"""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 datetime import datetime, timezone

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

from app.userscope import owned_by
from app.plex.models import PlexItem, PlexState
from app.plex.cards import ShowState

# Sort sentinel for a rail row whose timestamp is missing, so `key=lambda r: r[0] or NO_TS` reads the
# same at every rail that merges two type-homogeneous lists in Python.
#
# It is NOT a crash fix, whatever the commit that introduced it says. The `(ts is not None, ts)`
# key it replaced cannot raise: tuple comparison finds the first UNEQUAL element via `==`, so two
# `(False, None)` keys compare equal and `None < None` is never reached — verified by execution
# during a review, over every permutation of null/non-null rows. What the sentinel
# buys is one idiom instead of two, and a key that says "missing sorts last" outright rather than
# encoding it in a boolean flag. A BARE `r[0]` would genuinely raise, which is the mutation the
# rails' tests do guard against.
NO_TS = datetime.min.replace(tzinfo=timezone.utc)


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 show_state(total: int, watched: int, inprog: int) -> ShowState:
    """`show_status` plus whether an episode holds a resume point (the card's `ShowState`)."""
    return ShowState(show_status(total, watched, inprog), (inprog or 0) > 0)


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:
        # The LAST in-progress episode in broadcast order — no timestamp is consulted. Home's
        # `discover.queries.next_episode` picks the same one, so both Resume buttons agree.
        resume = inprog[-1]
    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, and (d) the browse "last watched" sort. `include_resumed` adds `resumed_at`
    = max(coalesce(progress_updated_at, watched_at)) across the show's episodes — i.e. how recently ANY
    episode was last touched (resumed OR marked watched) — so callers can order shows by recency. A
    fully-watched show (no resume progress) still gets a timestamp from its episodes' watched_at."""
    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(func.coalesce(ps.progress_updated_at, ps.watched_at)).label("resumed_at")
        )
    return (
        select(*cols)
        .outerjoin(ps, and_(ps.item_id == PlexItem.id, owned_by(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, ShowState]:
    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_state(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 `ShowState`). 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(
                owned_by(PlexState.user_id, user_id), PlexState.item_id.in_(item_ids)
            )
        ).scalars()
    }