"""Shared FastAPI dependencies and helpers for the v1 API."""

from __future__ import annotations

from collections.abc import Awaitable, Callable

from fastapi import HTTPException, status
from pydantic import BaseModel
from redis.asyncio import Redis

from app.services.cache import cache_get_json, cache_set_json


def not_found(entity_type: str, aurora_id_str: str) -> HTTPException:
    return HTTPException(
        status_code=status.HTTP_404_NOT_FOUND,
        detail={"code": f"{entity_type}_not_found", "message": f"No such {entity_type}: {aurora_id_str}"},
    )


async def cached_response[T: BaseModel](
    redis: Redis,
    key: str,
    model: type[T],
    loader: Callable[[], Awaitable[T]],
    ttl: int | None = None,
) -> T:
    """Serve `model` from Redis if present, otherwise call `loader`, cache
    the result, and return it. Fails open to `loader` on any cache error."""

    cached = await cache_get_json(redis, key)
    if cached is not None:
        return model.model_validate(cached)

    result = await loader()
    await cache_set_json(redis, key, result.model_dump(mode="json"), ttl=ttl)
    return result