import asyncio
import logging

from sqlalchemy import select, func, update
from sqlalchemy.ext.asyncio import AsyncSession

from app.db.models import ClassMembership, Notification, User
from app.services.email_service import send_class_notification_email

logger = logging.getLogger(__name__)


async def create_notification(
    db: AsyncSession,
    user_id: int,
    type: str,
    title: str,
    content: str | None = None,
    related_id: int | None = None,
) -> Notification:
    notification = Notification(
        user_id=user_id,
        type=type,
        title=title,
        content=content,
        related_id=related_id,
    )
    db.add(notification)
    await db.commit()
    await db.refresh(notification)
    return notification


async def create_notifications_for_class(
    db: AsyncSession,
    class_id: int,
    type: str,
    title: str,
    content: str | None = None,
    related_id: int | None = None,
    exclude_user_id: int | None = None,
    email_subject: str | None = None,
    email_body: str | None = None,
    email_action_path: str | None = None,
):
    """Create in-app notifications + send email for all active users in a class."""
    result = await db.execute(
        select(User.id, User.email)
        .join(ClassMembership, ClassMembership.user_id == User.id)
        .where(
            ClassMembership.class_id == class_id,
            User.status == "approved",
        )
    )
    rows = result.all()

    emails: list[str] = []
    for uid, email in rows:
        notification = Notification(
            user_id=uid,
            type=type,
            title=title,
            content=content,
            related_id=related_id,
        )
        db.add(notification)
        emails.append(email)

    await db.commit()

    # Send email notification in background (fire-and-forget)
    if email_subject and emails:
        from app.config import settings
        action_url = f"{settings.frontend_url}{email_action_path}" if email_action_path else None
        asyncio.create_task(_safe_send_emails(emails, email_subject, title, email_body or content or "", action_url))


async def _safe_send_emails(
    emails: list[str], subject: str, title: str, body: str, action_url: str | None
):
    """Fire-and-forget email sending with error logging."""
    try:
        await send_class_notification_email(emails, subject, title, body, action_url)
    except Exception as e:
        logger.error(f"Failed to send class notification emails: {e}")


async def list_notifications(
    db: AsyncSession, user_id: int, page: int = 1, page_size: int = 20
) -> tuple[list[Notification], int]:
    total_result = await db.execute(
        select(func.count(Notification.id)).where(Notification.user_id == user_id)
    )
    total = total_result.scalar() or 0

    result = await db.execute(
        select(Notification)
        .where(Notification.user_id == user_id)
        .order_by(Notification.created_at.desc())
        .offset((page - 1) * page_size)
        .limit(page_size)
    )
    notifications = list(result.scalars().all())
    return notifications, total


async def get_unread_count(db: AsyncSession, user_id: int) -> int:
    result = await db.execute(
        select(func.count(Notification.id)).where(
            Notification.user_id == user_id,
            Notification.is_read == False,
        )
    )
    return result.scalar() or 0


async def mark_as_read(db: AsyncSession, notification_id: int, user_id: int) -> bool:
    result = await db.execute(
        update(Notification)
        .where(Notification.id == notification_id, Notification.user_id == user_id)
        .values(is_read=True)
    )
    await db.commit()
    return result.rowcount > 0


async def mark_all_as_read(db: AsyncSession, user_id: int) -> int:
    result = await db.execute(
        update(Notification)
        .where(Notification.user_id == user_id, Notification.is_read == False)
        .values(is_read=True)
    )
    await db.commit()
    return result.rowcount