"""Geplante Erinnerungs-Jobs (agent-11 PR3).

AsyncIOScheduler läuft im FastAPI-Event-Loop. Jeder Job öffnet eine eigene
DB-Session mit RLS-Bypass (interner Job ohne Tenant-Kontext) und holt vor dem
Versand einen Redis-Tageslock, damit bei mehreren Prozessen nicht doppelt
gemailt wird. Die run_*-Funktionen sind ohne Scheduler aufrufbar (Tests +
manueller Trigger über die API) und können auf eine Firma eingegrenzt werden.
"""
from __future__ import annotations

import logging
from datetime import date

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.core.config import settings
from app.core.notifications import pref_enabled
from app.models.absence import Absence, AbsenceStatus
from app.models.absence_type import AbsenceCategory, AbsenceType
from app.models.company import Company
from app.models.user import User, UserRole
from app.models.vacation_balance import VacationBalance
from app.services.absence_service import absence_service
from app.services.email_service import email_service

log = logging.getLogger(__name__)

_APPROVER_ROLES = (UserRole.MANAGER, UserRole.HR, UserRole.COMPANY_ADMIN)
_HR_ROLES = (UserRole.HR, UserRole.COMPANY_ADMIN)

_scheduler = None


def _fmt(d: date) -> str:
    return d.strftime("%d.%m.%Y")


async def _active_companies(db: AsyncSession, company_id) -> list[Company]:
    q = select(Company).where(Company.is_active.is_(True))
    if company_id:
        q = q.where(Company.id == company_id)
    return list((await db.scalars(q)).all())


async def _recipients(db: AsyncSession, company_id, roles) -> list[User]:
    return list((await db.scalars(
        select(User).where(
            User.company_id == company_id,
            User.is_active.is_(True),
            User.role.in_(roles),
        )
    )).all())


# ── Job-Logik ────────────────────────────────────────────────────────────────

async def run_pending_approvals(db: AsyncSession, company_id=None) -> int:
    """Zusammenfassung offener Anträge an alle Genehmiger je Firma. Liefert # Mails."""
    sent = 0
    for company in await _active_companies(db, company_id):
        rows = (await db.execute(
            select(Absence, User, AbsenceType)
            .join(User, Absence.user_id == User.id)
            .join(AbsenceType, Absence.type_id == AbsenceType.id)
            .where(User.company_id == company.id, Absence.status == AbsenceStatus.PENDING)
            .order_by(Absence.start_date)
        )).all()
        if not rows:
            continue
        items = [{
            "user_name": u.full_name, "type_name": t.name,
            "start": _fmt(a.start_date), "end": _fmt(a.end_date),
            "working_days": float(a.working_days),
        } for a, u, t in rows]

        for approver in await _recipients(db, company.id, _APPROVER_ROLES):
            if not approver.email or not pref_enabled(approver, "pending_approvals"):
                continue
            await email_service.send_pending_approvals_digest(approver, items, db)
            sent += 1
    return sent


async def run_carryover_expiry(db: AsyncSession, company_id=None) -> int:
    """Erinnert Mitarbeiter an bald verfallenden Resturlaub (Vorlauf konfigurierbar)."""
    today = date.today()
    year = today.year
    sent = 0
    for company in await _active_companies(db, company_id):
        expires_at, expired = absence_service._carryover_expired(company, year)
        if expires_at is None or expired:
            continue
        if (expires_at - today).days > settings.carryover_reminder_days:
            continue
        balances = (await db.execute(
            select(VacationBalance, User)
            .join(User, VacationBalance.user_id == User.id)
            .where(
                User.company_id == company.id, User.is_active.is_(True),
                VacationBalance.year == year, VacationBalance.carried_over > 0,
            )
        )).all()
        for bal, user in balances:
            expiring = max(0, bal.carried_over - bal.used_days)  # Übertrag zuerst verbraucht
            if expiring <= 0 or not user.email or not pref_enabled(user, "carryover_expiry"):
                continue
            await email_service.send_carryover_expiry_reminder(user, expiring, expires_at, db)
            sent += 1
    return sent


async def run_certificate_overdue(db: AsyncSession, company_id=None) -> int:
    """Meldet HR fehlende AU-Bescheinigungen (knüpft an agent-05)."""
    today = date.today()
    sent = 0
    for company in await _active_companies(db, company_id):
        rows = (await db.execute(
            select(Absence, User)
            .join(User, Absence.user_id == User.id)
            .join(AbsenceType, Absence.type_id == AbsenceType.id)
            .where(
                User.company_id == company.id,
                AbsenceType.category == AbsenceCategory.SICK,
                Absence.certificate_required_by.isnot(None),
                Absence.certificate_required_by < today,
                Absence.certificate_received_at.is_(None),
                Absence.status == AbsenceStatus.APPROVED,
            )
            .order_by(Absence.start_date)
        )).all()
        if not rows:
            continue
        items = [{
            "user_name": u.full_name, "start": _fmt(a.start_date),
            "due": _fmt(a.certificate_required_by),
        } for a, u in rows]

        for hr in await _recipients(db, company.id, _HR_ROLES):
            if not hr.email or not pref_enabled(hr, "certificate_overdue"):
                continue
            await email_service.send_certificate_overdue_digest(hr, items, db)
            sent += 1
    return sent


async def run_all_reminders(db: AsyncSession, company_id=None) -> dict:
    return {
        "pending_approvals": await run_pending_approvals(db, company_id),
        "carryover_expiry": await run_carryover_expiry(db, company_id),
        "certificate_overdue": await run_certificate_overdue(db, company_id),
    }


# ── Scheduler-Verdrahtung ────────────────────────────────────────────────────

def _acquire_daily_lock(name: str) -> bool:
    """True, wenn dieser Prozess den heutigen Job ausführen darf (Redis SET NX).
    Ohne Redis: immer True (Single-Prozess-Annahme)."""
    from app.core.redis import get_redis_client
    redis = get_redis_client()
    if redis is None:
        return True
    key = f"reminder_lock:{name}:{date.today().isoformat()}"
    try:
        return bool(redis.set(key, "1", nx=True, ex=23 * 3600))
    except Exception as exc:
        log.warning("Reminder-Lock fehlgeschlagen (%s) – führe trotzdem aus: %s", name, exc)
        return True


async def _run_job(name: str, fn) -> None:
    if not _acquire_daily_lock(name):
        log.info("Reminder-Job %s bereits von anderem Prozess übernommen.", name)
        return
    from sqlalchemy import text
    from app.core.database import AsyncSessionLocal
    try:
        async with AsyncSessionLocal() as db:
            await db.execute(text("SET LOCAL app.bypass_rls = 'on'"))
            count = await fn(db)
            await db.commit()
        log.info("Reminder-Job %s: %s Mail(s) versendet.", name, count)
    except Exception as exc:
        log.exception("Reminder-Job %s fehlgeschlagen: %s", name, exc)


def start() -> None:
    global _scheduler
    if _scheduler is not None:
        return
    try:
        from apscheduler.schedulers.asyncio import AsyncIOScheduler
        from apscheduler.triggers.cron import CronTrigger
    except Exception as exc:
        log.warning("APScheduler nicht verfügbar – Erinnerungen deaktiviert: %s", exc)
        return

    _scheduler = AsyncIOScheduler()
    hour = settings.reminder_hour
    _scheduler.add_job(_run_job, CronTrigger(hour=hour, minute=0),
                       args=["pending_approvals", run_pending_approvals], id="pending_approvals")
    _scheduler.add_job(_run_job, CronTrigger(hour=hour, minute=10),
                       args=["carryover_expiry", run_carryover_expiry], id="carryover_expiry")
    _scheduler.add_job(_run_job, CronTrigger(hour=hour, minute=20),
                       args=["certificate_overdue", run_certificate_overdue], id="certificate_overdue")
    _scheduler.start()
    log.info("Reminder-Scheduler gestartet (täglich ab %02d:00 Uhr).", hour)


def shutdown() -> None:
    global _scheduler
    if _scheduler is not None:
        _scheduler.shutdown(wait=False)
        _scheduler = None