"""Idempotency-Key handling for state-mutating POSTs (``API-STANDARD.md`` §7)."""

from __future__ import annotations

import hashlib
from collections.abc import Callable
from functools import wraps
from typing import Any

from django.core.cache import cache

__all__ = ["idempotent"]

_TTL_SECONDS = 24 * 60 * 60


def _cache_key(request: Any, idempotency_key: str) -> str:
    from infrasynth.tenancy.context import get_current_tenant

    tenant = get_current_tenant()
    tenant_part = str(tenant.pk) if tenant is not None else "anon"
    fingerprint = hashlib.sha256(f"{request.method}:{request.path}".encode()).hexdigest()[:16]
    return f"tenant:{tenant_part}:idempotency:{idempotency_key}:{fingerprint}"


def idempotent(view_method: Callable[..., Any]) -> Callable[..., Any]:
    """Replays the first successful response for a repeated ``Idempotency-Key``.

    Views that create real-world side effects (checkout, invitation acceptance)
    apply this to the action method. Without the header the request is a no-op.
    """

    @wraps(view_method)
    def wrapper(self: Any, request: Any, *args: Any, **kwargs: Any) -> Any:
        from rest_framework.response import Response

        key = request.headers.get("Idempotency-Key")
        if not key:
            return view_method(self, request, *args, **kwargs)

        cache_key = _cache_key(request, key)
        cached = cache.get(cache_key)
        if cached is not None:
            response = Response(cached["data"], status=cached["status"])
            response["Idempotent-Replay"] = "true"
            return response

        response = view_method(self, request, *args, **kwargs)
        if 200 <= response.status_code < 300:
            try:
                cache.set(cache_key, {"data": response.data, "status": response.status_code}, _TTL_SECONDS)
            except Exception:  # noqa: BLE001 - never fail a request over cache serialization
                pass
        return response

    return wrapper