import pyotp
import otpauth
from rest_framework import serializers, exceptions
from otpauth.models import OTPSeed

# For accessing / modifying the data -- currently unused
class OTPSerializer(serializers.ModelSerializer):
    class Meta:
        model = OTPSeed
        fields = ('name', 'realm', 'seed')
        read_only_fields = ('seed',)

    def create(self, validated_data):
        validated_data['seed'] = pyotp.random_base32()
        return OTPSeed.objects.create(**validated_data)

class TokenSerializer(serializers.Serializer):
    """ This class is mainly / only used for authentication"""

    auth_name = serializers.CharField(max_length=128)
    auth_token = serializers.CharField(max_length=128)
    auth_realm = serializers.CharField(max_length=128)

    token_name = 'auth_token'
    name_name = 'auth_name'
    realm_name = 'auth_realm'

    def save(self):
        auth_token = self.validated_data.get(self.token_name)
        auth_name =  self.validated_data.get(self.name_name)
        auth_realm =  self.validated_data.get(self.realm_name)

        # only 2 special realms can login
        if not auth_realm in ["ungleich-admin", "ungleich-auth" ]:
            raise exceptions.AuthenticationFailed()

        print("auth: [{}]{}@'{}' {} + {})".format(self.name_name, auth_name, auth_realm, auth_token, self.validated_data))

        # 1. Verify that the connection might authenticate
        try:
            db_instance = otpauth.models.OTPSeed.objects.get(name=auth_name, realm=auth_realm)
        except (OTPSeed.MultipleObjectsReturned, OTPSeed.DoesNotExist):
            print("does not exist")
            raise exceptions.AuthenticationFailed()

        totp = pyotp.TOTP(db_instance.seed)
        print("calculated token = {}".format(totp.now()))

        if not totp.verify(auth_token, valid_window=3):
            raise exceptions.AuthenticationFailed()

        return (db_instance, auth_token)

# For verifying somebody else's token
class VerifySerializer(TokenSerializer):
    name = serializers.CharField(max_length=128)
    token = serializers.CharField(max_length=128)
    realm = serializers.CharField(max_length=128)

    token_name = 'token'
    name_name = 'name'
    realm_name = 'realm'

    def save(self):
        auth_realm = self.validated_data.get("auth_realm")

        if not auth_realm == "ungleich-auth":
            raise exceptions.AuthenticationFailed()

        # Do the authentication part
        super().save()