serializers.py

from rest_framework import serializers
from django.utils import timezone

from common.serializers import CurrentUserProfileDefault
from . import models


class TaskSerializer(serializers.ModelSerializer):
    created_by = serializers.HiddenField(default=CurrentUserProfileDefault())

    class Meta:
        model = models.Task
        read_only_fields = ('created_by', 'created_at', 'updated_at')
        fields = '__all__'

    def validate(self, data):
        if timezone.now() >= data['deadline']:
            raise serializers.ValidationError('Please, enter appropriate deadline.')
        return data


class SolutionSerializer(serializers.ModelSerializer):
    created_at = serializers.DateTimeField(read_only=True)
    updated_at = serializers.DateTimeField(read_only=True)
    created_by = serializers.HiddenField(default=CurrentUserProfileDefault())

    class Meta:
        model = models.Solution
        read_only_fields = ('created_by', 'created_at', 'updated_at', 'ready')
        fields = (
            'task',
            'created_at',
            'updated_at',
            'accepted',
            'files',
            'created_by',
            'corrected',
            'note',
        )

    def validate(self, data):
        if timezone.now() > data['task'].deadline:
            raise serializers.ValidationError('You late.')
        return data

    def create(self, validated_data):
        validated_data['accepted'] = False
        validated_data['corrected'] = False
        validated_data['note'] = ''
        return self.Meta.model.objects.create(**validated_data)