import abc
from collections.abc import Sequence
from dataclasses import dataclass, field
from typing import Any, ClassVar, Generic, TypeVar, cast, get_args

import sqlalchemy as sa
from sqlalchemy import Result
from sqlalchemy.orm.interfaces import ORMOption

from .base import Database

T = TypeVar("T")


@dataclass
class Repository(abc.ABC, Generic[T]):
    db: Database
    model: type[T] = field(init=False)

    default_options: ClassVar[Sequence[ORMOption]] = []

    def __post_init__(self) -> None:
        orig_bases = getattr(self.__class__, "__orig_bases__")
        self.model = cast(type[T], get_args(orig_bases[0])[0])

    async def all(self) -> list[T]:
        query = sa.select(self.model).options(*self.default_options)
        result: Result[Any] = await self.db.session.execute(query)
        return list(result.scalars().all())

    async def get(self, ident: Any) -> T | None:
        return await self.db.session.get(
            self.model, ident=ident, options=self.default_options
        )

    async def first(self) -> T | None:
        query = sa.select(self.model).options(*self.default_options)
        result: Result[Any] = await self.db.session.execute(query)
        return result.scalars().first()

    async def count(self) -> int:
        query = sa.select(sa.func.count()).select_from(sa.select(self.model).subquery())
        result: Any = await self.db.session.execute(query)
        return cast(int, result.scalar_one())

    def add(self, obj: Any) -> None:
        self.db.session.add(obj)

    async def delete(self, obj: Any) -> None:
        await self.db.session.delete(obj)