Improve data file handling for file batches.

Leverages a FormAlchemy "extension" of sorts.

tailbone/forms/renderers/batch.py

@@ -0,0 +1,64 @@
+# -*- coding: utf-8 -*-
+################################################################################
+#
+#  Rattail -- Retail Software Framework
+#  Copyright © 2010-2015 Lance Edgar
+#
+#  This file is part of Rattail.
+#
+#  Rattail is free software: you can redistribute it and/or modify it under the
+#  terms of the GNU Affero General Public License as published by the Free
+#  Software Foundation, either version 3 of the License, or (at your option)
+#  any later version.
+#
+#  Rattail 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 Affero General Public License for
+#  more details.
+#
+#  You should have received a copy of the GNU Affero General Public License
+#  along with Rattail.  If not, see <http://www.gnu.org/licenses/>.
+#
+################################################################################
+"""
+Batch Field Renderers
+"""
+
+from __future__ import unicode_literals
+
+import os
+import stat
+import random
+
+from formalchemy.ext import fsblob
+
+
+class FileFieldRenderer(fsblob.FileFieldRenderer):
+    """
+    Custom file field renderer for batches based on a single source data file.
+    In edit mode, shows a file upload field.  In readonly mode, shows the
+    filename and its size.
+    """
+
+    @classmethod
+    def new(cls, view):
+        name = 'Configured%s_%s' % (cls.__name__, str(random.random())[2:])
+        return type(str(name), (cls,), dict(view=view))
+
+    @property
+    def storage_path(self):
+        return self.view.upload_dir
+
+    def get_size(self):
+        size = super(FileFieldRenderer, self).get_size()
+        if size:
+            return size
+        batch = self.field.parent.model
+        path = os.path.join(self.view.handler.datadir(batch), self.field.value)
+        if os.path.isfile(path):
+            return os.stat(path)[stat.ST_SIZE]
+        return 0
+
+    def get_url(self, filename):
+        batch = self.field.parent.model
+        return self.view.request.route_url('{0}.download'.format(self.view.route_prefix), uuid=batch.uuid)