"""Runtime fallback policy shared by auth/session routes.

The in-process stores exist only to keep local development usable when Docker or
NAS PostgreSQL is offline. Staging/prod must fail loudly instead of becoming a
second source of truth.
"""

from __future__ import annotations

from typing import NoReturn

from fastapi import HTTPException, status

from .config import settings


def runtime_fallback_allowed() -> bool:
    return settings.environment == "dev"


def raise_runtime_fallback_disabled(feature: str) -> NoReturn:
    raise HTTPException(
        status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
        detail=(
            f"{feature} persistence unavailable; runtime fallback is disabled "
            f"in {settings.environment}"
        ),
    )


def require_runtime_fallback_allowed(feature: str) -> None:
    if not runtime_fallback_allowed():
        raise_runtime_fallback_disabled(feature)