siftlode/backend/tests/test_playlist_move.py

"""E10 S2 — the one-step "move this video to another list" endpoint, and the `updated_at` touch
the rail's "recently changed" sort reads.

Two properties are load-bearing and neither is visible from the happy path alone:

1. **The move is one transaction.** The client-side shape it replaces (add to the target, then
   remove from the source) leaves the video in BOTH lists when the second call fails. So the
   tests assert the *pair* of lists after every call, never just the destination.
2. **`updated_at` tracks item edits.** `UpdatedAtMixin.onupdate` only fires on an UPDATE of the
   playlist row, and add/remove/reorder/move write `playlist_items` — so the timestamp is bumped
   explicitly, and a regression there would silently degrade the sort to "renames only".
"""

from datetime import datetime, timedelta, timezone

from app.models import Channel, Playlist, PlaylistItem, Video


def _seed_videos(db, ids):
    db.add(Channel(id="UCtest", title="Test"))
    now = datetime.now(timezone.utc)
    for v in ids:
        db.add(Video(id=v, channel_id="UCtest", published_at=now))
    db.commit()


def _playlist(db, user, name, video_ids, **kw):
    pl = Playlist(user_id=user.id, name=name, **kw)
    db.add(pl)
    db.flush()
    for i, vid in enumerate(video_ids):
        db.add(PlaylistItem(playlist_id=pl.id, video_id=vid, position=i))
    db.commit()
    return pl


def _ids(db, pl_id):
    return [
        it.video_id
        for it in db.execute(
            PlaylistItem.__table__.select()
            .where(PlaylistItem.playlist_id == pl_id)
            .order_by(PlaylistItem.position)
        ).all()
    ]


def _move(client, src, video_id, dst):
    return client.post(
        f"/api/playlists/{src}/items/{video_id}/move", json={"target_playlist_id": dst}
    )


def test_move_leaves_the_video_in_exactly_one_list(db, make_user, as_user):
    user = make_user()
    _seed_videos(db, ["v1", "v2"])
    src = _playlist(db, user, "Source", ["v1", "v2"])
    dst = _playlist(db, user, "Target", [])

    r = _move(as_user(user), src.id, "v1", dst.id)
    assert r.status_code == 200
    assert r.json() == {
        "ok": True,
        "from_playlist_id": src.id,
        "to_playlist_id": dst.id,
        "video_id": "v1",
    }
    db.expire_all()
    assert _ids(db, src.id) == ["v2"]
    assert _ids(db, dst.id) == ["v1"]


def test_move_appends_to_the_end_of_the_target(db, make_user, as_user):
    user = make_user()
    _seed_videos(db, ["v1", "v2", "v3"])
    src = _playlist(db, user, "Source", ["v3"])
    dst = _playlist(db, user, "Target", ["v1", "v2"])

    assert _move(as_user(user), src.id, "v3", dst.id).status_code == 200
    db.expire_all()
    assert _ids(db, dst.id) == ["v1", "v2", "v3"]


def test_move_into_a_list_that_already_has_it_is_a_removal_not_a_duplicate(db, make_user, as_user):
    user = make_user()
    _seed_videos(db, ["v1"])
    src = _playlist(db, user, "Source", ["v1"])
    dst = _playlist(db, user, "Target", ["v1"])

    assert _move(as_user(user), src.id, "v1", dst.id).status_code == 200
    db.expire_all()
    assert _ids(db, src.id) == []
    assert _ids(db, dst.id) == ["v1"]  # exactly one row, not two


def test_move_to_the_same_list_is_refused(db, make_user, as_user):
    user = make_user()
    _seed_videos(db, ["v1"])
    src = _playlist(db, user, "Source", ["v1"])

    r = _move(as_user(user), src.id, "v1", src.id)
    assert r.status_code == 400
    assert r.json()["detail"] == {"code": "playlist_move", "reason": "same_playlist"}
    db.expire_all()
    assert _ids(db, src.id) == ["v1"]


def test_move_of_a_video_that_left_the_source_reports_it(db, make_user, as_user):
    user = make_user()
    _seed_videos(db, ["v1"])
    src = _playlist(db, user, "Source", [])
    dst = _playlist(db, user, "Target", [])

    r = _move(as_user(user), src.id, "v1", dst.id)
    assert r.status_code == 404
    assert r.json()["detail"] == {"code": "playlist_move", "reason": "not_in_playlist"}


def test_move_into_someone_elses_list_404s_and_changes_nothing(db, make_user, as_user):
    user, other = make_user(), make_user()
    _seed_videos(db, ["v1"])
    src = _playlist(db, user, "Mine", ["v1"])
    theirs = _playlist(db, other, "Theirs", [])

    assert _move(as_user(user), src.id, "v1", theirs.id).status_code == 404
    db.expire_all()
    assert _ids(db, src.id) == ["v1"]
    assert _ids(db, theirs.id) == []


def test_a_list_that_is_not_yours_answers_with_a_reason_the_ui_can_translate(
    db, make_user, as_user
):
    # The one 404 a user meets in practice (the list went away in another tab). It used to be a bare
    # English "Unknown playlist", which the Hungarian UI then showed verbatim.
    user, other = make_user(), make_user()
    _seed_videos(db, ["v1"])
    theirs = _playlist(db, other, "Theirs", ["v1"])

    r = as_user(user).delete(f"/api/playlists/{theirs.id}/items/v1")
    assert r.status_code == 404
    assert r.json()["detail"] == {"code": "not_found", "reason": "playlist"}
    db.expire_all()
    assert _ids(db, theirs.id) == ["v1"]


def test_a_move_into_a_list_that_is_gone_names_the_target_not_the_list_on_screen(
    db, make_user, as_user
):
    # Both lists 404'd with the same reason, which the UI reads as "THIS playlist doesn't exist any
    # more" — said about the source the reader is looking at, which is still there.
    user = make_user()
    _seed_videos(db, ["v1"])
    src = _playlist(db, user, "Mine", ["v1"])
    gone = _playlist(db, user, "Gone", [])
    gone_id = gone.id
    db.delete(gone)
    db.commit()

    r = _move(as_user(user), src.id, "v1", gone_id)
    assert r.status_code == 404
    assert r.json()["detail"] == {"code": "not_found", "reason": "move_target"}
    db.expire_all()
    assert _ids(db, src.id) == ["v1"]


def test_a_refused_playlist_action_answers_with_a_reason_the_ui_can_translate(
    db, make_user, as_user
):
    # The rest of the router's refusals were bare English too ("The Watch later list can't be
    # deleted.", "YouTube delete failed.", ...), shown verbatim under the Hungarian UI.
    user = make_user()
    client = as_user(user)
    wl = client.post("/api/playlists/watch-later", json={"video_id": "nope"})
    assert wl.status_code == 404
    assert wl.json()["detail"] == {"code": "not_found", "reason": "video"}
    _seed_videos(db, ["v1"])
    saved = client.post("/api/playlists/watch-later", json={"video_id": "v1"})
    wl_id = saved.json()["playlist_id"]
    r = client.delete(f"/api/playlists/{wl_id}")
    assert r.status_code == 400
    assert r.json()["detail"] == {"code": "playlist", "reason": "watch_later_undeletable"}


def test_move_marks_both_linked_sides_dirty(db, make_user, as_user):
    """A move edits two YouTube mirrors at once — the source lost an item, the target gained one.
    Marking only the source is the asymmetric fix this repo keeps re-learning."""
    user = make_user()
    _seed_videos(db, ["v1"])
    src = _playlist(db, user, "Src", ["v1"], yt_playlist_id="PLsrc", synced_video_ids='["v1"]')
    dst = _playlist(db, user, "Dst", [], yt_playlist_id="PLdst", synced_video_ids="[]")
    # Baseline: both are in sync with YouTube before the move.
    src.dirty = False
    dst.dirty = False
    db.commit()

    assert _move(as_user(user), src.id, "v1", dst.id).status_code == 200
    db.expire_all()
    assert db.get(Playlist, src.id).dirty is True
    assert db.get(Playlist, dst.id).dirty is True


def test_item_edits_bump_updated_at(db, make_user, as_user):
    """The rail's "recently changed first" sort reads this. Adding, moving and reordering all
    write `playlist_items` only, so nothing here is covered by the ORM's `onupdate`."""
    user = make_user()
    _seed_videos(db, ["v1", "v2"])
    src = _playlist(db, user, "Source", ["v1", "v2"])
    dst = _playlist(db, user, "Target", [])
    old = datetime.now(timezone.utc) - timedelta(days=3)
    src.updated_at = old
    dst.updated_at = old
    db.commit()
    client = as_user(user)

    assert client.post(f"/api/playlists/{dst.id}/items", json={"video_id": "v1"}).status_code == 200
    db.expire_all()
    assert db.get(Playlist, dst.id).updated_at > old

    dst.updated_at = old
    db.commit()
    assert (
        client.put(f"/api/playlists/{src.id}/order", json={"video_ids": ["v2", "v1"]}).status_code
        == 200
    )
    db.expire_all()
    assert db.get(Playlist, src.id).updated_at > old

    src.updated_at = old
    dst.updated_at = old
    db.commit()
    assert _move(client, src.id, "v2", dst.id).status_code == 200
    db.expire_all()
    # BOTH sides of a move are "recently changed" — the target is where the reader will look.
    assert db.get(Playlist, src.id).updated_at > old
    assert db.get(Playlist, dst.id).updated_at > old

    # …and removing one, the fourth item-only write (it had no test: E10 review coverage debt).
    src.updated_at = old
    db.commit()
    assert client.delete(f"/api/playlists/{src.id}/items/v1").status_code == 200
    db.expire_all()
    assert db.get(Playlist, src.id).updated_at > old


def test_the_list_endpoint_publishes_updated_at(db, make_user, as_user):
    user = make_user()
    _playlist(db, user, "Solo", [])
    rows = as_user(user).get("/api/playlists").json()
    assert len(rows) == 1
    assert rows[0]["updated_at"]  # the rail cannot sort by a field the API never sends


def test_a_target_that_already_had_it_is_not_recently_changed(db, make_user, as_user):
    """Moving into a list that already holds the video only removes it from the source: the
    target did not change, and bumping it promoted an untouched list in the rail's sort."""
    user = make_user()
    _seed_videos(db, ["v1"])
    src = _playlist(db, user, "Source", ["v1"])
    dst = _playlist(db, user, "Target", ["v1"])
    old = datetime.now(timezone.utc) - timedelta(days=3)
    src.updated_at = old
    dst.updated_at = old
    db.commit()

    assert _move(as_user(user), src.id, "v1", dst.id).status_code == 200
    db.expire_all()
    assert db.get(Playlist, src.id).updated_at > old
    assert db.get(Playlist, dst.id).updated_at == old


def test_a_concurrent_add_to_the_target_lands_as_the_already_present_move(
    db, make_user, as_user, monkeypatch
):
    """The already-in-target check is a read, not a lock: another tab's add (or the scheduler's
    YouTube merge) can commit the same video to the target in between, and the re-parent then
    hits uq_playlist_video. That is the idempotent outcome arriving late — not a raw 500."""
    from app.db import SessionLocal
    from app.routes import playlists as plroutes

    user = make_user()
    _seed_videos(db, ["v1"])
    src = _playlist(db, user, "Source", ["v1"])
    dst = _playlist(db, user, "Target", [])
    real = plroutes._next_item_position

    def add_first(session, playlist_id):
        with SessionLocal() as other:  # the other tab, committing between check and re-parent
            other.add(PlaylistItem(playlist_id=dst.id, video_id="v1", position=0))
            other.commit()
        return real(session, playlist_id)

    monkeypatch.setattr(plroutes, "_next_item_position", add_first)
    assert _move(as_user(user), src.id, "v1", dst.id).status_code == 200
    db.expire_all()
    assert _ids(db, src.id) == []
    assert _ids(db, dst.id) == ["v1"]