mediagoblin/db/extratypes.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011, 2012 MediaGoblin contributors.  See AUTHORS.
   3 #
   4 # This program is free software: you can redistribute it and/or modify
   5 # it under the terms of the GNU Affero General Public License as published by
   6 # the Free Software Foundation, either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Affero General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Affero General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17
  18 from sqlalchemy.ext.mutable import Mutable
  19 from sqlalchemy.types import TypeDecorator, Unicode, TEXT
  20 import json
  21
  22
  23 class PathTupleWithSlashes(TypeDecorator):
  24     "Represents a Tuple of strings as a slash separated string."
  25
  26     impl = Unicode
  27
  28     def process_bind_param(self, value, dialect):
  29         if value is not None:
  30             if len(value) == 0:
  31                 value = None
  32             else:
  33                 value = '/'.join(value)
  34         return value
  35
  36     def process_result_value(self, value, dialect):
  37         if value is not None:
  38             value = tuple(value.split('/'))
  39         return value
  40
  41
  42 # The following  two classes and only these two classes is in very
  43 # large parts based on example code from sqlalchemy.
  44 #
  45 # The original copyright notice and license follows:
  46 #     Copyright (C) 2005-2011 the SQLAlchemy authors and contributors <see AUTHORS file>
  47 #
  48 #     This module is part of SQLAlchemy and is released under
  49 #     the MIT License: http://www.opensource.org/licenses/mit-license.php
  50 #
  51 class JSONEncoded(TypeDecorator):
  52     "Represents an immutable structure as a json-encoded string."
  53
  54     impl = TEXT
  55
  56     def process_bind_param(self, value, dialect):
  57         if value is not None:
  58             value = json.dumps(value)
  59         return value
  60
  61     def process_result_value(self, value, dialect):
  62         if value is not None:
  63             value = json.loads(value)
  64         return value
  65
  66
  67 class MutationDict(Mutable, dict):
  68     @classmethod
  69     def coerce(cls, key, value):
  70         "Convert plain dictionaries to MutationDict."
  71
  72         if not isinstance(value, MutationDict):
  73             if isinstance(value, dict):
  74                 return MutationDict(value)
  75
  76             # this call will raise ValueError
  77             return Mutable.coerce(key, value)
  78         else:
  79             return value
  80
  81     def __setitem__(self, key, value):
  82         "Detect dictionary set events and emit change events."
  83
  84         dict.__setitem__(self, key, value)
  85         self.changed()
  86
  87     def __delitem__(self, key):
  88         "Detect dictionary del events and emit change events."
  89
  90         dict.__delitem__(self, key)
  91         self.changed()