"""Периодическое сканирование хостов с устаревшим agent.heartbeat (proactive host_silence)."""

from __future__ import annotations

import logging
from dataclasses import dataclass
from datetime import datetime, timedelta, timezone

from sqlalchemy import func, select, text
from sqlalchemy.exc import IntegrityError
from sqlalchemy.orm import Session

from app.config import get_settings
from app.models import Host, Problem
from app.services.problem_rules import RULE_HOST_SILENCE, RuleMatch, build_fingerprint, host_silence_match_for_host

logger = logging.getLogger(__name__)

ACTIVE_HOST_SILENCE_STATUSES = ("open", "acknowledged")
_HOST_SILENCE_SCAN_LOCK_KEY = 915_001_001


@dataclass(frozen=True)
class HostSilenceScanResult:
    host_id: int
    hostname: str
    problem: Problem
    created: bool


def _host_silence_scan_lock(db: Session) -> bool:
    """Один scan за раз (uvicorn workers + systemd timer)."""
    bind = db.get_bind()
    if bind.dialect.name != "postgresql":
        return True
    acquired = db.execute(
        text("SELECT pg_try_advisory_xact_lock(:key)"),
        {"key": _HOST_SILENCE_SCAN_LOCK_KEY},
    ).scalar()
    return bool(acquired)


def _find_active_host_silence_problem(
    db: Session,
    *,
    host_id: int,
    hostname: str | None,
) -> Problem | None:
    active = db.scalar(
        select(Problem)
        .where(
            Problem.host_id == host_id,
            Problem.rule_id == RULE_HOST_SILENCE,
            Problem.status.in_(ACTIVE_HOST_SILENCE_STATUSES),
        )
        .order_by(Problem.last_seen_at.desc())
        .limit(1)
    )
    if active is not None:
        return active

    name = (hostname or "").strip()
    if not name:
        return None

    sibling = db.scalar(
        select(Problem)
        .join(Host, Problem.host_id == Host.id)
        .where(
            Problem.rule_id == RULE_HOST_SILENCE,
            Problem.status.in_(ACTIVE_HOST_SILENCE_STATUSES),
            func.lower(Host.hostname) == name.lower(),
        )
        .order_by(Problem.last_seen_at.desc())
        .limit(1)
    )
    if sibling is not None and sibling.host_id != host_id:
        sibling.host_id = host_id
        db.flush()
    return sibling


def _apply_host_silence_refresh(
    problem: Problem,
    *,
    host_id: int,
    match: RuleMatch,
    fingerprint: str,
    ref: datetime,
) -> None:
    problem.host_id = host_id
    problem.summary = match.summary
    problem.title = match.title
    problem.fingerprint = fingerprint
    problem.last_seen_at = ref
    problem.updated_at = ref


def open_or_refresh_host_silence_problem(
    db: Session,
    host_id: int,
    match: RuleMatch,
    *,
    now: datetime | None = None,
    hostname: str | None = None,
) -> tuple[Problem | None, bool]:
    """
    Открыть или обновить open/ack Problem host_silence без ingest-события.

    Returns (problem, created). problem is None when suppressed by manual-resolve cooldown.
    """
    ref = now or datetime.now(timezone.utc)
    if hostname is None:
        host = db.get(Host, host_id)
        hostname = host.hostname if host is not None else None

    fingerprint = build_fingerprint(
        host_id,
        match.correlation_type,
        match.rule_id,
        match.fingerprint_suffix,
    )

    active_problem = _find_active_host_silence_problem(db, host_id=host_id, hostname=hostname)
    if active_problem is not None:
        _apply_host_silence_refresh(
            active_problem,
            host_id=host_id,
            match=match,
            fingerprint=fingerprint,
            ref=ref,
        )
        db.flush()
        return active_problem, False

    settings = get_settings()
    cooldown_hours = settings.sac_host_silence_manual_resolve_cooldown_hours
    if cooldown_hours > 0:
        cooldown = timedelta(hours=cooldown_hours)
        manual_recent = db.scalar(
            select(Problem)
            .where(
                Problem.host_id == host_id,
                Problem.rule_id == match.rule_id,
                Problem.fingerprint == fingerprint,
                Problem.status == "resolved",
                Problem.resolved_by == "manual",
                Problem.updated_at >= ref - cooldown,
            )
            .order_by(Problem.updated_at.desc())
            .limit(1)
        )
        if manual_recent is not None:
            logger.debug(
                "host_silence suppressed (manual cooldown %sh) host_id=%s problem_id=%s",
                cooldown_hours,
                host_id,
                manual_recent.id,
            )
            return None, False

        manual_expired = db.scalar(
            select(Problem)
            .where(
                Problem.host_id == host_id,
                Problem.rule_id == match.rule_id,
                Problem.fingerprint == fingerprint,
                Problem.status == "resolved",
                Problem.resolved_by == "manual",
                Problem.updated_at < ref - cooldown,
            )
            .order_by(Problem.updated_at.desc())
            .limit(1)
        )
        if manual_expired is not None:
            active_problem = _find_active_host_silence_problem(db, host_id=host_id, hostname=hostname)
            if active_problem is not None:
                _apply_host_silence_refresh(
                    active_problem,
                    host_id=host_id,
                    match=match,
                    fingerprint=fingerprint,
                    ref=ref,
                )
                db.flush()
                return active_problem, False

            manual_expired.status = "open"
            manual_expired.resolved_by = None
            _apply_host_silence_refresh(
                manual_expired,
                host_id=host_id,
                match=match,
                fingerprint=fingerprint,
                ref=ref,
            )
            db.flush()
            return manual_expired, True

    problem = Problem(
        host_id=host_id,
        title=match.title,
        summary=match.summary,
        severity=match.severity,
        status="open",
        rule_id=match.rule_id,
        fingerprint=fingerprint,
        event_count=0,
        last_seen_at=ref,
    )
    try:
        with db.begin_nested():
            db.add(problem)
            db.flush()
    except IntegrityError:
        active_problem = _find_active_host_silence_problem(db, host_id=host_id, hostname=hostname)
        if active_problem is None:
            raise
        _apply_host_silence_refresh(
            active_problem,
            host_id=host_id,
            match=match,
            fingerprint=fingerprint,
            ref=ref,
        )
        db.flush()
        return active_problem, False
    return problem, True


def run_host_silence_scan(db: Session, *, now: datetime | None = None) -> list[HostSilenceScanResult]:
    """Найти stale-хосты и создать/обновить Problems rule:host_silence."""
    if not _host_silence_scan_lock(db):
        logger.debug("host_silence scan skipped (another runner holds advisory lock)")
        return []

    ref = now or datetime.now(timezone.utc)
    hosts = db.scalars(select(Host).order_by(Host.id)).all()
    results: list[HostSilenceScanResult] = []

    for host in hosts:
        match = host_silence_match_for_host(db, host.id, hostname=host.hostname, now=ref)
        if match is None:
            continue
        problem, created = open_or_refresh_host_silence_problem(
            db,
            host.id,
            match,
            now=ref,
            hostname=host.hostname,
        )
        if problem is None:
            continue
        results.append(
            HostSilenceScanResult(
                host_id=host.id,
                hostname=host.hostname,
                problem=problem,
                created=created,
            )
        )
        if created:
            logger.info(
                "host_silence scan: new problem host=%s id=%s problem_id=%s",
                host.hostname,
                host.id,
                problem.id,
            )

    return results


def dispatch_host_silence_notifications(db: Session, results: list[HostSilenceScanResult]) -> int:
    """Telegram/webhook/email только для вновь созданных Problems."""
    from app.services.notify_dispatch import notify_problem

    sent = 0
    for item in results:
        if not item.created:
            continue
        try:
            notify_problem(item.problem, event=None, db=db)
            sent += 1
        except Exception:
            logger.exception(
                "host_silence notify failed host=%s problem_id=%s",
                item.hostname,
                item.problem.id,
            )
    return sent