from __future__ import annotations

from datetime import date, timedelta

from app.extensions import db
from app.models import InAppNotification, Month, NotificationPreference, User


class NotificationService:
    def __init__(self, month_service, push_service, threshold: float):
        self.month_service = month_service
        self.push_service = push_service
        self.threshold = threshold

    def run_monthly_checks(self, today: date | None = None) -> int:
        today = today or date.today()
        current_month = self.month_service.ensure_month(today)
        next_month_date = (today.replace(day=28) + timedelta(days=4)).replace(day=1)
        next_month = Month.query.filter_by(
            label=f"{next_month_date.year:04d}-{next_month_date.month:02d}"
        ).first()
        summary = self.month_service.compute_summary(current_month)
        count = 0
        for user in User.query.filter_by(is_active=True).all():
            pref = user.notification_preference or NotificationPreference(user_id=user.id)
            if pref.id is None:
                db.session.add(pref)
                db.session.flush()
            if pref.notify_month_end and next_month is None and today.day >= 25:
                self._notify(
                    user,
                    "month_end",
                    "Folgemonat fehlt",
                    "Der nächste Monat ist noch nicht vorbereitet. Öffne Saldo und prüfe die Planung.",
                    "/months/",
                )
                count += 1
            if pref.notify_missing_distribution and summary.remainder != summary.allocation_total:
                self._notify(
                    user,
                    "missing_distribution",
                    "Restverteilung unvollständig",
                    "Die geplante Verteilung deckt den aktuellen Restbetrag noch nicht vollständig ab.",
                    f"/planning/{current_month.label}",
                )
                count += 1
            if pref.notify_missing_values and abs(float(summary.deltas["income_delta"])) >= self.threshold:
                self._notify(
                    user,
                    "income_change",
                    "Einkommen hat sich deutlich verändert",
                    "Durch eine Einkommensänderung sollten die Vorschläge und Verteilungen geprüft werden.",
                    f"/planning/{current_month.label}",
                )
                count += 1
        db.session.commit()
        return count

    def _notify(self, user, kind: str, title: str, body: str, action_url: str) -> None:
        notification = InAppNotification(
            user_id=user.id, type=kind, title=title, body=body, action_url=action_url
        )
        db.session.add(notification)
        self.push_service.send_to_user(user, title=title, body=body, url=action_url)