERATELY NOT COPIED FROM note_versions (milestone 323). Both of its
guards defend against note autosave, which fires every 60 seconds and would
otherwise burn every slot. Rules have no autosave — every version here comes
from a deliberate `update_rule` — so both guards would only ever discard a real
edit:
- No `MIN_VERSION_INTERVAL_SECONDS`. Two deliberate edits four minutes apart
are two edits.
- No `MAX_VERSIONS` and no pruning. A rule is edited a handful of times in its
life; a cap invites losing the one edit somebody needed.
TEXT ONLY. A rule's topic, its Systems tags and its typed edges are not here.
They have their own lifecycle, and folding them in would make one word,
"version", mean two things — the rule's wording, and the rule's place in the
graph.
"""
from sqlalchemy import select
from scribe.models import async_session
from scribe.models.rule_version import RuleVersion
# The columns a version carries, and therefore the ones whose change is worth
# a snapshot. `order_index` and `arose_from_id` are editable through
# update_rule and are deliberately absent: reordering a rulebook is not an
# edit to what any rule says, and a run of "moved rule 4 above rule 3"
# snapshots would bury the edits somebody is actually looking for.
SNAPSHOT_FIELDS = (
"title", "statement", "why", "how_to_apply", "when_to_apply",
"tier", "kind", "verify_with", "expires_when",
)
def snapshot(rule) -> dict:
"""The rule's text right now, as a plain dict.
Plain values rather than the ORM object because the caller has to hold
this ACROSS the mutation — a live `rule` would show the new text by the
time it was read, which is the one thing the snapshot must not do.
"""
return {f: getattr(rule, f) for f in SNAPSHOT_FIELDS}
def record_if_changed(session, rule, actor_user_id: int | None, before: dict):
"""Add a version holding `before`, unless the edit changed no text.
Git semantics, and not a nicety: `update_rule` is reached by callers that
resend every field, so without this a form saved twice would file a second
identical snapshot and the history would stop reading as a list of edits.
Session-BOUND, unlike `note_versions.create_version` which opens its own.
The version and the edit that caused it commit together or not at all;
a separate session could leave a snapshot behind after the update it
describes had failed, which is a history entry for an edit that never
happened.
"""
if snapshot(rule) == before:
return None
version = RuleVersion(
rule_id=rule.id, user_id=actor_user_id, **before,
)
session.add(version)
return version
async def list_versions(rule_id: int) -> list[RuleVersion]:
"""Newest first — the reader's question is "what did this just say?"."""
async with async_session() as session:
return list((await session.execute(
select(RuleVersion)
.where(RuleVersion.rule_id == rule_id)
.order_by(RuleVersion.created_at.desc(), RuleVersion.id.desc())
)).scalars().all())