from __future__ import annotations

import uuid

from sqlalchemy import delete, func, select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import selectinload

from app.models.enums import NotificationType, SeverityLevel
from app.models.notification_destination import (
    NotificationDestination,
    NotificationDestinationCompany,
)


def _with_companies(stmt):
    return stmt.options(
        selectinload(NotificationDestination.company_links).selectinload(
            NotificationDestinationCompany.company
        )
    )


class NotificationDestinationRepository:
    def __init__(self, db: AsyncSession) -> None:
        self.db = db

    async def list_for_user(self, user_id: uuid.UUID) -> list[NotificationDestination]:
        result = await self.db.execute(
            _with_companies(
                select(NotificationDestination)
                .where(NotificationDestination.user_id == user_id)
                .order_by(NotificationDestination.created_at.desc())
            )
        )
        return list(result.scalars().all())

    async def list_for_company(self, company_id: uuid.UUID) -> list[NotificationDestination]:
        """Only destinations actually linked to this company - what alert
        dispatch notifies, as opposed to list_for_user's "everything this
        user owns" (used by the Settings page)."""
        result = await self.db.execute(
            select(NotificationDestination)
            .join(
                NotificationDestinationCompany,
                NotificationDestinationCompany.destination_id == NotificationDestination.id,
            )
            .where(NotificationDestinationCompany.company_id == company_id)
        )
        return list(result.scalars().all())

    async def get_for_user(
        self, destination_id: uuid.UUID, user_id: uuid.UUID
    ) -> NotificationDestination | None:
        result = await self.db.execute(
            _with_companies(
                select(NotificationDestination).where(
                    NotificationDestination.id == destination_id,
                    NotificationDestination.user_id == user_id,
                )
            )
        )
        return result.scalar_one_or_none()

    async def find_by_value(
        self, user_id: uuid.UUID, type: NotificationType, destination_value: str
    ) -> NotificationDestination | None:
        """Case-insensitive for email (RFC-technically case-sensitive local
        parts exist, but no real provider treats them that way and users
        retype casing inconsistently), exact for everything else."""
        normalized = destination_value.strip()
        stmt = select(NotificationDestination).where(
            NotificationDestination.user_id == user_id, NotificationDestination.type == type
        )
        if type == NotificationType.EMAIL:
            stmt = stmt.where(
                func.lower(NotificationDestination.destination_value) == normalized.lower()
            )
        else:
            stmt = stmt.where(NotificationDestination.destination_value == normalized)
        result = await self.db.execute(_with_companies(stmt))
        return result.scalar_one_or_none()

    async def create(
        self,
        *,
        user_id: uuid.UUID,
        type: NotificationType,
        destination_value: str,
        minimum_severity: SeverityLevel,
        enabled: bool,
    ) -> NotificationDestination:
        destination = NotificationDestination(
            user_id=user_id,
            type=type,
            destination_value=destination_value,
            minimum_severity=minimum_severity,
            enabled=enabled,
        )
        self.db.add(destination)
        await self.db.flush()
        return destination

    async def link_company(self, destination_id: uuid.UUID, company_id: uuid.UUID) -> None:
        exists = await self.db.execute(
            select(func.count())
            .select_from(NotificationDestinationCompany)
            .where(
                NotificationDestinationCompany.destination_id == destination_id,
                NotificationDestinationCompany.company_id == company_id,
            )
        )
        if int(exists.scalar_one()) > 0:
            return
        self.db.add(
            NotificationDestinationCompany(destination_id=destination_id, company_id=company_id)
        )
        await self.db.flush()

    async def unlink_company(self, destination_id: uuid.UUID, company_id: uuid.UUID) -> None:
        await self.db.execute(
            delete(NotificationDestinationCompany).where(
                NotificationDestinationCompany.destination_id == destination_id,
                NotificationDestinationCompany.company_id == company_id,
            )
        )
        await self.db.flush()

    async def company_link_count(self, destination_id: uuid.UUID) -> int:
        result = await self.db.execute(
            select(func.count())
            .select_from(NotificationDestinationCompany)
            .where(NotificationDestinationCompany.destination_id == destination_id)
        )
        return int(result.scalar_one())

    async def delete_orphaned_for_user(self, user_id: uuid.UUID) -> None:
        """Deletes any of this user's destinations that ended up linked to
        zero companies - called after a company delete, since that cascades
        the join rows for it but leaves the destination row itself behind
        even when it was the destination's only remaining link."""
        destinations = await self.list_for_user(user_id)
        for destination in destinations:
            if await self.company_link_count(destination.id) == 0:
                await self.delete(destination)

    async def delete(self, destination: NotificationDestination) -> None:
        await self.db.delete(destination)
        await self.db.flush()