import re

from django.core.exceptions import ValidationError
from django.core.validators import RegexValidator


def validate_lower(value):
    if value != value.lower():
        raise ValidationError(
            "Invalid value (not lowercase): %(value)s",
            code="invalid",
            params={"value": value},
        )


def validate_upper(value):
    if value != value.upper():
        raise ValidationError(
            "Invalid value (not uppercase): %(value)s",
            code="invalid",
            params={"value": value},
        )


validate_domain_name = [
    validate_lower,
    RegexValidator(
        regex=r"^(([a-z0-9_-]{1,63})\.)*[a-z0-9-]{1,63}$",
        message="Domain names must be labels separated by dots. Labels may consist of up to 63 letters, digits, "
        "hyphens, and underscores. The last label may not contain an underscore.",
        code="invalid_domain_name",
        flags=re.IGNORECASE,
    ),
]