# common/private_files/views.py
import os
from django.apps import apps
from django.http import FileResponse, Http404, HttpResponseBadRequest
from django.contrib.auth.decorators import login_required
from django.core import signing
from django.core.signing import BadSignature, SignatureExpired
from django.utils.encoding import smart_str
from django.utils.translation import gettext as _

from django.conf import settings
from .registry import get_guard

_TOKEN_MAX_AGE = getattr(settings, "PRIVATE_FILES_TOKEN_MAX_AGE", 14400)



@login_required
def private_file_download(request):
    """
    Accès générique: app=<app>&model=<Model>&pk=<id>&field=<field>&token=<signed>
    """
    app_label = request.GET.get("app")
    model_name = request.GET.get("model")
    pk = request.GET.get("pk")
    field_name = request.GET.get("field")
    token = request.GET.get("token")

    if not all([app_label, model_name, pk, field_name]):
        return HttpResponseBadRequest("Missing params")

    # Vérifie le token signé (facultatif si tu ne veux pas signer)
    if token:
        try:
            signing.loads(token, salt="private-files", max_age=_TOKEN_MAX_AGE)
        except (BadSignature, SignatureExpired):
            raise Http404(_("Lien expiré ou invalide"))

    # Récupère le modèle et l’objet
    try:
        model = apps.get_model(app_label, model_name)
    except LookupError:
        raise Http404(_("Modèle inconnu"))

    obj = model._default_manager.select_related().filter(pk=pk).first()
    if not obj:
        raise Http404(_("Objet introuvable"))

    # Récupère le guard
    guard = get_guard(app_label, model_name, field_name)
    if guard is None:
        # Par défaut, refuse si pas de guard enregistré (sécurité par défaut)
        raise Http404(_("Fichier non exposé"))

    # Vérif d’accès
    if not guard(obj, request.user):
        from django.core.exceptions import PermissionDenied
        raise PermissionDenied(_("Accès refusé"))

    # Ouvre le FileField
    f = getattr(obj, field_name, None)
    if not f or not getattr(f, "storage", None) or not f.name or not f.storage.exists(f.name):
        raise Http404(_("Fichier introuvable"))

    resp = FileResponse(f.open("rb"))
    resp["Content-Disposition"] = f'inline; filename="{smart_str(os.path.basename(f.name))}"'
    resp['X-Frame-Options'] = 'ALLOWALL' # Permet l’affichage dans un iframe
    return resp