user_views.py

from django.db.models import QuerySet
from django.shortcuts import get_object_or_404

from rest_framework.permissions import IsAuthenticated
from rest_framework.exceptions import PermissionDenied
from rest_framework.generics import (
    ListAPIView,
    CreateAPIView,
    RetrieveAPIView,
    RetrieveUpdateAPIView,
)

from user.models import User
from post.models import Post
from post.serializers import PostSerializer
from user.serializers import UserSerializer
from user.permissions import UserIsOwnerOrReadOnly


class UserRegistrationAPIView(CreateAPIView):
    serializer_class = UserSerializer


class UserUpdateAPIView(RetrieveUpdateAPIView):
    lookup_url_kwarg = 'username'
    queryset = User.objects.all()
    lookup_field = 'username__iexact'
    serializer_class = UserSerializer
    permission_classes = (IsAuthenticated, UserIsOwnerOrReadOnly)


class UserFollowingListAPIView(ListAPIView):
    serializer_class = UserSerializer
    permission_classes = (IsAuthenticated,)

    def get_queryset(self) -> QuerySet:
        return self.request.user.following


class UserFollowersListAPIView(ListAPIView):
    serializer_class = UserSerializer
    permission_classes = (IsAuthenticated,)

    def get_queryset(self) -> QuerySet:
        return self.request.user.followers


class UserDetailAPIView(RetrieveAPIView):
    lookup_url_kwarg = 'username'
    queryset = User.objects.all()
    lookup_field = 'username__iexact'
    serializer_class = UserSerializer


class UserPostListAPIView(ListAPIView):
    serializer_class = PostSerializer
    permission_classes = (IsAuthenticated,)

    def get_queryset(self) -> QuerySet:
        username = self.kwargs['username']
        user = get_object_or_404(User, username__iexact=username)
        if user in self.request.user.following or not user.private:
            return Post.objects.filter(user__username__iexact=username)
        else:
            raise PermissionDenied('Follow user to see their posts.')