--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/plugins/muc/presence_broadcast.lib.lua	Sun Oct 20 21:58:16 2019 +0200
@@ -0,0 +1,87 @@
+-- Prosody IM
+-- Copyright (C) 2008-2010 Matthew Wild
+-- Copyright (C) 2008-2010 Waqas Hussain
+-- Copyright (C) 2014 Daurnimator
+--
+-- This project is MIT/X11 licensed. Please see the
+-- COPYING file in the source package for more information.
+--
+
+local st = require "util.stanza";
+
+local valid_roles = { "visitor", "participant", "moderator" };
+local default_broadcast = {
+	none = true;
+	visitor = true;
+	participant = true;
+	moderator = true;
+};
+
+local function get_presence_broadcast(room)
+	return room._data.presence_broadcast or default_broadcast;
+end
+
+local function set_presence_broadcast(room, broadcast_roles)
+	broadcast_roles = broadcast_roles or default_broadcast;
+
+	-- Ensure that unavailable presence is always sent when role changes to none
+	broadcast_roles.none = true;
+
+	local changed = false;
+	local old_broadcast_roles = get_presence_broadcast(room);
+	for _, role in ipairs(valid_roles) do
+		if old_broadcast_roles[role] ~= broadcast_roles[role] then
+			changed = true;
+		end
+	end
+
+	if not changed then return false; end
+
+	room._data.presence_broadcast = broadcast_roles;
+
+	for _, occupant in room:each_occupant() do
+		local x = st.stanza("x", {xmlns = "http://jabber.org/protocol/muc#user";});
+		local role = occupant.role or "none";
+		if broadcast_roles[role] and not old_broadcast_roles[role] then
+			-- Presence broadcast is now enabled, so announce existing user
+			room:publicise_occupant_status(occupant, x);
+		elseif old_broadcast_roles[role] and not broadcast_roles[role] then
+			-- Presence broadcast is now disabled, so mark existing user as unavailable
+			room:publicise_occupant_status(occupant, x, nil, nil, nil, nil, true);
+		end
+	end
+
+	return true;
+end
+
+module:hook("muc-config-form", function(event)
+	local values = {};
+	for role, value in pairs(get_presence_broadcast(event.room)) do
+		if value then
+			values[#values + 1] = role;
+		end
+	end
+
+	table.insert(event.form, {
+		name = "muc#roomconfig_presencebroadcast";
+		type = "list-multi";
+		label = "Roles for which Presence is Broadcasted";
+		value = values;
+		options = valid_roles;
+	});
+end, 70-7);
+
+module:hook("muc-config-submitted/muc#roomconfig_presencebroadcast", function(event)
+	local broadcast_roles = {};
+	for _, role in ipairs(event.value) do
+		broadcast_roles[role] = true;
+	end
+	if set_presence_broadcast(event.room, broadcast_roles) then
+		event.status_codes["104"] = true;
+	end
+end);
+
+return {
+	get = get_presence_broadcast;
+	set = set_presence_broadcast;
+};