--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/app/soc/logic/tags.py	Sat Nov 14 18:20:06 2009 +0100
@@ -0,0 +1,91 @@
+#!/usr/bin/python2.5
+#
+# Copyright 2009 the Melange authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""The module which contains functions to manage tags in Melange.
+"""
+
+__authors__ = [
+  '"Daniel Hans" <daniel.m.hans@gmail.com>',
+]
+
+
+class TagsService(object):
+  """Helper class for tags corresponding to a model.
+  """
+
+  def __init__(self, tag_names):
+    """Defines tag names.
+    """
+
+    self.tag_names = tag_names
+
+  def prepareTagsForStoring(self, fields, scope):
+    """For those fields which represent task values it prepares actual
+    tag entries.
+
+    Args:
+      fields: a dict mapping tag names with values
+      scope: scope for the tag that will be stored
+    """
+
+    for tag_name, tag_value in fields.iteritems():
+      if tag_name in self.tag_names:
+        fields[tag_name] = {'tags': tag_value, 'scope': scope}
+
+  def setTagValuesForEntity(self, entity, fields):
+    """Sets tag values for a particular entity based on fields dictionary.
+
+    Args:
+      entity: an entity which is to be tagged
+      fields: a dict mapping tag names with values
+    """
+
+    if not entity:
+      return None
+
+    for tag_name, tag_value in fields.iteritems():
+      if tag_name in self.tag_names:
+        setattr(entity, tag_name, tag_value)
+
+    return entity
+
+  def removeAllTagsForEntity(self, entity):
+    """Removes all tags defined for a particular entity.
+
+    Args:
+      entity: entity which the tags will be removed for
+    """
+
+    self.removeTagsForEntity(entity, self.tag_names)
+
+  def removeTagsForEntity(self, entity, tag_names):
+    """Removes all tags values for a particular entity based on tag_names
+    list with name of the tags that are to be removed.
+
+    Args:
+      entity: entity which the tags will be removed for
+      tag_names: list of tags to remove
+    """
+
+    if not entity:
+      return
+
+    for tag_name in tag_names:
+      if tag_name in tag_names:
+        cls = entity.tags_class(tag_name)
+        tags = cls.get_tags_for_key(entity.key())
+        for tag in tags:
+          tag.remove_tagged(entity.key())