from typing import TypeVar, Generic, Type, Any, Sequence
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy import select, update as sa_update, delete as sa_delete
from sqlalchemy.sql import Select

T = TypeVar("T")


class RepositoryBase(Generic[T]):
    def __init__(self, model: Type[T], session: AsyncSession):
        self.model = model
        self.session = session

    def _build_select(self, **filters: Any) -> Select[tuple[T]]:
        stmt = select(self.model)

        for field, value in filters.items():
            column = getattr(self.model, field, None)
            if column is None:
                raise ValueError(f"{self.model.__name__} has no attribute '{field}'")
            stmt = stmt.where(column == value)

        return stmt

    async def get(self, **filters: Any) -> T | None:
        stmt = self._build_select(**filters)
        result = await self.session.execute(stmt)
        return result.scalar_one_or_none()

    async def list(self, **filters: Any) -> Sequence[T]:
        stmt = self._build_select(**filters)
        result = await self.session.execute(stmt)
        return result.scalars().all()

    async def create(self, obj: T) -> T:
        self.session.add(obj)
        await self.session.flush()
        await self.session.refresh(obj)
        return obj

    async def delete(self, **filters: Any) -> int:
        stmt = sa_delete(self.model)

        for field, value in filters.items():
            column = getattr(self.model, field)
            stmt = stmt.where(column == value)

        result = await self.session.execute(stmt)
        return result.rowcount if result.rowcount != -1 else 0

    async def update(self, filters: dict[str, Any], values: dict[str, Any]) -> int:
        stmt = sa_update(self.model)

        for field, value in filters.items():
            stmt = stmt.where(getattr(self.model, field) == value)

        stmt = stmt.values(**values)
        result = await self.session.execute(stmt)
        return result.rowcount if result.rowcount != -1 else 0