from django.db import models
from backend.models.basic_module import BasicModule, BasicModuleSerializer, BasicModuleViewSet
from backend.models.university import University
from rest_framework import serializers
from backend.utils import get_model_config, get_viewset_permissions


def semester_error(semester_name):
    raise serializers.ValidationError(
        "Inconsistent {} semester dates".format(semester_name))


class UniversitySemestersDates(BasicModule):
    model_config = get_model_config("UniversitySemestersDates")

    university = models.OneToOneField(
        University, on_delete=models.CASCADE, related_name='university_semesters_dates', primary_key=True, null=False)

    spring_begin = models.DateField(null=True, blank=True)
    spring_end = models.DateField(null=True, blank=True)
    autumn_begin = models.DateField(null=True, blank=True)
    autumn_end = models.DateField(null=True, blank=True)

    @classmethod
    def get_serializer(cls):
        return UniversitySemestersDatesSerializer


class UniversitySemestersDatesSerializer(BasicModuleSerializer):

    def my_validate(self, attrs):
        attrs = super(UniversitySemestersDatesSerializer, self).my_validate(attrs)

        s_b, s_e = attrs['spring_begin'], attrs['spring_end']
        a_b, a_e = attrs['autumn_begin'], attrs['autumn_end']

        def test(begin, end, name):
            ok = (begin is None and end is None) or (
                begin is not None and end is not None)
            if not ok:
                semester_error(name)
            if begin is not None and (begin > end):
                semester_error(name)

        test(s_b, s_e, 'spring')
        test(a_b, a_e, 'autumn')

        if s_b is None and a_b is None:
            semester_error('autaumn and spring')

        return attrs

    class Meta:
        model = UniversitySemestersDates
        fields = '__all__'


class UniversitySemestersDatesViewSet(BasicModuleViewSet):
    permission_classes = get_viewset_permissions(
        "UniversitySemestersDatesViewSet")
    queryset = UniversitySemestersDates.objects.all()  # pylint: disable=E1101
    serializer_class = UniversitySemestersDatesSerializer