import ipaddress
import re
from pathlib import Path
from urllib.parse import urlsplit, urlunsplit

from django.core.exceptions import ValidationError
from django.utils.deconstruct import deconstructible
from django.utils.encoding import punycode
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 = 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 = punycode(netloc)  # 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 = punycode(domain_part)
            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)
        limit_value = self.limit_value() if callable(self.limit_value) else self.limit_value
        params = {'limit_value': limit_value, 'show_value': cleaned, 'value': value}
        if self.compare(cleaned, limit_value):
            raise ValidationError(self.message, code=self.code, params=params)

    def __eq__(self, other):
        if not isinstance(other, self.__class__):
            return NotImplemented
        return (
            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 = {
        'invalid': _('Enter a number.'),
        '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 in {'F', 'n', 'N'}:
            raise ValidationError(self.messages['invalid'])
        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 = Path(value.name).suffix[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]


def validate_image_file_extension(value):
    return FileExtensionValidator(allowed_extensions=get_available_image_extensions())(value)


@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
        )
