"""Background poller that maintains live game-server state in the DB.

Modeled on l4d2web/services/job_worker.py:617-647. This module owns:
  - per-server snapshot writes with run-length encoding into
    `server_live_state`
  - player-session lifecycle in `server_player_session` (Task 7)
  - Steam profile enrichment into `steam_user_profile` (Task 8)
  - retention pruning and stuck-session closure (Task 10)

This file is built up across Tasks 6-10.
"""
from __future__ import annotations

import logging
import threading
import time
from datetime import datetime, UTC
from typing import Callable

from sqlalchemy import select

from l4d2web.db import session_scope
from l4d2web.models import (
    Server,
    ServerLiveState,
)
from l4d2web.services.rcon import RconError, StatusResponse, query_status


logger = logging.getLogger(__name__)


def _now() -> datetime:
    return datetime.now(UTC).replace(tzinfo=None)


def poll_once() -> None:
    """One pass over all running servers with a configured rcon_password."""
    with session_scope() as db:
        servers = db.scalars(
            select(Server)
            .where(Server.actual_state == "running")
            .where(Server.rcon_password != "")
        ).all()
        targets = [(s.id, s.port, s.rcon_password) for s in servers]

    for server_id, port, password in targets:
        try:
            status = query_status("127.0.0.1", port, password, timeout=2.0)
        except RconError:
            logger.warning("rcon query failed for server %d", server_id, exc_info=True)
            continue

        _record_snapshot(server_id, status)


def _record_snapshot(server_id: int, status: StatusResponse) -> None:
    """RLE write: bump last_seen_at if state matches, else insert a new row."""
    now = _now()
    with session_scope() as db:
        latest = db.scalars(
            select(ServerLiveState)
            .where(ServerLiveState.server_id == server_id)
            .order_by(ServerLiveState.started_at.desc())
            .limit(1)
        ).first()

        if latest is not None and _matches(latest, status):
            latest.last_seen_at = now
            return

        db.add(
            ServerLiveState(
                server_id=server_id,
                started_at=now,
                last_seen_at=now,
                players=status.players,
                max_players=status.max_players,
                bots=status.bots,
                map=status.map,
                hibernating=status.hibernating,
            )
        )


def _matches(row: ServerLiveState, status: StatusResponse) -> bool:
    return (
        row.players == status.players
        and row.max_players == status.max_players
        and row.bots == status.bots
        and row.map == status.map
        and row.hibernating == status.hibernating
    )