feat: Move checks for moderator in pre-join and filter extra presences.

We will filter the initial presence where participant is announced as `participant` and shortly after that we send a second presence with the new `moderator` role.

resources/prosody-plugins/mod_muc_allowners.lua

+local filters = require 'util.filters';
 local jid = require "util.jid";
+local jid_bare = require "util.jid".bare;
 local um_is_admin = require "core.usermanager".is_admin;
 local util = module:require "util";
 local is_healthcheck_room = util.is_healthcheck_room;
 local extract_subdomain = util.extract_subdomain;
+local presence_check_status = util.presence_check_status;
+local MUC_NS = 'http://jabber.org/protocol/muc';
 
 local moderated_subdomains;
 local moderated_rooms;
     return um_is_admin(jid, module.host);
 end
 
+-- List of the bare_jids of all occupants that are currently joining (went through pre-join) and will be promoted
+-- as moderators. As pre-join (where added) and joined event (where removed) happen one after another this list should
+-- have length of 1
+local joining_moderator_participants = {};
+
 -- Checks whether the jid is moderated, the room name is in moderated_rooms
 -- or if the subdomain is in the moderated_subdomains
 -- @return returns on of the:
     return false;
 end
 
-module:hook("muc-occupant-joined", function (event)
+module:hook("muc-occupant-pre-join", function (event)
     local room, occupant = event.room, event.occupant;
 
-    if is_healthcheck_room(room.jid) or is_admin(occupant.jid) then
+    if is_healthcheck_room(room.jid) or is_admin(occupant.bare_jid) then
         return;
     end
 
         end
     end
 
-    room:set_affiliation(true, occupant.bare_jid, "owner");
+    -- mark this participant that it will be promoted and is currently joining
+    joining_moderator_participants[occupant.bare_jid] = true;
+end, 2);
+
+module:hook("muc-occupant-joined", function (event)
+    local room, occupant = event.room, event.occupant;
+
+    local promote_to_moderator = joining_moderator_participants[occupant.bare_jid];
+    -- clear it
+    joining_moderator_participants[occupant.bare_jid] = nil;
+
+    if promote_to_moderator ~= nil then
+        room:set_affiliation(true, occupant.bare_jid, "owner");
+    end
 end, 2);
 
 module:hook("muc-occupant-left", function (event)
 end, 2);
 
 module:hook_global('config-reloaded', load_config);
+
+-- Filters self-presences to a jid that exist in joining_participants array
+-- We want to filter those presences where we send first `participant` and just after it `moderator`
+function filter_stanza(stanza)
+    if not stanza.attr or not stanza.attr.to or stanza.name ~= "presence" then
+        return stanza;
+    end
+
+    -- Allow self-presence (code=110)
+    local bare_to = jid_bare(stanza.attr.to);
+
+    if joining_moderator_participants[bare_to] then
+        if presence_check_status(stanza:get_child('x', MUC_NS..'#user'), '110') then
+            return nil;
+        end
+    end
+
+    return stanza;
+end
+function filter_session(session)
+    -- domain mapper is filtering on default priority 0, and we need it after that
+    filters.add_filter(session, 'stanzas/out', filter_stanza, -1);
+end
+
+-- enable filtering presences
+filters.add_filter_hook(filter_session);

resources/prosody-plugins/mod_muc_lobby_rooms.lua

 local NOTIFY_LOBBY_ACCESS_GRANTED = 'LOBBY-ACCESS-GRANTED';
 local NOTIFY_LOBBY_ACCESS_DENIED = 'LOBBY-ACCESS-DENIED';
 
-local is_healthcheck_room = module:require 'util'.is_healthcheck_room;
+local util = module:require "util";
+local is_healthcheck_room = util.is_healthcheck_room;
+local presence_check_status = util.presence_check_status;
 
 local main_muc_component_config = module:get_option_string('main_muc');
 if main_muc_component_config == nil then
 local lobby_muc_service;
 local main_muc_service;
 
-function check_status(muc_x, status)
-    if not muc_x then
-        return false;
-    end
-
-    for statusNode in muc_x:childtags('status') do
-        if statusNode.attr.code == status then
-            return true;
-        end
-    end
-
-    return false;
-end
-
 function broadcast_json_msg(room, from, json_msg)
     json_msg.type = NOTIFY_JSON_MESSAGE_TYPE;
 
 
     if from_domain == lobby_muc_component_config then
         if stanza.name == 'presence' then
-            local muc_x = stanza:get_child('x', MUC_NS..'#user');
-
-            if check_status(muc_x, '110') then
+            if presence_check_status(stanza:get_child('x', MUC_NS..'#user'), '110') then
                 return stanza;
             end
 
     -- listens for kicks in lobby room, 307 is the status for kick according to xep-0045
     host_module:hook('muc-broadcast-presence', function (event)
         local actor, occupant, room, x = event.actor, event.occupant, event.room, event.x;
-        if check_status(x, '307') then
+        if presence_check_status(x, '307') then
             local display_name = occupant:get_presence():get_child_text(
                 'nick', 'http://jabber.org/protocol/nick');
             -- we need to notify in the main room

resources/prosody-plugins/util.lib.lua

     return content;
 end
 
+-- Checks whether there is status in the <x node
+-- @param muc_x the <x element from presence
+-- @param status checks for this status
+-- @returns true if the status is found, false otherwise or if no muc_x is provided.
+function presence_check_status(muc_x, status)
+    if not muc_x then
+        return false;
+    end
+
+    for statusNode in muc_x:childtags('status') do
+        if statusNode.attr.code == status then
+            return true;
+        end
+    end
+
+    return false;
+end
+
 return {
     extract_subdomain = extract_subdomain;
     is_feature_allowed = is_feature_allowed;
     is_healthcheck_room = is_healthcheck_room;
     get_room_from_jid = get_room_from_jid;
     async_handler_wrapper = async_handler_wrapper;
+    presence_check_status = presence_check_status;
     room_jid_match_rewrite = room_jid_match_rewrite;
     room_jid_split_subdomain = room_jid_split_subdomain;
     internal_room_jid_match_rewrite = internal_room_jid_match_rewrite;