import json

from pywebpush import WebPushException, webpush
from sqlalchemy import select
from sqlalchemy.orm import Session

from app.config import settings
from app.models.push_subscription import PushSubscription
from app.schemas.push import PushSubscribeRequest


def list_subscriptions(db: Session, user_id: int) -> list[PushSubscription]:
    return list(db.scalars(select(PushSubscription).where(PushSubscription.user_id == user_id)))


def save_subscription(
    db: Session, user_id: int, data: PushSubscribeRequest, user_agent: str | None = None
) -> PushSubscription:
    existing = db.scalar(select(PushSubscription).where(PushSubscription.endpoint == data.endpoint))
    if existing:
        existing.user_id = user_id  # 같은 기기에서 다른 유저가 재구독하면 소유자를 갱신한다.
        existing.p256dh_key = data.keys.p256dh
        existing.auth_key = data.keys.auth
        db.commit()
        return existing

    sub = PushSubscription(
        user_id=user_id,
        endpoint=data.endpoint,
        p256dh_key=data.keys.p256dh,
        auth_key=data.keys.auth,
        user_agent=user_agent,
    )
    db.add(sub)
    db.commit()
    db.refresh(sub)
    return sub


def delete_subscription(db: Session, endpoint: str) -> None:
    existing = db.scalar(select(PushSubscription).where(PushSubscription.endpoint == endpoint))
    if existing:
        db.delete(existing)
        db.commit()


def send_to_user(db: Session, user_id: int, title: str, body: str, url: str = "/today") -> int:
    """해당 유저의 구독자에게만 알림을 보낸다. 만료된(410/404) 구독은 자동으로 삭제한다. 성공 발송 건수를 반환."""
    payload = json.dumps({"title": title, "body": body, "url": url}, ensure_ascii=False)
    sent = 0
    for sub in list_subscriptions(db, user_id):
        try:
            webpush(
                subscription_info={
                    "endpoint": sub.endpoint,
                    "keys": {"p256dh": sub.p256dh_key, "auth": sub.auth_key},
                },
                data=payload,
                vapid_private_key=settings.vapid_private_key,
                vapid_claims={"sub": settings.vapid_subject},
            )
            sent += 1
        except WebPushException as exc:
            status_code = exc.response.status_code if exc.response is not None else None
            if status_code in (404, 410):
                db.delete(sub)
                db.commit()
            # 그 외 오류(일시적 네트워크 문제 등)는 건너뛰고 다음 구독자에게 계속 발송한다.
    return sent