Move storage.stream._StreamToken to types.RoomStreamToken

synapse/types.py

@@ -121,4 +121,56 @@ class StreamToken(
         return StreamToken(**d)
 
 
+class RoomStreamToken(namedtuple("_StreamToken", "topological stream")):
+    """Tokens are positions between events. The token "s1" comes after event 1.
+
+            s0    s1
+            |     |
+        [0] V [1] V [2]
+
+    Tokens can either be a point in the live event stream or a cursor going
+    through historic events.
+
+    When traversing the live event stream events are ordered by when they
+    arrived at the homeserver.
+
+    When traversing historic events the events are ordered by their depth in
+    the event graph "topological_ordering" and then by when they arrived at the
+    homeserver "stream_ordering".
+
+    Live tokens start with an "s" followed by the "stream_ordering" id of the
+    event it comes after. Historic tokens start with a "t" followed by the
+    "topological_ordering" id of the event it comes after, follewed by "-",
+    followed by the "stream_ordering" id of the event it comes after.
+    """
+    __slots__ = []
+
+    @classmethod
+    def parse(cls, string):
+        try:
+            if string[0] == 's':
+                return cls(topological=None, stream=int(string[1:]))
+            if string[0] == 't':
+                parts = string[1:].split('-', 1)
+                return cls(topological=int(parts[0]), stream=int(parts[1]))
+        except:
+            pass
+        raise SynapseError(400, "Invalid token %r" % (string,))
+
+    @classmethod
+    def parse_stream_token(cls, string):
+        try:
+            if string[0] == 's':
+                return cls(topological=None, stream=int(string[1:]))
+        except:
+            pass
+        raise SynapseError(400, "Invalid token %r" % (string,))
+
+    def __str__(self):
+        if self.topological is not None:
+            return "t%d-%d" % (self.topological, self.stream)
+        else:
+            return "s%d" % (self.stream,)
+
+
 ClientInfo = namedtuple("ClientInfo", ("device_id", "token_id"))