siftlode/backend/app/routes/plex/discover.py

"""Plex Discover: the rail-surface read-model (E5 S4).

A consolidated payload for the dedicated Discover landing — a stack of horizontal rails:
Continue watching · Recently added · Browse-by-genre tiles · Because you watched X — plus a
separate, reshuffling Surprise-me sample. Serve-from-DB only: the recommendation rail reads the
recs the S2 TMDB engine already persisted (`PlexItem.recommendations`), never a live TMDB call, and
every card comes from the same `movie_card`/`show_card` serializers the grid uses (so rails inherit
S1's `art` + S3's rating/summary for free). The rails carry EN metadata (like the other non-grid
card paths); the HU overlay coalesces only in the main grid.

The sidebar metadata filters (genre / rating / year / collection / …) narrow EVERY rail too, so the
Discover surface behaves like the Browse grid — the same `LibraryFilters` / `meta_filter_conds` the
grid uses, applied to each rail's movie + show query (a rail may legitimately come back empty, which
the client hides). Genre-language matches the grid; duration is movie-only.
"""

from fastapi import APIRouter, Depends, Query
from sqlalchemy import and_, func, or_, select
from sqlalchemy.orm import Session

from app.auth import current_user
from app.db import get_db
from app.models import PlexItem, PlexShow, PlexState, User
from app.plex import rollup
from app.plex.cards import movie_card, show_card
from app.plex.query import (
    LibraryFilters,
    apply_meta_filters,
    apply_show_state_filter,
    genres_col,
    meta_filter_conds,
    top_art_keys,
)
from app.plex.tmdb import resolve_recs
from app.routes.plex._shared import _content_libs, _norm_lang

router = APIRouter(prefix="/api/plex", tags=["plex"])

RAIL_LIMIT = 20
GENRE_TILES = 12


def _scope_libs(db: Session, scope: str) -> tuple[list[int], list[int]]:
    """The movie/show library ids visible for this scope (empty list = out of scope)."""
    movie_ids, show_ids = _content_libs(db)
    return (
        movie_ids if scope in ("movie", "both") else [],
        show_ids if scope in ("show", "both") else [],
    )


def _movie_meta(q, p: dict, lang: str, f: LibraryFilters):
    """Apply the shared metadata filters + movie-only duration to a movie query (same as the grid)."""
    q = apply_meta_filters(q, PlexItem, p, lang)
    if f.duration_min is not None:
        q = q.where(PlexItem.duration_s >= f.duration_min)
    if f.duration_max is not None:
        q = q.where(PlexItem.duration_s <= f.duration_max)
    return q


def _movie_cards(db: Session, uid: int, items: list[PlexItem]) -> list[dict]:
    sts = rollup.item_state_map(db, uid, [it.id for it in items])
    return [movie_card(it, sts.get(it.id)) for it in items]


def _show_cards(db: Session, uid: int, shows: list[PlexShow]) -> list[dict]:
    statuses = rollup.state_map(db, uid, [s.id for s in shows])
    return [show_card(s, statuses.get(s.id, "new")) for s in shows]


def _recently_added(
    db: Session, uid: int, movie_ids: list[int], show_ids: list[int], p: dict, lang: str, f: LibraryFilters
) -> list[dict]:
    """Newest movies + shows, interleaved by `added_at` desc into one rail."""
    movies = (
        db.execute(
            _movie_meta(
                select(PlexItem).where(
                    PlexItem.kind == "movie", PlexItem.library_id.in_(movie_ids)
                ),
                p, lang, f,
            )
            .order_by(PlexItem.added_at.desc().nullslast())
            .limit(RAIL_LIMIT)
        ).scalars().all()
        if movie_ids
        else []
    )
    shows = (
        db.execute(
            apply_meta_filters(
                select(PlexShow).where(PlexShow.library_id.in_(show_ids)), PlexShow, p, lang
            )
            .order_by(PlexShow.added_at.desc().nullslast())
            .limit(RAIL_LIMIT)
        ).scalars().all()
        if show_ids
        else []
    )
    # Merge the two type-homogeneous lists by added_at, then serialize each side in one batch so the
    # per-card state lookups stay batched (no N+1). The `(is not None, value)` key sorts a missing
    # timestamp last under reverse.
    tagged = [(m.added_at, "movie", m) for m in movies] + [
        (s.added_at, "show", s) for s in shows
    ]
    tagged.sort(key=lambda t: (t[0] is not None, t[0]), reverse=True)
    top = tagged[:RAIL_LIMIT]
    # Key the serialized cards back by rating_key (globally unique in Plex — a movie and a show never
    # share one), so the merge doesn't depend on object identity staying alive.
    top_movies = [o for _, kind, o in top if kind == "movie"]
    top_shows = [o for _, kind, o in top if kind == "show"]
    mcards = {m.rating_key: c for m, c in zip(top_movies, _movie_cards(db, uid, top_movies))}
    scards = {s.rating_key: c for s, c in zip(top_shows, _show_cards(db, uid, top_shows))}
    return [
        mcards[o.rating_key] if kind == "movie" else scards[o.rating_key]
        for _, kind, o in top
    ]


def _continue_watching(
    db: Session, uid: int, movie_ids: list[int], show_ids: list[int], p: dict, lang: str, f: LibraryFilters
) -> list[dict]:
    """Resume rail: in-progress movies + partially-watched shows, most-recently-progressed first.
    A movie's resume time is its own `progress_updated_at`; a show's is the max across its episodes."""
    rows: list[tuple[object, dict]] = []  # (resumed_at, card)

    if movie_ids:
        mq = (
            select(PlexItem, PlexState)
            .join(
                PlexState,
                and_(PlexState.item_id == PlexItem.id, PlexState.user_id == uid),
            )
            .where(
                PlexItem.kind == "movie",
                PlexItem.library_id.in_(movie_ids),
                PlexState.position_seconds > 0,
                # A NULL status is still "started" (mirrors apply_movie_state_filter's in_progress) —
                # `notin_` alone would drop it, since `NULL NOT IN (...)` is NULL, not TRUE.
                or_(
                    PlexState.status.is_(None),
                    PlexState.status.notin_(["watched", "hidden"]),
                ),
            )
        )
        mrows = db.execute(
            _movie_meta(mq, p, lang, f)
            .order_by(PlexState.progress_updated_at.desc().nullslast())
            .limit(RAIL_LIMIT)
        ).all()
        for it, st in mrows:
            rows.append((st.progress_updated_at, movie_card(it, st)))

    if show_ids:
        # Reuse the shared per-show episode rollup (total/watched/inprog) rather than re-inlining it, plus
        # its `resumed_at` = max(progress_updated_at); the in-progress predicate comes from the same shared
        # `apply_show_state_filter` the grid uses, so the rail can't drift from the grid's definition.
        prog = rollup.agg_subquery(db, uid, include_resumed=True).subquery()
        sq = apply_show_state_filter(
            select(PlexShow, prog.c.resumed_at).join(prog, prog.c.show_id == PlexShow.id),
            prog.c.total,
            prog.c.watched,
            prog.c.inprog,
            "in_progress",
        ).where(PlexShow.library_id.in_(show_ids))
        srows = db.execute(
            apply_meta_filters(sq, PlexShow, p, lang)
            .order_by(prog.c.resumed_at.desc().nullslast())
            .limit(RAIL_LIMIT)
        ).all()
        for sh, resumed_at in srows:
            rows.append((resumed_at, show_card(sh, "in_progress")))

    rows.sort(key=lambda r: (r[0] is not None, r[0]), reverse=True)
    return [card for _, card in rows[:RAIL_LIMIT]]


def _genre_tiles(
    db: Session, movie_ids: list[int], show_ids: list[int], p: dict, lang: str
) -> list[dict]:
    """The most-common genres across the scope, as {value, count} tiles → tap to filter the grid.
    The genre vocabulary is language-specific (coalesce(genres_hu, genres) in HU), matching the grid.
    The active metadata filters narrow the counts too, so the tiles agree with the filtered rails."""
    counts: dict[str, int] = {}
    for model, ids in ((PlexItem, movie_ids), (PlexShow, show_ids)):
        if not ids:
            continue
        gcol = genres_col(model, lang)
        base = select(func.jsonb_array_elements_text(gcol).label("g")).where(
            model.library_id.in_(ids),
            func.jsonb_typeof(gcol) == "array",
            *meta_filter_conds(model, p, lang),
        )
        if model is PlexItem:
            base = base.where(model.kind == "movie")
        expanded = base.subquery()
        for g, c in db.execute(
            select(expanded.c.g, func.count()).group_by(expanded.c.g)
        ).all():
            counts[g] = counts.get(g, 0) + c
    top = sorted(counts.items(), key=lambda kv: (-kv[1], kv[0]))[:GENRE_TILES]
    # A 2×2 poster collage per tile: the top movies in that genre (color hash is the client fallback).
    art = top_art_keys(
        db,
        PlexItem,
        movie_ids,
        genres_col(PlexItem, lang),
        [g for g, _ in top],
        extra_conds=(PlexItem.kind == "movie", *meta_filter_conds(PlexItem, p, lang)),
    )
    return [{"value": g, "count": c, "art": art.get(g, [])} for g, c in top]


def _because_you_watched(
    db: Session, uid: int, movie_ids: list[int], show_ids: list[int], p: dict, lang: str, f: LibraryFilters
) -> dict | None:
    """Recommendations anchored on the user's most-recently-watched, TMDB-enriched movie. Only the
    recs that resolve to OUR library (by guid) become cards — the rest aren't actionable here. Returns
    None (rail hidden) when there's no enriched watch history or none of its recs are in the library.
    The metadata filters narrow the resolved recs (not the anchor pick) so the rail matches the grid."""
    if not movie_ids:
        return None
    anchor = db.execute(
        select(PlexItem)
        .join(
            PlexState,
            and_(PlexState.item_id == PlexItem.id, PlexState.user_id == uid),
        )
        .where(
            PlexItem.kind == "movie",
            PlexItem.library_id.in_(movie_ids),
            PlexState.status == "watched",
            PlexItem.recommendations.isnot(None),
        )
        .order_by(PlexState.watched_at.desc().nullslast())
        .limit(1)
    ).scalars().first()
    if anchor is None:
        return None
    resolved = resolve_recs(db, anchor.recommendations)
    # Preserve TMDB's recommendation order, keep only in-library hits, and drop the anchor itself.
    rks = [
        r["rating_key"]
        for r in resolved
        if r.get("in_library") and r.get("rating_key") != anchor.rating_key
    ]
    if not rks:
        return None
    movies = {
        m.rating_key: m
        for m in db.execute(
            _movie_meta(
                select(PlexItem).where(
                    PlexItem.kind == "movie", PlexItem.rating_key.in_(rks)
                ),
                p, lang, f,
            )
        ).scalars().all()
    }
    shows = {
        s.rating_key: s
        for s in db.execute(
            apply_meta_filters(
                select(PlexShow).where(PlexShow.rating_key.in_(rks)), PlexShow, p, lang
            )
        ).scalars().all()
    }
    ordered_movies = [movies[rk] for rk in rks if rk in movies]
    ordered_shows = [shows[rk] for rk in rks if rk in shows]
    # rating_key is globally unique in Plex, so it keys the serialized cards back safely (no id()).
    mcards = {m.rating_key: c for m, c in zip(ordered_movies, _movie_cards(db, uid, ordered_movies))}
    scards = {s.rating_key: c for s, c in zip(ordered_shows, _show_cards(db, uid, ordered_shows))}
    items: list[dict] = []
    for rk in rks:
        if rk in mcards:
            items.append(mcards[rk])
        elif rk in scards:
            items.append(scards[rk])
    if not items:
        return None
    return {"anchor": {"id": anchor.rating_key, "title": anchor.title}, "items": items}


@router.get("/discover")
def discover(
    scope: str = "both",
    lang: str = "en",
    f: LibraryFilters = Depends(),
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    """The Discover landing payload — every rail in one pass (serve-from-DB), narrowed by the active
    sidebar filters. Empty rails come back as empty lists (the client hides them); `because_you_watched`
    is null when there's no anchor."""
    lang = _norm_lang(lang)
    p = f.as_dict()
    movie_ids, show_ids = _scope_libs(db, scope)
    return {
        "scope": scope,
        "continue_watching": _continue_watching(db, user.id, movie_ids, show_ids, p, lang, f),
        "recently_added": _recently_added(db, user.id, movie_ids, show_ids, p, lang, f),
        "genres": _genre_tiles(db, movie_ids, show_ids, p, lang),
        "because_you_watched": _because_you_watched(db, user.id, movie_ids, show_ids, p, lang, f),
    }


@router.get("/surprise")
def surprise(
    scope: str = "both",
    lang: str = "en",
    limit: int = Query(default=RAIL_LIMIT, ge=1, le=40),
    f: LibraryFilters = Depends(),
    user: User = Depends(current_user),
    db: Session = Depends(get_db),
) -> dict:
    """A fresh random sample for the reshuffling Surprise-me rail (a random draw each call), narrowed by
    the active filters. Movies and shows are drawn separately then interleaved so a lopsided library
    doesn't crowd out one type."""
    lang = _norm_lang(lang)
    p = f.as_dict()
    movie_ids, show_ids = _scope_libs(db, scope)
    movies = (
        db.execute(
            _movie_meta(
                select(PlexItem).where(
                    PlexItem.kind == "movie", PlexItem.library_id.in_(movie_ids)
                ),
                p, lang, f,
            )
            .order_by(func.random())
            .limit(limit)
        ).scalars().all()
        if movie_ids
        else []
    )
    shows = (
        db.execute(
            apply_meta_filters(
                select(PlexShow).where(PlexShow.library_id.in_(show_ids)), PlexShow, p, lang
            )
            .order_by(func.random())
            .limit(limit)
        ).scalars().all()
        if show_ids
        else []
    )
    mcards = _movie_cards(db, user.id, movies)
    scards = _show_cards(db, user.id, shows)
    # Interleave movie/show cards, then trim to `limit`.
    items: list[dict] = []
    for i in range(max(len(mcards), len(scards))):
        if i < len(mcards):
            items.append(mcards[i])
        if i < len(scards):
            items.append(scards[i])
    return {"scope": scope, "items": items[:limit]}