from django.db import models
from backend.models.module import BasicModule, BasicModuleSerializer, BasicModuleViewSet
from backend.models.university import University
from rest_framework import serializers


def check_nones(val1, val2):
    if val1 is None and val2 is not None:
        raise serializers.ValidationError("Check your dates")

    if val2 is None and val1 is not None:
        raise serializers.ValidationError("Check your dates")

    return val1 is None and val2 is None


class UniversitySemestersDates(BasicModule):

    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 validate(self, attrs):
        spring_ok = check_nones(attrs['spring_begin'], attrs['spring_end'])
        autumn_ok = check_nones(attrs['autumn_begin'], attrs['autumn_end'])

        if not spring_ok:
            spring_ok = attrs['spring_begin'] < attrs['spring_end']

        if not autumn_ok:
            autumn_ok = attrs['autumn_begin'] < attrs['autumn_end']
        # no check if spring_end < autumn_begin in case info is not available

        if not (spring_ok and autumn_ok):
            raise serializers.ValidationError(
                "Check your dates !")  # TODO better error

        return attrs

    class Meta:
        model = UniversitySemestersDates
        fields = '__all__'


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