--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/muc/gc3.lib.lua	Thu Jun 26 15:17:57 2025 +0100
@@ -0,0 +1,57 @@
+
+local jid_bare = require "prosody.util.jid".bare;
+
+local st = require "prosody.util.stanza";
+
+local muc_util = module:require "muc/util";
+local valid_affiliations = muc_util.valid_affiliations;
+
+local xmlns_gc3 = "urn:xmpp:gc3:tmp"
+
+--luacheck: ignore 113/get_room_from_jid
+
+function fetch_participant_list(room, stanza, origin)
+	local from_jid = stanza.attr.from;
+	local from_aff = room:get_affiliation(from_jid);
+	local from_rank = valid_affiliations[from_aff or "none"];
+
+	local required_aff_rank = valid_affiliations[room:get_members_only() and "member" or "none"];
+	if from_rank < required_aff_rank then
+		origin.send(st.error_reply(stanza, "auth", "forbidden"));
+		return true;
+	end
+
+	local can_see_real_jids = not room:is_anonymous_for(from_jid);
+
+	local reply = st.reply(stanza)
+		:tag("participants", { xmlns = xmlns_gc3 });
+
+	for jid, aff in room:each_affiliation() do
+		local nick = room:get_registered_nick(jid);
+		local visible_jid = can_see_real_jids and jid or nil;
+		reply:text_tag("item", nil, {
+			affiliation = aff;
+			jid = visible_jid;
+			nick = nick;
+			id = room:get_occupant_id_from_jid(jid);
+		});
+	end
+
+	origin.send(reply);
+	return true;
+end
+
+local function room_event_handler(handler, allow_nonexistent)
+	return function (event)
+		local origin, stanza = event.origin, event.stanza;
+		local room_jid = jid_bare(stanza.attr.to);
+		local room = get_room_from_jid(room_jid);
+		if not room and allow_nonexistent ~= true then
+			origin.send(st.error_reply(stanza, "cancel", "item-not-found"));
+			return true;
+		end
+		return handler(room, stanza, origin);
+	end;
+end
+
+module:hook("iq-get/bare/"..xmlns_gc3..":participants", room_event_handler(fetch_participant_list));