from typing import List, Optional
from sqlmodel import Session, select
from models import Notification, NotificationType, User, UserVerticalPreference, Show, PreferenceTier

class NotificationService:
    def __init__(self, session: Session):
        self.session = session

    def create_notification(
        self,
        user_id: int,
        type: NotificationType,
        title: str,
        message: str,
        link: Optional[str] = None
    ) -> Notification:
        notification = Notification(
            user_id=user_id,
            type=type,
            title=title,
            message=message,
            link=link
        )
        self.session.add(notification)
        self.session.commit()
        self.session.refresh(notification)
        return notification

    def get_user_notifications(
        self, 
        user_id: int, 
        limit: int = 50, 
        offset: int = 0
    ) -> List[Notification]:
        query = select(Notification).where(Notification.user_id == user_id).order_by(Notification.created_at.desc()).offset(offset).limit(limit)
        return self.session.exec(query).all()
        
    def mark_as_read(self, notification_id: int, user_id: int) -> bool:
        notification = self.session.get(Notification, notification_id)
        if notification and notification.user_id == user_id:
            notification.is_read = True
            self.session.add(notification)
            self.session.commit()
            return True
        return False
        
    def mark_all_as_read(self, user_id: int):
        statement = select(Notification).where(Notification.user_id == user_id).where(Notification.is_read == False)
        unread = self.session.exec(statement).all()
        for note in unread:
            note.is_read = True
            self.session.add(note)
        self.session.commit()

    def check_show_alert(self, show: Show):
        """
        Check if any users want to be notified about this new show.
        This roughly matches users who:
        1. Follow the vertical (UserVerticalPreference)
        2. Have notify_on_show = True
        3. Valid Tier (Usually Headliner/MainStage)
        """
        # Find users who subscribe to this band
        # Filtering logic:
        # - Matches vertical_id
        # - notify_on_show is True
        # - Tier is HEADLINER (for high priority) or specific preference
        # For now, let's alert all who have notify_on_show=True for this vertical
        
        subscriptions = self.session.exec(
            select(UserVerticalPreference)
            .where(UserVerticalPreference.vertical_id == show.vertical_id)
            .where(UserVerticalPreference.notify_on_show == True)
        ).all()

        for sub in subscriptions:
            # We can customize message based on tier if needed
            title = f"New Show Added: {show.vertical.name}"
            date_str = show.date.strftime("%b %d, %Y")
            message = f"{show.vertical.name} at {show.venue.name} on {date_str}"
            link = f"/{show.vertical.slug}/shows/{show.slug}"
            
            self.create_notification(
                user_id=sub.user_id,
                type=NotificationType.SHOW_ALERT,
                title=title,
                message=message,
                link=link
            )