import json

from django.db.models import Q
from django.http import FileResponse, HttpResponseNotAllowed, JsonResponse
from django.shortcuts import get_object_or_404
from django.utils import timezone
from django.views.decorators.csrf import csrf_exempt

from .attribution import annotation_layer, apply_attribution
from .models import Project, Revision


def _auth(request):
    """None if logged in, else a 401 JSON response (so fetch() doesn't get a
    login redirect)."""
    if not request.user.is_authenticated:
        return JsonResponse({"detail": "authentication required"}, status=401)
    return None


def _visible(request):
    """Projects the user owns or collaborates on."""
    return Project.objects.filter(
        Q(owner=request.user) | Q(collaborators=request.user)).distinct()


def _owned(request, pk):
    return get_object_or_404(_visible(request), pk=pk)


def projects(request):
    """GET /api/projects/ — the projects the user owns or collaborates on."""
    if (resp := _auth(request)):
        return resp
    rows = _visible(request).values("id", "name", "fps", "updated", "owner__username")
    return JsonResponse(list(rows), safe=False)


@csrf_exempt  # dev convenience: session-auth API without a CSRF token round-trip
def scene(request, pk):
    """GET/PUT /api/projects/<pk>/scene/ — read or replace the timeline scene."""
    if (resp := _auth(request)):
        return resp
    project = _owned(request, pk)
    if request.method == "GET":
        return JsonResponse({"fps": project.fps, "scene": project.scene})
    if request.method == "PUT":
        data = json.loads(request.body or "{}")
        summary = None
        if "scene" in data:
            project.scene, summary, _ = apply_attribution(
                project.scene, data["scene"], request.user.get_username(),
                timezone.now().isoformat())
            Revision.objects.create(project=project, user=request.user,
                                    summary=summary,
                                    annotations=annotation_layer(project.scene))
        if "fps" in data:
            project.fps = data["fps"]
        project.save(update_fields=["scene", "fps", "updated"])
        return JsonResponse({"ok": True, "updated": project.updated, "summary": summary})
    return HttpResponseNotAllowed(["GET", "PUT"])


def revisions(request, pk):
    """GET /api/projects/<pk>/revisions/ — the save history (who/when/what)."""
    if (resp := _auth(request)):
        return resp
    project = _owned(request, pk)
    rows = project.revisions.values("id", "user__username", "created", "summary")
    return JsonResponse(list(rows), safe=False)


def otio(request, pk):
    """GET /api/projects/<pk>/otio/ — serve the uploaded OTIO file."""
    if (resp := _auth(request)):
        return resp
    project = _owned(request, pk)
    if not project.otio:
        return JsonResponse({"detail": "no otio uploaded"}, status=404)
    return FileResponse(project.otio.open("rb"), content_type="application/json")