"""Статус агентов по событиям agent.heartbeat / report.daily.* в БД."""

from datetime import datetime, timezone

from sqlalchemy import func, select
from sqlalchemy.orm import Session

from app.models import Event, Host

HEARTBEAT_TYPE = "agent.heartbeat"
DAILY_REPORT_SSH = "report.daily.ssh"
DAILY_REPORT_RDP = "report.daily.rdp"
DAILY_REPORT_TYPES = (DAILY_REPORT_SSH, DAILY_REPORT_RDP)


def max_event_time_by_host(db: Session, event_type: str) -> dict[int, datetime]:
    rows = db.execute(
        select(Event.host_id, func.max(Event.received_at))
        .where(Event.type == event_type)
        .group_by(Event.host_id)
    ).all()
    return {int(host_id): ts for host_id, ts in rows if ts is not None}


def max_daily_report_time_by_host(db: Session) -> dict[int, datetime]:
    rows = db.execute(
        select(Event.host_id, func.max(Event.received_at))
        .where(Event.type.in_(DAILY_REPORT_TYPES))
        .group_by(Event.host_id)
    ).all()
    return {int(host_id): ts for host_id, ts in rows if ts is not None}


def agent_status(
    last_heartbeat_at: datetime | None,
    *,
    stale_minutes: int,
    now: datetime | None = None,
) -> str:
    """
    online — heartbeat не старше порога;
    stale — был хост, но heartbeat устарел или отсутствует;
    unknown — heartbeat ещё не приходил.
    """
    if last_heartbeat_at is None:
        return "unknown"
    ref = now or datetime.now(timezone.utc)
    hb = last_heartbeat_at
    if hb.tzinfo is None:
        hb = hb.replace(tzinfo=timezone.utc)
    age_sec = (ref - hb).total_seconds()
    if age_sec > stale_minutes * 60:
        return "stale"
    return "online"


def count_stale_hosts(db: Session, stale_minutes: int) -> int:
    hb_map = max_event_time_by_host(db, HEARTBEAT_TYPE)
    host_ids = db.scalars(select(Host.id)).all()
    return sum(
        1
        for host_id in host_ids
        if agent_status(hb_map.get(host_id), stale_minutes=stale_minutes) == "stale"
    )