Add a Workspace class

1 files changed, 104 insertions, 0 deletions

diff --git a/morphlib/workspace.py b/morphlib/workspace.py
new file mode 100644
index 00000000..5a2eb86b
--- /dev/null
+++ b/morphlib/workspace.py
@@ -0,0 +1,104 @@
+# 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 =*=
+
+
+'''A module to create, query, and manipulate Morph workspaces.'''
+
+
+import os
+
+import morphlib
+
+
+class WorkspaceDirExists(morphlib.Error):
+
+    def __init__(self, dirname):
+        self.msg = (
+            'can only initialize empty directory as a workspace: %s' %
+            dirname)
+
+
+class NotInWorkspace(morphlib.Error):
+
+    def __init__(self, dirname):
+        self.msg = 'Directory %s is not in a workspace' % dirname
+
+
+class Workspace(object):
+
+    '''A Morph workspace.
+
+    This class should be instantiated with the open() or create()
+    functions in this module.
+
+    '''
+
+    def __init__(self, root_directory):
+        self.root = root_directory
+
+
+def open(dirname):
+    '''Open an existing workspace.
+
+    The given directory name may be to a subdirectory of the
+    workspace. This makes it easy to instantiate the Workspace
+    class even when the user invokes Morph in a subdirectory.
+    The workspace MUST exist already, or NotInWorkspace is
+    raised.
+
+    Return a Workspace instance.
+
+    '''
+
+    root = _find_root(dirname)
+    if root is None:
+        raise NotInWorkspace(dirname)
+    return Workspace(root)
+
+
+def create(dirname):
+    '''Create a new workspace.
+
+    The given directory must not be inside an existing workspace.
+    The workspace directory is created, unless it already exists.  If it
+    does exist, it must be empty. Otherwise WorkspaceDirExists is raised.
+
+    '''
+
+    root = _find_root(dirname)
+    if root is not None:
+        raise WorkspaceDirExists(root)
+
+    if os.path.exists(dirname):
+        if os.listdir(dirname):
+            raise WorkspaceDirExists(dirname)
+    else:
+        os.mkdir(dirname)
+    os.mkdir(os.path.join(dirname, '.morph'))
+    return Workspace(dirname)
+
+
+def _find_root(dirname):
+    '''Find the workspace root directory at or above a given directory.'''
+
+    dirname = os.path.normpath(os.path.abspath(dirname))
+    while not os.path.isdir(os.path.join(dirname, '.morph')):
+        if dirname == '/':
+            return None
+        dirname = os.path.dirname(dirname)
+    return dirname
+