"""Удаление хоста и связанных events/problems (ручная очистка UI)."""

from __future__ import annotations

from dataclasses import dataclass

from sqlalchemy import delete, or_, select
from sqlalchemy.orm import Session

from app.models import Event, Host, Problem, ProblemEvent


@dataclass(frozen=True)
class HostDeleteResult:
    host_id: int
    hostname: str
    deleted_events: int
    deleted_problems: int


def delete_host_and_related(db: Session, host_id: int) -> HostDeleteResult | None:
    host = db.get(Host, host_id)
    if host is None:
        return None

    hostname = host.hostname
    event_ids = list(db.scalars(select(Event.id).where(Event.host_id == host_id)).all())
    problem_ids = list(db.scalars(select(Problem.id).where(Problem.host_id == host_id)).all())

    if event_ids or problem_ids:
        link_filter = []
        if event_ids:
            link_filter.append(ProblemEvent.event_id.in_(event_ids))
        if problem_ids:
            link_filter.append(ProblemEvent.problem_id.in_(problem_ids))
        db.execute(delete(ProblemEvent).where(or_(*link_filter)))

    if problem_ids:
        db.execute(delete(Problem).where(Problem.id.in_(problem_ids)))
    if event_ids:
        db.execute(delete(Event).where(Event.id.in_(event_ids)))

    db.delete(host)
    db.flush()

    return HostDeleteResult(
        host_id=host_id,
        hostname=hostname,
        deleted_events=len(event_ids),
        deleted_problems=len(problem_ids),
    )