from django.core.exceptions import ValidationError
from django.core.validators import MinValueValidator, MaxValueValidator
from django.db import models
from netaddr import AddrFormatError, EUI, mac_unix_expanded

from ipam.constants import BGP_ASN_MAX, BGP_ASN_MIN


class ASNField(models.BigIntegerField):
    description = "32-bit ASN field"
    default_validators = [
        MinValueValidator(BGP_ASN_MIN),
        MaxValueValidator(BGP_ASN_MAX),
    ]

    def formfield(self, **kwargs):
        defaults = {
            'min_value': BGP_ASN_MIN,
            'max_value': BGP_ASN_MAX,
        }
        defaults.update(**kwargs)
        return super().formfield(**defaults)


class mac_unix_expanded_uppercase(mac_unix_expanded):
    word_fmt = '%.2X'


class MACAddressField(models.Field):
    description = "PostgreSQL MAC Address field"

    def python_type(self):
        return EUI

    def from_db_value(self, value, expression, connection):
        return self.to_python(value)

    def to_python(self, value):
        if value is None:
            return value
        try:
            return EUI(value, version=48, dialect=mac_unix_expanded_uppercase)
        except AddrFormatError as e:
            raise ValidationError("Invalid MAC address format: {}".format(value))

    def db_type(self, connection):
        return 'macaddr'

    def get_prep_value(self, value):
        if not value:
            return None
        return str(self.to_python(value))