Add utilities for listing and finding extensions.

1 files changed, 143 insertions, 0 deletions

diff --git a/morphlib/extensions.py b/morphlib/extensions.py
new file mode 100644
index 00000000..57649cf1
--- /dev/null
+++ b/morphlib/extensions.py
@@ -0,0 +1,143 @@
+# Copyright (C) 2014  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 cliapp
+import morphlib
+import glob
+import os
+import sysbranchdir
+import stat
+import tempfile
+
+def _get_root_repo(build_ref_prefix):
+    system_branch = morphlib.sysbranchdir.open_from_within('.')
+    root_repo_dir = morphlib.gitdir.GitDirectory(
+            system_branch.get_git_directory_name(
+                system_branch.root_repository_url))
+    build_branch = morphlib.buildbranch.BuildBranch(system_branch,
+                                                    build_ref_prefix,
+                                                    push_temporary=False)
+    ref = build_branch.root_ref
+
+    return (build_branch.root_ref, root_repo_dir)
+
+def _get_morph_extension_directory():
+    code_dir = os.path.dirname(morphlib.__file__)
+    return os.path.join(code_dir, 'exts')
+
+def _list_repo_extension_filenames(build_ref_prefix,
+                                   kind): #pragma: no cover
+    (ref, repo_dir) = _get_root_repo(build_ref_prefix)
+    files = repo_dir.list_files(ref)
+    return (f for f in files if os.path.splitext(f)[1] == kind)
+
+def _list_morph_extension_filenames(kind):
+    return glob.glob(os.path.join(_get_morph_extension_directory(),
+                                  '*' + kind))
+
+def _get_extension_name(filename):
+    return os.path.basename(filename)
+
+def _get_repo_extension_contents(build_ref_prefix, name, kind):
+    (ref, repo_dir) = _get_root_repo(build_ref_prefix)
+    return repo_dir.get_file_from_ref(ref, name + kind)
+
+def _get_morph_extension_filename(name, kind):
+    return os.path.join(_get_morph_extension_directory(), name + kind)
+
+def _is_executable(filename):
+    st = os.stat(filename)
+    mask = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
+    return (stat.S_IMODE(st.st_mode) & mask) != 0
+
+def _list_extensions(build_ref_prefix, kind):
+    repo_extension_filenames = []
+    try:
+        repo_extension_filenames = \
+                _list_repo_extension_filenames(build_ref_prefix, kind)
+    except (sysbranchdir.NotInSystemBranch):
+        # Squash this and just return no system branch extensions
+        pass
+    morph_extension_filenames = _list_morph_extension_filenames(kind)
+
+    repo_extension_names = \
+            (_get_extension_name(f) for f in repo_extension_filenames)
+    morph_extension_names = \
+            (_get_extension_name(f) for f in morph_extension_filenames)
+
+    extension_names = set(repo_extension_names)
+    extension_names.update(set(morph_extension_names))
+    return list(extension_names)
+
+def list_extensions(build_ref_prefix, kind=None):
+    """
+    List all available extensions by 'kind'.
+
+    'kind' should be one of '.write' or '.configure'.
+    If 'kind' is not provided available extensions of both
+    types will be returned.
+    """
+    if kind:
+        return _list_extensions(build_ref_prefix, kind)
+    else:
+        configure_extensions = _list_extensions(build_ref_prefix, '.configure')
+        write_extensions = _list_extensions(build_ref_prefix, '.write')
+
+        return configure_extensions + write_extensions
+
+class get_extension_filename():
+    """
+    Find the filename of an extension by its 'name' and 'kind'.
+
+    'kind' should be one of '.configure' or '.write'. 
+
+    If the extension is in the build repository then a temporary
+    file will be created, which will be deleted on exting the with block.
+    """
+    def __init__(self, build_ref_prefix, name, kind):
+        self.build_ref_prefix = build_ref_prefix
+        self.name = name
+        self.kind = kind
+        self.delete = False
+
+    def __enter__(self):
+        ext_filename = None
+        try:
+            ext_contents = _get_repo_extension_contents(self.build_ref_prefix,
+                                                        self.name,
+                                                        self.kind)
+        except cliapp.AppException, sysbranchdir.NotInSystemBranch:
+            # Not found: look for it in the Morph code.
+            ext_filename = _get_morph_extension_filename(self.name, self.kind)
+            if not os.path.exists(ext_filename):
+                raise morphlib.Error(
+                    'Could not find extension %s%s' % (self.name, self.kind))
+            if not _is_executable(ext_filename):
+                raise morphlib.Error(
+                    'Extension not executable: %s' % ext_filename)
+        else:
+            # Found it in the system morphology's repository.
+            fd, ext_filename = tempfile.mkstemp()
+            os.write(fd, ext_contents)
+            os.close(fd)
+            os.chmod(ext_filename, 0700)
+            self.delete = True
+
+        self.ext_filename = ext_filename
+        return ext_filename
+
+    def __exit__(self, type, value, trace):
+        if self.delete:
+            os.remove(self.ext_filename)