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import math
import random
import logging
from django.contrib.sites.models import Site
from django.core.urlresolvers import reverse
import brevisurl.settings
from brevisurl import Error
from brevisurl.backends.base import BaseBrevisUrlBackend
from brevisurl.models import ShortUrl
log = logging.getLogger(__name__)
class TokensExhaustedError(Error):
"""Exception is raised when tokens are exhausted."""
class BrevisUrlBackend(BaseBrevisUrlBackend):
PROTOCOL = 'http'
def shorten_url(self, original_url):
"""
:raises: ImproperlyConfigured, django.core.exceptions.ValidationError
:raises: brevisurl.backends.local.TokensExhaustedError
"""
try:
short_url = ShortUrl.objects.get(backend=self.class_path, original_url=original_url)
log.info('Url "%s" already shortened to "%s"', original_url, short_url.shortened_url)
return short_url
except ShortUrl.DoesNotExist:
pass
try:
short_url = ShortUrl()
if self.kwargs.get('domain') is not None:
short_url.shortened_url = '{0}{1}'.format(self.kwargs.get('domain').rstrip('/'),
reverse('brevisurl_redirect',
kwargs={'token': self.__generate_token()}))
elif brevisurl.settings.LOCAL_BACKEND_DOMAIN is not None:
short_url.shortened_url = '{0}{1}'.format(brevisurl.settings.LOCAL_BACKEND_DOMAIN.rstrip('/'),
reverse('brevisurl_redirect',
kwargs={'token': self.__generate_token()}))
else:
current_site = Site.objects.get_current()
short_url.shortened_url = '{0}://{1}{2}'.format(self.PROTOCOL, current_site.domain,
reverse('brevisurl_redirect',
kwargs={'token': self.__generate_token()}))
short_url.original_url = original_url
short_url.backend = self.class_path
short_url.save()
log.info('Url "%s" shortened to "%s"', original_url, short_url.shortened_url)
return short_url
except Exception:
if self.fail_silently:
return None
else:
log.exception('Unknown exception raised while shortening url "%s"', original_url)
raise
def __generate_token(self):
chars = brevisurl.settings.LOCAL_BACKEND_TOKEN_CHARS
size = brevisurl.settings.LOCAL_BACKEND_TOKEN_LENGTH
if ShortUrl.objects.count() >= math.pow(len(chars), size):
raise TokensExhaustedError('Consider incrementing the token length or change the char list')
random.shuffle(chars)
while True:
token = ''.join([random.choice(chars) for x in range(size)])
if not ShortUrl.objects.filter(backend=self.class_path, shortened_url__endswith=token).count():
break
return token
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