--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_muc_notifications/mod_muc_notifications.lua	Fri Mar 29 17:03:05 2019 +0100
@@ -0,0 +1,67 @@
+-- mod_muc_notifications
+--
+-- Copyright (C) 2019 Marcos de Vera Piquero <marcos.devera@quobis.com>
+--
+-- This file is MIT/X11 licensed.
+--
+-- A module to notify non-present members of messages in a group chat
+--
+
+local id = require"util.id"
+local st = require"util.stanza"
+
+local use_invite = module:get_option_boolean("muc_notification_invite", false)
+
+-- Given a stanza, compute if it qualifies as important (notifiable)
+-- return true for message stanzas with non-empty body
+-- Should probably use something similar to muc-message-is-historic event
+local function is_important(stanza)
+	local body = stanza:find("body#")
+	return body and #body
+end
+
+local function handle_muc_message(event)
+	-- event.room and event.stanza are available
+	local room = event.room
+	local stanza = event.stanza
+	for jid, aff in pairs(room._affiliations) do
+		if aff ~= "outcast" then
+			local is_occupant = false
+			for _, occupant in pairs(room._occupants) do
+				if occupant.bare_jid == jid then
+					is_occupant = true
+					break
+				end
+			end
+			if not is_occupant and is_important(stanza) then
+				-- send notification to jid
+				local attrs = {
+					to = jid,
+					id = id.short(),
+					from = room.jid,
+				}
+				local not_attrs = {
+					xmlns = "http://quobis.com/xmpp/muc#push",
+					jid = room.jid,
+				}
+				local reason = "You have messages in group chat "..room:get_name()
+				local notification = st.message(attrs)
+					:body(reason):up()
+					:tag("notification", not_attrs):up()
+					:tag("no-store", {xmlns = "urn:xmpp:hints"})
+				local invite = st.message(attrs):tag("x", {xmlns = "http://jabber.org/protocol/muc#user"})
+					:tag("invite", {from = stanza.attr.from})
+					:tag("reason"):text(reason):up():up():up()
+					:tag("notification", not_attrs):up()
+					:tag("no-store", {xmlns = "urn:xmpp:hints"})
+				module:log("debug", "notifying with %s", tostring(use_invite and invite or notification))
+				module:send(use_invite and invite or notification)
+				module:log("debug", "sent notification of MUC message %s", use_invite and invite or notification)
+			end
+		end
+	end
+end
+
+module:hook("muc-broadcast-message", handle_muc_message)
+
+module:log("debug", "Module loaded")