morphlib: Add MorphologyFinder class

MorphologyFinder is a small wrapper on top of GitDirectory that
allows the inspection of morphologies in the repository.

Its purpose is to isolate the logic for reading morphologies into one
place.

It is used by passing a GitDirectory and optionally a ref to the
MorpholgyFinder constructor, then list_morphologies and read_morphology
may be used.

The ref is passed directly to the GitDirectory, so its semantics for
a ref of None or omitted are used. i.e. It uses the working tree.

Ref resolving is deferred until a morphology is listed or read, so
it will not raise an exception for an invalid ref until then.

1 files changed, 71 insertions, 0 deletions

diff --git a/morphlib/morphologyfinder.py b/morphlib/morphologyfinder.py
new file mode 100644
index 00000000..affa0e97
--- /dev/null
+++ b/morphlib/morphologyfinder.py
@@ -0,0 +1,71 @@
+# Copyright (C) 2013  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.
+#
+# =*= License: GPL-2 =*=
+
+
+import cliapp
+
+import morphlib
+
+
+class MorphologyFinder(object):
+
+    '''Abstract away finding morphologies in a git repository.
+
+    This class provides an abstraction layer between a git repository
+    and the morphologies contained in it.
+
+    '''
+
+    def __init__(self, gitdir, ref=None):
+        self.gitdir = gitdir
+        self.ref = ref
+
+    def read_morphology(self, name):
+        '''Return the un-parsed text of a morphology.
+        
+        For the given morphology name, locate and return the contents
+        of the morphology as a string.
+
+        Also returns a string describing where in the repository the
+        morphology is located.
+
+        Parsing of this morphology into a form useful for manipulating
+        is handled by the MorphologyLoader class.
+        
+        '''
+        filename = '%s.morph' % name
+        return self.gitdir.read_file(filename, self.ref), filename
+
+    def list_morphologies(self):
+        '''Return the names of all morphologies in the (repo, ref).
+
+        Finds all morphologies in the git directory at the specified
+        ref. Morphology names are returned instead of filenames,
+        so the implementation may change how morphologies are stored
+        in git repositories.
+
+        '''
+
+        def is_morphology_path(path):
+            return path.endswith('.morph')
+
+        def transform_path_to_name(path):
+            return path[:-len('.morph')]
+
+        return (transform_path_to_name(path)
+                for path in self.gitdir.list_files(self.ref)
+                if is_morphology_path(path))