# Τεκμηρίωση του Django - 1.10.7

# Πηγαίος κώδικας για το django.contrib.auth.password_validation

    from __future__ import unicode_literals

    import gzip
    import os
    import re
    from difflib import SequenceMatcher

    from django.conf import settings
    from django.core.exceptions import ImproperlyConfigured, ValidationError
    from django.utils import lru_cache
    from django.utils._os import upath
    from django.utils.encoding import force_text
    from django.utils.functional import lazy
    from django.utils.html import format_html
    from django.utils.module_loading import import_string
    from django.utils.six import string_types, text_type
    from django.utils.translation import ugettext as _, ungettext

    @lru_cache.lru_cache(maxsize=None)
    def get_default_password_validators():
        return get_password_validators(settings.AUTH_PASSWORD_VALIDATORS)

    def get_password_validators(validator_config):
        validators = []
        for validator in validator_config:
            try:
                klass = import_string(validator['NAME'])
            except ImportError:
                msg = "The module in NAME could not be imported: %s. Check your AUTH_PASSWORD_VALIDATORS setting."
                raise ImproperlyConfigured(msg % validator['NAME'])
            validators.append(klass(**validator.get('OPTIONS', {})))

        return validators

    def validate_password(password, user=None, password_validators=None):
        """
        Validate whether the password meets all validator requirements.

        If the password is valid, return ``None``.
        If the password is invalid, raise ValidationError with all error messages.
        """
        errors = []
        if password_validators is None:
            password_validators = get_default_password_validators()
        for validator in password_validators:
            try:
                validator.validate(password, user)
            except ValidationError as error:
                errors.append(error)
        if errors:
            raise ValidationError(errors)

    def password_changed(password, user=None, password_validators=None):
        """
        Inform all validators that have implemented a password_changed() method
        that the password has been changed.
        """
        if password_validators is None:
            password_validators = get_default_password_validators()
        for validator in password_validators:
            password_changed = getattr(validator, 'password_changed', lambda *a: None)
            password_changed(password, user)

    def password_validators_help_texts(password_validators=None):
        """
        Return a list of all help texts of all configured validators.
        """
        help_texts = []
        if password_validators is None:
            password_validators = get_default_password_validators()
        for validator in password_validators:
            help_texts.append(validator.get_help_text())
        return help_texts

    def _password_validators_help_text_html(password_validators=None):
        """
        Return an HTML string with all help texts of all configured validators
        in an <ul>.
        """
        help_texts = password_validators_help_texts(password_validators)
        help_items = [format_html('<li>{}</li>', help_text) for help_text in help_texts]
        return '<ul>%s</ul>' % ''.join(help_items) if help_items else ''
    password_validators_help_text_html = lazy(_password_validators_help_text_html, text_type)

    class MinimumLengthValidator(object):
        """
        Validate whether the password is of a minimum length.
        """
        def __init__(self, min_length=8):
            self.min_length = min_length

        def validate(self, password, user=None):
            if len(password) < self.min_length:
                raise ValidationError(
                    ungettext(
                        "This password is too short. It must contain at least %(min_length)d character.",
                        "This password is too short. It must contain at least %(min_length)d characters.",
                        self.min_length
                    ),
                    code='password_too_short',
                    params={'min_length': self.min_length},
                )

        def get_help_text(self):
            return ungettext(
                "Your password must contain at least %(min_length)d character.",
                "Your password must contain at least %(min_length)d characters.",
                self.min_length
            ) % {'min_length': self.min_length}

    class UserAttributeSimilarityValidator(object):
        """
        Validate whether the password is sufficiently different from the user's
        attributes.

        If no specific attributes are provided, look at a sensible list of
        defaults. Attributes that don't exist are ignored. Comparison is made to
        not only the full attribute value, but also its components, so that, for
        example, a password is validated against either part of an email address,
        as well as the full address.
        """
        DEFAULT_USER_ATTRIBUTES = ('username', 'first_name', 'last_name', 'email')

        def __init__(self, user_attributes=DEFAULT_USER_ATTRIBUTES, max_similarity=0.7):
            self.user_attributes = user_attributes
            self.max_similarity = max_similarity

        def validate(self, password, user=None):
            if not user:
                return

            for attribute_name in self.user_attributes:
                value = getattr(user, attribute_name, None)
                if not value or not isinstance(value, string_types):
                    continue
                value_parts = re.split('\W+', value) + [value]
                for value_part in value_parts:
                    if SequenceMatcher(a=password.lower(), b=value_part.lower()).quick_ratio() > self.max_similarity:
                        verbose_name = force_text(user._meta.get_field(attribute_name).verbose_name)
                        raise ValidationError(
                            _("The password is too similar to the %(verbose_name)s."),
                            code='password_too_similar',
                            params={'verbose_name': verbose_name},
                        )

        def get_help_text(self):
            return _("Your password can't be too similar to your other personal information.")

    class CommonPasswordValidator(object):
        """
        Validate whether the password is a common password.

        The password is rejected if it occurs in a provided list, which may be gzipped.
        The list Django ships with contains 1000 common passwords, created by Mark Burnett:
        https://xato.net/passwords/more-top-worst-passwords/
        """
        DEFAULT_PASSWORD_LIST_PATH = os.path.join(
            os.path.dirname(os.path.realpath(upath(__file__))), 'common-passwords.txt.gz'
        )

        def __init__(self, password_list_path=DEFAULT_PASSWORD_LIST_PATH):
            try:
                common_passwords_lines = gzip.open(password_list_path).read().decode('utf-8').splitlines()
            except IOError:
                with open(password_list_path) as f:
                    common_passwords_lines = f.readlines()

            self.passwords = {p.strip() for p in common_passwords_lines}

        def validate(self, password, user=None):
            if password.lower().strip() in self.passwords:
                raise ValidationError(
                    _("This password is too common."),
                    code='password_too_common',
                )

        def get_help_text(self):
            return _("Your password can't be a commonly used password.")

    class NumericPasswordValidator(object):
        """
        Validate whether the password is alphanumeric.
        """
        def validate(self, password, user=None):
            if password.isdigit():
                raise ValidationError(
                    _("This password is entirely numeric."),
                    code='password_entirely_numeric',
                )

        def get_help_text(self):
            return _("Your password can't be entirely numeric.")