"""Roll a show's episodes up into a single watch-state (new | in_progress | watched) + on-deck.

Drives the show/season grid badges and the Resume / Play-from-start / mark-all buttons.
"""

from sqlalchemy import and_, case, func, or_, select
from sqlalchemy.orm import Session, aliased

from app.models import PlexItem, PlexState


def show_status(total: int, watched: int, inprog: int) -> str:
    """Roll a show's episodes up into a single watch state: fully watched, partially started, or new."""
    if total and watched >= total:
        return "watched"
    if (watched or 0) > 0 or (inprog or 0) > 0:
        return "in_progress"
    return "new"


def rollup(cards: list[dict]) -> dict:
    """From ORDERED episode cards → the aggregate watch status, the "on deck" episode to Resume (the
    last in-progress one, else the first unwatched), the first episode (for Play from the start), and
    the episode count. Drives the show/season Resume + Play + mark-all buttons."""
    total = len(cards)
    watched = sum(1 for c in cards if c.get("status") == "watched")
    inprog = [
        c for c in cards if (c.get("position_seconds") or 0) > 0 and c.get("status") != "watched"
    ]
    resume = None
    if inprog:
        resume = inprog[-1]  # continue the latest-started episode
    else:
        resume = next((c for c in cards if c.get("status") != "watched"), None)
    return {
        "status": show_status(total, watched, len(inprog)),
        "resume": resume,
        "first": cards[0] if cards else None,
        "episode_count": total,
    }


def agg_subquery(db: Session, user_id: int, include_resumed: bool = False):
    """Per-show episode counts for a user: total, watched, in-progress. Reused to (a) filter the show
    grid by aggregate watch-state, (b) compute each card's badge, and (c) drive the Discover
    continue-watching rail. `include_resumed` adds `resumed_at` = max(progress_updated_at) across the
    show's episodes, so the rail can order shows by how recently they were last progressed."""
    ps = aliased(PlexState)
    cols = [
        PlexItem.show_id.label("show_id"),
        func.count(PlexItem.id).label("total"),
        func.count(case((ps.status == "watched", 1))).label("watched"),
        func.count(
            case(
                (
                    and_(
                        ps.position_seconds > 0,
                        or_(ps.status.is_(None), ps.status != "watched"),
                    ),
                    1,
                )
            )
        ).label("inprog"),
    ]
    if include_resumed:
        cols.append(func.max(ps.progress_updated_at).label("resumed_at"))
    return (
        select(*cols)
        .outerjoin(ps, and_(ps.item_id == PlexItem.id, ps.user_id == user_id))
        .where(PlexItem.kind == "episode", PlexItem.show_id.isnot(None))
        .group_by(PlexItem.show_id)
    )


def state_map(db: Session, user_id: int, show_ids: list[int]) -> dict[int, str]:
    if not show_ids:
        return {}
    rows = db.execute(agg_subquery(db, user_id).where(PlexItem.show_id.in_(show_ids))).all()
    return {r.show_id: show_status(r.total, r.watched, r.inprog) for r in rows}


def item_state_map(db: Session, user_id: int, item_ids: list[int]) -> dict[int, PlexState]:
    """A user's PlexState rows for a set of leaf items (movies or episodes), keyed by item_id — the
    leaf analogue of `state_map` (which rolls a show's episodes up to a status string). One batched
    fetch, so the caller serializes cards without a per-card query. Empty in → empty dict (no `IN ()`)."""
    if not item_ids:
        return {}
    return {
        s.item_id: s
        for s in db.execute(
            select(PlexState).where(PlexState.user_id == user_id, PlexState.item_id.in_(item_ids))
        ).scalars()
    }