"""FastAPI-приложение внутреннего API рекомендаций."""

import asyncio
import hmac
import logging
from collections.abc import Awaitable, Callable
from typing import Annotated

from fastapi import Depends, FastAPI, Header, HTTPException, status
from fastapi.responses import JSONResponse

from pipu_rec.settings import Settings

Check = Callable[[], Awaitable[None]]

log = logging.getLogger(__name__)

CHECK_TIMEOUT_S = 2.0


def create_app(settings: Settings, checks: dict[str, Check] | None = None) -> FastAPI:
    app = FastAPI(title="pipu-recommender", version=settings.version, docs_url=None, redoc_url=None)
    checks = checks or {}

    def require_token(authorization: Annotated[str, Header()] = "") -> None:
        scheme, _, token = authorization.partition(" ")
        expected = settings.internal_token
        if scheme != "Bearer" or not expected or not hmac.compare_digest(token, expected):
            raise HTTPException(status.HTTP_401_UNAUTHORIZED, detail="auth.invalid_internal_token")

    @app.get("/healthz")
    async def healthz() -> dict[str, str]:
        return {"status": "ok"}

    async def run_check(name: str, check: Check) -> str:
        try:
            await asyncio.wait_for(check(), CHECK_TIMEOUT_S)
        except Exception as exc:
            log.warning("readiness check %s failed: %r", name, exc)
            return "fail"
        return "ok"

    @app.get("/readyz")
    async def readyz() -> JSONResponse:
        # Проверки параллельные, каждая ограничена таймаутом; причину ошибки пишем только в лог.
        names = list(checks)
        outcomes = await asyncio.gather(*(run_check(n, checks[n]) for n in names))
        results = dict(zip(names, outcomes, strict=True))
        healthy = all(v == "ok" for v in results.values())
        return JSONResponse(
            {"status": "ok" if healthy else "degraded", "checks": results},
            status_code=status.HTTP_200_OK if healthy else status.HTTP_503_SERVICE_UNAVAILABLE,
        )

    @app.get("/internal/status", dependencies=[Depends(require_token)])
    async def internal_status() -> dict[str, object]:
        return {"version": settings.version, "models": [], "ranker": "heuristic-v1"}

    return app