# coding=utf-8
"""
Django Extensions additional model fields
"""
import re
import six
import string
import warnings

try:
    import uuid
    HAS_UUID = True
except ImportError:
    HAS_UUID = False

try:
    import shortuuid
    HAS_SHORT_UUID = True
except ImportError:
    HAS_SHORT_UUID = False

from django.core.exceptions import ImproperlyConfigured
from django.db.models import DateTimeField, CharField, SlugField
from django.utils.crypto import get_random_string
from django.template.defaultfilters import slugify

try:
    from django.utils.timezone import now as datetime_now
    assert datetime_now
except ImportError:
    import datetime
    datetime_now = datetime.datetime.now

try:
    from django.utils.encoding import force_unicode  # NOQA
except ImportError:
    from django.utils.encoding import force_text as force_unicode  # NOQA


MAX_UNIQUE_QUERY_ATTEMPTS = 100


class UniqueFieldMixin(object):

    def check_is_bool(self, attrname):
        if not isinstance(getattr(self, attrname), bool):
            raise ValueError("'{}' argument must be True or False".format(attrname))

    @staticmethod
    def _get_fields(model_cls):
        if hasattr(model_cls._meta, 'get_fields'):
            # verbosity due to replacement of deprecated model_cls._meta.get_fields_with_model(),
            # as explained here: https://docs.djangoproject.com/en/1.9/ref/models/meta/#migrating-from-the-old-api
            return [
                (f, f.model if f.model != model_cls else None) for f in model_cls._meta.get_fields()
                if not f.is_relation or f.one_to_one or (f.many_to_one and f.related_model)
            ]
        else:
            # prior to 1.9
            return model_cls._meta.get_fields_with_model()

    def get_queryset(self, model_cls, slug_field):
        for field, model in self._get_fields(model_cls):
            if model and field == slug_field:
                return model._default_manager.all()
        return model_cls._default_manager.all()

    def find_unique(self, model_instance, field, iterator, *args):
        # exclude the current model instance from the queryset used in finding
        # next valid hash
        queryset = self.get_queryset(model_instance.__class__, field)
        if model_instance.pk:
            queryset = queryset.exclude(pk=model_instance.pk)

        # form a kwarg dict used to impliment any unique_together contraints
        kwargs = {}
        for params in model_instance._meta.unique_together:
            if self.attname in params:
                for param in params:
                    kwargs[param] = getattr(model_instance, param, None)

        new = six.next(iterator)
        kwargs[self.attname] = new
        while not new or queryset.filter(**kwargs):
            new = six.next(iterator)
            kwargs[self.attname] = new
        setattr(model_instance, self.attname, new)
        return new


class AutoSlugField(UniqueFieldMixin, SlugField):
    """ AutoSlugField

    By default, sets editable=False, blank=True.

    Required arguments:

    populate_from
        Specifies which field or list of fields the slug is populated from.

    Optional arguments:

    separator
        Defines the used separator (default: '-')

    overwrite
        If set to True, overwrites the slug on every save (default: False)

    Inspired by SmileyChris' Unique Slugify snippet:
    http://www.djangosnippets.org/snippets/690/
    """
    def __init__(self, *args, **kwargs):
        kwargs.setdefault('blank', True)
        kwargs.setdefault('editable', False)

        populate_from = kwargs.pop('populate_from', None)
        if populate_from is None:
            raise ValueError("missing 'populate_from' argument")
        else:
            self._populate_from = populate_from

        self.slugify_function = kwargs.pop('slugify_function', slugify)
        self.separator = kwargs.pop('separator', six.u('-'))
        self.overwrite = kwargs.pop('overwrite', False)
        self.check_is_bool('overwrite')
        self.allow_duplicates = kwargs.pop('allow_duplicates', False)
        self.check_is_bool('allow_duplicates')
        super(AutoSlugField, self).__init__(*args, **kwargs)

    def _slug_strip(self, value):
        """
        Cleans up a slug by removing slug separator characters that occur at
        the beginning or end of a slug.

        If an alternate separator is used, it will also replace any instances
        of the default '-' separator with the new separator.
        """
        re_sep = '(?:-|%s)' % re.escape(self.separator)
        value = re.sub('%s+' % re_sep, self.separator, value)
        return re.sub(r'^%s+|%s+$' % (re_sep, re_sep), '', value)

    def slugify_func(self, content):
        if content:
            return self.slugify_function(content)
        return ''

    def slug_generator(self, original_slug, start):
        yield original_slug
        for i in range(start, MAX_UNIQUE_QUERY_ATTEMPTS):
            slug = original_slug
            end = '%s%s' % (self.separator, i)
            end_len = len(end)
            if self.slug_len and len(slug) + end_len > self.slug_len:
                slug = slug[:self.slug_len - end_len]
                slug = self._slug_strip(slug)
            slug = '%s%s' % (slug, end)
            yield slug
        raise RuntimeError('max slug attempts for %s exceeded (%s)' %
            (original_slug, MAX_UNIQUE_QUERY_ATTEMPTS))

    def create_slug(self, model_instance, add):
        # get fields to populate from and slug field to set
        if not isinstance(self._populate_from, (list, tuple)):
            self._populate_from = (self._populate_from, )
        slug_field = model_instance._meta.get_field(self.attname)

        if add or self.overwrite:
            # slugify the original field content and set next step to 2
            slug_for_field = lambda field: self.slugify_func(getattr(model_instance, field))
            slug = self.separator.join(map(slug_for_field, self._populate_from))
            start = 2
        else:
            # get slug from the current model instance
            slug = getattr(model_instance, self.attname)
            # model_instance is being modified, and overwrite is False,
            # so instead of doing anything, just return the current slug
            return slug

        # strip slug depending on max_length attribute of the slug field
        # and clean-up
        self.slug_len = slug_field.max_length
        if self.slug_len:
            slug = slug[:self.slug_len]
        slug = self._slug_strip(slug)
        original_slug = slug

        if self.allow_duplicates:
            return slug

        return super(AutoSlugField, self).find_unique(
            model_instance, slug_field, self.slug_generator(original_slug, start))

    def pre_save(self, model_instance, add):
        value = force_unicode(self.create_slug(model_instance, add))
        return value

    def get_internal_type(self):
        return "SlugField"

    def south_field_triple(self):
        """Returns a suitable description of this field for South."""
        # We'll just introspect the _actual_ field.
        from south.modelsinspector import introspector
        field_class = '%s.AutoSlugField' % self.__module__
        args, kwargs = introspector(self)
        kwargs.update({
            'populate_from': repr(self._populate_from),
            'separator': repr(self.separator),
            'overwrite': repr(self.overwrite),
            'allow_duplicates': repr(self.allow_duplicates),
        })
        # That's our definition!
        return field_class, args, kwargs

    def deconstruct(self):
        name, path, args, kwargs = super(AutoSlugField, self).deconstruct()
        kwargs['populate_from'] = self._populate_from
        if not self.separator == six.u('-'):
            kwargs['separator'] = self.separator
        if self.overwrite is not False:
            kwargs['overwrite'] = True
        if self.allow_duplicates is not False:
            kwargs['allow_duplicates'] = True
        return name, path, args, kwargs


class RandomCharField(UniqueFieldMixin, CharField):
    """ RandomCharField

    By default, sets editable=False, blank=True, unique=False.

    Required arguments:

    length
        Specifies the length of the field

    Optional arguments:

    unique
        If set to True, duplicate entries are not allowed (default: False)

    lowercase
        If set to True, lowercase the alpha characters (default: False)

    uppercase
        If set to True, uppercase the alpha characters (default: False)

    include_alpha
        If set to True, include alpha characters (default: True)

    include_digits
        If set to True, include digit characters (default: True)

    include_punctuation
        If set to True, include punctuation characters (default: False)
    """
    def __init__(self, *args, **kwargs):
        kwargs.setdefault('blank', True)
        kwargs.setdefault('editable', False)

        self.length = kwargs.pop('length', None)
        if self.length is None:
            raise ValueError("missing 'length' argument")
        kwargs['max_length'] = self.length

        self.lowercase = kwargs.pop('lowercase', False)
        self.check_is_bool('lowercase')
        self.uppercase = kwargs.pop('uppercase', False)
        self.check_is_bool('uppercase')
        if self.uppercase and self.lowercase:
            raise ValueError("the 'lowercase' and 'uppercase' arguments are mutually exclusive")
        self.include_digits = kwargs.pop('include_digits', True)
        self.check_is_bool('include_digits')
        self.include_alpha = kwargs.pop('include_alpha', True)
        self.check_is_bool('include_alpha')
        self.include_punctuation = kwargs.pop('include_punctuation', False)
        self.check_is_bool('include_punctuation')

        # Set unique=False unless it's been set manually.
        if 'unique' not in kwargs:
            kwargs['unique'] = False

        super(RandomCharField, self).__init__(*args, **kwargs)

    def random_char_generator(self, chars):
        for i in range(MAX_UNIQUE_QUERY_ATTEMPTS):
            yield ''.join(get_random_string(self.length, chars))
        raise RuntimeError('max random character attempts exceeded (%s)' %
            MAX_UNIQUE_QUERY_ATTEMPTS)

    def pre_save(self, model_instance, add):
        if not add and getattr(model_instance, self.attname) != '':
            return getattr(model_instance, self.attname)

        population = ''
        if self.include_alpha:
            if self.lowercase:
                population += string.ascii_lowercase
            elif self.uppercase:
                population += string.ascii_uppercase
            else:
                population += string.ascii_letters

        if self.include_digits:
            population += string.digits

        if self.include_punctuation:
            population += string.punctuation

        random_chars = self.random_char_generator(population)
        if not self.unique:
            new = six.next(random_chars)
            setattr(model_instance, self.attname, new)
            return new

        return super(RandomCharField, self).find_unique(
            model_instance,
            model_instance._meta.get_field(self.attname),
            random_chars,
        )

    def internal_type(self):
        return "CharField"

    def south_field_triple(self):
        """Returns a suitable description of this field for South."""
        # We'll just introspect the _actual_ field.
        from south.modelsinspector import introspector
        field_class = '%s.RandomCharField' % self.__module__
        args, kwargs = introspector(self)
        kwargs.update({
            'lowercase': repr(self.lowercase),
            'include_digits': repr(self.include_digits),
            'include_aphla': repr(self.include_alpha),
            'include_punctuation': repr(self.include_punctuation),
            'length': repr(self.length),
            'unique': repr(self.unique),
        })
        del kwargs['max_length']
        # That's our definition!
        return field_class, args, kwargs

    def deconstruct(self):
        name, path, args, kwargs = super(RandomCharField, self).deconstruct()
        kwargs['length'] = self.length