xmpp: Have the [CSIManager] remember its last state

lib/xmpp/connection.dart

@@ -19,6 +19,7 @@ import "package:moxxyv2/xmpp/managers/attributes.dart";
 import "package:moxxyv2/xmpp/managers/namespaces.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0030.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0198.dart";
+import "package:moxxyv2/xmpp/xeps/xep_0352.dart";
 import "package:moxxyv2/xmpp/xeps/xep_0368.dart";
 
 import "package:uuid/uuid.dart";
@@ -153,6 +154,11 @@ class XmppConnection {
     return getManagerById(smManager);
   }
 
+  /// Returns the registered [CSIManager], if one is registered.
+  CSIManager? getCSIManager() {
+    return getManagerById(csiManager);
+  }
+  
   /// Set the connection settings of this connection.
   void setConnectionSettings(ConnectionSettings settings) {
     _connectionSettings = settings;
@@ -479,6 +485,12 @@ class XmppConnection {
           _routingState = RoutingState.handleStanzas;
           _setConnectionState(XmppConnectionState.connected);
 
+          // Restore the CSI state if we have a manager
+          final csiManager = getCSIManager();
+          if (csiManager != null) {
+            csiManager.restoreCSIState();
+          }
+          
           final h = int.parse(node.attributes["h"]!);
           _sendEvent(StreamResumedEvent(h: h));
         } else if (node.tag == "failed") {

lib/xmpp/xeps/xep_0352.dart

@@ -21,13 +21,28 @@ class CSIInactiveNonza extends XMLNode {
   );
 }
 
-// TODO: Remember the CSI state in case we resume a stream
 class CSIManager extends XmppManagerBase {
+  bool _isActive;
+
+  CSIManager() : _isActive = true, super(); 
+
   @override
   String getId() => csiManager;
 
+  /// To be called after a stream has been resumed as CSI does not
+  /// survive a stream resumption.
+  void restoreCSIState() {
+    if (_isActive) {
+      setActive();
+    } else {
+      setInactive();
+    }
+  }
+  
   /// Tells the server to top optimizing traffic
   void setActive() {
+    _isActive = true;
+
     final attrs = getAttributes();
     if (attrs.isStreamFeatureSupported(csiXmlns)) {
       attrs.sendNonza(CSIActiveNonza());
@@ -36,6 +51,8 @@ class CSIManager extends XmppManagerBase {
 
   /// Tells the server to optimize traffic following XEP-0352
   void setInactive() {
+    _isActive = false;
+
     final attrs = getAttributes();
     if (attrs.isStreamFeatureSupported(csiXmlns)) {
       attrs.sendNonza(CSIInactiveNonza());