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FabledCurator/backend/app/services/gallery_service.py
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feat(gallery): composable scroll filter (multi-tag AND, media, sort)
Phase 1 backend for the gallery filter bar. Extends scroll/timeline/jump
from a single mutually-exclusive filter to a composable one:

- tag_ids: image must carry ALL of them (one correlated EXISTS per tag —
  AND, no row multiplication), replacing the single-tag JOIN.
- artist_id composes with tags; media_type ('image'|'video') narrows by
  mime; post_id stays the exclusive post-detail path.
- sort ('newest'|'oldest') flips the effective_date/id cursor comparison
  and ordering; the cursor value is unchanged (direction comes from the
  request). jump_cursor honors sort too.
- Shared _apply_scope helper applied across scroll/timeline/jump so the
  timeline sidebar reflects the filtered set. API _parse_filters parses
  tag_id (comma list), artist_id, media, sort.

Tests: multi-tag AND, media filter, sort reversal (service + API);
post_id-excludes-others; single tag_id back-compat.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-03 23:50:19 -04:00

446 lines
17 KiB
Python

"""Cursor-paginated gallery queries.
Cursor format: opaque base64-encoded "<iso8601_effective_date>:<image_id>".
Pagination key is (effective_date DESC, id DESC) where effective_date is
COALESCE(post.post_date, image_record.created_at) so the gallery surfaces
images by ORIGINAL publish date when known, falling back to FC's scan
date. Important for migrated content: ~57k IR images scanned in a single
week would otherwise all share the same created_at and pile up in one
month bucket. The effective_date spreads them across the years they
were originally published.
Decoding rejects malformed cursors with a ValueError; the API layer
translates that to HTTP 400.
"""
import base64
from dataclasses import dataclass
from datetime import datetime
from sqlalchemy import Select, and_, exists, func, or_, select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import aliased
from ..models import Artist, ImageProvenance, ImageRecord, Post, Tag
from ..models.tag import image_tag
CURSOR_SEPARATOR = "|"
def encode_cursor(effective_date: datetime, image_id: int) -> str:
raw = f"{effective_date.isoformat()}{CURSOR_SEPARATOR}{image_id}"
return base64.urlsafe_b64encode(raw.encode()).decode()
def decode_cursor(cursor: str) -> tuple[datetime, int]:
try:
raw = base64.urlsafe_b64decode(cursor.encode()).decode()
ts_part, id_part = raw.split(CURSOR_SEPARATOR, 1)
return datetime.fromisoformat(ts_part), int(id_part)
except Exception as exc:
raise ValueError(f"invalid cursor: {cursor!r}") from exc
def _effective_date_col():
"""The materialized gallery sort key: image_record.effective_date
(alembic 0035) = COALESCE(primary post's post_date, created_at),
maintained at write time by the importer.
Canonical sort/group/filter key across the gallery so images attached
to a post surface at their original publish date, not their FC import
date — and, now that it's a single indexed column rather than a
COALESCE across the Post outer join, the cursor scroll is an index
range scan instead of a full re-sort per page.
"""
return ImageRecord.effective_date
def _outer_join_primary_post(stmt: Select) -> Select:
"""LEFT JOIN Post on ImageRecord.primary_post_id so the COALESCE
above sees Post.post_date when available. Images without a post
survive the join as NULL on the Post side; COALESCE handles it."""
return stmt.outerjoin(Post, Post.id == ImageRecord.primary_post_id)
@dataclass(frozen=True)
class GalleryImage:
id: int
path: str
sha256: str
mime: str
width: int | None
height: int | None
created_at: datetime # FC's row-insert time
effective_date: datetime # COALESCE(post.post_date, created_at)
posted_at: datetime | None # post.post_date if known, else None
thumbnail_url: str
artist: dict | None = None
@dataclass(frozen=True)
class GalleryPage:
images: list[GalleryImage]
next_cursor: str | None
date_groups: list[tuple[int, int, list[int]]] # (year, month, [image_id...])
@dataclass(frozen=True)
class TimelineBucket:
year: int
month: int
count: int
def thumbnail_url(thumbnail_path: str | None, sha256_hex: str, mime: str) -> str:
"""Return the URL to fetch a thumbnail.
Prefers the stored thumbnail_path verbatim — Quart serves /images/*
1:1 from the volume (frontend.py:20-36), so the URL IS the disk
path. Falls back to deriving from (sha256, mime) only when the
record's thumbnail_path is NULL (thumbnailer hasn't run yet); that
URL will 404 until backfill catches it, same as before the path
was tracked.
Pre-2026-05-30 this was derived only from (sha256, mime), which
disagreed with the actual on-disk extension when the thumbnailer
chose its format from transparency rather than MIME — every PNG
source without alpha (extension was .jpg on disk) and every WebP
source with alpha (extension was .png on disk) silently 404'd
despite the thumbnail file existing.
"""
if thumbnail_path:
return thumbnail_path
# Fallback for records with no thumbnail recorded yet — preserves
# prior behavior (URL exists but 404s until backfill regenerates).
ext = ".png" if mime in ("image/png", "image/gif") else ".jpg"
bucket = sha256_hex[:3]
return f"/images/thumbs/{bucket}/{sha256_hex}{ext}"
def _require_single_filter(tag_ids, post_id, artist_id) -> None:
"""post_id is the post-detail view — it can't combine with the
composable filters. tag_ids + artist_id (+ media_type) compose freely
(AND)."""
if post_id is not None and (tag_ids or artist_id is not None):
raise ValueError(
"post_id cannot be combined with tag or artist filters"
)
def _apply_scope(stmt, *, tag_ids, post_id, artist_id, media_type):
"""Apply the composable gallery filters to a statement already joined
to Post via _outer_join_primary_post.
- tag_ids: image must carry ALL of them — one correlated EXISTS per tag
(AND), which avoids the row-multiplication a multi-join would cause.
- post_id / artist_id: provenance EXISTS (post_id is exclusive, guarded
by _require_single_filter).
- media_type: 'image' | 'video' narrows by mime prefix.
"""
for tid in tag_ids or []:
stmt = stmt.where(
exists().where(
image_tag.c.image_record_id == ImageRecord.id,
image_tag.c.tag_id == tid,
)
)
prov = _provenance_clause(post_id, artist_id)
if prov is not None:
stmt = stmt.where(prov)
if media_type == "image":
stmt = stmt.where(ImageRecord.mime.like("image/%"))
elif media_type == "video":
stmt = stmt.where(ImageRecord.mime.like("video/%"))
return stmt
def _provenance_clause(post_id, artist_id):
"""Correlated EXISTS clause (NOT a join) so an image with multiple
matching provenance rows is returned exactly once and the
(effective_date DESC, id DESC) cursor ordering is unaffected."""
if post_id is not None:
return exists().where(
ImageProvenance.image_record_id == ImageRecord.id,
ImageProvenance.post_id == post_id,
)
if artist_id is not None:
# Use Post.artist_id (alembic 0030 denormalized column) instead
# of joining through ImageProvenance.source_id → Source.artist_id.
# The denormalization is the always-present linkage; the source
# path now drops NULL-source provenance rows (filesystem-imported
# content) which would otherwise vanish from artist-filtered
# gallery views.
# ALIAS Post: the gallery query outer-joins Post on
# ImageRecord.primary_post_id (`_outer_join_primary_post`).
# SQLAlchemy would otherwise correlate a bare `Post` reference
# in this EXISTS subquery to that outer Post (which is NULL for
# images with no primary post), and the filter would silently
# match nothing.
post_inner = aliased(Post)
return exists().where(
ImageProvenance.image_record_id == ImageRecord.id,
ImageProvenance.post_id == post_inner.id,
post_inner.artist_id == artist_id,
)
return None
async def _artists_for(session, image_ids: list[int]) -> dict[int, dict]:
"""Map image_id -> {"name","slug"} via the canonical
image_record.artist_id (FC-2d-vii-c). Bounded by page size."""
if not image_ids:
return {}
stmt = (
select(ImageRecord.id, Artist.name, Artist.slug)
.join(Artist, Artist.id == ImageRecord.artist_id)
.where(ImageRecord.id.in_(image_ids))
)
return {
img_id: {"name": name, "slug": slug}
for img_id, name, slug in (await session.execute(stmt)).all()
}
class GalleryService:
def __init__(self, session: AsyncSession):
self.session = session
async def scroll(
self,
cursor: str | None,
limit: int = 50,
tag_ids: list[int] | None = None,
post_id: int | None = None,
artist_id: int | None = None,
media_type: str | None = None,
sort: str = "newest",
) -> GalleryPage:
if limit < 1 or limit > 200:
raise ValueError("limit must be between 1 and 200")
_require_single_filter(tag_ids, post_id, artist_id)
eff = _effective_date_col()
stmt = select(ImageRecord, Post.post_date, eff.label("eff"))
stmt = _outer_join_primary_post(stmt)
stmt = _apply_scope(
stmt, tag_ids=tag_ids, post_id=post_id,
artist_id=artist_id, media_type=media_type,
)
descending = sort != "oldest"
if cursor:
cur_ts, cur_id = decode_cursor(cursor)
# The cursor is just (last eff, last id); the request's sort
# decides which side of it the next page lies on.
if descending:
stmt = stmt.where(
or_(eff < cur_ts, and_(eff == cur_ts, ImageRecord.id < cur_id))
)
else:
stmt = stmt.where(
or_(eff > cur_ts, and_(eff == cur_ts, ImageRecord.id > cur_id))
)
if descending:
stmt = stmt.order_by(eff.desc(), ImageRecord.id.desc())
else:
stmt = stmt.order_by(eff.asc(), ImageRecord.id.asc())
stmt = stmt.limit(limit + 1)
rows = (await self.session.execute(stmt)).all()
next_cursor = None
if len(rows) > limit:
last_record, _last_posted_at, last_eff = rows[limit - 1]
next_cursor = encode_cursor(last_eff, last_record.id)
rows = rows[:limit]
artists = await _artists_for(
self.session, [r[0].id for r in rows]
)
images = [
GalleryImage(
id=record.id,
path=record.path,
sha256=record.sha256,
mime=record.mime,
width=record.width,
height=record.height,
created_at=record.created_at,
effective_date=eff_date,
posted_at=posted_at,
thumbnail_url=thumbnail_url(record.thumbnail_path, record.sha256, record.mime),
artist=artists.get(record.id),
)
for record, posted_at, eff_date in rows
]
return GalleryPage(
images=images,
next_cursor=next_cursor,
date_groups=_group_by_year_month(images),
)
async def timeline(
self,
tag_ids: list[int] | None = None,
post_id: int | None = None,
artist_id: int | None = None,
media_type: str | None = None,
) -> list[TimelineBucket]:
eff = _effective_date_col()
year_col = func.date_part("year", eff).label("yr")
month_col = func.date_part("month", eff).label("mo")
stmt = select(
year_col, month_col, func.count(ImageRecord.id).label("cnt")
)
stmt = _outer_join_primary_post(stmt)
_require_single_filter(tag_ids, post_id, artist_id)
stmt = _apply_scope(
stmt, tag_ids=tag_ids, post_id=post_id,
artist_id=artist_id, media_type=media_type,
)
stmt = stmt.group_by(year_col, month_col).order_by(year_col.desc(), month_col.desc())
rows = (await self.session.execute(stmt)).all()
return [TimelineBucket(year=int(r.yr), month=int(r.mo), count=int(r.cnt)) for r in rows]
async def jump_cursor(
self, year: int, month: int, tag_ids: list[int] | None = None,
post_id: int | None = None, artist_id: int | None = None,
media_type: str | None = None, sort: str = "newest",
) -> str | None:
"""Returns a cursor that, when passed to scroll() with the same sort,
positions at the first image of the given year-month. None if the
bucket is empty.
"""
from sqlalchemy import extract
eff = _effective_date_col()
stmt = select(ImageRecord, eff.label("eff")).where(
extract("year", eff) == year,
extract("month", eff) == month,
)
stmt = _outer_join_primary_post(stmt)
_require_single_filter(tag_ids, post_id, artist_id)
stmt = _apply_scope(
stmt, tag_ids=tag_ids, post_id=post_id,
artist_id=artist_id, media_type=media_type,
)
descending = sort != "oldest"
if descending:
stmt = stmt.order_by(eff.desc(), ImageRecord.id.desc())
else:
stmt = stmt.order_by(eff.asc(), ImageRecord.id.asc())
first = (await self.session.execute(stmt.limit(1))).first()
if first is None:
return None
record, eff_date = first
# Cursor is exclusive; nudge the id one past the boundary row (in the
# scan direction) so the row itself is the first result of scroll().
boundary = record.id + 1 if descending else record.id - 1
return encode_cursor(eff_date, boundary)
async def get_image_with_tags(self, image_id: int) -> dict | None:
record = await self.session.get(ImageRecord, image_id)
if record is None:
return None
tag_stmt = (
select(Tag)
.join(image_tag, image_tag.c.tag_id == Tag.id)
.where(image_tag.c.image_record_id == image_id)
.order_by(Tag.kind.asc(), Tag.name.asc())
)
tags = (await self.session.execute(tag_stmt)).scalars().all()
# Fetch the canonical post.post_date for this image (if any) so
# the modal can show "Posted on <date>" alongside import date.
posted_at = None
if record.primary_post_id is not None:
posted_at = (await self.session.execute(
select(Post.post_date).where(Post.id == record.primary_post_id)
)).scalar_one_or_none()
neighbors = await self._neighbors(record)
# Direct artist FK — used by the modal's ProvenancePanel as a
# fallback when ImageProvenance is empty (i.e., filesystem-
# imported images without a post-track provenance row). The
# source of truth for richer post-level data is still
# ImageProvenance/Post; this is just the "we at least know who
# made it" line.
artist = None
if record.artist_id is not None:
artist = await self.session.get(Artist, record.artist_id)
return {
"id": record.id,
"path": record.path,
"sha256": record.sha256,
"mime": record.mime,
"width": record.width,
"height": record.height,
"size_bytes": record.size_bytes,
"integrity_status": record.integrity_status,
"created_at": record.created_at.isoformat(),
"posted_at": posted_at.isoformat() if posted_at else None,
"thumbnail_url": thumbnail_url(record.thumbnail_path, record.sha256, record.mime),
"image_url": f"/images/{record.path.split('/images/', 1)[-1]}",
"artist": (
{"id": artist.id, "name": artist.name, "slug": artist.slug}
if artist is not None else None
),
"tags": [
{
"id": t.id,
"name": t.name,
"kind": t.kind.value if hasattr(t.kind, "value") else t.kind,
"fandom_id": t.fandom_id,
}
for t in tags
],
"neighbors": neighbors,
}
async def _neighbors(self, record: ImageRecord) -> dict:
# The boundary image's sort key is materialized on the row now
# (alembic 0035) — read it directly instead of re-deriving COALESCE
# via an extra Post lookup.
boundary_eff = record.effective_date
eff = _effective_date_col()
prev_stmt = _outer_join_primary_post(
select(ImageRecord.id).where(
or_(
eff > boundary_eff,
and_(
eff == boundary_eff,
ImageRecord.id > record.id,
),
)
)
).order_by(eff.asc(), ImageRecord.id.asc()).limit(1)
next_stmt = _outer_join_primary_post(
select(ImageRecord.id).where(
or_(
eff < boundary_eff,
and_(
eff == boundary_eff,
ImageRecord.id < record.id,
),
)
)
).order_by(eff.desc(), ImageRecord.id.desc()).limit(1)
prev_id = (await self.session.execute(prev_stmt)).scalar_one_or_none()
next_id = (await self.session.execute(next_stmt)).scalar_one_or_none()
return {"prev_id": prev_id, "next_id": next_id}
def _group_by_year_month(
images: list[GalleryImage],
) -> list[tuple[int, int, list[int]]]:
"""Group by effective_date's year/month so migrated content surfaces
in the publish-date buckets, not the FC-scan-date bucket."""
groups: list[tuple[int, int, list[int]]] = []
for img in images:
y, m = img.effective_date.year, img.effective_date.month
if groups and groups[-1][0] == y and groups[-1][1] == m:
groups[-1][2].append(img.id)
else:
groups.append((y, m, [img.id]))
return groups