android/app/src/main/kotlin/im/cwtch/flwtch/MainActivity.kt

@@ -331,8 +331,9 @@ class MainActivity: FlutterActivity() {
                 val conversation: Int = call.argument("conversation") ?: 0
                 val indexI: Int = call.argument("index") ?: 0
                 val count: Int = call.argument("count") ?: 1
+                val ucount : Int = maxOf(1, count) // don't allow negative counts
 
-                result.success(Cwtch.getMessages(profile, conversation.toLong(), indexI.toLong(), count.toLong()))
+                result.success(Cwtch.getMessages(profile, conversation.toLong(), indexI.toLong(), ucount.toLong()))
                 return
             }
             "SendMessage" -> {

lib/models/contact.dart

@@ -230,6 +230,7 @@ class ContactInfoState extends ChangeNotifier {
     return this._newMarkerMsgIndex;
   }
 
+  int get totalMessages => this._totalMessages;
   int get totalMessages => this._totalMessages;
 
   set totalMessages(int newVal) {

lib/models/messagecache.dart

@@ -30,22 +30,27 @@ class LocalIndexMessage {
     this.messageId = messageId;
     this.cacheOnly = cacheOnly;
     this.isLoading = isLoading;
-    if (isLoading) {
-      loader = Completer<void>();
-      loaded = loader.future;
+    loader = Completer<void>();
+    loaded = loader.future;
+    if (!isLoading) {
+      loader.complete(); // complete this
     }
   }
 
   void finishLoad(int messageId) {
     this.messageId = messageId;
-    isLoading = false;
-    loader.complete(true);
+    if (!loader.isCompleted) {
+      isLoading = false;
+      loader.complete(true);
+    }
   }
 
   void failLoad() {
     this.messageId = null;
-    isLoading = false;
-    loader.complete(true);
+    if (!loader.isCompleted) {
+      isLoading = false;
+      loader.complete(true);
+    }
   }
 
   Future<void> waitForLoad() {
@@ -95,7 +100,7 @@ class MessageCache extends ChangeNotifier {
     this._storageMessageCount = newval;
   }
 
-  // On android reconnect, if backend supplied message count > UI message count, add the differnce to the front of the index
+  // On android reconnect, if backend supplied message count > UI message count, add the difference to the front of the index
   void addFrontIndexGap(int count) {
     this._indexUnsynced = count;
   }

lib/models/profile.dart

@@ -1,4 +1,5 @@
 import 'dart:convert';
+import 'dart:math';
 
 import 'package:cwtch/config.dart';
 import 'package:cwtch/models/remoteserver.dart';
@@ -248,8 +249,22 @@ class ProfileInfoState extends ChangeNotifier {
         if (profileContact != null) {
           profileContact.status = contact["status"];
 
-          var newCount = contact["numMessages"];
+          var newCount = contact["numMessages"] as int;
           if (newCount != profileContact.totalMessages) {
+            if (newCount < profileContact.totalMessages) {
+              // on Android, when sharing a file the UI may be briefly unloaded for the
+              // OS to display the file management/selection screen. Afterwards a
+              // call to ReconnectCwtchForeground will be made which will refresh all values (including count of numMessages)
+              // **at the same time** the foreground will increment .totalMessages and send a new message to the backend.
+              // This will result in a negative number of messages being calculated here, and an incorrect totalMessage count.
+              // This bug is exacerbated in debug mode, and when multiple files are sent in succession. Both cases result in multiple ReconnectCwtchForeground
+              // events that have the potential to conflict with currentMessageCounts.
+              // Note that *if* a new message came in at the same time, we would be unable to distinguish this case - as such this is specific instance of a more general problem
+              // TODO: A true-fix to this bug is to implement a syncing step in the foreground where totalMessages and inFlightMessages can be distinguished
+              // This requires a change to the backend to confirm submission of an inFlightMessage, which will be implemented in #664
+              EnvironmentConfig.debugLog("Conflicting message counts: $newCount ${profileContact.totalMessages}");
+              newCount = max(newCount, profileContact.totalMessages);
+            }
             profileContact.messageCache.addFrontIndexGap(newCount - profileContact.totalMessages);
           }
           profileContact.totalMessages = newCount;