class PageSerializer(serializers.ModelSerializer):
    class Meta:
        model = Page
        fields = '__all__'


class TreeBooksSerializer(serializers.ModelSerializer):

    pages = serializers.SerializerMethodField()

    def get_pages(self, obj):
        qs = self.context.get('qs')
        for book in qs.books.all():
            if book.id == obj.id:
                pages = book.pages.all()
        return PageSerializer(pages, many=True).data

    class Meta:
        model = Book
        fields = '__all__'


class TreeSerializer(serializers.ModelSerializer):

    books = serializers.SerializerMethodField()

    def get_books(self, obj):
        qs = Publisher.objects.filter(id=obj.id).prefetch_related('books', 'books__pages').first()
        books = [book for book in qs.books.all()]
        return TreeBooksSerializer(books, many=True, context={'qs': qs}).data

    class Meta:
        model = Publisher
        fields = '__all__'