refactor(capture): the HTTP layer reads through queries and writes through the service

Capture's routes (downloads, files, public watch links) and the token list no longer build SQL, call
the session or set a model's fields: reads are downloads/queries, writes the unit's service (service,
folders, links, quota), and each write flushes for the handler to commit. Whose a row is goes
through userscope (owned_by, owned_row), which owned_or_404 now uses too.

The fence holds Capture below its routes as well: it reads only Catalog's and Plex's tables, writes
no other unit's, filters owners through userscope and commits only in its jobs and the upload
ingest. A test per service use case, among them that the tray lists only the caller's files.

backend/app/downloads/credentials.py

@@ -35,6 +35,7 @@ from app.downloads import formats
 from app.downloads.adapters import _host_is
 from app.downloads.models import DownloadCredential, MediaAsset
 from app.security import decrypt_optional, encrypt
+from app.userscope import owned_by
 
 log = logs.get_logger(__name__)
 
@@ -157,7 +158,7 @@ def salt_for_enqueue(db: Session, user_id: int, url: str | None) -> str | None:
 def get_credential(db: Session, user_id: int, host_key: str) -> DownloadCredential | None:
     return db.execute(
         select(DownloadCredential).where(
-            DownloadCredential.user_id == user_id, DownloadCredential.host_key == host_key
+            owned_by(DownloadCredential.user_id, user_id), DownloadCredential.host_key == host_key
         )
     ).scalar_one_or_none()
 
@@ -214,7 +215,7 @@ def status_list(db: Session, user_id: int) -> list[dict]:
     have = {
         c.host_key: c
         for c in db.execute(
-            select(DownloadCredential).where(DownloadCredential.user_id == user_id)
+            select(DownloadCredential).where(owned_by(DownloadCredential.user_id, user_id))
         ).scalars()
     }
     out = []

backend/app/downloads/folders.py

@@ -33,6 +33,7 @@ from sqlalchemy.orm import Session
 from app import sysconfig
 from app.downloads.status import JobStatus
 from app.downloads.models import DownloadJob, FileFolder, MediaAsset
+from app.userscope import owned_by
 
 
 class FolderKind(StrEnum):
@@ -106,7 +107,9 @@ def source_key_for(db: Session, job: DownloadJob) -> str:
 def source_folder(db: Session, user_id: int, key: str) -> FileFolder:
     """The user's source folder for `key`, made on first use. A race on the unique (user, key) is
     settled by re-selecting, inside a SAVEPOINT so the caller's own pending writes survive."""
-    stmt = select(FileFolder).where(FileFolder.user_id == user_id, FileFolder.source_key == key)
+    stmt = select(FileFolder).where(
+        owned_by(FileFolder.user_id, user_id), FileFolder.source_key == key
+    )
     folder = db.execute(stmt).scalar_one_or_none()
     if folder is not None:
         return folder
@@ -131,7 +134,7 @@ def hub_folder(db: Session, user_id: int) -> FileFolder:
     """The user's Hub folder, made on first use; a race on its one-per-user index is settled like
     `source_folder`'s."""
     stmt = select(FileFolder).where(
-        FileFolder.user_id == user_id, FileFolder.kind == FolderKind.HUB
+        owned_by(FileFolder.user_id, user_id), FileFolder.kind == FolderKind.HUB
     )
     folder = db.execute(stmt).scalar_one_or_none()
     if folder is not None:
@@ -310,3 +313,28 @@ def delete_own(db: Session, folder: FileFolder) -> int:
     db.flush()  # the files leave before the folder goes: its foreign key RESTRICTs the delete
     db.delete(folder)
     return len(jobs)
+
+
+def create_own(db: Session, user_id: int, name: str) -> FileFolder:
+    """A new folder of the user's own; FolderError("file_folder_name_taken") when they already have
+    one by that name (the unique (user, lower(name)))."""
+    folder = FileFolder(user_id=user_id, kind=FolderKind.OWN, name=name)
+    try:
+        with db.begin_nested():
+            db.add(folder)
+            db.flush()
+    except IntegrityError as e:
+        raise FolderError("file_folder_name_taken") from e
+    return folder
+
+
+def rename(db: Session, folder: FileFolder, name: str) -> None:
+    """Rename one of the user's own folders (a source folder's name is its origin's)."""
+    if folder.kind != FolderKind.OWN:
+        raise FolderError("file_folder_not_own")
+    folder.name = name
+    try:
+        with db.begin_nested():
+            db.flush()
+    except IntegrityError as e:
+        raise FolderError("file_folder_name_taken") from e

backend/app/downloads/links.py

@@ -15,20 +15,24 @@ grant appended to the file URL, so the raw password never rides in the media URL
 import hashlib
 import hmac
 import secrets
-from datetime import datetime, timezone
+from datetime import datetime, timedelta, timezone
 
 from sqlalchemy import select
+from sqlalchemy import update as sql_update
 from sqlalchemy.orm import Session
 
-from app import security
+from app import audit, security
 from app.config import settings
 from app.downloads import storage
 from app.downloads.status import JobStatus
 from app.downloads.models import DownloadJob, DownloadLink, FileFolder, MediaAsset
+from app.models import User
+from app.utils import iso
+from app.userscope import owned_by
 
 _GRANT_TTL = 6 * 3600  # a watch session's grant is good for 6h, then the viewer re-unlocks
-# The most files a folder link lists: as many as the owner's own Files list shows (`routes.files.
-# MAX_LIST`; a test holds the two equal — this layer may not import that one).
+# The most files a folder link lists: as many as the owner's own Files list shows
+# (`queries.MAX_LIST`; a test holds the two equal — `queries` imports this module).
 FOLDER_MAX = 500
 
 
@@ -59,7 +63,7 @@ def in_folder(folder: FileFolder) -> tuple:
     moved out stops opening through the link at its next request; one moved in starts."""
     return (
         DownloadJob.folder_id == folder.id,
-        DownloadJob.user_id == folder.user_id,
+        owned_by(DownloadJob.user_id, folder.user_id),
         DownloadJob.status == JobStatus.DONE,
     )
 
@@ -170,3 +174,117 @@ def public_meta(
         "file_url": file_url,
         "poster_url": poster_url,
     }
+
+
+# --- the owner's writes --------------------------------------------------------------------
+# Each flushes and records its audit row; the handler commits.
+
+
+def expiry(days: int | None) -> datetime | None:
+    """None/0/negative → no expiry; otherwise N days out, capped at ~10 years."""
+    if not days or days <= 0:
+        return None
+    return datetime.now(timezone.utc) + timedelta(days=min(days, 3650))
+
+
+def audit_view(link: DownloadLink) -> dict:
+    """A link's settings as the audit records them: whether it has a password, never which."""
+    return {
+        "allow_download": link.allow_download,
+        "has_password": link.password_hash is not None,
+        "expires_at": iso(link.expires_at),
+    }
+
+
+def create(
+    db: Session,
+    user: User,
+    *,
+    password: str,
+    allow_download: bool,
+    expires_days: int | None,
+    **target: int,
+) -> tuple[DownloadLink, str]:
+    """A link to `target` (`job_id=` or `folder_id=`, already checked to be the user's), and the
+    token it is opened by — which is in hand only now."""
+    token = new_token()
+    link = DownloadLink(
+        **target,
+        created_by=user.id,
+        allow_download=allow_download,
+        password_hash=security.hash_password(password) if password else None,
+        expires_at=expiry(expires_days),
+    )
+    seal(link, token)
+    db.add(link)
+    db.flush()
+    audit.record(
+        db,
+        user.id,
+        audit.AuditAction.DOWNLOAD_LINK_CREATE,
+        target_type="download_link",
+        target_id=link.id,
+        after={**target, **audit_view(link)},
+    )
+    return link, token
+
+
+def update(
+    db: Session,
+    user: User,
+    link: DownloadLink,
+    *,
+    allow_download: bool | None = None,
+    expires_days: int | None = None,
+    password: str | None = None,
+    sent: frozenset[str] = frozenset(),
+) -> None:
+    """Change what the caller sent (`sent` names the fields, so `expires_days=None` can mean "never
+    expires"). Setting, clearing or changing the password bumps its version, so any grant issued
+    under the previous one stops working now rather than living out its TTL."""
+    before = audit_view(link)
+    if "allow_download" in sent:
+        link.allow_download = bool(allow_download)
+    if "expires_days" in sent:
+        link.expires_at = expiry(expires_days)
+    if "password" in sent:
+        pw = (password or "").strip()
+        link.password_hash = security.hash_password(pw) if pw else None
+        link.password_version += 1
+    after = audit_view(link)
+    if after != before or "password" in sent:
+        audit.record(
+            db,
+            user.id,
+            audit.AuditAction.DOWNLOAD_LINK_UPDATE,
+            target_type="download_link",
+            target_id=link.id,
+            before=before,
+            after=after,
+        )
+    db.flush()
+
+
+def revoke(db: Session, user: User, link: DownloadLink) -> None:
+    link_id = link.id
+    db.delete(link)
+    audit.record(
+        db,
+        user.id,
+        audit.AuditAction.DOWNLOAD_LINK_REVOKE,
+        target_type="download_link",
+        target_id=link_id,
+        after={"job_id": link.job_id} if link.job_id is not None else {"folder_id": link.folder_id},
+    )
+    db.flush()
+
+
+def count_view(db: Session, link: DownloadLink) -> None:
+    """One more opening of the link. In SQL, not `+= 1` on the loaded row: two opens at once would
+    both write the same count."""
+    db.execute(
+        sql_update(DownloadLink)
+        .where(DownloadLink.id == link.id)
+        .values(view_count=DownloadLink.view_count + 1)
+        .execution_options(synchronize_session=False)
+    )

backend/app/downloads/queries.py

@@ -0,0 +1,406 @@
+"""Capture's reads: what the library, the download tray, the share dialogs and the public watch pages
+show. Each returns rows or plain values and writes nothing; whose a row is goes through
+`userscope.owned_by` / `owned_row`, so a row of someone else's reads as a missing one.
+
+The HTTP layer (`routes.downloads`, `routes.files`, `routes.public`) asks here and serializes; the
+writes are the service's (`service`, `folders`, `links`, `quota`)."""
+
+from collections.abc import Sequence
+from datetime import datetime, timezone
+
+from sqlalchemy import func, or_, select
+from sqlalchemy.orm import Session
+
+from app.apitokens import FilesCaller, Right
+from app.collation import collated
+from app.downloads import folders, links, quota
+from app.downloads.models import (
+    DownloadJob,
+    DownloadLink,
+    DownloadProfile,
+    DownloadQuota,
+    DownloadShare,
+    FileFolder,
+    LibraryState,
+    MediaAsset,
+)
+from app.downloads.status import FINISHED, JobStatus
+from app.models import User
+from app.userscope import owned_by, owned_row
+from app.utils import like_escape
+
+# Cap a listing so a heavy library can't return an unbounded result set (the old Download Center's
+# own cap; far beyond any real library).
+MAX_LIST = 500
+
+
+# --- jobs and their files ------------------------------------------------------------------
+
+
+def own_job(db: Session, user: User, job_id: int) -> DownloadJob | None:
+    return owned_row(db, DownloadJob, job_id, user)
+
+
+def job(db: Session, job_id: int) -> DownloadJob | None:
+    """A job by id, whoever's — for a public link, which already names its job."""
+    return db.get(DownloadJob, job_id)
+
+
+def accessible_job(db: Session, user: User, job_id: int) -> DownloadJob | None:
+    """A file the caller may read: their own, or one shared with them."""
+    row = db.get(DownloadJob, job_id)
+    if row is None:
+        return None
+    if row.user_id == user.id or shared_with(db, job_id, user) is not None:
+        return row
+    return None
+
+
+def readable_job(db: Session, caller: FilesCaller, job_id: int) -> DownloadJob | None:
+    """A file `caller` may read: as `accessible_job` for the user; for a token, one of the user's
+    own in a folder it may read."""
+    if caller.grants is None:
+        return accessible_job(db, caller.user, job_id)
+    row = own_job(db, caller.user, job_id)
+    if row is None or not caller.may(row.folder_id, Right.READ):
+        return None
+    return row
+
+
+def asset_of(db: Session, job: DownloadJob | None) -> MediaAsset | None:
+    """The file under a job, if it has one yet."""
+    return db.get(MediaAsset, job.asset_id) if job is not None and job.asset_id else None
+
+
+def assets_for(db: Session, jobs: Sequence[DownloadJob]) -> dict[int, MediaAsset]:
+    ids = {j.asset_id for j in jobs if j.asset_id}
+    if not ids:
+        return {}
+    rows = db.execute(select(MediaAsset).where(MediaAsset.id.in_(ids))).scalars()
+    return {a.id: a for a in rows}
+
+
+def positions_for(db: Session, user: User, jobs: Sequence[DownloadJob]) -> dict[int, int]:
+    """`user`'s resume point in each of `jobs` that has one (the library player's `library_states`)."""
+    ids = [j.id for j in jobs]
+    if not ids:
+        return {}
+    rows = db.execute(
+        select(LibraryState.job_id, LibraryState.position_seconds).where(
+            owned_by(LibraryState.user_id, user), LibraryState.job_id.in_(ids)
+        )
+    ).all()
+    return {job_id: pos for job_id, pos in rows}
+
+
+def source_keys(db: Session, jobs: Sequence[DownloadJob]) -> dict[int, str]:
+    """Where each file came from (its source folder's key), for the list's Source column, the
+    "back to its source folder" move and the download tray's site: a file in a source folder has its
+    folder's key; one moved into an own folder (or someone else's, shared) is traced back by
+    `folders.source_key_for`."""
+    ids = {j.folder_id for j in jobs if j.folder_id is not None}
+    by_id = (
+        {f.id: f for f in db.execute(select(FileFolder).where(FileFolder.id.in_(ids))).scalars()}
+        if ids
+        else {}
+    )
+    out: dict[int, str] = {}
+    for j in jobs:
+        folder = by_id.get(j.folder_id) if j.folder_id is not None else None
+        if folder is not None and folder.kind == folders.FolderKind.SOURCE and folder.source_key:
+            out[j.id] = folder.source_key
+        else:
+            out[j.id] = folders.source_key_for(db, j)
+    return out
+
+
+def queue(db: Session, user: User, recent: datetime) -> list[DownloadJob]:
+    """The download tray: what is waiting, running, paused or failed, and what finished (done or
+    canceled) since `recent`. A done job is timed from when it became done, never from its last
+    write: a rename, a move or the GC's expiry warning touches an old file's row, and the tray would
+    announce it as just finished."""
+    return list(
+        db.execute(
+            select(DownloadJob)
+            .where(
+                owned_by(DownloadJob.user_id, user),
+                DownloadJob.status.not_in(FINISHED)
+                | ((DownloadJob.status == JobStatus.DONE) & (DownloadJob.ready_at >= recent))
+                | ((DownloadJob.status == JobStatus.CANCELED) & (DownloadJob.updated_at >= recent)),
+            )
+            .order_by(DownloadJob.created_at.desc(), DownloadJob.id.desc())
+            .limit(MAX_LIST)
+        ).scalars()
+    )
+
+
+def statuses_by_source(db: Session, user: User, statuses: Sequence[str]) -> list[tuple[str, str]]:
+    """(source_ref, status) of each of `user`'s jobs in one of `statuses`."""
+    return list(
+        db.execute(
+            select(DownloadJob.source_ref, DownloadJob.status).where(
+                owned_by(DownloadJob.user_id, user), DownloadJob.status.in_(tuple(statuses))
+            )
+        ).tuples()
+    )
+
+
+def library(
+    db: Session,
+    user: User,
+    *,
+    folder_id: int | None,
+    listable: set[int] | None,
+    shared: bool,
+    term: str,
+    sort: str,
+    order: str,
+    lang: str,
+) -> list[DownloadJob]:
+    """The caller's done files (optionally one folder's, or only in the folders a token may list),
+    or the ones shared with them; searched by name and channel, sorted by when they were added, by
+    name (in the reader's alphabet) or by size. A file is added to its owner's list when it is done,
+    not when it was asked for (a download that failed for days and then went through is new); one
+    shared with the caller, when it was shared."""
+    stmt = (
+        select(DownloadJob)
+        .join(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
+        .where(DownloadJob.status == JobStatus.DONE)
+    )
+    if shared:
+        stmt = stmt.join(DownloadShare, DownloadShare.job_id == DownloadJob.id).where(
+            owned_by(DownloadShare.to_user_id, user)
+        )
+    else:
+        stmt = stmt.where(owned_by(DownloadJob.user_id, user))
+        if folder_id is not None:
+            stmt = stmt.where(DownloadJob.folder_id == folder_id)
+        elif listable is not None:
+            stmt = stmt.where(DownloadJob.folder_id.in_(listable))
+    name = func.coalesce(DownloadJob.display_name, MediaAsset.title, "")
+    if term:
+        like = f"%{like_escape(term)}%"
+        stmt = stmt.where(
+            or_(
+                name.ilike(like),
+                func.coalesce(DownloadJob.display_uploader, MediaAsset.uploader, "").ilike(like),
+            )
+        )
+    key = {
+        "added": DownloadShare.created_at if shared else DownloadJob.ready_at,
+        "name": collated(name, lang),
+        "size": MediaAsset.size_bytes,
+    }[sort]
+    first = key.asc() if order == "asc" else key.desc()
+    tie = DownloadJob.id.asc() if order == "asc" else DownloadJob.id.desc()
+    return list(db.execute(stmt.order_by(first.nulls_last(), tie).limit(MAX_LIST)).scalars())
+
+
+def recent_jobs(db: Session) -> list[DownloadJob]:
+    """Everyone's newest jobs, for the admin's list."""
+    return list(
+        db.execute(
+            select(DownloadJob)
+            .order_by(DownloadJob.created_at.desc(), DownloadJob.id.desc())
+            .limit(MAX_LIST)
+        ).scalars()
+    )
+
+
+# --- shares --------------------------------------------------------------------------------
+
+
+def shared_with(db: Session, job_id: int, user: User | int) -> DownloadShare | None:
+    """The grant that hands this job to `user`, if there is one."""
+    return db.execute(
+        select(DownloadShare).where(
+            DownloadShare.job_id == job_id, owned_by(DownloadShare.to_user_id, user)
+        )
+    ).scalar_one_or_none()
+
+
+def shared_at(db: Session, user: User, jobs: Sequence[DownloadJob]) -> dict[int, datetime]:
+    rows = db.execute(
+        select(DownloadShare.job_id, DownloadShare.created_at).where(
+            owned_by(DownloadShare.to_user_id, user),
+            DownloadShare.job_id.in_([j.id for j in jobs]),
+        )
+    ).all()
+    return {job_id: at for job_id, at in rows}
+
+
+# --- folders -------------------------------------------------------------------------------
+
+
+def own_folder(db: Session, user: User, folder_id: int) -> FileFolder | None:
+    return owned_row(db, FileFolder, folder_id, user)
+
+
+def folders_by_id(db: Session, ids: set[int]) -> dict[int, FileFolder]:
+    """These folders, by id — for a reader that already knows which ones (a token's grants)."""
+    if not ids:
+        return {}
+    return {f.id: f for f in db.execute(select(FileFolder).where(FileFolder.id.in_(ids))).scalars()}
+
+
+def folders_with_totals(
+    db: Session, user: User, listable: set[int] | None
+) -> list[tuple[FileFolder, int, int]]:
+    """The user's folders (only `listable` ones, when given) with how many done files each holds and
+    their size. A source folder its files have all left stays (count 0)."""
+    done = (DownloadJob.folder_id == FileFolder.id) & (DownloadJob.status == JobStatus.DONE)
+    stmt = select(
+        FileFolder,
+        func.count(DownloadJob.id),
+        func.coalesce(func.sum(MediaAsset.size_bytes), 0),
+    ).where(owned_by(FileFolder.user_id, user))
+    if listable is not None:
+        stmt = stmt.where(FileFolder.id.in_(listable))
+    rows = db.execute(
+        stmt.outerjoin(DownloadJob, done)
+        .outerjoin(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
+        .group_by(FileFolder.id)
+        .order_by(FileFolder.kind.desc(), FileFolder.source_key, FileFolder.name, FileFolder.id)
+    ).tuples()
+    return [(f, count, int(size or 0)) for f, count, size in rows]
+
+
+def folder_totals(db: Session, folder_id: int) -> tuple[int, int]:
+    count, size = db.execute(
+        select(func.count(DownloadJob.id), func.coalesce(func.sum(MediaAsset.size_bytes), 0))
+        .select_from(DownloadJob)
+        .outerjoin(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
+        .where(DownloadJob.folder_id == folder_id, DownloadJob.status == JobStatus.DONE)
+    ).one()
+    return count, int(size)
+
+
+def linked_folders(db: Session, folder_ids: list[int]) -> set[int]:
+    """Which of these folders a live public link opens (one not past its expiry)."""
+    now = datetime.now(timezone.utc)
+    rows = db.execute(
+        select(DownloadLink.folder_id).where(
+            DownloadLink.folder_id.in_(folder_ids),
+            or_(DownloadLink.expires_at.is_(None), DownloadLink.expires_at > now),
+        )
+    ).scalars()
+    return {folder_id for folder_id in rows if folder_id is not None}
+
+
+# --- links ---------------------------------------------------------------------------------
+
+
+def own_link(db: Session, user: User, link_id: int) -> DownloadLink | None:
+    """A link to one of the user's files or folders."""
+    link = db.get(DownloadLink, link_id)
+    if link is None:
+        return None
+    target = (
+        db.get(DownloadJob, link.job_id)
+        if link.job_id is not None
+        else db.get(FileFolder, link.folder_id)
+    )
+    if target is None or target.user_id != user.id:
+        return None
+    return link
+
+
+def links_to(
+    db: Session, *, job_id: int | None = None, folder_id: int | None = None
+) -> list[DownloadLink]:
+    """The links to one file or one folder, newest first."""
+    target = (
+        DownloadLink.job_id == job_id if job_id is not None else DownloadLink.folder_id == folder_id
+    )
+    return list(
+        db.execute(select(DownloadLink).where(target).order_by(DownloadLink.id.desc())).scalars()
+    )
+
+
+def link_folder(db: Session, link: DownloadLink) -> FileFolder | None:
+    return db.get(FileFolder, link.folder_id) if link.folder_id is not None else None
+
+
+def folder_job(db: Session, folder: FileFolder, job_id: int) -> DownloadJob | None:
+    """One of the files a link to `folder` reaches (`links.in_folder`), while it is in it."""
+    return db.execute(
+        select(DownloadJob).where(DownloadJob.id == job_id, *links.in_folder(folder))
+    ).scalar_one_or_none()
+
+
+def owner_suspended(db: Session, job: DownloadJob) -> bool:
+    """The job's owner is suspended (or gone): the worker leaves their queued jobs where they are."""
+    owner = db.get(User, job.user_id)
+    return owner is None or owner.is_suspended
+
+
+# --- profiles ------------------------------------------------------------------------------
+
+
+def profiles_for(db: Session, user: User) -> list[DownloadProfile]:
+    """The built-in format profiles, then the user's own."""
+    return list(
+        db.execute(
+            select(DownloadProfile)
+            .where(DownloadProfile.is_builtin.is_(True) | owned_by(DownloadProfile.user_id, user))
+            .order_by(
+                DownloadProfile.is_builtin.desc(), DownloadProfile.sort_order, DownloadProfile.id
+            )
+        ).scalars()
+    )
+
+
+def own_profile(db: Session, user: User, profile_id: int) -> DownloadProfile | None:
+    """One of the user's own profiles (a built-in is no one's to change)."""
+    p = owned_row(db, DownloadProfile, profile_id, user)
+    return None if p is None or p.is_builtin else p
+
+
+def usable_profile(db: Session, user: User, profile_id: int) -> DownloadProfile | None:
+    """A profile the user may enqueue with: a built-in, or their own."""
+    p = db.get(DownloadProfile, profile_id)
+    if p is None or (not p.is_builtin and p.user_id != user.id):
+        return None
+    return p
+
+
+def default_profile(db: Session) -> DownloadProfile | None:
+    """The first built-in, for an enqueue that named no format."""
+    return db.execute(
+        select(DownloadProfile)
+        .where(DownloadProfile.is_builtin.is_(True))
+        .order_by(DownloadProfile.sort_order)
+        .limit(1)
+    ).scalar_one_or_none()
+
+
+# --- storage and quota (admin) -------------------------------------------------------------
+
+
+def storage_totals(db: Session) -> tuple[int, int, int]:
+    """(files on disk, their bytes, every asset row). On disk is `quota.ON_DISK`: ready files, and
+    uploads waiting for or failed in their conversion — the same disk the footprint and the GC cap
+    count."""
+    on_disk = db.execute(
+        select(func.count(), func.coalesce(func.sum(MediaAsset.size_bytes), 0)).where(quota.ON_DISK)
+    ).one()
+    total_assets = db.execute(select(func.count()).select_from(MediaAsset)).scalar_one()
+    return on_disk[0], int(on_disk[1]), total_assets
+
+
+def done_files_per_user(db: Session) -> dict[int, int]:
+    """How many finished files each user's Files lists."""
+    return dict(
+        db.execute(
+            select(DownloadJob.user_id, func.count())
+            .where(DownloadJob.status == JobStatus.DONE)
+            .group_by(DownloadJob.user_id)
+        )
+        .tuples()
+        .all()
+    )
+
+
+def custom_quota(db: Session, user_id: int) -> DownloadQuota | None:
+    """The admin's own limits for this user, if any were set."""
+    return db.get(DownloadQuota, user_id)

backend/app/downloads/quota.py

@@ -27,6 +27,7 @@ from sqlalchemy.orm import Session
 from app import sysconfig
 from app.downloads.status import JobKind, JobStatus
 from app.downloads.models import DownloadJob, DownloadQuota, MediaAsset
+from app.userscope import owned_by
 
 # Jobs a user is considered to be "holding" (occupy a job slot / footprint). Terminal failures
 # (error, canceled) don't count.
@@ -85,7 +86,7 @@ def footprint(db: Session, user_id: int) -> int:
     held_assets = (
         select(DownloadJob.asset_id)
         .where(
-            DownloadJob.user_id == user_id,
+            owned_by(DownloadJob.user_id, user_id),
             or_(
                 DownloadJob.status.in_(_HOLDING),
                 and_(DownloadJob.job_kind == JobKind.UPLOAD, DownloadJob.status == JobStatus.ERROR),
@@ -109,7 +110,7 @@ def _count(db: Session, user_id: int, states) -> int:
         db.execute(
             select(func.count())
             .select_from(DownloadJob)
-            .where(DownloadJob.user_id == user_id, DownloadJob.status.in_(states))
+            .where(owned_by(DownloadJob.user_id, user_id), DownloadJob.status.in_(states))
         ).scalar()
         or 0
     )
@@ -201,3 +202,46 @@ def usage(db: Session, user_id: int) -> dict:
         "max_jobs": lim.max_jobs,
         "unlimited": lim.unlimited,
     }
+
+
+def set_custom(
+    db: Session,
+    user_id: int,
+    *,
+    max_bytes: int | None = None,
+    max_concurrent: int | None = None,
+    max_jobs: int | None = None,
+    unlimited: bool | None = None,
+) -> None:
+    """The admin's own limits for a user: starts from what applies now, then each value given (a
+    size floored at 0, a count at 1). The handler commits."""
+    row = db.get(DownloadQuota, user_id)
+    if row is None:
+        cur = resolve(db, user_id)
+        row = DownloadQuota(
+            user_id=user_id,
+            max_bytes=cur.max_bytes,
+            max_concurrent=cur.max_concurrent,
+            max_jobs=cur.max_jobs,
+            unlimited=cur.unlimited,
+        )
+        db.add(row)
+    if max_bytes is not None:
+        row.max_bytes = max(0, max_bytes)
+    if max_concurrent is not None:
+        row.max_concurrent = max(1, max_concurrent)
+    if max_jobs is not None:
+        row.max_jobs = max(1, max_jobs)
+    if unlimited is not None:
+        row.unlimited = unlimited
+    db.flush()
+
+
+def reset_custom(db: Session, user_id: int) -> bool:
+    """Back to the defaults; False when the user had no limits of their own."""
+    row = db.get(DownloadQuota, user_id)
+    if row is None:
+        return False
+    db.delete(row)
+    db.flush()
+    return True

backend/app/downloads/service.py

@@ -1,16 +1,19 @@
-"""Enqueue + cache resolution for the download center (the per-user layer over MediaAsset).
+"""Capture's writes: enqueue + cache resolution, the job transitions, and what the library's
+dialogs change (profiles, resume points, shares, a file's display fields).
 
 `enqueue` is the single entry point used by the API: it resolves (or creates) the shared
 MediaAsset for the requested source+format, links a per-user DownloadJob to it, and — on a
 cache hit (asset already ready) — marks the job done instantly with no re-download. The worker
-handles everything else. State transitions used by the routes (pause/resume/cancel/delete) and
-the worker live in `worker.py` / the routes; this module owns enqueue + asset bookkeeping.
+handles everything else. Every function here flushes and leaves the commit to its caller (the
+handler); the folder, link and quota writes are `folders`, `links` and `quota`.
 """
 
 import uuid
 from datetime import datetime, timezone
 
+from sqlalchemy import delete as delete_rows
 from sqlalchemy import func, select, update
+from sqlalchemy.dialects.postgresql import insert as pg_insert
 from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
 
@@ -21,10 +24,17 @@ from app.downloads import credentials
 from app.downloads import edit as editmod
 from app.downloads import folders, formats, mediakind, quota, storage
 from app.downloads.status import HOLDING, JobKind, JobStatus
-from app.models import DISPLAY_TEXT_MAX, Channel, PlexItem, PlexShow, Video
-from app.downloads.models import DownloadJob, MediaAsset
+from app.models import DISPLAY_TEXT_MAX, Channel, PlexItem, PlexShow, User, Video
+from app.downloads.models import (
+    DownloadJob,
+    DownloadProfile,
+    DownloadShare,
+    LibraryState,
+    MediaAsset,
+)
 from app.plex import lookups as plex_lookups
 from app.plex import paths as plex_paths
+from app.userscope import owned_by, owned_row
 
 
 class EditError(Exception):
@@ -223,8 +233,7 @@ def enqueue(
         folders.stamp_done(db, job)
         asset.last_access_at = datetime.now(timezone.utc)
 
-    db.commit()
-    db.refresh(job)
+    db.flush()
     return job
 
 
@@ -303,8 +312,7 @@ def enqueue_edit(
         folders.stamp_done(db, job)
         asset.last_access_at = datetime.now(timezone.utc)
 
-    db.commit()
-    db.refresh(job)
+    db.flush()
     return job
 
 
@@ -392,8 +400,7 @@ def enqueue_clip(
         folders.stamp_done(db, job)
         asset.last_access_at = datetime.now(timezone.utc)
 
-    db.commit()
-    db.refresh(job)
+    db.flush()
     return job
 
 
@@ -501,8 +508,8 @@ def release_asset(db: Session, job: DownloadJob) -> None:
 # --- Job state transitions ---------------------------------------------------------------------
 # The single home for the pause/resume/cancel/delete/redownload transitions + their asset
 # bookkeeping (release, failed-asset reset, fresh-asset rebuild), so the routes are thin callers and
-# the worker/GC could share the same definitions (B-sub-8). Each commits its own transition; the
-# route keeps only auth + HTTP mapping + serialization.
+# the worker/GC could share the same definitions (B-sub-8). Each flushes its transition and the caller
+# commits it; the route keeps only auth + HTTP mapping + serialization.
 
 
 def pause(db: Session, job: DownloadJob) -> None:
@@ -510,7 +517,7 @@ def pause(db: Session, job: DownloadJob) -> None:
     in any other state."""
     if job.status in (JobStatus.QUEUED, JobStatus.RUNNING):
         job.status = JobStatus.PAUSED
-        db.commit()
+        db.flush()
 
 
 def resume(db: Session, job: DownloadJob) -> None:
@@ -534,7 +541,7 @@ def resume(db: Session, job: DownloadJob) -> None:
                 asset.status = "pending"
                 asset.error = None
         job.status = JobStatus.QUEUED
-        db.commit()
+        db.flush()
 
 
 def _follow_the_cookie(db: Session, job: DownloadJob, asset: MediaAsset) -> MediaAsset:
@@ -569,14 +576,14 @@ def cancel(db: Session, job: DownloadJob) -> None:
     if job.status not in (JobStatus.DONE, JobStatus.CANCELED):
         release_asset(db, job)  # release while the job still counts as holding
         job.status = JobStatus.CANCELED
-        db.commit()
+        db.flush()
 
 
 def delete(db: Session, job: DownloadJob) -> None:
     """Delete a job, releasing its asset hold first (which frees the file iff this was the last holder)."""
     release_asset(db, job)
     db.delete(job)
-    db.commit()
+    db.flush()
 
 
 def redownload(db: Session, job: DownloadJob) -> None:
@@ -625,4 +632,181 @@ def redownload(db: Session, job: DownloadJob) -> None:
     job.queue_pos = next_queue_pos(db)  # tail of the queue, not its stale original slot
     job.expires_at = None  # stamped again when the rebuild is done
     job.expiry_warned = False
-    db.commit()
+    db.flush()
+
+
+# --- the library's writes ------------------------------------------------------------------
+# What the HTTP layer changes for a user: each flushes, the handler commits.
+
+
+def lock_own_job(db: Session, user: User, job_id: int) -> DownloadJob | None:
+    """One of the user's jobs, re-read under a row lock, for a transition that moves its asset's ref
+    count (resume, cancel, delete, redownload) or writes the status those decide on (pause). Two
+    overlapping requests for one job run one after the other and the second decides on the first's
+    committed result — never both releasing the same hold, and never a pause turning a job a cancel
+    just released back into a holder; either can free a file another job still holds. None: not
+    theirs, or gone.
+
+    The asset is locked BEFORE the job: the order a finishing worker child takes them in
+    (`finalize_if_running`), so the two can never deadlock."""
+    while True:
+        owned = owned_row(db, DownloadJob, job_id, user)
+        if owned is None:
+            return None
+        asset_id = owned.asset_id
+        if asset_id is not None:
+            db.execute(select(MediaAsset.id).where(MediaAsset.id == asset_id).with_for_update())
+        job = db.execute(
+            select(DownloadJob)
+            .where(DownloadJob.id == job_id)
+            .with_for_update()
+            .execution_options(populate_existing=True)
+        ).scalar_one_or_none()
+        if job is None:
+            return None
+        if job.asset_id == asset_id:
+            return job
+        db.rollback()  # another request moved the job to another asset meanwhile: lock that one
+
+
+def hold_for_share(db: Session, user: User, job_id: int) -> DownloadJob | None:
+    """One of the user's files, held (FOR SHARE) for the rest of the transaction: a delete of it at
+    the same moment (the user's, or the retention sweep's) waits and takes the new link with it,
+    rather than failing the link's foreign key — or, done first, leaves None."""
+    if owned_row(db, DownloadJob, job_id, user) is None:
+        return None
+    return db.execute(
+        select(DownloadJob)
+        .where(DownloadJob.id == job_id)
+        .with_for_update(read=True)
+        .execution_options(populate_existing=True)
+    ).scalar_one_or_none()
+
+
+def create_profile(db: Session, user: User, name: str, spec: dict) -> DownloadProfile:
+    """A format profile of the user's own, after their others."""
+    maxpos = db.execute(
+        select(func.coalesce(func.max(DownloadProfile.sort_order), 100)).where(
+            owned_by(DownloadProfile.user_id, user)
+        )
+    ).scalar_one()
+    p = DownloadProfile(
+        user_id=user.id, name=name[:80], spec=spec, is_builtin=False, sort_order=maxpos + 1
+    )
+    db.add(p)
+    db.flush()
+    return p
+
+
+def update_profile(profile: DownloadProfile, *, name: str | None, spec: dict | None) -> None:
+    """Rename a profile and/or replace its spec; None leaves that one as it is."""
+    if name is not None:
+        profile.name = name[:80]
+    if spec is not None:
+        profile.spec = spec
+
+
+def delete_profile(db: Session, profile: DownloadProfile) -> None:
+    db.delete(profile)
+    db.flush()
+
+
+def set_position(db: Session, user: User, job_id: int, position: int) -> None:
+    """The library player's resume point in a file the user can play; 0 clears it.
+
+    A clear is a statement, not a loaded row's delete: the periodic checkpoint and the pagehide beacon
+    of one stop may both clear it, and the second then deletes nothing rather than failing. A set is
+    an upsert, one row per (user, job) even when two checkpoints race, not a read-then-insert that
+    the second would fail on the unique key."""
+    if not position:
+        db.execute(
+            delete_rows(LibraryState).where(
+                owned_by(LibraryState.user_id, user), LibraryState.job_id == job_id
+            )
+        )
+        return
+    now = datetime.now(timezone.utc)
+    db.execute(
+        pg_insert(LibraryState)
+        .values(user_id=user.id, job_id=job_id, position_seconds=position, progress_updated_at=now)
+        .on_conflict_do_update(
+            constraint="uq_library_user_job",
+            set_={"position_seconds": position, "progress_updated_at": now},
+        )
+    )
+
+
+def share(db: Session, job: DownloadJob, sender: User, recipient: User) -> bool:
+    """Hand a file to another user, with a notice for them; False when it was already theirs."""
+    from app.notifications import create_notification
+
+    exists = db.execute(
+        select(DownloadShare.id).where(
+            DownloadShare.job_id == job.id, owned_by(DownloadShare.to_user_id, recipient)
+        )
+    ).first()
+    if exists is not None:
+        return False
+    db.add(DownloadShare(job_id=job.id, from_user_id=sender.id, to_user_id=recipient.id))
+    create_notification(
+        db,
+        user_id=recipient.id,
+        type="download_shared",
+        title=(job.display_name or "A download") + " was shared with you",
+        # The client names the notice in the reader's language from `data`; the title is the
+        # English fallback only.
+        data={
+            "kind": "download_shared",
+            "from": sender.email,
+            "job_id": job.id,
+            "title": job.display_name,
+        },
+        commit=False,
+    )
+    db.flush()
+    return True
+
+
+def unshare(db: Session, job_id: int, recipient: User) -> bool:
+    """Take a file back from one user (its owner's act, or the recipient's own dismissal); False
+    when it was not theirs."""
+    row = db.execute(
+        select(DownloadShare).where(
+            DownloadShare.job_id == job_id, owned_by(DownloadShare.to_user_id, recipient)
+        )
+    ).scalar_one_or_none()
+    if row is None:
+        return False
+    db.delete(row)
+    db.flush()
+    return True
+
+
+# The display fields a user may set on their file; the file on disk keeps its own name.
+DISPLAY_FIELDS = frozenset(
+    {"display_name", "display_uploader", "display_uploader_url", "extra_links"}
+)
+
+
+def set_display(job: DownloadJob, **fields: object) -> None:
+    """Set a file's display fields (each already cleaned by the caller); a field not given is left."""
+    unknown = set(fields) - DISPLAY_FIELDS
+    if unknown:
+        raise ValueError(f"not a display field: {sorted(unknown)}")
+    for name, value in fields.items():
+        setattr(job, name, value)
+
+
+def touch(asset: MediaAsset) -> None:
+    """The file was just served: the cache's idle clock starts again."""
+    asset.last_access_at = datetime.now(timezone.utc)
+
+
+def store_sha256(db: Session, asset_id: int, digest: str) -> None:
+    """Keep a file's hash once it is known — only where none is, so a concurrent hash of the same
+    file never overwrites the first."""
+    db.execute(
+        update(MediaAsset)
+        .where(MediaAsset.id == asset_id, MediaAsset.sha256.is_(None))
+        .values(sha256=digest)
+    )

backend/app/routes/_common.py

@@ -16,6 +16,7 @@ from app.db import Base
 from app.models import POSITION_MAX_S, User
 from app.issues import gitea
 from app.refusal import refused
+from app.userscope import owned_row
 from app.youtube.client import YouTubeError, refusal_reason
 
 M = TypeVar("M", bound=Base)
@@ -90,8 +91,8 @@ def owned_or_404(
     else 404s (NOT 403) on purpose — a 403 would confirm the id exists to a stranger.
     It replaced the near-identical per-route ownership helpers, and is called directly — a thin
     `_own_x` wrapper around it is the ad-hoc shape CLAUDE.md's patterns table rules out."""
-    obj = get_or_404(db, model, id_, what=what, lock=lock)
-    if getattr(obj, owner_attr) != user.id:
+    obj = owned_row(db, model, id_, user, owner_attr=owner_attr, lock=lock)
+    if obj is None:
         raise not_found(what)
     return obj
 

backend/app/routes/downloads.py

@@ -3,23 +3,22 @@
 All routes are behind `current_user`; admin routes add `admin_user`. Live job state is polled by the
 frontend (the worker is a separate process); this module never downloads — it enqueues, manages job
 state, and shares finished files. The library itself — listing, renaming, moving, deleting and
-serving a done file, and uploading one — is `routes.files`.
+serving a done file, and uploading one — is `routes.files`. Reads come from `downloads.queries`,
+writes go through Capture's service (`service`, `links`, `quota`); this module validates, answers in
+HTTP and commits.
 """
 
 import re
-from typing import Literal
+from typing import TYPE_CHECKING, Literal
 from datetime import datetime, timedelta, timezone
 from urllib.parse import parse_qs, urlparse
 
 from fastapi import APIRouter, Depends, HTTPException
 from fastapi.responses import FileResponse
 from pydantic import BaseModel, Field
-from sqlalchemy import delete, func, select
-from sqlalchemy.dialects.postgresql import insert as pg_insert
 from sqlalchemy.orm import Session
 
 from app.mailtext import lang_for_user
-from app.collation import collated
 from app import audit, sysconfig
 from app.auth import admin_user, current_user
 from app.config import settings
@@ -29,44 +28,32 @@ from app.downloads import credentials as dlcreds
 from app.downloads import edit as editmod
 from app.downloads import folders
 from app.downloads import links as linksmod
-from app.downloads import quota, service, storage
+from app.downloads import queries, quota, service, storage
 from app.downloads import urlguard
 from app.downloads.folders import FolderKind
-from app.downloads.status import FINISHED, NOT_REFETCHABLE, JobStatus
+from app.downloads.status import NOT_REFETCHABLE, JobStatus
 from app.models import User, display_text
-from app.downloads.models import (
-    DownloadJob,
-    DownloadLink,
-    FileFolder,
-    DownloadProfile,
-    DownloadQuota,
-    DownloadShare,
-    LibraryState,
-    MediaAsset,
-)
 from app.routes._common import (
     ProgressIn,
     get_or_404,
     kept_position,
     not_found,
-    owned_or_404,
 )
 from app.routes.files import (
-    MAX_LIST,
     accessible_job,
-    assets_for,
+    own_folder,
+    own_job,
     own_job_for_update,
-    positions_for,
     quota_detail,
     serialize,
     serialize_job,
-    source_keys,
 )
-from app.security import hash_password
-from app.userscope import is_messageable_user, messageable_clauses
-from app.utils import iso
+from app.userscope import emails_of, is_messageable_user, messageable_others, user_by_email
 from app.refusal import refused
 
+if TYPE_CHECKING:
+    from app.downloads.models import DownloadJob, DownloadLink, DownloadProfile, FileFolder
+
 router = APIRouter(prefix="/api/downloads", tags=["downloads"])
 admin_router = APIRouter(prefix="/api/admin/downloads", tags=["admin-downloads"])
 
@@ -118,7 +105,7 @@ def resolve_source(raw: str) -> tuple[str, str]:
 # --- profiles ------------------------------------------------------------------------------
 
 
-def _serialize_profile(p: DownloadProfile) -> dict:
+def _serialize_profile(p: "DownloadProfile") -> dict:
     return {
         "id": p.id,
         "name": p.name,
@@ -130,18 +117,7 @@ def _serialize_profile(p: DownloadProfile) -> dict:
 
 @router.get("/profiles")
 def list_profiles(user: User = Depends(current_user), db: Session = Depends(get_db)) -> list[dict]:
-    rows = (
-        db.execute(
-            select(DownloadProfile)
-            .where((DownloadProfile.is_builtin.is_(True)) | (DownloadProfile.user_id == user.id))
-            .order_by(
-                DownloadProfile.is_builtin.desc(), DownloadProfile.sort_order, DownloadProfile.id
-            )
-        )
-        .scalars()
-        .all()
-    )
-    return [_serialize_profile(p) for p in rows]
+    return [_serialize_profile(p) for p in queries.profiles_for(db, user)]
 
 
 class CreateProfileIn(BaseModel):
@@ -157,15 +133,7 @@ def create_profile(
     spec = body.spec
     if not name:
         raise refused(400, "profile_name_required")
-    maxpos = db.execute(
-        select(func.coalesce(func.max(DownloadProfile.sort_order), 100)).where(
-            DownloadProfile.user_id == user.id
-        )
-    ).scalar_one()
-    p = DownloadProfile(
-        user_id=user.id, name=name[:80], spec=spec, is_builtin=False, sort_order=maxpos + 1
-    )
-    db.add(p)
+    p = service.create_profile(db, user, name, spec)
     db.commit()
     return _serialize_profile(p)
 
@@ -182,31 +150,32 @@ def update_profile(
     user: User = Depends(current_user),
     db: Session = Depends(get_db),
 ) -> dict:
-    p = db.get(DownloadProfile, profile_id)
-    if p is None or p.is_builtin or p.user_id != user.id:
-        raise not_found("profile")
+    p = _own_profile(db, user, profile_id)
     sent = body.model_fields_set
+    name = None
     if "name" in sent:
         name = (body.name or "").strip()
         if not name:
             raise refused(400, "profile_name_required")
-        p.name = name[:80]
-    if "spec" in sent:
-        if body.spec is None:
-            raise refused(400, "spec_not_object")
-        p.spec = body.spec
+    if "spec" in sent and body.spec is None:
+        raise refused(400, "spec_not_object")
+    service.update_profile(p, name=name, spec=body.spec if "spec" in sent else None)
     db.commit()
     return _serialize_profile(p)
 
 
+def _own_profile(db: Session, user: User, profile_id: int) -> "DownloadProfile":
+    p = queries.own_profile(db, user, profile_id)
+    if p is None:
+        raise not_found("profile")
+    return p
+
+
 @router.delete("/profiles/{profile_id}")
 def delete_profile(
     profile_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
-    p = db.get(DownloadProfile, profile_id)
-    if p is None or p.is_builtin or p.user_id != user.id:
-        raise not_found("profile")
-    db.delete(p)
+    service.delete_profile(db, _own_profile(db, user, profile_id))
     db.commit()
     return {"deleted": profile_id}
 
@@ -276,18 +245,13 @@ def _resolve_spec(
     """Pick the format spec for an enqueue: an explicit profile_id (builtin or the user's own),
     an inline spec, or the first builtin as a fallback."""
     if profile_id is not None:
-        p = db.get(DownloadProfile, profile_id)
-        if p is None or (not p.is_builtin and p.user_id != user.id):
+        p = queries.usable_profile(db, user, profile_id)
+        if p is None:
             raise not_found("profile")
         return p.spec, p.id
     if spec is not None:
         return spec, None
-    fallback = db.execute(
-        select(DownloadProfile)
-        .where(DownloadProfile.is_builtin.is_(True))
-        .order_by(DownloadProfile.sort_order)
-        .limit(1)
-    ).scalar_one_or_none()
+    fallback = queries.default_profile(db)
     if fallback is None:
         raise refused(400, "no_profile")
     return fallback.spec, fallback.id
@@ -325,6 +289,7 @@ def enqueue_download(
         job = service.enqueue(db, user.id, source_kind, source_ref, spec, profile_id, display_name)
     except quota.QuotaExceeded as e:
         raise HTTPException(status_code=422, detail=quota_detail(e)) from e
+    db.commit()
     return serialize_job(db, job)
 
 
@@ -354,6 +319,7 @@ def enqueue_edit(
         raise HTTPException(status_code=422, detail=quota_detail(e)) from e
     except service.EditError as e:
         raise HTTPException(status_code=400, detail={"code": "edit", "reason": e.reason}) from e
+    db.commit()
     return serialize_job(db, job)
 
 
@@ -397,38 +363,22 @@ def enqueue_clip(
         raise HTTPException(status_code=status, detail=detail) from e
     except quota.QuotaExceeded as e:
         raise HTTPException(status_code=422, detail=quota_detail(e)) from e
+    db.commit()
     return serialize_job(db, job)
 
 
 # How long a finished job stays in the queue: the tray polls it from every page and must see a job
 # turn done (its "Done · Open" row and the done notice) — the finished file itself is the library's.
-# A done job is timed from when it became done, never from its last write: a rename, a move or the
-# GC's expiry warning touches an old file's row, and the tray would announce it as just finished.
 QUEUE_RECENT = timedelta(minutes=10)
 
 
 @router.get("")
 def list_downloads(user: User = Depends(current_user), db: Session = Depends(get_db)) -> list[dict]:
     """The queue: what is waiting, running, paused or failed, and what finished a moment ago."""
-    recent = datetime.now(timezone.utc) - QUEUE_RECENT
-    jobs = (
-        db.execute(
-            select(DownloadJob)
-            .where(
-                DownloadJob.user_id == user.id,
-                DownloadJob.status.not_in(FINISHED)
-                | ((DownloadJob.status == JobStatus.DONE) & (DownloadJob.ready_at >= recent))
-                | ((DownloadJob.status == JobStatus.CANCELED) & (DownloadJob.updated_at >= recent)),
-            )
-            .order_by(DownloadJob.created_at.desc(), DownloadJob.id.desc())
-            .limit(MAX_LIST)
-        )
-        .scalars()
-        .all()
-    )
-    assets = assets_for(db, jobs)
-    positions = positions_for(db, user, jobs)
-    sources = source_keys(db, jobs)
+    jobs = queries.queue(db, user, datetime.now(timezone.utc) - QUEUE_RECENT)
+    assets = queries.assets_for(db, jobs)
+    positions = queries.positions_for(db, user, jobs)
+    sources = queries.source_keys(db, jobs)
     return [
         {
             **serialize(j, assets.get(j.asset_id) if j.asset_id is not None else None),
@@ -452,14 +402,8 @@ _INDEX_RANK: dict[str, int] = {
 def my_download_index(user: User = Depends(current_user), db: Session = Depends(get_db)) -> dict:
     """source_ref -> best active status, for the feed's per-card "downloaded / queued" badge.
     Small + cheap so the feed can poll it without loading the full job list."""
-    rows = db.execute(
-        select(DownloadJob.source_ref, DownloadJob.status).where(
-            DownloadJob.user_id == user.id,
-            DownloadJob.status.in_(tuple(_INDEX_RANK)),
-        )
-    ).all()
     out: dict[str, str] = {}
-    for ref, status in rows:
+    for ref, status in queries.statuses_by_source(db, user, tuple(_INDEX_RANK)):
         if _INDEX_RANK.get(status, 0) > _INDEX_RANK.get(out.get(ref, ""), 0):
             out[ref] = status
     return out
@@ -471,6 +415,7 @@ def pause_download(
 ) -> dict:
     job = own_job_for_update(db, user, job_id)
     service.pause(db, job)
+    db.commit()
     return serialize_job(db, job)
 
 
@@ -480,6 +425,7 @@ def resume_download(
 ) -> dict:
     job = own_job_for_update(db, user, job_id)
     service.resume(db, job)
+    db.commit()
     return serialize_job(db, job)
 
 
@@ -507,6 +453,7 @@ def redownload_download(
     if job.status in (JobStatus.QUEUED, JobStatus.RUNNING, JobStatus.PAUSED):
         raise refused(409, "still_downloading")
     service.redownload(db, job)
+    db.commit()
     return serialize_job(db, job)
 
 
@@ -516,6 +463,7 @@ def cancel_download(
 ) -> dict:
     job = own_job_for_update(db, user, job_id)
     service.cancel(db, job)
+    db.commit()
     return serialize_job(db, job)
 
 
@@ -533,24 +481,7 @@ def set_library_progress(
     one shared with them). A position too early or too close to the end clears it instead."""
     accessible_job(db, user, job_id)
     position = kept_position(body)
-    mine = (LibraryState.user_id == user.id) & (LibraryState.job_id == job_id)
-    if not position:
-        # A statement, not a loaded row's delete: the periodic checkpoint and the pagehide beacon of
-        # one stop may both clear it, and the second then deletes nothing rather than failing.
-        db.execute(delete(LibraryState).where(mine))
-        db.commit()
-        return {"ok": True, "job_id": job_id, "position_seconds": 0}
-    now = datetime.now(timezone.utc)
-    # One row per (user, job) even when two checkpoints race (the same pair): an upsert, not a
-    # read-then-insert that the second would fail on the unique key.
-    db.execute(
-        pg_insert(LibraryState)
-        .values(user_id=user.id, job_id=job_id, position_seconds=position, progress_updated_at=now)
-        .on_conflict_do_update(
-            constraint="uq_library_user_job",
-            set_={"position_seconds": position, "progress_updated_at": now},
-        )
-    )
+    service.set_position(db, user, job_id, position)
     db.commit()
     return {"ok": True, "job_id": job_id, "position_seconds": position}
 
@@ -563,8 +494,7 @@ def storyboard_meta(
 
     Best-effort: for a very long/high-res source the sprite may not generate in time — then
     `available` is False and the editor shows a plain timeline."""
-    job = accessible_job(db, user, job_id)
-    asset = db.get(MediaAsset, job.asset_id) if job.asset_id else None
+    asset = queries.asset_of(db, accessible_job(db, user, job_id))
     if asset is None or asset.status != "ready" or not asset.rel_path:
         raise refused(409, "download_not_ready")
     meta = editmod.ensure_storyboard(asset, settings.files_root)
@@ -584,8 +514,7 @@ def storyboard_meta(
 @router.get("/{job_id}/poster.jpg")
 def poster_image(job_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)):
     """The locally-generated poster frame for a download whose source had no thumbnail."""
-    job = accessible_job(db, user, job_id)
-    asset = db.get(MediaAsset, job.asset_id) if job.asset_id else None
+    asset = queries.asset_of(db, accessible_job(db, user, job_id))
     if asset is None or not asset.poster_path:
         raise not_found("poster")
     path = storage.safe_abs_path(settings.files_root, asset.poster_path)
@@ -598,8 +527,7 @@ def poster_image(job_id: int, user: User = Depends(current_user), db: Session =
 def storyboard_image(
     job_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
 ):
-    job = accessible_job(db, user, job_id)
-    asset = db.get(MediaAsset, job.asset_id) if job.asset_id else None
+    asset = queries.asset_of(db, accessible_job(db, user, job_id))
     if asset is None or not asset.storyboard_path:
         raise not_found("filmstrip")
     path = storage.safe_abs_path(settings.files_root, asset.storyboard_path)
@@ -622,45 +550,20 @@ def share_download(
     user: User = Depends(current_user),
     db: Session = Depends(get_db),
 ) -> dict:
-    job = owned_or_404(db, DownloadJob, job_id, user, what="download")
+    job = own_job(db, user, job_id)
     if job.status != JobStatus.DONE or job.asset_id is None:
         raise refused(409, "share_unfinished")
     target = body.email.strip().lower()
     if not target:
         raise refused(400, "recipient_required")
-    recipient = db.execute(
-        select(User).where(func.lower(User.email) == target)
-    ).scalar_one_or_none()
+    recipient = user_by_email(db, target)
     # Uniform "no user" for a missing OR non-messageable (suspended/deactivated) target, so
     # sharing can't be used to probe which addresses exist or to reach a suspended account.
-    if not is_messageable_user(recipient):
+    if recipient is None or not is_messageable_user(recipient):
         raise not_found("recipient")
     if recipient.id == user.id:
         raise refused(400, "share_own")
-    exists = db.execute(
-        select(DownloadShare.id).where(
-            DownloadShare.job_id == job_id, DownloadShare.to_user_id == recipient.id
-        )
-    ).first()
-    if exists is None:
-        db.add(DownloadShare(job_id=job_id, from_user_id=user.id, to_user_id=recipient.id))
-        from app.notifications import create_notification
-
-        create_notification(
-            db,
-            user_id=recipient.id,
-            type="download_shared",
-            title=(job.display_name or "A download") + " was shared with you",
-            # The client names the notice in the reader's language from `data`; the title is the
-            # English fallback only.
-            data={
-                "kind": "download_shared",
-                "from": user.email,
-                "job_id": job_id,
-                "title": job.display_name,
-            },
-            commit=False,
-        )
+    if service.share(db, job, user, recipient):
         db.commit()
     return {"ok": True, "shared_with": recipient.email}
 
@@ -672,22 +575,10 @@ def unshare_download(
     user: User = Depends(current_user),
     db: Session = Depends(get_db),
 ) -> dict:
-    owned_or_404(
-        db, DownloadJob, job_id, user, what="download"
-    )  # ownership guard (404s if not the caller's job)
-    recipient = db.execute(
-        select(User).where(func.lower(User.email) == email.strip().lower())
-    ).scalar_one_or_none()
-    if recipient is not None:
-        row = db.execute(
-            select(DownloadShare).where(
-                DownloadShare.job_id == job_id,
-                DownloadShare.to_user_id == recipient.id,
-            )
-        ).scalar_one_or_none()
-        if row is not None:
-            db.delete(row)
-            db.commit()
+    own_job(db, user, job_id)  # ownership guard (404s if not the caller's job)
+    recipient = user_by_email(db, email)
+    if recipient is not None and service.unshare(db, job_id, recipient):
+        db.commit()
     return {"ok": True}
 
 
@@ -700,54 +591,26 @@ def share_recipients(
 ) -> list[dict]:
     """Registered users this user can share a download with (excludes self + any non-messageable
     account — suspended or deactivated — so the picker never leaks those addresses)."""
-    rows = (
-        db.execute(
-            select(User)
-            .where(User.id != user.id, *messageable_clauses())
-            .order_by(collated(User.email, lang_for_user(user)))
-        )
-        .scalars()
-        .all()
-    )
+    rows = messageable_others(db, user, lang_for_user(user))
     return [{"id": u.id, "email": u.email, "display_name": u.display_name} for u in rows]
 
 
 # --- public watch links (share by link) ----------------------------------------------------
 
 
-def _own_link(db: Session, user: User, link_id: int) -> DownloadLink:
-    link = db.get(DownloadLink, link_id)
+def _own_link(db: Session, user: User, link_id: int) -> "DownloadLink":
+    link = queries.own_link(db, user, link_id)
     if link is None:
         raise not_found("link")
-    target = (
-        db.get(DownloadJob, link.job_id)
-        if link.job_id is not None
-        else db.get(FileFolder, link.folder_id)
-    )
-    if target is None or target.user_id != user.id:
-        raise not_found("link")
     return link
 
 
-def _link_expiry(days: int | None) -> datetime | None:
-    # None/0/negative → no expiry; otherwise N days out, capped at ~10 years. The Pydantic model
-    # already coerced/validated the type, so a non-number is a 422 before we get here.
-    if not days or days <= 0:
-        return None
-    return datetime.now(timezone.utc) + timedelta(days=min(days, 3650))
-
-
-def _links_of(db: Session, *where) -> list[dict]:
-    rows = db.execute(select(DownloadLink).where(*where).order_by(DownloadLink.id.desc()))
-    return [linksmod.owner_view(row) for row in rows.scalars()]
-
-
 @router.get("/{job_id}/links")
 def list_links(
     job_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> list[dict]:
-    owned_or_404(db, DownloadJob, job_id, user, what="download")
-    return _links_of(db, DownloadLink.job_id == job_id)
+    own_job(db, user, job_id)
+    return [linksmod.owner_view(link) for link in queries.links_to(db, job_id=job_id)]
 
 
 class CreateLinkIn(BaseModel):
@@ -763,30 +626,18 @@ class CreateLinkIn(BaseModel):
 
 def _new_link(
     db: Session, user: User, body: CreateLinkIn, **target: int
-) -> tuple[DownloadLink, str]:
-    """Make a link to `target` (`job_id=` or `folder_id=`, already checked to be the user's), and
-    the token it is opened by — which is in hand only now."""
-    pw = body.password.strip()
-    token = linksmod.new_token()
-    link = DownloadLink(
-        **target,
-        created_by=user.id,
-        allow_download=body.allow_download,
-        password_hash=hash_password(pw) if pw else None,
-        expires_at=_link_expiry(body.expires_days),
-    )
-    linksmod.seal(link, token)
-    db.add(link)
-    db.flush()
-    audit.record(
+) -> tuple["DownloadLink", str]:
+    """A link to `target` (`job_id=` or `folder_id=`, already checked to be the user's) and its
+    token (`links.create`). The Pydantic model already coerced the expiry, so a non-number is a 422
+    before this runs."""
+    return linksmod.create(
         db,
-        user.id,
-        audit.AuditAction.DOWNLOAD_LINK_CREATE,
-        target_type="download_link",
-        target_id=link.id,
-        after={**target, **_link_audit(link)},
+        user,
+        password=body.password.strip(),
+        allow_download=body.allow_download,
+        expires_days=body.expires_days,
+        **target,
     )
-    return link, token
 
 
 @router.post("/{job_id}/links")
@@ -804,28 +655,20 @@ def create_link(
     return linksmod.owner_view(link, token=token)
 
 
-def _shareable_job(db: Session, user: User, job_id: int) -> DownloadJob:
-    """One of the user's files, held (FOR SHARE) for the rest of the transaction: a delete of it at
-    the same moment (the user's, or the retention sweep's) waits and takes the new link with it,
-    rather than failing the link's foreign key — or, done first, leaves a 404."""
-    owned_or_404(db, DownloadJob, job_id, user, what="download")
-    job = db.execute(
-        select(DownloadJob)
-        .where(DownloadJob.id == job_id)
-        .with_for_update(read=True)
-        .execution_options(populate_existing=True)
-    ).scalar_one_or_none()
+def _shareable_job(db: Session, user: User, job_id: int) -> "DownloadJob":
+    """One of the user's files, held for the link's transaction (`service.hold_for_share`)."""
+    job = service.hold_for_share(db, user, job_id)
     if job is None:
         raise not_found("download")
     return job
 
 
-def _shareable_folder(db: Session, user: User, folder_id: int) -> FileFolder:
+def _shareable_folder(db: Session, user: User, folder_id: int) -> "FileFolder":
     """One of the user's own folders. A source folder lets its files go on its own clock, and the Hub
     is the user's channel to a machine of theirs: neither is a shelf to hand out. Held (FOR SHARE)
     for the rest of the transaction, so a delete of it at the same moment waits and takes the new
     link with it, rather than failing the link's foreign key."""
-    owned_or_404(db, FileFolder, folder_id, user, what="folder")
+    own_folder(db, user, folder_id)
     try:
         folder = folders.own_folder(db, user.id, folder_id)
     except folders.FolderError as e:
@@ -839,8 +682,8 @@ def _shareable_folder(db: Session, user: User, folder_id: int) -> FileFolder:
 def list_folder_links(
     folder_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> list[dict]:
-    owned_or_404(db, FileFolder, folder_id, user, what="folder")
-    return _links_of(db, DownloadLink.folder_id == folder_id)
+    own_folder(db, user, folder_id)
+    return [linksmod.owner_view(link) for link in queries.links_to(db, folder_id=folder_id)]
 
 
 @router.post("/folders/{folder_id}/links")
@@ -856,15 +699,6 @@ def create_folder_link(
     return linksmod.owner_view(link, token=token)
 
 
-def _link_audit(link: DownloadLink) -> dict:
-    """A link's settings as the audit records them: whether it has a password, never which."""
-    return {
-        "allow_download": link.allow_download,
-        "has_password": link.password_hash is not None,
-        "expires_at": iso(link.expires_at),
-    }
-
-
 class UpdateLinkIn(BaseModel):
     allow_download: bool | None = None
     expires_days: int | None = None
@@ -879,29 +713,15 @@ def update_link(
     db: Session = Depends(get_db),
 ) -> dict:
     link = _own_link(db, user, link_id)
-    before = _link_audit(link)
-    sent = body.model_fields_set
-    if "allow_download" in sent:
-        link.allow_download = bool(body.allow_download)
-    if "expires_days" in sent:
-        link.expires_at = _link_expiry(body.expires_days)
-    if "password" in sent:
-        pw = (body.password or "").strip()
-        link.password_hash = hash_password(pw) if pw else None
-        # Bump the version so any grant issued under the previous password stops working now, rather
-        # than living out its 6h TTL (setting/clearing/changing the password all count as a rotation).
-        link.password_version += 1
-    after = _link_audit(link)
-    if after != before or "password" in sent:
-        audit.record(
-            db,
-            user.id,
-            audit.AuditAction.DOWNLOAD_LINK_UPDATE,
-            target_type="download_link",
-            target_id=link_id,
-            before=before,
-            after=after,
-        )
+    linksmod.update(
+        db,
+        user,
+        link,
+        allow_download=body.allow_download,
+        expires_days=body.expires_days,
+        password=body.password,
+        sent=frozenset(body.model_fields_set),
+    )
     db.commit()
     return linksmod.owner_view(link)
 
@@ -910,16 +730,7 @@ def update_link(
 def revoke_link(
     link_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
-    link = _own_link(db, user, link_id)
-    db.delete(link)
-    audit.record(
-        db,
-        user.id,
-        audit.AuditAction.DOWNLOAD_LINK_REVOKE,
-        target_type="download_link",
-        target_id=link_id,
-        after={"job_id": link.job_id} if link.job_id is not None else {"folder_id": link.folder_id},
-    )
+    linksmod.revoke(db, user, _own_link(db, user, link_id))
     db.commit()
     return {"ok": True, "deleted": link_id}
 
@@ -931,20 +742,9 @@ def revoke_link(
 def admin_list_downloads(
     admin: User = Depends(admin_user), db: Session = Depends(get_db)
 ) -> list[dict]:
-    jobs = (
-        db.execute(
-            select(DownloadJob)
-            .order_by(DownloadJob.created_at.desc(), DownloadJob.id.desc())
-            .limit(MAX_LIST)
-        )
-        .scalars()
-        .all()
-    )
-    assets = assets_for(db, jobs)
-    emails = {
-        u.id: u.email
-        for u in db.execute(select(User).where(User.id.in_({j.user_id for j in jobs}))).scalars()
-    }
+    jobs = queries.recent_jobs(db)
+    assets = queries.assets_for(db, jobs)
+    emails = emails_of(db, {j.user_id for j in jobs})
     out = []
     for j in jobs:
         data = serialize(j, assets.get(j.asset_id) if j.asset_id is not None else None)
@@ -956,27 +756,11 @@ def admin_list_downloads(
 
 @admin_router.get("/storage")
 def admin_storage(admin: User = Depends(admin_user), db: Session = Depends(get_db)) -> dict:
-    # Every file on disk (`quota.ON_DISK`): ready ones, and uploads waiting for or failed in their
-    # conversion — the same disk the footprint and the GC cap count.
-    on_disk = db.execute(
-        select(func.count(), func.coalesce(func.sum(MediaAsset.size_bytes), 0)).where(quota.ON_DISK)
-    ).one()
-    total_assets = db.execute(select(func.count()).select_from(MediaAsset)).scalar()
+    files_on_disk, total_bytes, total_assets = queries.storage_totals(db)
     # EVERY user, not only those holding a file: a quota is set before anyone downloads.
-    emails: dict[int, str] = {
-        uid: email
-        for uid, email in db.execute(select(User.id, User.email).order_by(User.email)).tuples()
-    }
+    emails = emails_of(db)
     uids = list(emails)
-    # What each one's Files lists: their finished files.
-    files: dict[int, int] = {
-        uid: n
-        for uid, n in db.execute(
-            select(DownloadJob.user_id, func.count())
-            .where(DownloadJob.status == JobStatus.DONE)
-            .group_by(DownloadJob.user_id)
-        ).tuples()
-    }
+    files = queries.done_files_per_user(db)
 
     def row(uid: int) -> dict:
         lim = quota.resolve(db, uid)
@@ -990,8 +774,8 @@ def admin_storage(admin: User = Depends(admin_user), db: Session = Depends(get_d
         }
 
     return {
-        "files_on_disk": on_disk[0],
-        "total_bytes": int(on_disk[1]),
+        "files_on_disk": files_on_disk,
+        "total_bytes": total_bytes,
         "total_assets": total_assets,
         "total_cap_bytes": sysconfig.get_int(db, "download_total_max_bytes"),
         "per_user": [row(uid) for uid in uids],
@@ -1003,10 +787,9 @@ def admin_get_quota(
     user_id: int, admin: User = Depends(admin_user), db: Session = Depends(get_db)
 ) -> dict:
     lim = quota.resolve(db, user_id)
-    row = db.get(DownloadQuota, user_id)
     return {
         "user_id": user_id,
-        "custom": row is not None,
+        "custom": queries.custom_quota(db, user_id) is not None,
         "max_bytes": lim.max_bytes,
         "max_concurrent": lim.max_concurrent,
         "max_jobs": lim.max_jobs,
@@ -1031,25 +814,14 @@ def admin_set_quota(
     db: Session = Depends(get_db),
 ) -> dict:
     get_or_404(db, User, user_id, what="user")
-    cur = quota.resolve(db, user_id)
-    row = db.get(DownloadQuota, user_id)
-    if row is None:
-        row = DownloadQuota(
-            user_id=user_id,
-            max_bytes=cur.max_bytes,
-            max_concurrent=cur.max_concurrent,
-            max_jobs=cur.max_jobs,
-            unlimited=cur.unlimited,
-        )
-        db.add(row)
-    if body.max_bytes is not None:
-        row.max_bytes = max(0, body.max_bytes)
-    if body.max_concurrent is not None:
-        row.max_concurrent = max(1, body.max_concurrent)
-    if body.max_jobs is not None:
-        row.max_jobs = max(1, body.max_jobs)
-    if body.unlimited is not None:
-        row.unlimited = body.unlimited
+    quota.set_custom(
+        db,
+        user_id,
+        max_bytes=body.max_bytes,
+        max_concurrent=body.max_concurrent,
+        max_jobs=body.max_jobs,
+        unlimited=body.unlimited,
+    )
     db.commit()
     return admin_get_quota(user_id, admin, db)
 
@@ -1058,8 +830,6 @@ def admin_set_quota(
 def admin_reset_quota(
     user_id: int, admin: User = Depends(admin_user), db: Session = Depends(get_db)
 ) -> dict:
-    row = db.get(DownloadQuota, user_id)
-    if row is not None:
-        db.delete(row)
+    if quota.reset_custom(db, user_id):
         db.commit()
     return admin_get_quota(user_id, admin, db)

backend/app/routes/files.py

@@ -5,8 +5,10 @@ the per-user layer (name, folder, kept, expiry, shares and links all hang off it
 bytes. Folders are rows (`downloads.folders`), so a rename or a move never touches the disk.
 
 In-flight jobs are not here: they are the download tray's (`routes.downloads`). The helpers above
-the routes are shared with that module — serialization, the ownership locks, the upload spool —
-because a download and a library file are one row at two moments.
+the routes are shared with that module — serialization, the ownership checks, the upload spool —
+because a download and a library file are one row at two moments. What is read comes from
+`downloads.queries`, what is written goes through Capture's service (`service`, `folders`); this
+module validates, answers in HTTP and commits.
 
 A machine with an API token (`app.apitokens`) may use the routes that take `files_caller`: list the
 folders and files, fetch a file and its hash, upload, delete — each only in a folder its token was
@@ -19,49 +21,37 @@ import hashlib
 import os
 import tempfile
 import threading
-from collections.abc import AsyncIterator, Sequence
+from collections.abc import AsyncIterator
 from dataclasses import dataclass
-from datetime import datetime, timezone
 from pathlib import Path
-from typing import BinaryIO, Literal
+from typing import TYPE_CHECKING, BinaryIO, Literal
 from urllib.parse import unquote, urlparse
 
 from fastapi import APIRouter, Depends, HTTPException, Query, Request
 from fastapi.responses import FileResponse, Response
 from pydantic import BaseModel, Field
-from sqlalchemy import func, or_, select, update
-from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
 
 from app import audit, sysconfig
 from app.apitokens import FilesCaller, Right, files_caller
 from app.audit import AuditAction
 from app.auth import current_user
-from app.collation import collated
 from app.config import settings
 from app.db import get_db, release_read_connection
-from app.downloads import folders, preview, quota, service, storage
+from app.downloads import folders, preview, queries, quota, service, storage
 from app.downloads import upload as uploadmod
 from app.downloads.status import JobStatus
 from app.mailtext import lang_for_user
 from app.models import DISPLAY_TEXT_MAX, User, display_text
-from app.downloads.models import (
-    DownloadJob,
-    DownloadLink,
-    DownloadShare,
-    FileFolder,
-    LibraryState,
-    MediaAsset,
-)
 from app.refusal import refused
-from app.routes._common import capped_stream_to, not_found, owned_or_404
-from app.utils import iso, like_escape
+from app.routes._common import capped_stream_to, not_found
+from app.utils import iso
+
+if TYPE_CHECKING:
+    from app.downloads.models import DownloadJob, FileFolder, MediaAsset
 
 router = APIRouter(prefix="/api/files", tags=["files"])
 
-# Cap the listing so a heavy library can't return an unbounded result set (the old Download Center's
-# own cap; far beyond any real library).
-MAX_LIST = 500
 # The longest a folder may keep a file, in days — ten years is "forever" in all but name.
 _MAX_RETENTION_DAYS = 3650
 _HASH_CHUNK = 1 << 20
@@ -73,7 +63,7 @@ _HASHING = threading.BoundedSemaphore(_HASHERS)
 # --- shared with routes.downloads -------------------------------------------------------
 
 
-def serialize(job: DownloadJob, asset: MediaAsset | None) -> dict:
+def serialize(job: "DownloadJob", asset: "MediaAsset | None") -> dict:
     ready = asset is not None and asset.status == "ready" and bool(asset.rel_path)
     return {
         "id": job.id,
@@ -133,58 +123,18 @@ def serialize(job: DownloadJob, asset: MediaAsset | None) -> dict:
     }
 
 
-def assets_for(db: Session, jobs: Sequence[DownloadJob]) -> dict[int, MediaAsset]:
-    ids = {j.asset_id for j in jobs if j.asset_id}
-    if not ids:
-        return {}
-    rows = db.execute(select(MediaAsset).where(MediaAsset.id.in_(ids))).scalars()
-    return {a.id: a for a in rows}
-
-
-def positions_for(db: Session, user: User, jobs: Sequence[DownloadJob]) -> dict[int, int]:
-    """`user`'s resume point in each of `jobs` that has one (the library player's `library_states`)."""
-    ids = [j.id for j in jobs]
-    if not ids:
-        return {}
-    rows = db.execute(
-        select(LibraryState.job_id, LibraryState.position_seconds).where(
-            LibraryState.user_id == user.id, LibraryState.job_id.in_(ids)
-        )
-    ).all()
-    return {job_id: pos for job_id, pos in rows}
-
-
-def serialize_job(db: Session, job: DownloadJob) -> dict:
+def serialize_job(db: Session, job: "DownloadJob") -> dict:
     """Resolve a job's cache asset (if any) and serialize the pair — the resolve-then-serialize step
     every single-job handler shares."""
-    asset = db.get(MediaAsset, job.asset_id) if job.asset_id else None
-    return serialize(job, asset)
+    return serialize(job, queries.asset_of(db, job))
 
 
-def own_job_for_update(db: Session, user: User, job_id: int) -> DownloadJob:
-    """The ownership check (`owned_or_404`) for a transition that moves its asset's ref count (resume, cancel, delete, redownload)
-    or writes the status those decide on (pause). The job is re-read under a row lock, so two
-    overlapping requests for one job run one after the other and the second decides on the first's
-    committed result — never both releasing the same hold, and never a pause turning a job a cancel
-    just released back into a holder; either can free a file another job still holds.
-
-    The asset is locked BEFORE the job: the order a finishing worker child takes them in
-    (`service.finalize_if_running`), so the two can never deadlock."""
-    while True:
-        asset_id = owned_or_404(db, DownloadJob, job_id, user, what="download").asset_id
-        if asset_id is not None:
-            db.execute(select(MediaAsset.id).where(MediaAsset.id == asset_id).with_for_update())
-        job = db.execute(
-            select(DownloadJob)
-            .where(DownloadJob.id == job_id)
-            .with_for_update()
-            .execution_options(populate_existing=True)
-        ).scalar_one_or_none()
-        if job is None:
-            raise not_found("download")
-        if job.asset_id == asset_id:
-            return job
-        db.rollback()  # another request moved the job to another asset meanwhile: lock that one
+def own_job_for_update(db: Session, user: User, job_id: int) -> "DownloadJob":
+    """One of the user's jobs under its row lock (`service.lock_own_job`), or a 404."""
+    job = service.lock_own_job(db, user, job_id)
+    if job is None:
+        raise not_found("download")
+    return job
 
 
 def quota_detail(e: quota.QuotaExceeded) -> dict:
@@ -320,30 +270,32 @@ async def spool_upload(
         tmp_path.unlink(missing_ok=True)
 
 
-def accessible_job(db: Session, user: User, job_id: int) -> DownloadJob:
-    """A file the caller may read: their own, or one shared with them."""
-    job = db.get(DownloadJob, job_id)
+def accessible_job(db: Session, user: User, job_id: int) -> "DownloadJob":
+    """A file the caller may read (`queries.accessible_job`: their own, or shared with them)."""
+    job = queries.accessible_job(db, user, job_id)
     if job is None:
         raise not_found("download")
-    if job.user_id == user.id:
-        return job
-    shared = db.execute(
-        select(DownloadShare.id).where(
-            DownloadShare.job_id == job_id, DownloadShare.to_user_id == user.id
-        )
-    ).first()
-    if shared is None:
-        raise not_found("download")
     return job
 
 
-def readable_job(db: Session, caller: FilesCaller, job_id: int) -> DownloadJob:
-    """A file `caller` may read: as `accessible_job` for the user; for a token, one of the user's
-    own in a folder it may read."""
-    if caller.grants is None:
-        return accessible_job(db, caller.user, job_id)
-    job = db.get(DownloadJob, job_id)
-    if job is None or job.user_id != caller.user.id or not caller.may(job.folder_id, Right.READ):
+def own_job(db: Session, user: User, job_id: int) -> "DownloadJob":
+    job = queries.own_job(db, user, job_id)
+    if job is None:
+        raise not_found("download")
+    return job
+
+
+def own_folder(db: Session, user: User, folder_id: int) -> "FileFolder":
+    folder = queries.own_folder(db, user, folder_id)
+    if folder is None:
+        raise not_found("folder")
+    return folder
+
+
+def readable_job(db: Session, caller: FilesCaller, job_id: int) -> "DownloadJob":
+    """A file `caller` may read (`queries.readable_job`), or a 404."""
+    job = queries.readable_job(db, caller, job_id)
+    if job is None:
         raise not_found("download")
     return job
 
@@ -351,7 +303,7 @@ def readable_job(db: Session, caller: FilesCaller, job_id: int) -> DownloadJob:
 # --- folders -------------------------------------------------------------------------------
 
 
-def _serialize_folder(folder: FileFolder, count: int, size: int, linked: bool = False) -> dict:
+def _serialize_folder(folder: "FileFolder", count: int, size: int, linked: bool = False) -> dict:
     return {
         "id": folder.id,
         "kind": folder.kind,
@@ -367,18 +319,6 @@ def _serialize_folder(folder: FileFolder, count: int, size: int, linked: bool =
     }
 
 
-def _linked(db: Session, folder_ids: list[int]) -> set[int]:
-    """Which of these folders a live public link opens (one not past its expiry)."""
-    now = datetime.now(timezone.utc)
-    rows = db.execute(
-        select(DownloadLink.folder_id).where(
-            DownloadLink.folder_id.in_(folder_ids),
-            or_(DownloadLink.expires_at.is_(None), DownloadLink.expires_at > now),
-        )
-    ).scalars()
-    return {folder_id for folder_id in rows if folder_id is not None}
-
-
 @router.get("/folders")
 def list_folders(
     caller: FilesCaller = Depends(files_caller), db: Session = Depends(get_db)
@@ -386,23 +326,9 @@ def list_folders(
     """The caller's folders with how many files each holds and their size (a token: the ones it may
     list). A source folder its files have all left stays (count 0): the client decides whether to
     show it."""
-    done = (DownloadJob.folder_id == FileFolder.id) & (DownloadJob.status == JobStatus.DONE)
-    stmt = select(
-        FileFolder,
-        func.count(DownloadJob.id),
-        func.coalesce(func.sum(MediaAsset.size_bytes), 0),
-    ).where(FileFolder.user_id == caller.user.id)
-    listable = caller.folders_with(Right.LIST)
-    if listable is not None:
-        stmt = stmt.where(FileFolder.id.in_(listable))
-    rows = db.execute(
-        stmt.outerjoin(DownloadJob, done)
-        .outerjoin(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
-        .group_by(FileFolder.id)
-        .order_by(FileFolder.kind.desc(), FileFolder.source_key, FileFolder.name, FileFolder.id)
-    ).all()
-    linked = _linked(db, [f.id for f, _, _ in rows])
-    return [_serialize_folder(f, count, int(size), f.id in linked) for f, count, size in rows]
+    rows = queries.folders_with_totals(db, caller.user, caller.folders_with(Right.LIST))
+    linked = queries.linked_folders(db, [f.id for f, _, _ in rows])
+    return [_serialize_folder(f, count, size, f.id in linked) for f, count, size in rows]
 
 
 class FolderIn(BaseModel):
@@ -420,13 +346,10 @@ def _folder_name(raw: str) -> str:
 def create_folder(
     body: FolderIn, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
-    folder = FileFolder(user_id=user.id, kind=folders.FolderKind.OWN, name=_folder_name(body.name))
     try:
-        with db.begin_nested():
-            db.add(folder)
-            db.flush()
-    except IntegrityError as e:  # the unique (user, lower(name)): one folder per name
-        raise refused(409, "file_folder_name_taken") from e
+        folder = folders.create_own(db, user.id, _folder_name(body.name))
+    except folders.FolderError as e:
+        raise refused(409, e.reason) from e
     audit.record(
         db, user.id, AuditAction.FILE_FOLDER_CREATE, target_type="file_folder", target_id=folder.id
     )
@@ -449,17 +372,13 @@ def update_folder(
 ) -> dict:
     """Rename one of the caller's own folders (a source folder's name is its origin's), and/or set
     how long any of their folders keeps a file (`folders.set_retention`)."""
-    folder = owned_or_404(db, FileFolder, folder_id, user, what="folder")
+    folder = own_folder(db, user, folder_id)
     sent = body.model_fields_set
     if "name" in sent:
-        if folder.kind != folders.FolderKind.OWN:
-            raise refused(409, "file_folder_not_own")
-        folder.name = _folder_name(body.name or "")
         try:
-            with db.begin_nested():
-                db.flush()
-        except IntegrityError as e:
-            raise refused(409, "file_folder_name_taken") from e
+            folders.rename(db, folder, _folder_name(body.name or ""))
+        except folders.FolderError as e:
+            raise refused(409, e.reason) from e
         audit.record(
             db,
             user.id,
@@ -484,18 +403,9 @@ def update_folder(
                 after={"retention_days": body.retention_days},
             )
     db.commit()
-    count, size = _folder_totals(db, folder.id)
-    return _serialize_folder(folder, count, size, folder.id in _linked(db, [folder.id]))
-
-
-def _folder_totals(db: Session, folder_id: int) -> tuple[int, int]:
-    count, size = db.execute(
-        select(func.count(DownloadJob.id), func.coalesce(func.sum(MediaAsset.size_bytes), 0))
-        .select_from(DownloadJob)
-        .outerjoin(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
-        .where(DownloadJob.folder_id == folder_id, DownloadJob.status == JobStatus.DONE)
-    ).one()
-    return count, int(size)
+    count, size = queries.folder_totals(db, folder.id)
+    linked = folder.id in queries.linked_folders(db, [folder.id])
+    return _serialize_folder(folder, count, size, linked)
 
 
 @router.delete("/folders/{folder_id}")
@@ -503,7 +413,7 @@ def delete_folder(
     folder_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
     """Delete one of the caller's own folders; its files go back to their source folders."""
-    folder = owned_or_404(db, FileFolder, folder_id, user, what="folder")
+    folder = own_folder(db, user, folder_id)
     try:
         moved = folders.delete_own(db, folder)
     except folders.FolderError as e:
@@ -545,13 +455,7 @@ def remove_shared_with_me(
     """Remove a file that was shared WITH this user from their 'Shared with me' list. Deletes
     only the recipient's share grant — the owner's job and the physical file are untouched (this is
     a per-user dismissal, not a delete)."""
-    row = db.execute(
-        select(DownloadShare).where(
-            DownloadShare.job_id == job_id, DownloadShare.to_user_id == user.id
-        )
-    ).scalar_one_or_none()
-    if row is not None:
-        db.delete(row)
+    if service.unshare(db, job_id, user):
         db.commit()
     return {"ok": True, "removed": job_id}
 
@@ -580,46 +484,22 @@ def list_files(
             raise refused(403, "api_token_scope")
         if folder_id is not None and folder_id not in listable:
             raise not_found("folder")
-    stmt = (
-        select(DownloadJob)
-        .join(MediaAsset, MediaAsset.id == DownloadJob.asset_id)
-        .where(DownloadJob.status == JobStatus.DONE)
-    )
     shared = scope == "shared"
-    if shared:
-        stmt = stmt.join(DownloadShare, DownloadShare.job_id == DownloadJob.id).where(
-            DownloadShare.to_user_id == user.id
-        )
-    else:
-        stmt = stmt.where(DownloadJob.user_id == user.id)
-        if folder_id is not None:
-            stmt = stmt.where(DownloadJob.folder_id == folder_id)
-        elif listable is not None:
-            stmt = stmt.where(DownloadJob.folder_id.in_(listable))
-    name = func.coalesce(DownloadJob.display_name, MediaAsset.title, "")
-    term = q.strip()
-    if term:
-        like = f"%{like_escape(term)}%"
-        stmt = stmt.where(
-            or_(
-                name.ilike(like),
-                func.coalesce(DownloadJob.display_uploader, MediaAsset.uploader, "").ilike(like),
-            )
-        )
-    # A file is added to its owner's list when it is done, not when it was asked for (a download that
-    # failed for days and then went through is new); one shared with the caller, when it was shared.
-    key = {
-        "added": DownloadShare.created_at if shared else DownloadJob.ready_at,
-        "name": collated(name, lang_for_user(user)),
-        "size": MediaAsset.size_bytes,
-    }[sort]
-    first = key.asc() if order == "asc" else key.desc()
-    tie = DownloadJob.id.asc() if order == "asc" else DownloadJob.id.desc()
-    jobs = db.execute(stmt.order_by(first.nulls_last(), tie).limit(MAX_LIST)).scalars().all()
-    assets = assets_for(db, jobs)
-    positions = positions_for(db, user, jobs)
-    shared_at = _shared_at(db, user, jobs) if shared else {}
-    sources = source_keys(db, jobs)
+    jobs = queries.library(
+        db,
+        user,
+        folder_id=folder_id,
+        listable=listable,
+        shared=shared,
+        term=q.strip(),
+        sort=sort,
+        order=order,
+        lang=lang_for_user(user),
+    )
+    assets = queries.assets_for(db, jobs)
+    positions = queries.positions_for(db, user, jobs)
+    shared_at = queries.shared_at(db, user, jobs) if shared else {}
+    sources = queries.source_keys(db, jobs)
     return [
         {
             **serialize(j, assets.get(j.asset_id) if j.asset_id is not None else None),
@@ -632,36 +512,6 @@ def list_files(
     ]
 
 
-def source_keys(db: Session, jobs: Sequence[DownloadJob]) -> dict[int, str]:
-    """Where each file came from (its source folder's key), for the list's Source column, the
-    "back to its source folder" move and the download tray's site: a file in a source folder has its folder's key; one moved into
-    an own folder (or someone else's, shared) is traced back by `folders.source_key_for`."""
-    ids = {j.folder_id for j in jobs if j.folder_id is not None}
-    by_id = (
-        {f.id: f for f in db.execute(select(FileFolder).where(FileFolder.id.in_(ids))).scalars()}
-        if ids
-        else {}
-    )
-    out: dict[int, str] = {}
-    for j in jobs:
-        folder = by_id.get(j.folder_id) if j.folder_id is not None else None
-        if folder is not None and folder.kind == folders.FolderKind.SOURCE and folder.source_key:
-            out[j.id] = folder.source_key
-        else:
-            out[j.id] = folders.source_key_for(db, j)
-    return out
-
-
-def _shared_at(db: Session, user: User, jobs: Sequence[DownloadJob]) -> dict[int, datetime]:
-    rows = db.execute(
-        select(DownloadShare.job_id, DownloadShare.created_at).where(
-            DownloadShare.to_user_id == user.id,
-            DownloadShare.job_id.in_([j.id for j in jobs]),
-        )
-    ).all()
-    return {job_id: at for job_id, at in rows}
-
-
 _MAX_EXTRA_LINKS = 8
 
 
@@ -709,18 +559,20 @@ def update_file(
     """Rename a file and its channel, set its reference links (all display-only: the file on disk
     keeps its own name), move it to another folder (`folders.move`), or keep it until deleted /
     hand it back to its folder's retention."""
-    job = owned_or_404(db, DownloadJob, job_id, user, what="download")
+    job = own_job(db, user, job_id)
     sent = body.model_fields_set
+    display: dict[str, object] = {}
     if "name" in sent:
-        job.display_name = display_text(body.name)
+        display["display_name"] = display_text(body.name)
     if "uploader" in sent:
-        job.display_uploader = display_text(body.uploader)
+        display["display_uploader"] = display_text(body.uploader)
     if "uploader_url" in sent:
-        job.display_uploader_url = _clean_url(body.uploader_url)
+        display["display_uploader_url"] = _clean_url(body.uploader_url)
     if "extra_links" in sent:
         raw = body.extra_links or []
         cleaned = [u for u in (_clean_url(x) for x in raw) if u][:_MAX_EXTRA_LINKS]
-        job.extra_links = cleaned or None
+        display["extra_links"] = cleaned or None
+    service.set_display(job, **display)
     if "folder_id" in sent:
         if body.folder_id is None:
             raise refused(400, "file_folder_gone")
@@ -766,7 +618,8 @@ def delete_file(
         target_id=job_id,
         summary=caller.via,
     )
-    service.delete(db, job)  # commits, the audit row with it
+    service.delete(db, job)
+    db.commit()  # the audit row with it
     return {"ok": True, "deleted": job_id}
 
 
@@ -785,7 +638,7 @@ def upload_file(
     return serialize_job(db, ingest_spooled(db, upload))
 
 
-def ingest_spooled(db: Session, upload: SpooledUpload) -> DownloadJob:
+def ingest_spooled(db: Session, upload: SpooledUpload) -> "DownloadJob":
     """The spooled upload into the library (`upload.ingest_upload`, which commits its own rows),
     its refusals answered as HTTP."""
     if upload.size == 0:
@@ -809,8 +662,8 @@ def ingest_spooled(db: Session, upload: SpooledUpload) -> DownloadJob:
     return job
 
 
-def _ready_file(db: Session, job: DownloadJob) -> tuple[MediaAsset, Path]:
-    asset = db.get(MediaAsset, job.asset_id) if job.asset_id else None
+def _ready_file(db: Session, job: "DownloadJob") -> tuple["MediaAsset", Path]:
+    asset = queries.asset_of(db, job)
     if asset is None or asset.status != "ready" or not asset.rel_path:
         raise refused(409, "download_not_ready")
     path = storage.safe_abs_path(settings.files_root, asset.rel_path)
@@ -819,7 +672,7 @@ def _ready_file(db: Session, job: DownloadJob) -> tuple[MediaAsset, Path]:
     return asset, path
 
 
-def serve_file(db: Session, job: DownloadJob) -> FileResponse:
+def serve_file(db: Session, job: "DownloadJob") -> FileResponse:
     """The file of `job` (the caller may read it), range-aware, named by the user's display name.
 
     The served Content-Type comes from the ffprobe-verified media_kind + a container allow-list
@@ -837,7 +690,7 @@ def serve_file(db: Session, job: DownloadJob) -> FileResponse:
     if asset.sha256:
         digest = base64.b64encode(bytes.fromhex(asset.sha256)).decode()
         headers["Repr-Digest"] = f"sha-256=:{digest}:"
-    asset.last_access_at = datetime.now(timezone.utc)  # the handler commits it
+    service.touch(asset)  # the handler commits it
     media_type = storage.served_media_type(asset.media_kind, asset.container)
     if media_type is None:
         return FileResponse(
@@ -892,13 +745,13 @@ def preview_file(
         text = preview.text_utf8(head)
         if text is None:
             raise refused(415, "file_no_preview")
-        asset.last_access_at = datetime.now(timezone.utc)
+        service.touch(asset)
         db.commit()
         return Response(text, media_type=preview.media_type(kind, asset.container), headers=headers)
     filename = storage.download_filename(
         job.display_name or asset.title or asset.source_ref, asset.container, path
     )
-    asset.last_access_at = datetime.now(timezone.utc)
+    service.touch(asset)
     db.commit()
     return FileResponse(
         path,
@@ -934,10 +787,6 @@ def get_sha256(
     finally:
         _HASHING.release()
     digest = h.hexdigest()
-    db.execute(
-        update(MediaAsset)
-        .where(MediaAsset.id == asset_id, MediaAsset.sha256.is_(None))
-        .values(sha256=digest)
-    )
+    service.store_sha256(db, asset_id, digest)
     db.commit()
     return {"sha256": digest}

backend/app/routes/public.py

@@ -6,24 +6,26 @@ the app or any account data. Password-protected links exchange the password once
 a short-lived signed grant that the media URL carries (a `<video src>` can't send a header).
 """
 
+from typing import TYPE_CHECKING
+
 from fastapi import APIRouter, Depends, Request
 from fastapi.responses import FileResponse
 from pydantic import BaseModel
-from sqlalchemy import select, update
 from sqlalchemy.orm import Session
 
 from app.config import settings
 from app.db import get_db
 from app.downloads import links as linksmod
-from app.downloads import storage
+from app.downloads import queries, storage
 from app.downloads.status import JobStatus
-from app.models import User
-from app.downloads.models import DownloadJob, DownloadLink, FileFolder, MediaAsset
 from app.ratelimit import RateLimiter, client_key
 from app.security import verify_password
 from app.refusal import refused
 from app.routes._common import not_found
 
+if TYPE_CHECKING:
+    from app.downloads.models import DownloadJob, DownloadLink, FileFolder, MediaAsset
+
 router = APIRouter(prefix="/api/public", tags=["public"])
 
 # Slow password guessing on a link (the token itself is 192-bit, so it needs no throttle). Counted per
@@ -38,26 +40,25 @@ _unlock_limit = RateLimiter(max_events=10, window_seconds=300)
 _unlock_failures = RateLimiter(max_events=50, window_seconds=300)
 
 
-def _link_or_404(db: Session, token: str) -> DownloadLink:
+def _link_or_404(db: Session, token: str) -> "DownloadLink":
     link = linksmod.find(db, token)
     if link is None or linksmod.is_expired(link):
         raise refused(404, "link_gone")
     return link
 
 
-def _being_made(db: Session, job: DownloadJob) -> bool:
+def _being_made(db: Session, job: "DownloadJob") -> bool:
     """The job is running, or queued for a worker that will take it: the worker leaves a suspended
     owner's queued jobs where they are (`worker._claim_job`), as long as the suspension lasts."""
     if job.status == JobStatus.RUNNING:
         return True
     if job.status != JobStatus.QUEUED:
         return False
-    owner = db.get(User, job.user_id)
-    return owner is not None and not owner.is_suspended
+    return not queries.owner_suspended(db, job)
 
 
-def _ready_job(db: Session, job: DownloadJob | None) -> tuple[DownloadJob, MediaAsset]:
-    asset = db.get(MediaAsset, job.asset_id) if job and job.asset_id else None
+def _ready_job(db: Session, job: "DownloadJob | None") -> tuple["DownloadJob", "MediaAsset"]:
+    asset = queries.asset_of(db, job)
     if (
         job is not None
         and asset is not None
@@ -79,25 +80,24 @@ def _ready_job(db: Session, job: DownloadJob | None) -> tuple[DownloadJob, Media
     return job, asset
 
 
-def _ready_target(db: Session, link: DownloadLink) -> tuple[DownloadJob, MediaAsset]:
+def _ready_target(db: Session, link: "DownloadLink") -> tuple["DownloadJob", "MediaAsset"]:
     """A file link's file. A folder link names no one file: its files are asked for by id."""
     if link.job_id is None:
         raise refused(404, "video_gone")
-    return _ready_job(db, db.get(DownloadJob, link.job_id))
+    return _ready_job(db, queries.job(db, link.job_id))
 
 
-def _link_folder(db: Session, link: DownloadLink) -> FileFolder:
-    folder = db.get(FileFolder, link.folder_id) if link.folder_id is not None else None
+def _link_folder(db: Session, link: "DownloadLink") -> "FileFolder":
+    folder = queries.link_folder(db, link)
     if folder is None:
         raise refused(404, "link_gone")
     return folder
 
 
-def _folder_job(db: Session, link: DownloadLink, job_id: int) -> tuple[DownloadJob, MediaAsset]:
-    folder = _link_folder(db, link)
-    job = db.execute(
-        select(DownloadJob).where(DownloadJob.id == job_id, *linksmod.in_folder(folder))
-    ).scalar_one_or_none()
+def _folder_job(
+    db: Session, link: "DownloadLink", job_id: int
+) -> tuple["DownloadJob", "MediaAsset"]:
+    job = queries.folder_job(db, _link_folder(db, link), job_id)
     if job is None:
         raise refused(404, "video_gone")
     return _ready_job(db, job)
@@ -114,7 +114,7 @@ def _file_url(token: str, grant: str | None = None, job_id: int | None = None) -
 
 
 def _poster_url(
-    token: str, asset: MediaAsset, grant: str | None = None, job_id: int | None = None
+    token: str, asset: "MediaAsset", grant: str | None = None, job_id: int | None = None
 ) -> str | None:
     if not asset.poster_path:
         return None
@@ -122,7 +122,7 @@ def _poster_url(
     return f"{url}?g={grant}" if grant else url
 
 
-def _folder_meta(db: Session, link: DownloadLink, token: str, grant: str | None) -> dict:
+def _folder_meta(db: Session, link: "DownloadLink", token: str, grant: str | None) -> dict:
     """A folder link's page: the folder's name and each file's own watch metadata
     (`linksmod.folder_files`: ready, on disk, newest first)."""
     folder = _link_folder(db, link)
@@ -148,7 +148,7 @@ def _folder_meta(db: Session, link: DownloadLink, token: str, grant: str | None)
     }
 
 
-def _file_meta(db: Session, link: DownloadLink, token: str, grant: str | None) -> dict:
+def _file_meta(db: Session, link: "DownloadLink", token: str, grant: str | None) -> dict:
     job, asset = _ready_target(db, link)
     return {
         "needs_password": False,
@@ -159,20 +159,14 @@ def _file_meta(db: Session, link: DownloadLink, token: str, grant: str | None) -
     }
 
 
-def _opened(db: Session, link: DownloadLink, token: str, grant: str | None = None) -> dict:
+def _opened(db: Session, link: "DownloadLink", token: str, grant: str | None = None) -> dict:
     """The page an open link shows, counted as one view (the handler commits the count)."""
     meta = (
         _folder_meta(db, link, token, grant)
         if link.folder_id is not None
         else _file_meta(db, link, token, grant)
     )
-    # In SQL, not `+= 1` on the loaded row: two opens at once would both write the same count.
-    db.execute(
-        update(DownloadLink)
-        .where(DownloadLink.id == link.id)
-        .values(view_count=DownloadLink.view_count + 1)
-        .execution_options(synchronize_session=False)
-    )
+    linksmod.count_view(db, link)
     return meta
 
 
@@ -218,13 +212,13 @@ def watch_unlock(
     return {"ok": True, **meta}
 
 
-def _granted(link: DownloadLink, token: str, g: str | None) -> None:
+def _granted(link: "DownloadLink", token: str, g: str | None) -> None:
     """A password link's files want the grant its unlock handed out."""
     if link.password_hash and not linksmod.check_grant(token, g, link.password_version):
         raise refused(403, "share_password_required")
 
 
-def _serve(link: DownloadLink, asset: MediaAsset) -> FileResponse:
+def _serve(link: "DownloadLink", asset: "MediaAsset") -> FileResponse:
     """Range-aware stream of a shared file. Inline by default (plays in the page); an
     `allow_download` link serves it as an attachment."""
     path = storage.safe_abs_path(settings.files_root, asset.rel_path)
@@ -253,7 +247,7 @@ def _serve(link: DownloadLink, asset: MediaAsset) -> FileResponse:
     )
 
 
-def _poster(asset: MediaAsset) -> FileResponse:
+def _poster(asset: "MediaAsset") -> FileResponse:
     if not asset.poster_path:
         raise not_found("poster")
     path = storage.safe_abs_path(settings.files_root, asset.poster_path)

backend/app/routes/tokens.py

@@ -21,9 +21,8 @@ from app.apitokens import GRANT_COLUMNS, Right
 from app.audit import AuditAction
 from app.auth import current_user
 from app.db import get_db
-from app.downloads import folders
+from app.downloads import folders, queries
 from app.models import ApiToken, ApiTokenGrant, User
-from app.downloads.models import FileFolder
 from app.refusal import refused
 from app.routes._common import owned_or_404
 from app.security import hash_token
@@ -51,12 +50,16 @@ class TokenIn(BaseModel):
 
 
 def _serialize(db: Session, token: ApiToken) -> dict:
-    rows = db.execute(
-        select(ApiTokenGrant, FileFolder)
-        .join(FileFolder, FileFolder.id == ApiTokenGrant.folder_id)
-        .where(ApiTokenGrant.token_id == token.id)
-        .order_by(FileFolder.id)
-    ).all()
+    grants = list(
+        db.execute(
+            select(ApiTokenGrant)
+            .where(ApiTokenGrant.token_id == token.id)
+            .order_by(ApiTokenGrant.folder_id)
+        ).scalars()
+    )
+    # The folders are Capture's: read through its queries, not its table.
+    by_id = queries.folders_by_id(db, {g.folder_id for g in grants})
+    rows = [(g, by_id[g.folder_id]) for g in grants if g.folder_id in by_id]
     now = datetime.now(timezone.utc)
     return {
         "id": token.id,

backend/app/userscope.py

@@ -1,13 +1,54 @@
-"""Shared "who is an active, non-suspended account" predicate.
+"""Whose a row is, and who an account is to the others — one place for both.
 
-Used wherever a user must be filtered out of a recipient list or rejected as a target: the download
-share-by-email and recipient-picker endpoints. Kept in one place so the two forms (SQL clauses for a
-query, Python check for a loaded row) can't drift apart, and so a route module doesn't have to import
-another route module just to reuse the rule.
+**Ownership.** A user-owned table says whose a row is in one column (`user_id`, or `to_user_id` for
+something handed to them). A unit's reads and writes name that column through `owned_by` and fetch a
+row by id through `owned_row`, never with an inline `Model.user_id == …`: the rule "a row owned by
+someone else is answered like a missing one" then lives here, and a contract test
+(`test_unit_fences.py`) holds a switched-on unit to it.
+
+**Recipients.** "An active, non-suspended account" — the download share-by-email and the recipient
+picker filter on it. Kept here so the two forms (SQL clauses for a query, a Python check for a loaded
+row) can't drift apart.
 """
 
+from typing import Any, TypeVar
+
+from sqlalchemy import ColumnElement, func, select
+from sqlalchemy.orm import InstrumentedAttribute, Session
+
+from app.collation import collated
+from app.db import Base
 from app.models import User
 
+M = TypeVar("M", bound=Base)
+
+
+def _owner_id(owner: User | int) -> int:
+    return owner if isinstance(owner, int) else owner.id
+
+
+def owned_by(column: InstrumentedAttribute, owner: User | int) -> ColumnElement[bool]:
+    """`column` — a table's owner column — names `owner`."""
+    return column == _owner_id(owner)
+
+
+def owned_row(
+    db: Session,
+    model: type[M],
+    id_: Any,
+    owner: User | int,
+    *,
+    owner_attr: str = "user_id",
+    lock: bool = False,
+) -> M | None:
+    """The row of `model` with this primary key when `owner` owns it, else None — a row of someone
+    else's is the same answer as a missing one, so a caller can never tell the two apart. `lock`
+    takes it FOR UPDATE (past the identity map)."""
+    row = db.get(model, id_, with_for_update=True if lock else None)
+    if row is None or getattr(row, owner_attr) != _owner_id(owner):
+        return None
+    return row
+
 
 def messageable_clauses() -> list:
     """SQL clauses for "an active, non-suspended account" — splat into a recipient query."""
@@ -20,3 +61,30 @@ def messageable_clauses() -> list:
 def is_messageable_user(u: User | None) -> bool:
     """Python mirror of `messageable_clauses()` for an already-loaded row (a share recipient)."""
     return bool(u and u.is_active and not u.is_suspended)
+
+
+def user_by_email(db: Session, email: str) -> User | None:
+    """The account with this address, matched without regard to case."""
+    return db.execute(
+        select(User).where(func.lower(User.email) == email.strip().lower())
+    ).scalar_one_or_none()
+
+
+def messageable_others(db: Session, user: User, lang: str) -> list[User]:
+    """Every account `user` may hand something to: active, not suspended, not themselves; in the
+    reader's alphabet by address."""
+    return list(
+        db.execute(
+            select(User)
+            .where(User.id != user.id, *messageable_clauses())
+            .order_by(collated(User.email, lang))
+        ).scalars()
+    )
+
+
+def emails_of(db: Session, ids: set[int] | None = None) -> dict[int, str]:
+    """Each account's address by id, in address order: these ids, or every account."""
+    stmt = select(User.id, User.email).order_by(User.email)
+    if ids is not None:
+        stmt = stmt.where(User.id.in_(ids))
+    return dict(db.execute(stmt).tuples().all())