Move get_interested_remotes back to presence handler

synapse/handlers/presence.py

@@ -633,9 +633,6 @@ class PresenceHandler(object):
             # Always notify self
             users_to_states.setdefault(state.user_id, []).append(state)
 
-        # TODO: de-dup hosts_to_states, as a single host might have multiple
-        # of same presence
-
         defer.returnValue((room_ids_to_states, users_to_states))
 
     @defer.inlineCallbacks
@@ -1318,3 +1315,52 @@ def handle_update(prev_state, new_state, is_mine, wheel_timer, now):
         persist_and_notify = True
 
     return new_state, persist_and_notify, federation_ping
+
+@defer.inlineCallbacks
+def get_interested_remotes(store, states):
+    """Given a list of presence states figure out which remote servers
+    should be sent which.
+
+    All the presence states should be for local users only.
+
+    Args:
+        store (DataStore)
+        states (list(UserPresenceState))
+
+    Returns:
+        Deferred list of ([destinations], [UserPresenceState]), where for
+        each row the list of UserPresenceState should be sent to each
+        destination
+    """
+    # First we look up the rooms each user is in (as well as any explicit
+    # subscriptions), then for each distinct room we look up the remote
+    # hosts in those rooms.
+    room_ids_to_states = {}
+    users_to_states = {}
+    for state in states.itervalues():
+        room_ids = yield store.get_rooms_for_user(state.user_id)
+        for room_id in room_ids:
+            room_ids_to_states.setdefault(room_id, []).append(state)
+
+        plist = yield store.get_presence_list_observers_accepted(
+            state.user_id,
+        )
+        for u in plist:
+            users_to_states.setdefault(u, []).append(state)
+
+    hosts_and_states = []
+    for room_id, states in room_ids_to_states.items():
+        if not local_states:
+            continue
+
+        hosts = yield store.get_hosts_in_room(room_id)
+        hosts_and_states.append((hosts, local_states))
+
+    for user_id, states in users_to_states.items():
+        if not local_states:
+            continue
+
+        host = get_domain_from_id(user_id)
+        hosts_and_states.append(([host], local_states))
+
+    defer.returnValue(hosts_and_states)