import time

from django.conf import settings
from rest_framework.exceptions import PermissionDenied
from rest_framework.permissions import AllowAny, IsAuthenticated
from rest_framework.response import Response
from rest_framework.views import APIView

from . import stats
from .system_info import get_os_info


def _worker_counts():
    """Active/queued background jobs (downloads and e621 match scans)."""
    from apps.library.models import DownloadTask, MatchTask

    active = DownloadTask.objects.filter(
        status=DownloadTask.STATUS_DOWNLOADING
    ).count() + MatchTask.objects.filter(status=MatchTask.STATUS_RUNNING).count()
    queued = DownloadTask.objects.filter(
        status=DownloadTask.STATUS_PENDING
    ).count() + MatchTask.objects.filter(status=MatchTask.STATUS_PENDING).count()
    return {"active": active, "queued": queued}


class StatusView(APIView):
    """Runtime status used by the SPA shell (storage line, status pill, footer)."""

    permission_classes = [AllowAny]

    def get(self, request):
        started = getattr(request, "start_time", time.perf_counter())
        payload = {
            "app": "J621",
            "env": settings.APP_ENV,
            "git_hash": settings.GIT_COMMIT_HASH,
            "version": settings.APP_VERSION,
            "os": get_os_info(),
            "watched_folder": settings.WATCHED_FOLDER,
            "e621_time_ms": None,  # e621 latency is measured client-side
            "workers": _worker_counts(),
        }
        payload["server_time_ms"] = round((time.perf_counter() - started) * 1000, 1)
        return Response(payload)


class StatsView(APIView):
    """Staff-only runtime statistics for the dashboard."""

    permission_classes = [IsAuthenticated]

    def get(self, request):
        user = request.user
        if not (
            user.is_staff or user.is_superuser or user.role == user.ROLE_STAFF
        ):
            raise PermissionDenied("Staff only.")
        from apps.library.tools import storage_info

        return Response(
            {
                "system": stats.system_stats(),
                "gpus": stats.gpu_stats(),
                "disk": storage_info(),
                "jobs": stats.jobs_stats(),
                "log": stats.log_tail(),
            }
        )