Files
siftlode/backend/app/sync/subscriptions.py
T
peter df4a79a1f1 fix(sync): an empty answer the remote's own count contradicts is not believed, one level down
E32 review round 1 (B1, B2, B3, B8).

- Plex watch reconcile: a section the server SAYS is empty (totalSize 0, nothing listed) is a
  complete listing. It read as "cut short" forever, so one empty library stopped un-watches from
  ever syncing. A listing with no total at all stays incomplete (the client now returns None for
  it instead of 0), and a whole scan that listed nothing still clears nothing. Tests now cover
  completeness across two sections, both orders.
- Plex collections: no members from a collection whose listing counts some (childCount) keeps
  the membership we hold, in the full sync and in the targeted resync after a write.
- YouTube playlists: no items for a playlist whose listing counts some (itemCount) keeps the
  mirror in the bulk pull, and is refused as retryable in "reset to YouTube" and in the push
  plan/merge, where it read as "YouTube deleted them all". The rule sits beside vanished().
- A playlist deleted on YouTube answered "reconnect your account"; it now says it is gone
  (errors.youtube.gone, HU+EN).
- The pure 3-way merge moved to sync/playlist_merge.py; playlists.py is back under 800 lines and
  off the size list.
2026-10-04 02:13:53 +02:00

233 lines
9.8 KiB
Python

"""Import the authenticated user's YouTube subscriptions and channel metadata."""
from collections.abc import Collection, Iterable
from datetime import datetime, timedelta, timezone
from sqlalchemy import or_, select
from sqlalchemy.orm import Session
from app import logs
from app.models import Channel, Subscription, User
from app.utils import normalize_description
from app.youtube.client import YouTubeClient, YouTubeError, best_thumbnail
log = logs.get_logger(__name__)
def _to_int(value) -> int | None:
try:
return int(value) if value is not None else None
# silent-ok: an upstream count we cannot read is stored as no count, which the card renders as
# absent rather than as zero. Per-channel over a whole subscription list, so it must stay quiet.
except (TypeError, ValueError):
return None
def _parse_dt(value: str | None) -> datetime | None:
if not value:
return None
try:
return datetime.fromisoformat(value.replace("Z", "+00:00"))
# silent-ok: as `_to_int` above — an unreadable upstream date becomes NULL, and every caller
# already treats a missing date as unknown.
except ValueError:
return None
def _external_links(branding: dict) -> list | None:
"""Channel "About" links. The API exposes a few in brandingSettings.channel.profileColor/
/... varies; the durable spot is brandingSettings.channel.links is gone post-2023, so we
read what's present (settings/links) defensively and keep [{title, url}] pairs."""
channel = branding.get("channel", {})
links = channel.get("links") or []
out = [
{"title": item.get("title"), "url": item.get("url")}
for item in links
if isinstance(item, dict) and item.get("url")
]
return out or None
# How old a channel's metadata may get before it is fetched again. Banners, avatars, descriptions and
# counts change on YouTube, and an old banner URL stops resolving at all — without a refresh a channel
# kept whatever it had the day it was first seen. A week keeps counts roughly current at almost no
# cost: `channels.list` is 1 quota unit per 50 channels, and only the stale ones are asked for.
DETAILS_MAX_AGE = timedelta(days=7)
def details_stale(channel: Channel, now: datetime) -> bool:
"""Whether `channel`'s metadata is missing or older than DETAILS_MAX_AGE (see `details_stale_clause`)."""
synced = channel.details_synced_at
return synced is None or synced < now - DETAILS_MAX_AGE
def details_stale_clause(now: datetime):
"""`details_stale` as a WHERE clause, so the batch import and a single channel agree on "stale"."""
return or_(
Channel.details_synced_at.is_(None),
Channel.details_synced_at < now - DETAILS_MAX_AGE,
)
def apply_channel_details(db: Session, items: list[dict], asked: Iterable[str]) -> None:
"""Write `channels.list`'s answer onto the rows. `asked` is every id the call asked for: one
YouTube did not return (terminated, deleted) is stamped as synced too — otherwise it stays
stale forever and every view / import asks for it again, spending quota on a known miss."""
now = datetime.now(timezone.utc)
returned = {item["id"] for item in items}
for cid in set(asked) - returned:
missing = db.get(Channel, cid)
if missing is not None:
missing.details_synced_at = now
for item in items:
channel = db.get(Channel, item["id"])
if channel is None:
continue
snippet = item.get("snippet", {})
content = item.get("contentDetails", {})
stats = item.get("statistics", {})
topics = item.get("topicDetails", {})
branding = item.get("brandingSettings", {})
channel.title = snippet.get("title") or channel.title
channel.handle = snippet.get("customUrl")
channel.description = normalize_description(snippet.get("description"))
channel.thumbnail_url = best_thumbnail(snippet.get("thumbnails")) or channel.thumbnail_url
channel.default_language = snippet.get("defaultLanguage")
channel.country = snippet.get("country")
channel.uploads_playlist_id = content.get("relatedPlaylists", {}).get("uploads")
channel.subscriber_count = _to_int(stats.get("subscriberCount"))
channel.video_count = _to_int(stats.get("videoCount"))
channel.total_view_count = _to_int(stats.get("viewCount"))
channel.published_at = _parse_dt(snippet.get("publishedAt"))
channel.banner_url = branding.get("image", {}).get("bannerExternalUrl")
channel.external_links = _external_links(branding)
channel.topic_categories = topics.get("topicCategories")
channel.keywords = (branding.get("channel") or {}).get("keywords")
channel.details_synced_at = now
def should_prune(fetched_count: int, existing_count: int) -> bool:
"""Whether an import may delete the local subscriptions missing from this fetch.
NEVER on an empty fetch that contradicts local state: the API can answer 200 with no items (a
transient blip, a scope/token edge), and pruning against that wipes every subscription the user
has — taking each row's `deep_requested` flag with it — in a single run. Someone who genuinely
unsubscribed from everything simply keeps their rows until a sync that returns something.
Pure so it can be tested without a database; its callers are `import_subscriptions` and, through
`vanished`, every mirror that drops what the remote no longer lists."""
return fetched_count > 0 or existing_count == 0
def vanished[K, V](existing: dict[K, V], listed: Collection[K]) -> list[V]:
"""The local mirrors whose key the remote listing no longer has — none at all when the listing
is an empty answer that contradicts them (`should_prune`). The YouTube playlist mirrors use it:
without it, one blip dropped every mirror (E32 S2)."""
if not should_prune(len(listed), len(existing)):
return []
return [row for key, row in existing.items() if key not in listed]
def blank_listing(listed: Collection, count: object) -> bool:
"""The same rule one level down: no members from a container whose own listing counts some (a
playlist's `itemCount`) is a blip, not a list emptied. Replacing or merging on it deleted every
mirrored item and reset the merge baseline (E32 review)."""
return not listed and isinstance(count, int) and count > 0
def refuse_blank_listing(listed: Collection, count: object) -> None:
"""`blank_listing` for a user-started pull or push: refused as retryable ("try again")."""
if blank_listing(listed, count):
raise YouTubeError(
"YouTube listed no items for a playlist it counts as non-empty",
reason="emptyAnswer",
path="playlistItems",
)
def import_subscriptions(db: Session, user: User) -> dict:
"""Pull all subscriptions for `user`, upsert channels + subscription links, prune
channels the user has unsubscribed from on YouTube, and fetch channel details for
any channel whose details are missing or stale (`DETAILS_MAX_AGE`)."""
fetched: dict[str, dict] = {}
new_channels = 0
with YouTubeClient(db, user) as yt:
for sub in yt.iter_subscriptions():
cid = sub.get("channel_id")
if cid:
fetched[cid] = sub
for cid, sub in fetched.items():
channel = db.get(Channel, cid)
if channel is None:
channel = Channel(
id=cid,
title=sub.get("title"),
description=normalize_description(sub.get("description")),
thumbnail_url=sub.get("thumbnail_url"),
)
db.add(channel)
new_channels += 1
sub_row = db.execute(
select(Subscription).where(
Subscription.user_id == user.id, Subscription.channel_id == cid
)
).scalar_one_or_none()
if sub_row is None:
sub_row = Subscription(user_id=user.id, channel_id=cid)
db.add(sub_row)
sub_row.yt_subscription_id = sub.get("yt_subscription_id")
db.flush()
# Prune subscriptions removed on YouTube — but only when this fetch is trustworthy
# (see `should_prune`).
removed = 0
existing = (
db.execute(select(Subscription).where(Subscription.user_id == user.id)).scalars().all()
)
prune_skipped = not should_prune(len(fetched), len(existing))
if prune_skipped:
log.warning(
"Subscription import (user %s): YouTube returned 0 subscriptions while %d exist "
"locally — skipping the prune (treating it as a transient empty response)",
user.id,
len(existing),
)
else:
for sub_row in existing:
if sub_row.channel_id not in fetched:
db.delete(sub_row)
removed += 1
db.commit()
# Fetch details for channels that don't have them yet, or had them too long ago.
need_details = (
db.execute(
select(Channel).where(
Channel.id.in_(fetched.keys()),
details_stale_clause(datetime.now(timezone.utc)),
)
)
.scalars()
.all()
)
detailed = 0
if need_details:
ids = [c.id for c in need_details]
items = yt.get_channels(ids)
apply_channel_details(db, items, ids)
detailed = len(items)
db.commit()
result = {
"subscriptions": len(fetched),
"channels_new": new_channels,
"channels_detailed": detailed,
"removed_stale": removed,
"prune_skipped": prune_skipped,
}
log.info("Subscription import (user %s): %s", user.id, result)
return result