--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libervia/backend/plugins/plugin_xep_0352.py	Fri Jun 02 11:49:51 2023 +0200
@@ -0,0 +1,83 @@
+#!/usr/bin/env python3
+
+
+# SAT plugin for Explicit Message Encryption
+# Copyright (C) 2009-2021 Jérôme Poisson (goffi@goffi.org)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from twisted.words.xish import domish
+from libervia.backend.core.i18n import _, D_
+from libervia.backend.core.constants import Const as C
+from libervia.backend.core.log import getLogger
+
+log = getLogger(__name__)
+
+PLUGIN_INFO = {
+    C.PI_NAME: "Client State Indication",
+    C.PI_IMPORT_NAME: "XEP-0352",
+    C.PI_TYPE: C.PLUG_TYPE_XEP,
+    C.PI_PROTOCOLS: ["XEP-0352"],
+    C.PI_DEPENDENCIES: [],
+    C.PI_MAIN: "XEP_0352",
+    C.PI_HANDLER: "no",
+    C.PI_DESCRIPTION: D_("Notify server when frontend is not actively used, to limit "
+                         "traffic and save bandwidth and battery life"),
+}
+
+NS_CSI = "urn:xmpp:csi:0"
+
+
+class XEP_0352(object):
+
+    def __init__(self, host):
+        log.info(_("Client State Indication plugin initialization"))
+        self.host = host
+        host.register_namespace("csi", NS_CSI)
+
+    def is_active(self, client):
+        try:
+            if not client._xep_0352_enabled:
+                return True
+            return client._xep_0352_active
+        except AttributeError:
+            # _xep_0352_active can not be set if is_active is called before
+            # profile_connected has been called
+            log.debug("is_active called when XEP-0352 plugin has not yet set the "
+                      "attributes")
+            return True
+
+    def profile_connected(self, client):
+        if (NS_CSI, 'csi') in client.xmlstream.features:
+            log.info(_("Client State Indication is available on this server"))
+            client._xep_0352_enabled = True
+            client._xep_0352_active = True
+        else:
+            log.warning(_("Client State Indication is not available on this server, some"
+                          " bandwidth optimisations can't be used."))
+            client._xep_0352_enabled = False
+
+    def set_inactive(self, client):
+        if self.is_active(client):
+            inactive_elt = domish.Element((NS_CSI, 'inactive'))
+            client.send(inactive_elt)
+            client._xep_0352_active = False
+            log.info("inactive state set")
+
+    def set_active(self, client):
+        if not self.is_active(client):
+            active_elt = domish.Element((NS_CSI, 'active'))
+            client.send(active_elt)
+            client._xep_0352_active = True
+            log.info("active state set")