Don't update presence status if not needed

Status messages are sent with every presence update by some XMPP
clients, which would previously result in corresponding changes being
made on the WhatsApp side, where no effective change in status has been
made since.

This commit implements naive caching for presence status in order to
avoid most double-sets, but which however will clear across restarts.

slidge_whatsapp/session.go

@@ -100,7 +100,7 @@ func (s *Session) Login() error {
 			select {
 			case <-timer.C:
 				if presence == PresenceAvailable {
-					s.GetContacts(false)
+					_, _ = s.GetContacts(false)
 					timer, timerStopped = newTimer(presenceRefreshInterval), false
 				} else {
 					timerStopped = true
@@ -112,7 +112,7 @@ func (s *Session) Login() error {
 					}
 					return
 				} else if timerStopped && p == PresenceAvailable {
-					s.GetContacts(false)
+					_, _ = s.GetContacts(false)
 					timer, timerStopped = newTimer(presenceRefreshInterval), false
 				}
 				presence = p

slidge_whatsapp/session.py

@@ -77,6 +77,7 @@ class Session(BaseSession[str, Recipient]):
         self.whatsapp.SetEventHandler(self._handle_event)
         self._connected = self.xmpp.loop.create_future()
         self.user_phone: Optional[str] = None
+        self._presence_status: str = ""
         self._lock = Lock()
 
     async def login(self):
@@ -318,9 +319,14 @@ class Session(BaseSession[str, Recipient]):
                 if merged_resource["show"] in ["chat", ""]
                 else whatsapp.PresenceUnavailable
             )
-            self.whatsapp.SendPresence(
-                presence, merged_resource["status"] if merged_resource["status"] else ""
+            status = (
+                merged_resource["status"]
+                if self._presence_status != merged_resource["status"]
+                else ""
             )
+            if status:
+                self._presence_status = status
+            self.whatsapp.SendPresence(presence, status)
 
     async def on_active(self, c: Recipient, thread=None):
         """