# dokumentasi Django 2.0.8

# Kode sumber untuk django.core.validators

    import ipaddress
    import os
    import re
    from urllib.parse import urlsplit, urlunsplit

    from django.core.exceptions import ValidationError
    from django.utils.deconstruct import deconstructible
    from django.utils.functional import SimpleLazyObject
    from django.utils.ipv6 import is_valid_ipv6_address
    from django.utils.translation import gettext_lazy as _, ngettext_lazy

    # These values, if given to validate(), will trigger the self.required check.
    EMPTY_VALUES = (None, '', [], (), {})

    def _lazy_re_compile(regex, flags=0):
        """Lazily compile a regex with flags."""
        def _compile():
            # Compile the regex if it was not passed pre-compiled.
            if isinstance(regex, str):
                return re.compile(regex, flags)
            else:
                assert not flags, "flags must be empty if regex is passed pre-compiled"
                return regex
        return SimpleLazyObject(_compile)

    @deconstructible
    class RegexValidator:
        regex = ''
        message = _('Enter a valid value.')
        code = 'invalid'
        inverse_match = False
        flags = 0

        def __init__(self, regex=None, message=None, code=None, inverse_match=None, flags=None):
            if regex is not None:
                self.regex = regex
            if message is not None:
                self.message = message
            if code is not None:
                self.code = code
            if inverse_match is not None:
                self.inverse_match = inverse_match
            if flags is not None:
                self.flags = flags
            if self.flags and not isinstance(self.regex, str):
                raise TypeError("If the flags are set, regex must be a regular expression string.")

            self.regex = _lazy_re_compile(self.regex, self.flags)

        def __call__(self, value):
            """
            Validate that the input contains (or does *not* contain, if
            inverse_match is True) a match for the regular expression.
            """
            regex_matches = bool(self.regex.search(str(value)))
            invalid_input = regex_matches if self.inverse_match else not regex_matches
            if invalid_input:
                raise ValidationError(self.message, code=self.code)

        def __eq__(self, other):
            return (
                isinstance(other, RegexValidator) and
                self.regex.pattern == other.regex.pattern and
                self.regex.flags == other.regex.flags and
                (self.message == other.message) and
                (self.code == other.code) and
                (self.inverse_match == other.inverse_match)
            )

    @deconstructible
    class URLValidator(RegexValidator):
        ul = '\u00a1-\uffff'  # unicode letters range (must not be a raw string)

        # IP patterns
        ipv4_re = r'(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)(?:\.(?:25[0-5]|2[0-4]\d|[0-1]?\d?\d)){3}'
        ipv6_re = r'\[[0-9a-f:\.]+\]'  # (simple regex, validated later)

        # Host patterns
        hostname_re = r'[a-z' + ul + r'0-9](?:[a-z' + ul + r'0-9-]{0,61}[a-z' + ul + r'0-9])?'
        # Max length for domain name labels is 63 characters per RFC 1034 sec. 3.1
        domain_re = r'(?:\.(?!-)[a-z' + ul + r'0-9-]{1,63}(?<!-))*'
        tld_re = (
            r'\.'                                # dot
            r'(?!-)'                             # can't start with a dash
            r'(?:[a-z' + ul + '-]{2,63}'         # domain label
            r'|xn--[a-z0-9]{1,59})'              # or punycode label
            r'(?<!-)'                            # can't end with a dash
            r'\.?'                               # may have a trailing dot
        )
        host_re = '(' + hostname_re + domain_re + tld_re + '|localhost)'

        regex = _lazy_re_compile(
            r'^(?:[a-z0-9\.\-\+]*)://'  # scheme is validated separately
            r'(?:\S+(?::\S*)?@)?'  # user:pass authentication
            r'(?:' + ipv4_re + '|' + ipv6_re + '|' + host_re + ')'
            r'(?::\d{2,5})?'  # port
            r'(?:[/?#][^\s]*)?'  # resource path
            r'\Z', re.IGNORECASE)
        message = _('Enter a valid URL.')
        schemes = ['http', 'https', 'ftp', 'ftps']

        def __init__(self, schemes=None, **kwargs):
            super().__init__(**kwargs)
            if schemes is not None:
                self.schemes = schemes

        def __call__(self, value):
            # Check first if the scheme is valid
            scheme = value.split('://')[0].lower()
            if scheme not in self.schemes:
                raise ValidationError(self.message, code=self.code)

            # Then check full URL
            try:
                super().__call__(value)
            except ValidationError as e:
                # Trivial case failed. Try for possible IDN domain
                if value:
                    try:
                        scheme, netloc, path, query, fragment = urlsplit(value)
                    except ValueError:  # for example, "Invalid IPv6 URL"
                        raise ValidationError(self.message, code=self.code)
                    try:
                        netloc = netloc.encode('idna').decode('ascii')  # IDN -> ACE
                    except UnicodeError:  # invalid domain part
                        raise e
                    url = urlunsplit((scheme, netloc, path, query, fragment))
                    super().__call__(url)
                else:
                    raise
            else:
                # Now verify IPv6 in the netloc part
                host_match = re.search(r'^\[(.+)\](?::\d{2,5})?$', urlsplit(value).netloc)
                if host_match:
                    potential_ip = host_match.groups()[0]
                    try:
                        validate_ipv6_address(potential_ip)
                    except ValidationError:
                        raise ValidationError(self.message, code=self.code)

            # The maximum length of a full host name is 253 characters per RFC 1034
            # section 3.1. It's defined to be 255 bytes or less, but this includes
            # one byte for the length of the name and one byte for the trailing dot
            # that's used to indicate absolute names in DNS.
            if len(urlsplit(value).netloc) > 253:
                raise ValidationError(self.message, code=self.code)

    integer_validator = RegexValidator(
        _lazy_re_compile(r'^-?\d+\Z'),
        message=_('Enter a valid integer.'),
        code='invalid',
    )

    def validate_integer(value):
        return integer_validator(value)

    @deconstructible
    class EmailValidator:
        message = _('Enter a valid email address.')
        code = 'invalid'
        user_regex = _lazy_re_compile(
            r"(^[-!#$%&'*+/=?^_`{}|~0-9A-Z]+(\.[-!#$%&'*+/=?^_`{}|~0-9A-Z]+)*\Z"  # dot-atom
            r'|^"([\001-\010\013\014\016-\037!#-\[\]-\177]|\\[\001-\011\013\014\016-\177])*"\Z)',  # quoted-string
            re.IGNORECASE)
        domain_regex = _lazy_re_compile(
            # max length for domain name labels is 63 characters per RFC 1034
            r'((?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+)(?:[A-Z0-9-]{2,63}(?<!-))\Z',
            re.IGNORECASE)
        literal_regex = _lazy_re_compile(
            # literal form, ipv4 or ipv6 address (SMTP 4.1.3)
            r'\[([A-f0-9:\.]+)\]\Z',
            re.IGNORECASE)
        domain_whitelist = ['localhost']

        def __init__(self, message=None, code=None, whitelist=None):
            if message is not None:
                self.message = message
            if code is not None:
                self.code = code
            if whitelist is not None:
                self.domain_whitelist = whitelist

        def __call__(self, value):
            if not value or '@' not in value:
                raise ValidationError(self.message, code=self.code)

            user_part, domain_part = value.rsplit('@', 1)

            if not self.user_regex.match(user_part):
                raise ValidationError(self.message, code=self.code)

            if (domain_part not in self.domain_whitelist and
                    not self.validate_domain_part(domain_part)):
                # Try for possible IDN domain-part
                try:
                    domain_part = domain_part.encode('idna').decode('ascii')
                except UnicodeError:
                    pass
                else:
                    if self.validate_domain_part(domain_part):
                        return
                raise ValidationError(self.message, code=self.code)

        def validate_domain_part(self, domain_part):
            if self.domain_regex.match(domain_part):
                return True

            literal_match = self.literal_regex.match(domain_part)
            if literal_match:
                ip_address = literal_match.group(1)
                try:
                    validate_ipv46_address(ip_address)
                    return True
                except ValidationError:
                    pass
            return False

        def __eq__(self, other):
            return (
                isinstance(other, EmailValidator) and
                (self.domain_whitelist == other.domain_whitelist) and
                (self.message == other.message) and
                (self.code == other.code)
            )

    validate_email = EmailValidator()

    slug_re = _lazy_re_compile(r'^[-a-zA-Z0-9_]+\Z')
    validate_slug = RegexValidator(
        slug_re,
        # Translators: "letters" means latin letters: a-z and A-Z.
        _("Enter a valid 'slug' consisting of letters, numbers, underscores or hyphens."),
        'invalid'
    )

    slug_unicode_re = _lazy_re_compile(r'^[-\w]+\Z')
    validate_unicode_slug = RegexValidator(
        slug_unicode_re,
        _("Enter a valid 'slug' consisting of Unicode letters, numbers, underscores, or hyphens."),
        'invalid'
    )

    def validate_ipv4_address(value):
        try:
            ipaddress.IPv4Address(value)
        except ValueError:
            raise ValidationError(_('Enter a valid IPv4 address.'), code='invalid')

    def validate_ipv6_address(value):
        if not is_valid_ipv6_address(value):
            raise ValidationError(_('Enter a valid IPv6 address.'), code='invalid')

    def validate_ipv46_address(value):
        try:
            validate_ipv4_address(value)
        except ValidationError:
            try:
                validate_ipv6_address(value)
            except ValidationError:
                raise ValidationError(_('Enter a valid IPv4 or IPv6 address.'), code='invalid')

    ip_address_validator_map = {
        'both': ([validate_ipv46_address], _('Enter a valid IPv4 or IPv6 address.')),
        'ipv4': ([validate_ipv4_address], _('Enter a valid IPv4 address.')),
        'ipv6': ([validate_ipv6_address], _('Enter a valid IPv6 address.')),
    }

    def ip_address_validators(protocol, unpack_ipv4):
        """
        Depending on the given parameters, return the appropriate validators for
        the GenericIPAddressField.
        """
        if protocol != 'both' and unpack_ipv4:
            raise ValueError(
                "You can only use `unpack_ipv4` if `protocol` is set to 'both'")
        try:
            return ip_address_validator_map[protocol.lower()]
        except KeyError:
            raise ValueError("The protocol '%s' is unknown. Supported: %s"
                             % (protocol, list(ip_address_validator_map)))

    def int_list_validator(sep=',', message=None, code='invalid', allow_negative=False):
        regexp = _lazy_re_compile(r'^%(neg)s\d+(?:%(sep)s%(neg)s\d+)*\Z' % {
            'neg': '(-)?' if allow_negative else '',
            'sep': re.escape(sep),
        })
        return RegexValidator(regexp, message=message, code=code)

    validate_comma_separated_integer_list = int_list_validator(
        message=_('Enter only digits separated by commas.'),
    )

    @deconstructible
    class BaseValidator:
        message = _('Ensure this value is %(limit_value)s (it is %(show_value)s).')
        code = 'limit_value'

        def __init__(self, limit_value, message=None):
            self.limit_value = limit_value
            if message:
                self.message = message

        def __call__(self, value):
            cleaned = self.clean(value)
            params = {'limit_value': self.limit_value, 'show_value': cleaned, 'value': value}
            if self.compare(cleaned, self.limit_value):
                raise ValidationError(self.message, code=self.code, params=params)

        def __eq__(self, other):
            return (
                isinstance(other, self.__class__) and
                self.limit_value == other.limit_value and
                self.message == other.message and
                self.code == other.code
            )

        def compare(self, a, b):
            return a is not b

        def clean(self, x):
            return x

    @deconstructible
    class MaxValueValidator(BaseValidator):
        message = _('Ensure this value is less than or equal to %(limit_value)s.')
        code = 'max_value'

        def compare(self, a, b):
            return a > b

    @deconstructible
    class MinValueValidator(BaseValidator):
        message = _('Ensure this value is greater than or equal to %(limit_value)s.')
        code = 'min_value'

        def compare(self, a, b):
            return a < b

    @deconstructible
    class MinLengthValidator(BaseValidator):
        message = ngettext_lazy(
            'Ensure this value has at least %(limit_value)d character (it has %(show_value)d).',
            'Ensure this value has at least %(limit_value)d characters (it has %(show_value)d).',
            'limit_value')
        code = 'min_length'

        def compare(self, a, b):
            return a < b

        def clean(self, x):
            return len(x)

    @deconstructible
    class MaxLengthValidator(BaseValidator):
        message = ngettext_lazy(
            'Ensure this value has at most %(limit_value)d character (it has %(show_value)d).',
            'Ensure this value has at most %(limit_value)d characters (it has %(show_value)d).',
            'limit_value')
        code = 'max_length'

        def compare(self, a, b):
            return a > b

        def clean(self, x):
            return len(x)

    @deconstructible
    class DecimalValidator:
        """
        Validate that the input does not exceed the maximum number of digits
        expected, otherwise raise ValidationError.
        """
        messages = {
            'max_digits': ngettext_lazy(
                'Ensure that there are no more than %(max)s digit in total.',
                'Ensure that there are no more than %(max)s digits in total.',
                'max'
            ),
            'max_decimal_places': ngettext_lazy(
                'Ensure that there are no more than %(max)s decimal place.',
                'Ensure that there are no more than %(max)s decimal places.',
                'max'
            ),
            'max_whole_digits': ngettext_lazy(
                'Ensure that there are no more than %(max)s digit before the decimal point.',
                'Ensure that there are no more than %(max)s digits before the decimal point.',
                'max'
            ),
        }

        def __init__(self, max_digits, decimal_places):
            self.max_digits = max_digits
            self.decimal_places = decimal_places

        def __call__(self, value):
            digit_tuple, exponent = value.as_tuple()[1:]
            if exponent >= 0:
                # A positive exponent adds that many trailing zeros.
                digits = len(digit_tuple) + exponent
                decimals = 0
            else:
                # If the absolute value of the negative exponent is larger than the
                # number of digits, then it's the same as the number of digits,
                # because it'll consume all of the digits in digit_tuple and then
                # add abs(exponent) - len(digit_tuple) leading zeros after the
                # decimal point.
                if abs(exponent) > len(digit_tuple):
                    digits = decimals = abs(exponent)
                else:
                    digits = len(digit_tuple)
                    decimals = abs(exponent)
            whole_digits = digits - decimals

            if self.max_digits is not None and digits > self.max_digits:
                raise ValidationError(
                    self.messages['max_digits'],
                    code='max_digits',
                    params={'max': self.max_digits},
                )
            if self.decimal_places is not None and decimals > self.decimal_places:
                raise ValidationError(
                    self.messages['max_decimal_places'],
                    code='max_decimal_places',
                    params={'max': self.decimal_places},
                )
            if (self.max_digits is not None and self.decimal_places is not None and
                    whole_digits > (self.max_digits - self.decimal_places)):
                raise ValidationError(
                    self.messages['max_whole_digits'],
                    code='max_whole_digits',
                    params={'max': (self.max_digits - self.decimal_places)},
                )

        def __eq__(self, other):
            return (
                isinstance(other, self.__class__) and
                self.max_digits == other.max_digits and
                self.decimal_places == other.decimal_places
            )

    @deconstructible
    class FileExtensionValidator:
        message = _(
            "File extension '%(extension)s' is not allowed. "
            "Allowed extensions are: '%(allowed_extensions)s'."
        )
        code = 'invalid_extension'

        def __init__(self, allowed_extensions=None, message=None, code=None):
            if allowed_extensions is not None:
                allowed_extensions = [allowed_extension.lower() for allowed_extension in allowed_extensions]
            self.allowed_extensions = allowed_extensions
            if message is not None:
                self.message = message
            if code is not None:
                self.code = code

        def __call__(self, value):
            extension = os.path.splitext(value.name)[1][1:].lower()
            if self.allowed_extensions is not None and extension not in self.allowed_extensions:
                raise ValidationError(
                    self.message,
                    code=self.code,
                    params={
                        'extension': extension,
                        'allowed_extensions': ', '.join(self.allowed_extensions)
                    }
                )

        def __eq__(self, other):
            return (
                isinstance(other, self.__class__) and
                self.allowed_extensions == other.allowed_extensions and
                self.message == other.message and
                self.code == other.code
            )

    def get_available_image_extensions():
        try:
            from PIL import Image
        except ImportError:
            return []
        else:
            Image.init()
            return [ext.lower()[1:] for ext in Image.EXTENSION]

    validate_image_file_extension = FileExtensionValidator(
        allowed_extensions=get_available_image_extensions(),
    )

    @deconstructible
    class ProhibitNullCharactersValidator:
        """Validate that the string doesn't contain the null character."""
        message = _('Null characters are not allowed.')
        code = 'null_characters_not_allowed'

        def __init__(self, message=None, code=None):
            if message is not None:
                self.message = message
            if code is not None:
                self.code = code

        def __call__(self, value):
            if '\x00' in str(value):
                raise ValidationError(self.message, code=self.code)

        def __eq__(self, other):
            return (
                isinstance(other, self.__class__) and
                self.message == other.message and
                self.code == other.code
            )