from django.shortcuts import get_object_or_404
from drf_spectacular.utils import OpenApiResponse, extend_schema
from rest_framework import viewsets
from rest_framework.exceptions import PermissionDenied
from rest_framework.generics import ListAPIView
from rest_framework.permissions import IsAuthenticated

from apps.announcements.models import Announcement
from apps.courses.api.permissions import IsCourseOwner, IsTeacher
from apps.courses.models import Course, CourseStatus
from apps.enrollments.api.permissions import IsStudent
from apps.enrollments.models import Enrollment

from .serializers import AnnouncementSerializer, AnnouncementWriteSerializer


@extend_schema(tags=["announcements"])
class InstructorAnnouncementViewSet(viewsets.ModelViewSet):
    """Instructor CRUD over announcements on their own courses."""

    permission_classes = [IsAuthenticated, IsTeacher, IsCourseOwner]
    queryset = Announcement.objects.all().select_related("course", "posted_by")
    filterset_fields = ["course"]
    ordering = ["-created_at"]

    def get_queryset(self):
        return super().get_queryset().filter(course__instructor=self.request.user)

    def get_serializer_class(self):
        if self.action in {"create", "update", "partial_update"}:
            return AnnouncementWriteSerializer
        return AnnouncementSerializer

    def perform_create(self, serializer):
        course = serializer.validated_data["course"]
        if course.instructor_id != self.request.user.id:
            raise PermissionDenied("You don't own this course.")
        announcement = serializer.save(posted_by=self.request.user)
        # Record activity event for the instructor's home feed
        from apps.enrollments.models import ActivityKind
        from apps.enrollments.services.events import record_event

        record_event(
            course=course,
            actor=self.request.user,
            kind=ActivityKind.ANNOUNCEMENT_POSTED.value,
            payload={
                "announcement_id": announcement.pk,
                "preview": (announcement.body or "")[:120],
            },
        )


class MyCourseAnnouncementsView(ListAPIView):
    """Student-facing list: announcements for a specific course the student is enrolled in."""

    permission_classes = [IsAuthenticated, IsStudent]
    serializer_class = AnnouncementSerializer
    pagination_class = None

    @extend_schema(
        tags=["announcements"],
        summary="My course announcements",
        description="Lists all announcements posted by the instructor on a course the student is enrolled in.",
        responses={
            200: AnnouncementSerializer(many=True),
            403: OpenApiResponse(description="Not enrolled."),
            404: OpenApiResponse(description="Course not found or not published."),
        },
    )
    def get(self, request, *args, **kwargs):
        return super().get(request, *args, **kwargs)

    def get_queryset(self):
        slug = self.kwargs["slug"]
        course = get_object_or_404(Course, slug=slug, status=CourseStatus.PUBLISHED)
        if not Enrollment.objects.filter(student=self.request.user, course=course).exists():
            raise PermissionDenied("You are not enrolled in this course.")
        return (
            Announcement.objects
            .filter(course=course)
            .select_related("posted_by")
            .order_by("-created_at")
        )