Add new RepoAliasResolver class to resolve repo names with aliases.

1 files changed, 83 insertions, 0 deletions

diff --git a/morphlib/repoaliasresolver.py b/morphlib/repoaliasresolver.py
new file mode 100644
index 00000000..3daf34dd
--- /dev/null
+++ b/morphlib/repoaliasresolver.py
@@ -0,0 +1,83 @@
+# Copyright (C) 2012  Codethink Limited
+# 
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; version 2 of the License.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+
+import logging
+import re
+
+
+class RepoAliasResolver(object):
+
+    def __init__(self, aliases):
+        self.aliases = aliases
+
+    def pull_url(self, reponame):
+        '''Expand a possibly shortened repo name to a pull url.'''
+        return self._expand_reponame(reponame, 'pullpat')
+
+    def push_url(self, reponame):
+        '''Expand a possibly shortened repo name to a push url.'''
+        return self._expand_reponame(reponame, 'pushpat')
+
+    def _expand_reponame(self, reponame, patname):
+        logging.debug('expanding: reponame=%s' % reponame)
+        logging.debug('expanding: patname=%s' % patname)
+
+        prefix, suffix = self._split_reponame(reponame)
+        logging.debug('expanding: prefix=%s' % prefix)
+        logging.debug('expanding: suffix=%s' % suffix)
+
+        # There was no prefix.
+        if prefix is None:
+            logging.debug('expanding: no prefix')
+            return reponame
+
+        pat = r'^(?P<prefix>[a-z0-9]+)=(?P<pullpat>[^#]+)#(?P<pushpat>[^#]+)$'
+        for alias in self.aliases:
+            logging.debug('expanding: alias="%s"' % alias)
+            m = re.match(pat, alias)
+            logging.debug('expanding: m=%s' % repr(m))
+            if m:
+                logging.debug('expanding: prefix group=%s' % m.group('prefix'))
+            if m and m.group('prefix') == prefix:
+                pullpat = m.group(patname)
+                logging.debug('expanding: pullpat=%s' % pullpat)
+                return self._apply_url_pattern(pullpat, suffix)
+
+        # Unknown prefix. Which means it may be a real URL instead.
+        # Let the caller deal with it.        
+        logging.debug('expanding: unknown prefix')
+        return reponame
+    
+    def _split_reponame(self, reponame):
+        '''Split reponame into prefix and suffix.
+        
+        The prefix is returned as None if there was no prefix.
+        
+        '''
+
+        pat = r'^(?P<prefix>[a-z0-9]+):(?P<rest>.*)$'
+        m = re.match(pat, reponame)
+        if m:
+            return m.group('prefix'), m.group('rest')
+        else:
+            return None, reponame
+    
+    def _apply_url_pattern(self, pattern, shortname):
+        if '%s' in pattern:
+            return shortname.join(pattern.split('%s'))
+        else:
+            return pattern + shortname
+