Suppress pushes for outgoing preview echoes

server/QMax.Api/Services/MaxBridgeSyncService.cs

@@ -127,13 +127,36 @@ public sealed class MaxBridgeSyncService(
                 changed++;
             }
 
+            var previewHint = MessageTextSanitizer.CleanChatPreview(update.LastMessagePreview);
+            var shouldLoadLastKnownMessage = !chatWasCreated &&
+                !string.IsNullOrWhiteSpace(previewHint) &&
+                !string.IsNullOrWhiteSpace(chat.LastMessagePreview) &&
+                string.Equals(MessageTextSanitizer.CleanChatPreview(chat.LastMessagePreview), previewHint, StringComparison.Ordinal) &&
+                update.LastMessageIsOutgoing != true &&
+                update.Messages.Count == 0 &&
+                HasListClockTime(update.LastMessageTimeText);
+            List<LastKnownMessageSnapshot> lastKnownMessages = !shouldLoadLastKnownMessage
+                ? []
+                : await db.Messages
+                    .Where(x =>
+                        x.ChatId == chat.Id &&
+                        x.DeletedAt == null &&
+                        x.Direction == MessageDirection.Outgoing &&
+                        x.Text == previewHint)
+                    .Select(x => new LastKnownMessageSnapshot(x.Direction, x.Text, x.SentAt))
+                    .ToListAsync(cancellationToken);
+            var lastKnownMessage = lastKnownMessages
+                .OrderByDescending(x => x.SentAt)
+                .FirstOrDefault();
+
             if (ApplyListPreview(
                 update,
                 chat,
                 chatWasCreated,
                 incrementUnread,
                 sendPushNotifications,
-                previewPushNotifications))
+                previewPushNotifications,
+                lastKnownMessage))
             {
                 changed++;
             }
@@ -255,7 +278,8 @@ public sealed class MaxBridgeSyncService(
         bool chatWasCreated,
         bool incrementUnread,
         bool sendPushNotifications,
-        ICollection<(Chat Chat, Message Message)> previewPushNotifications)
+        ICollection<(Chat Chat, Message Message)> previewPushNotifications,
+        LastKnownMessageSnapshot? lastKnownMessage)
     {
         var preview = MessageTextSanitizer.CleanChatPreview(update.LastMessagePreview);
         if (string.IsNullOrWhiteSpace(preview))
@@ -283,8 +307,10 @@ public sealed class MaxBridgeSyncService(
         chat.LastMessageAt = previewAt;
         chat.UpdatedAt = DateTimeOffset.UtcNow;
 
+        var echoesKnownOutgoing = IsKnownOutgoingPreviewEcho(lastKnownMessage, preview, previewAt);
         var shouldNotifyCandidate = !chatWasCreated &&
             !string.IsNullOrWhiteSpace(previousPreview) &&
+            !echoesKnownOutgoing &&
             update.LastMessageIsOutgoing != true &&
             update.Messages.Count == 0 &&
             IsFreshListPreview(update, previewAt);
@@ -317,6 +343,31 @@ public sealed class MaxBridgeSyncService(
         return true;
     }
 
+    private static bool IsKnownOutgoingPreviewEcho(
+        LastKnownMessageSnapshot? lastKnownMessage,
+        string preview,
+        DateTimeOffset previewAt)
+    {
+        if (lastKnownMessage is null ||
+            lastKnownMessage.Direction != MessageDirection.Outgoing ||
+            string.IsNullOrWhiteSpace(lastKnownMessage.Text))
+        {
+            return false;
+        }
+
+        var lastText = MessageTextSanitizer.CleanChatPreview(lastKnownMessage.Text);
+        if (!string.Equals(lastText, preview, StringComparison.Ordinal))
+        {
+            return false;
+        }
+
+        var sentAt = lastKnownMessage.SentAt.ToUniversalTime();
+        var previewUtc = previewAt.ToUniversalTime();
+        var now = DateTimeOffset.UtcNow;
+        return Math.Abs((sentAt - previewUtc).TotalMinutes) <= 30 ||
+            sentAt >= now.AddMinutes(-30);
+    }
+
     private static bool RememberPreviewNotification(Guid chatId, string preview, DateTimeOffset previewAt)
     {
         var now = DateTimeOffset.UtcNow;
@@ -755,4 +806,9 @@ public sealed class MaxBridgeSyncService(
             _ => null
         };
     }
+
+    private sealed record LastKnownMessageSnapshot(
+        MessageDirection Direction,
+        string? Text,
+        DateTimeOffset SentAt);
 }