Versioned Endpoint hack for Sessions

To maintain compatibility we must allow people to specify a versioned
URL in the service catalog but allow the plugins to return a different
URL to users.

We need this to be a general approach as other services will likely have
a similar problem with their catalog.

The expectation here is that a client will register the catalog hack at
import time rather than for every request.

Closes-Bug: #1335726
Change-Id: I244f0ec3acca39fd1b2a2c5883abc06ec10eddc7

1 files changed, 54 insertions, 0 deletions

diff --git a/keystoneclient/_discover.py b/keystoneclient/_discover.py
index 7ea396f..c9c9792 100644
--- a/keystoneclient/_discover.py
+++ b/keystoneclient/_discover.py
@@ -22,6 +22,7 @@ raw data specified in version discovery responses.
 """
 
 import logging
+import re
 
 from keystoneclient import exceptions
 from keystoneclient import utils
@@ -262,3 +263,56 @@ class Discover(object):
         """
         data = self.data_for(version, **kwargs)
         return data['url'] if data else None
+
+
+class _VersionHacks(object):
+    """A container to abstract the list of version hacks.
+
+    This could be done as simply a dictionary but is abstracted like this to
+    make for easier testing.
+    """
+
+    def __init__(self):
+        self._discovery_data = {}
+
+    def add_discover_hack(self, service_type, old, new=''):
+        """Add a new hack for a service type.
+
+        :param str service_type: The service_type in the catalog.
+        :param re.RegexObject old: The pattern to use.
+        :param str new: What to replace the pattern with.
+        """
+        hacks = self._discovery_data.setdefault(service_type, [])
+        hacks.append((old, new))
+
+    def get_discover_hack(self, service_type, url):
+        """Apply the catalog hacks and figure out an unversioned endpoint.
+
+        :param str service_type: the service_type to look up.
+        :param str url: The original url that came from a service_catalog.
+
+        :return: Either the unversioned url or the one from the catalog to try.
+        """
+        for old, new in self._discovery_data.get(service_type, []):
+            new_string, number_of_subs_made = old.subn(new, url)
+            if number_of_subs_made > 0:
+                return new_string
+
+        return url
+
+
+_VERSION_HACKS = _VersionHacks()
+_VERSION_HACKS.add_discover_hack('identity', re.compile('/v2.0/?$'), '/')
+
+
+def get_catalog_discover_hack(service_type, url):
+    """Apply the catalog hacks and figure out an unversioned endpoint.
+
+    This function is internal to keystoneclient.
+
+    :param str service_type: the service_type to look up.
+    :param str url: The original url that came from a service_catalog.
+
+    :return: Either the unversioned url or the one from the catalog to try.
+    """
+    return _VERSION_HACKS.get_discover_hack(service_type, url)