from dataclasses import dataclass
from typing import List, Set

from rest_framework.decorators import api_view
from rest_framework.exceptions import PermissionDenied
from rest_framework.response import Response

from vbv_lernwelt.core.models import User
from vbv_lernwelt.course.models import CourseSession, CourseSessionUser
from vbv_lernwelt.course.serializers import CourseSessionSerializer
from vbv_lernwelt.course.views import logger
from vbv_lernwelt.course_session_group.models import CourseSessionGroup
from vbv_lernwelt.learning_mentor.models import LearningMentor


@dataclass(frozen=True)
class CourseSessionWithRoles:
    _original: CourseSession
    roles: Set[str]

    def __getattr__(self, name: str):
        # Delegate attribute access to the _original CourseSession object
        return getattr(self._original, name)

    def save(self, *args, **kwargs):
        raise NotImplementedError("This proxy object cannot be saved.")


def get_course_sessions_with_roles_for_user(user: User) -> List[CourseSessionWithRoles]:
    result_course_sessions = {}

    # participant/member/expert course sessions
    csu_qs = CourseSessionUser.objects.filter(user=user).prefetch_related(
        "course_session", "course_session__course"
    )
    for csu in csu_qs:
        cs = csu.course_session
        # member/expert is mutually exclusive...
        cs.roles = {csu.role}
        result_course_sessions[cs.id] = cs

    # enrich with supervisor course sessions
    csg_qs = CourseSessionGroup.objects.filter(supervisor=user).prefetch_related(
        "course_session", "course_session__course"
    )
    for csg in csg_qs:
        for cs in csg.course_session.all():
            cs.roles = set()
            cs = result_course_sessions.get(cs.id, cs)

            cs.roles.add("SUPERVISOR")
            result_course_sessions[cs.id] = cs

    # enrich with mentor course sessions
    lm_qs = LearningMentor.objects.filter(mentor=user).prefetch_related(
        "course_session", "course_session__course"
    )
    for lm in lm_qs:
        cs = lm.course_session
        cs.roles = set()
        cs = result_course_sessions.get(cs.id, cs)

        cs.roles.add("LEARNING_MENTOR")
        result_course_sessions[cs.id] = cs

    return [
        CourseSessionWithRoles(cs, cs.roles) for cs in result_course_sessions.values()
    ]


@api_view(["GET"])
def get_dashboard_persons(request):
    try:
        course_sessions = get_course_sessions_with_roles_for_user(request.user)
        all_to_serialize = course_sessions

        return Response(
            status=200,
            data=CourseSessionSerializer(
                all_to_serialize, many=True, context={"user": request.user}
            ).data,
        )
    except PermissionDenied as e:
        raise e
    except Exception as e:
        logger.error(e, exc_info=True)
        return Response({"error": str(e)}, status=404)