1 files changed, 98 insertions, 0 deletions
diff --git a/synapse/util/jsonobject.py b/synapse/util/jsonobject.py
new file mode 100644
index 0000000000..190a80a322
--- /dev/null
+++ b/synapse/util/jsonobject.py
@@ -0,0 +1,98 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 matrix.org
+#
+# 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.
+
+import copy
+
+class JsonEncodedObject(object):
+    """ A common base class for defining protocol units that are represented
+    as JSON.
+
+    Attributes:
+        unrecognized_keys (dict): A dict containing all the key/value pairs we
+            don't recognize.
+    """
+
+    valid_keys = []  # keys we will store
+    """A list of strings that represent keys we know about
+    and can handle. If we have values for these keys they will be
+    included in the `dictionary` instance variable.
+    """
+
+    internal_keys = []  # keys to ignore while building dict
+    """A list of strings that should *not* be encoded into JSON.
+    """
+
+    required_keys = []
+    """A list of strings that we require to exist. If they are not given upon
+    construction it raises an exception.
+    """
+
+    def __init__(self, **kwargs):
+        """ Takes the dict of `kwargs` and loads all keys that are *valid*
+        (i.e., are included in the `valid_keys` list) into the dictionary`
+        instance variable.
+
+        Any keys that aren't recognized are added to the `unrecognized_keys`
+        attribute.
+
+        Args:
+            **kwargs: Attributes associated with this protocol unit.
+        """
+        for required_key in self.required_keys:
+            if required_key not in kwargs:
+                raise RuntimeError("Key %s is required" % required_key)
+
+        self.unrecognized_keys = {}  # Keys we were given not listed as valid
+        for k, v in kwargs.items():
+            if k in self.valid_keys or k in self.internal_keys:
+                self.__dict__[k] = v
+            else:
+                self.unrecognized_keys[k] = v
+
+    def get_dict(self):
+        """ Converts this protocol unit into a :py:class:`dict`, ready to be
+        encoded as JSON.
+
+        The keys it encodes are: `valid_keys` - `internal_keys`
+
+        Returns
+            dict
+        """
+        d = {
+            k: _encode(v) for (k, v) in self.__dict__.items()
+            if k in self.valid_keys and k not in self.internal_keys
+        }
+        d.update(self.unrecognized_keys)
+        return copy.deepcopy(d)
+
+    def get_full_dict(self):
+        d = {
+            k: v for (k, v) in self.__dict__.items()
+            if k in self.valid_keys or k in self.internal_keys
+        }
+        d.update(self.unrecognized_keys)
+        return copy.deepcopy(d)
+
+    def __str__(self):
+        return "(%s, %s)" % (self.__class__.__name__, repr(self.__dict__))
+
+def _encode(obj):
+    if type(obj) is list:
+        return [_encode(o) for o in obj]
+
+    if isinstance(obj, JsonEncodedObject):
+        return obj.get_dict()
+
+    return obj