import os
from django.conf import settings
from django.core.exceptions import PermissionDenied
from django.http import FileResponse, JsonResponse, Http404
from django.shortcuts import render, get_object_or_404
from django.contrib.auth.decorators import login_required

from documents.models import ManagedDocument
from documents.permissions import user_has_document_permission


def _get_document_by_code(doc_code):
    """Utility to fetch ManagedDocument by UUID string/object or integer PK."""
    try:
        return ManagedDocument.objects.get(uuid=doc_code)
    except (ManagedDocument.DoesNotExist, ValueError):
        # Fallback to PK lookup if integer passed
        if str(doc_code).isdigit():
            return get_object_or_404(ManagedDocument, pk=int(doc_code))
        raise Http404("Document non trouvé")


@login_required
def ifc_viewer_view(request, doc_code):
    """Renders the full-screen 3D IFC Viewer page for a given document code."""
    document = _get_document_by_code(doc_code)

    if not user_has_document_permission(request.user, document, required_permission=ManagedDocument.PERMISSION_VIEW):
        raise PermissionDenied("Vous n'avez pas la permission de visualiser ce document.")

    version = document.latest_version
    if not version or not version.file:
        raise Http404("Aucun fichier disponible pour ce document.")

    filename = version.filename
    ext = os.path.splitext(filename)[1].lower()

    context = {
        "document": document,
        "version": version,
        "filename": filename,
        "ext": ext,
        "doc_code": document.uuid,
    }
    return render(request, "bim/viewer.html", context)


@login_required
def ifc_file_download_view(request, doc_code):
    """Streams the IFC file for consumption by the WebGL 3D viewer."""
    document = _get_document_by_code(doc_code)

    if not user_has_document_permission(request.user, document, required_permission=ManagedDocument.PERMISSION_VIEW):
        raise PermissionDenied("Accès refusé.")

    version = document.latest_version
    if not version or not version.file:
        raise Http404("Fichier non trouvé.")

    response = FileResponse(
        version.file.open("rb"),
        content_type="application/octet-stream",
        filename=version.filename
    )
    # Enable CORS headers if viewer runs under different subdomains / frames
    response["Access-Control-Allow-Origin"] = "*"
    response["Accept-Ranges"] = "bytes"
    return response


@login_required
def ifc_document_info_api(request, doc_code):
    """API endpoint providing document metadata for the BIM viewer UI."""
    document = _get_document_by_code(doc_code)

    if not user_has_document_permission(request.user, document, required_permission=ManagedDocument.PERMISSION_VIEW):
        return JsonResponse({"error": "Accès refusé"}, status=403)

    version = document.latest_version
    file_size = version.file.size if version and version.file else 0

    return JsonResponse({
        "uuid": str(document.uuid),
        "id": document.id,
        "title": document.title,
        "description": document.description or "",
        "filename": version.filename if version else "",
        "version_number": version.version_number if version else 1,
        "file_size": file_size,
        "created_at": document.created_at.isoformat() if document.created_at else None,
        "updated_at": document.updated_at.isoformat() if document.updated_at else None,
    })