Require event format version to parse or create events

2 files changed, 73 insertions, 2 deletions

diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index 01db729847..e74ea33a7c 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -18,7 +18,11 @@ from distutils.util import strtobool
 
 import six
 
-from synapse.api.constants import KNOWN_ROOM_VERSIONS, EventFormatVersions
+from synapse.api.constants import (
+    KNOWN_EVENT_FORMAT_VERSIONS,
+    KNOWN_ROOM_VERSIONS,
+    EventFormatVersions,
+)
 from synapse.util.caches import intern_dict
 from synapse.util.frozenutils import freeze
 
@@ -254,3 +258,21 @@ def room_version_to_event_format(room_version):
         raise
 
     return EventFormatVersions.V1
+
+
+def event_type_from_format_version(format_version):
+    """Returns the python type to use to construct an Event object for the
+    given event format version.
+
+    Args:
+        format_version (int): The event format version
+
+    Returns:
+        type: A type that can be initialized as per the initializer of
+        `FrozenEvent`
+    """
+    if format_version not in KNOWN_EVENT_FORMAT_VERSIONS:
+        raise Exception(
+            "No event format %r" % (format_version,)
+        )
+    return FrozenEvent
diff --git a/synapse/events/builder.py b/synapse/events/builder.py
index e662eaef10..7e63371095 100644
--- a/synapse/events/builder.py
+++ b/synapse/events/builder.py
@@ -15,12 +15,39 @@
 
 import copy
 
+from synapse.api.constants import RoomVersions
 from synapse.types import EventID
 from synapse.util.stringutils import random_string
 
 from . import EventBase, FrozenEvent, _event_dict_property
 
 
+def get_event_builder(room_version, key_values={}, internal_metadata_dict={}):
+    """Generate an event builder appropriate for the given room version
+
+    Args:
+        room_version (str): Version of the room that we're creating an
+            event builder for
+        key_values (dict): Fields used as the basis of the new event
+        internal_metadata_dict (dict): Used to create the `_EventInternalMetadata`
+            object.
+
+    Returns:
+        EventBuilder
+    """
+    if room_version in {
+        RoomVersions.V1,
+        RoomVersions.V2,
+        RoomVersions.VDH_TEST,
+        RoomVersions.STATE_V2_TEST,
+    }:
+        return EventBuilder(key_values, internal_metadata_dict)
+    else:
+        raise Exception(
+            "No event format defined for version %r" % (room_version,)
+        )
+
+
 class EventBuilder(EventBase):
     def __init__(self, key_values={}, internal_metadata_dict={}):
         signatures = copy.deepcopy(key_values.pop("signatures", {}))
@@ -58,7 +85,29 @@ class EventBuilderFactory(object):
 
         return e_id.to_string()
 
-    def new(self, key_values={}):
+    def new(self, room_version, key_values={}):
+        """Generate an event builder appropriate for the given room version
+
+        Args:
+            room_version (str): Version of the room that we're creating an
+                event builder for
+            key_values (dict): Fields used as the basis of the new event
+
+        Returns:
+            EventBuilder
+        """
+
+        # There's currently only the one event version defined
+        if room_version not in {
+            RoomVersions.V1,
+            RoomVersions.V2,
+            RoomVersions.VDH_TEST,
+            RoomVersions.STATE_V2_TEST,
+        }:
+            raise Exception(
+                "No event format defined for version %r" % (room_version,)
+            )
+
         key_values["event_id"] = self.create_event_id()
 
         time_now = int(self.clock.time_msec())