"""Plex ↔ Siftlode watch-state sync.

Plex records watch state PER PLEX ACCOUNT; Siftlode records it per Siftlode user in `plex_states`.
A `PlexLink` row maps one Siftlode user to a Plex account. For the owner (MVP) that account is the
server admin (`uses_admin=True`), so the existing admin token already reads/writes the owner's state
— no separate Plex login.

Phase A (this module today): the one-time **"Plex is master" import** — read the owner account's
viewCount / viewOffset / lastViewedAt (present in the same cheap section listing the catalog mirror
already pages) and upsert them into the owner's `plex_states`. Plex wins on overlap; states that
exist only in Siftlode are left untouched (union, Plex-authoritative on the intersection).

Phases B (Siftlode→Plex push via scrobble/timeline) and C (incremental Plex→Siftlode via the watch
history + onDeck, last-write-wins) build on this and land in later ships.
"""
import logging
from datetime import datetime, timezone

from sqlalchemy import func
from sqlalchemy.dialects.postgresql import insert as pg_insert
from sqlalchemy.orm import Session

from app import sysconfig
from app.models import PlexItem, PlexLink, PlexState
from app.plex.client import PlexClient, PlexError, PlexNotConfigured
from app.plex.sync import (
    _TYPE_EPISODE,
    _TYPE_MOVIE,
    _enabled_section_keys,
    _epoch,
    _paginate,
)

log = logging.getLogger("siftlode.plex.watch")

# A resume position below this many seconds isn't worth mirroring — matches the player's own
# _PROGRESS_MIN_S (a stray few-second seek is not "in progress").
_PROGRESS_MIN_S = 5


def _plex_watch_to_state(
    view_count, view_offset_ms, last_viewed_at
) -> tuple[str, int, datetime | None, datetime | None] | None:
    """Translate a Plex leaf's per-account watch fields into a Siftlode state tuple
    ``(status, position_seconds, watched_at, progress_updated_at)``, or None when Plex holds no
    meaningful watch signal for it (so the import skips it and never clears a Siftlode-only state).

    In Siftlode's model (mirrors item_progress/item_state): a *watched* item is ``status="watched"``
    with position 0; an *in-progress* item keeps the default status and carries ``position_seconds``
    plus ``progress_updated_at``."""
    ts = _epoch(last_viewed_at)
    if view_count and int(view_count) > 0:
        return ("watched", 0, ts, ts)
    if view_offset_ms:
        pos = int(view_offset_ms) // 1000
        if pos >= _PROGRESS_MIN_S:
            return ("new", pos, None, ts)
    return None


def import_owner_watch_state(db: Session, link: PlexLink) -> dict:
    """One-time "Plex is master" import of the linked user's Plex watch state into their
    `plex_states`. Idempotent (safe to re-run — Plex simply re-wins on the intersection). Only
    touches items Plex has a watch record for; Siftlode-only states are preserved."""
    if not sysconfig.get_bool(db, "plex_enabled"):
        return {"skipped": "disabled"}

    # rating_key -> plex_items.id for every mirrored playable leaf (movie/episode).
    item_id_by_rk: dict[str, int] = {
        rk: iid for rk, iid in db.query(PlexItem.rating_key, PlexItem.id)
    }
    stats = {"watched": 0, "in_progress": 0, "scanned": 0}
    wanted = _enabled_section_keys(db)
    # Accumulate one row per item (keyed by item_id → inherently de-duped) then bulk-UPSERT. An upsert
    # is idempotent AND concurrency-safe: a repeated/overlapping enable (the toggle firing twice while
    # the multi-second import runs) can't raise a duplicate-key error — the conflict just re-updates.
    rows_by_item: dict[int, dict] = {}

    try:
        with PlexClient(db) as plex:
            for s in plex.sections():
                stype = s.get("type")
                if stype not in ("movie", "show"):
                    continue
                key = str(s.get("key"))
                if wanted is not None and key not in wanted:
                    continue
                item_type = _TYPE_MOVIE if stype == "movie" else _TYPE_EPISODE
                for meta in _paginate(plex, key, item_type):
                    stats["scanned"] += 1
                    item_id = item_id_by_rk.get(str(meta.get("ratingKey") or ""))
                    if item_id is None:
                        continue
                    res = _plex_watch_to_state(
                        meta.get("viewCount"),
                        meta.get("viewOffset"),
                        meta.get("lastViewedAt"),
                    )
                    if res is None:
                        continue
                    status, pos, watched_at, prog_at = res
                    rows_by_item[item_id] = {
                        "user_id": link.user_id,
                        "item_id": item_id,
                        "status": status,
                        "position_seconds": pos,
                        "watched_at": watched_at,
                        "progress_updated_at": prog_at,
                        # Mirrors Plex now — so Phase B's push doesn't bounce it straight back.
                        "synced_to_plex": True,
                    }
                    stats["watched" if status == "watched" else "in_progress"] += 1

            # Bulk upsert in chunks. Plex wins on the intersection; Siftlode-only states (item_ids not
            # in rows_by_item) are never referenced, so they're preserved untouched (union).
            rows = list(rows_by_item.values())
            for i in range(0, len(rows), 1000):
                stmt = pg_insert(PlexState).values(rows[i : i + 1000])
                stmt = stmt.on_conflict_do_update(
                    index_elements=[PlexState.user_id, PlexState.item_id],
                    set_={
                        "status": stmt.excluded.status,
                        "position_seconds": stmt.excluded.position_seconds,
                        "watched_at": stmt.excluded.watched_at,
                        "progress_updated_at": stmt.excluded.progress_updated_at,
                        "synced_to_plex": stmt.excluded.synced_to_plex,
                        "updated_at": func.now(),
                    },
                )
                db.execute(stmt)
            link.initial_import_done = True
            link.last_watch_sync_at = datetime.now(timezone.utc)
            db.commit()
    except PlexNotConfigured as e:
        return {"skipped": str(e)}
    except PlexError as e:
        db.rollback()
        log.warning("Plex watch import failed (user %s): %s", link.user_id, e)
        return {"error": str(e)}

    log.info("Plex watch import (user %s): %s", link.user_id, stats)
    return stats