from django.utils import timezone

from apps.account.models import User

from .models import Notification, NotificationRead

# آستانه‌ی هشدار پایان دوره‌ی آزمایشی — هر روزی که ≤ این عدد مانده باشد نشان داده می‌شود.
TRIAL_WARNING_DAYS = 3


class NotificationService:
    @staticmethod
    def notify(user: User, title: str, body: str = "") -> Notification:
        """اعلان شخصی برای یک کاربر مشخص می‌سازد."""
        return Notification.objects.create(user=user, title=title, body=body)

    @staticmethod
    def trial_warning(user: User) -> dict | None:
        if not user.is_in_trial or not user.trial_expires_at:
            return None
        days_left = (user.trial_expires_at - timezone.now()).days
        if days_left > TRIAL_WARNING_DAYS:
            return None
        return {
            "days_left": max(days_left, 0),
            "title": "دوره‌ی رایگانت داره تموم میشه!",
            "body": (
                f"فقط {max(days_left, 0)} روز از دوره‌ی آزمایشی‌ات مونده — برای این‌که کارت زمین نمونه، "
                "از فروشگاه یکی از ابزارها رو با جم فعال کن."
            ),
        }

    @staticmethod
    def list_for_user(user: User) -> dict:
        notifications = Notification.objects.filter(user=user) | Notification.objects.filter(user__isnull=True)
        notifications = notifications.order_by("-created_at")
        read_ids = set(NotificationRead.objects.filter(user=user).values_list("notification_id", flat=True))

        items = [
            {
                "id": n.id,
                "title": n.title,
                "body": n.body,
                "created_at": n.created_at,
                "is_read": n.id in read_ids,
            }
            for n in notifications
        ]
        unread_count = sum(1 for i in items if not i["is_read"])
        return {
            "unread_count": unread_count,
            "trial_warning": NotificationService.trial_warning(user),
            "items": items,
        }

    @staticmethod
    def mark_read(user: User, notification_id: int) -> None:
        NotificationRead.objects.get_or_create(user=user, notification_id=notification_id)

    @staticmethod
    def mark_all_read(user: User) -> None:
        notifications = Notification.objects.filter(user=user) | Notification.objects.filter(user__isnull=True)
        already_read = set(NotificationRead.objects.filter(user=user).values_list("notification_id", flat=True))
        NotificationRead.objects.bulk_create(
            [
                NotificationRead(user=user, notification_id=n.id)
                for n in notifications
                if n.id not in already_read
            ],
            ignore_conflicts=True,
        )