3 files changed, 94 insertions, 0 deletions
diff --git a/brevisurl/backends/__init__.py b/brevisurl/backends/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/brevisurl/backends/__init__.py
diff --git a/brevisurl/backends/base.py b/brevisurl/backends/base.py
new file mode 100644
index 0000000..3fc053a
--- /dev/null
+++ b/brevisurl/backends/base.py
@@ -0,0 +1,41 @@
+from abc import ABCMeta
+
+
+class BaseBrevisUrlBackend(object):
+    """Base class for brevisurl backend implementations. Subclasses must at least overwrite shorten_url()."""
+
+    __metaclass__ = ABCMeta
+
+
+    def __init__(self, fail_silently=False, **kwargs):
+        self.fail_silently = fail_silently
+        self.class_path = '{0}.{1}'.format(self.__module__, self.__class__.__name__)
+
+    def open(self):
+        """Open a network connection.
+
+        This method can be overwritten by backend implementations to
+        open a network connection.
+
+        It's up to the backend implementation to track the status of
+        a network connection if it's needed by the backend.
+
+        The default implementation does nothing.
+
+        """
+        pass
+
+    def close(self):
+        """Close a network connection."""
+        pass
+
+    def shorten_url(self, original_url):
+        """Shortens url into more compact form.
+
+        :param original_url: url that will be shortened
+        :type original_url: string
+        :returns: shortened url from original url
+        :rtype: brevisurl.models.ShortUrl
+
+        """
+        raise NotImplementedError
+\ No newline at end of file
diff --git a/brevisurl/backends/local.py b/brevisurl/backends/local.py
new file mode 100644
index 0000000..42d0263
--- /dev/null
+++ b/brevisurl/backends/local.py
@@ -0,0 +1,53 @@
+import string
+import random
+import logging
+
+from django.contrib.sites.models import Site
+
+from brevisurl.backends.base import BaseBrevisUrlBackend
+from brevisurl.models import ShortUrl
+
+
+log = logging.getLogger(__name__)
+
+
+class BrevisUrlBackend(BaseBrevisUrlBackend):
+
+    PROTOCOL = 'http'
+
+    def shorten_url(self, original_url):
+        """
+        :raises: ImproperlyConfigured, django.core.exceptions.ValidationError
+        """
+        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:
+            current_site = Site.objects.get_current()
+            short_url = ShortUrl()
+            short_url.original_url = original_url
+            short_url.shortened_url = '{0}://{1}/{2}'.format(self.PROTOCOL, current_site.domain,
+                                                             self.__generate_token())
+            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, size=5):
+        chars = list(string.ascii_letters + string.digits)
+        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
+\ No newline at end of file