import re

from django.core.validators import RegexValidator
from django.utils.translation import gettext_lazy as _


PHONE_NUMBER_REGEX = re.compile(r'^(?:1\d{10}|\+852\d{8}|\+853\d{8})$')


def normalize_phone_number(phone):
    """Normalize supported phone numbers before validation and persistence.

    Mainland China numbers keep the legacy 11-digit representation so existing
    accounts remain addressable without a data migration. Hong Kong and Macao
    numbers use E.164 representation to keep them globally unambiguous.
    """
    if phone is None:
        return None

    phone = re.sub(r'[\s()-]+', '', str(phone).strip())
    if phone.startswith('00'):
        phone = '+{}'.format(phone[2:])

    if re.fullmatch(r'\+861\d{10}', phone):
        return phone[3:]

    return phone


class PhoneNumberValidator(RegexValidator):
    regex = PHONE_NUMBER_REGEX
    message = _('invalid phone number')