mirror of
https://github.com/kuhyx/diet-guard.git
synced 2026-07-04 15:23:16 +02:00
82 lines
3.2 KiB
Python
82 lines
3.2 KiB
Python
|
"""Pure log-merge logic for diet_guard's cross-device sync.
|
||
|
|
|
||
|
|
No I/O here -- this module is unit-testable purely on in-memory ``DayLog``
|
||
|
|
values, like :mod:`diet_guard._slots`. Mirrored test-for-test by the Dart
|
||
|
|
port (``app/lib/services/sync_service.dart``), so the merge algorithm
|
||
|
|
canonically agrees on both sides of the sync.
|
||
|
|
"""
|
||
|
|
|
||
|
|
from __future__ import annotations
|
||
|
|
|
||
|
|
from typing import TYPE_CHECKING
|
||
|
|
|
||
|
|
if TYPE_CHECKING:
|
||
|
|
from diet_guard._state import DayLog
|
||
|
|
|
||
|
|
# A dedup key: ("id", <uuid string>) for any entry with one, else
|
||
|
|
# ("legacy", (time, desc)) for a pre-id entry written before this field
|
||
|
|
# existed -- two devices that both already had that same legacy entry would
|
||
|
|
# otherwise end up with two copies of it after a merge.
|
||
|
|
_Key = tuple[str, object]
|
||
|
|
|
||
|
|
|
||
|
|
def _entry_key(entry: dict[str, object]) -> _Key:
|
||
|
|
"""Return the dedup key for ``entry``."""
|
||
|
|
entry_id = entry.get("id")
|
||
|
|
if isinstance(entry_id, str) and entry_id:
|
||
|
|
return ("id", entry_id)
|
||
|
|
return ("legacy", (entry.get("time"), entry.get("desc")))
|
||
|
|
|
||
|
|
|
||
|
|
def _tombstone_wins(
|
||
|
|
candidate: dict[str, object],
|
||
|
|
existing: dict[str, object],
|
||
|
|
) -> bool:
|
||
|
|
"""Return True if ``candidate`` should replace ``existing`` for one key.
|
||
|
|
|
||
|
|
A tombstone always wins over a non-tombstoned copy of the same entry --
|
||
|
|
deletion is sticky, so a stale pre-undo copy pulled from another device
|
||
|
|
can never resurrect something the user explicitly removed. Otherwise,
|
||
|
|
keep whichever copy was seen first: two copies of the same id are
|
||
|
|
expected to be byte-identical in their macros/desc (the body is never
|
||
|
|
mutated after creation, only ``deleted``/``hmac``), so which one survives
|
||
|
|
does not change the merged result's content.
|
||
|
|
"""
|
||
|
|
return bool(candidate.get("deleted")) and not existing.get("deleted")
|
||
|
|
|
||
|
|
|
||
|
|
def merge_logs(local: DayLog, remote: DayLog) -> DayLog:
|
||
|
|
"""Return the union of ``local`` and ``remote``, tombstones winning by id.
|
||
|
|
|
||
|
|
Commutative and idempotent: ``merge_logs(a, b) == merge_logs(b, a)`` and
|
||
|
|
``merge_logs(x, x) == x`` (for an ``x`` with no duplicate keys), so
|
||
|
|
pull-order between devices never matters and a repeated sync tick is a
|
||
|
|
no-op. Each entry is re-bucketed under its own ``time``'s date rather
|
||
|
|
than the date key it arrived under, so a merge can't silently leave an
|
||
|
|
entry filed under the wrong day.
|
||
|
|
|
||
|
|
Args:
|
||
|
|
local: This device's current full log (including tombstones).
|
||
|
|
remote: Another device's last-pushed full log.
|
||
|
|
|
||
|
|
Returns:
|
||
|
|
The merged log, keyed by each entry's own date, each day's entries
|
||
|
|
sorted oldest-first (matching the existing on-disk convention).
|
||
|
|
"""
|
||
|
|
by_key: dict[_Key, dict[str, object]] = {}
|
||
|
|
for day_log in (local, remote):
|
||
|
|
for entries in day_log.values():
|
||
|
|
for entry in entries:
|
||
|
|
key = _entry_key(entry)
|
||
|
|
existing = by_key.get(key)
|
||
|
|
if existing is None or _tombstone_wins(entry, existing):
|
||
|
|
by_key[key] = entry
|
||
|
|
|
||
|
|
merged: DayLog = {}
|
||
|
|
for entry in by_key.values():
|
||
|
|
date_key = str(entry.get("time", ""))[:10]
|
||
|
|
merged.setdefault(date_key, []).append(entry)
|
||
|
|
for entries in merged.values():
|
||
|
|
entries.sort(key=lambda entry: str(entry.get("time", "")))
|
||
|
|
return merged
|