from django.db import connection
from rest_framework import generics, status
from rest_framework.exceptions import NotFound, ValidationError
from rest_framework.pagination import CursorPagination, LimitOffsetPagination
from rest_framework.response import Response
from rest_framework.views import APIView

from jobs.models import Job, JobEvent
from jobs.serializers import JobCreateSerializer, JobEventSerializer, JobSerializer
from jobs.services import create_job, job_stats, retry_failed_job


class JobEventCursorPagination(CursorPagination):
    page_size = 50
    page_size_query_param = "limit"
    max_page_size = 200
    ordering = "-id"


class JobLimitOffsetPagination(LimitOffsetPagination):
    default_limit = 25
    max_limit = 100


class HealthAPIView(APIView):
    def get(self, request):
        try:
            with connection.cursor() as cursor:
                cursor.execute("SELECT 1")
                cursor.fetchone()
        except Exception as exc:
            return Response(
                {"ok": False, "database": "error", "detail": str(exc)},
                status=status.HTTP_503_SERVICE_UNAVAILABLE,
            )
        return Response({"ok": True, "database": "ok"})


class JobListCreateAPIView(APIView):
    def get(self, request):
        queryset = Job.objects.order_by("-created_at")
        status_filter = request.query_params.get("status")
        type_filter = request.query_params.get("type")
        if status_filter:
            queryset = queryset.filter(status=status_filter)
        if type_filter:
            queryset = queryset.filter(type__icontains=type_filter)

        paginator = JobLimitOffsetPagination()
        page = paginator.paginate_queryset(queryset, request, view=self)
        return paginator.get_paginated_response(JobSerializer(page, many=True).data)

    def post(self, request):
        serializer = JobCreateSerializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        result = create_job(
            job_type=serializer.validated_data["type"],
            payload=serializer.validated_data.get("payload") or {},
            priority=serializer.validated_data.get("priority", 50),
            available_at=serializer.validated_data.get("available_at"),
            max_attempts=serializer.validated_data.get("max_attempts"),
            idempotency_key=serializer.validated_data.get("idempotency_key"),
        )
        return Response(
            JobSerializer(result.job).data,
            status=status.HTTP_201_CREATED if result.created else status.HTTP_200_OK,
        )


class JobDetailAPIView(generics.RetrieveAPIView):
    queryset = Job.objects.all()
    serializer_class = JobSerializer


class JobEventsAPIView(APIView):
    def get(self, request, pk):
        if not Job.objects.filter(id=pk).exists():
            raise NotFound("Job not found.")
        events = JobEvent.objects.filter(job_id=pk).order_by("id")
        return Response(JobEventSerializer(events, many=True).data)


class GlobalJobEventsAPIView(APIView):
    def get(self, request):
        queryset = JobEvent.objects.order_by("-id")
        event_type = request.query_params.get("type")
        job_id = request.query_params.get("job_id")
        if event_type:
            queryset = queryset.filter(type=event_type)
        if job_id:
            queryset = queryset.filter(job_id=job_id)

        paginator = JobEventCursorPagination()
        page = paginator.paginate_queryset(queryset, request, view=self)
        return paginator.get_paginated_response(JobEventSerializer(page, many=True).data)


class JobStatsAPIView(APIView):
    def get(self, request):
        return Response(job_stats())


class RetryJobAPIView(APIView):
    def post(self, request, pk):
        try:
            job = retry_failed_job(pk)
        except Job.DoesNotExist as exc:
            raise NotFound("Job not found.") from exc
        except ValueError as exc:
            raise ValidationError({"detail": str(exc)}) from exc
        return Response(JobSerializer(job).data)