from __future__ import annotations

from collections.abc import Callable

from app.core.interface import EngineBackend
from app.models import EngineKind

BackendFactory = Callable[[], EngineBackend]


class BackendRegistry:
    def __init__(self) -> None:
        self._factories: dict[EngineKind, BackendFactory] = {}

    def register(self, kind: EngineKind, factory: BackendFactory) -> None:
        if kind in self._factories:
            raise ValueError(f"backend already registered: {kind}")
        self._factories[kind] = factory

    def create(self, kind: EngineKind) -> EngineBackend:
        try:
            return self._factories[kind]()
        except KeyError as exc:
            raise KeyError(f"backend is not registered: {kind}") from exc

    def kinds(self) -> tuple[EngineKind, ...]:
        return tuple(self._factories)