Hydrate generic media previews before notifying

server/QMax.Api/Services/MaxBridgeSyncService.cs

@@ -45,7 +45,12 @@ public sealed class MaxBridgeSyncService(
             var update = await maxBridgeClient.FetchChatHistoryAsync(externalChatId, chatUrl, cancellationToken);
             return update is null
                 ? 0
-                : await ApplyUpdatesAsync([update], incrementUnread: false, sendPushNotifications: false, cancellationToken);
+                : await ApplyUpdatesAsync(
+                    [update],
+                    incrementUnread: false,
+                    sendPushNotifications: false,
+                    cancellationToken,
+                    allowGenericMediaHistoryFetch: false);
         }
         catch (Exception ex)
         {
@@ -58,7 +63,8 @@ public sealed class MaxBridgeSyncService(
         IReadOnlyList<MaxChatUpdate> updates,
         bool incrementUnread,
         bool sendPushNotifications,
-        CancellationToken cancellationToken)
+        CancellationToken cancellationToken,
+        bool allowGenericMediaHistoryFetch = true)
     {
         if (updates.Count == 0)
         {
@@ -74,6 +80,7 @@ public sealed class MaxBridgeSyncService(
         var createdMessages = new List<(Chat Chat, Message Message)>();
         var updatedMessages = new List<(Chat Chat, Message Message)>();
         var previewNotificationMessages = new List<(Chat Chat, Message Message)>();
+        var genericMediaHistoryRequests = new List<(string ExternalChatId, string? ChatUrl, DateTimeOffset PreviewAt)>();
         var trackedChatsByExternalId = new Dictionary<string, Chat>(StringComparer.Ordinal);
 
         foreach (var update in updates)
@@ -196,6 +203,14 @@ public sealed class MaxBridgeSyncService(
                 previewNotificationMessages.Add((chat, previewResult.NotificationMessage));
             }
 
+            if (allowGenericMediaHistoryFetch &&
+                previewResult.ShouldFetchHistory &&
+                previewResult.PreviewAt is { } previewAt &&
+                !await HasMessageAtOrAfterAsync(db, chat.Id, previewAt, cancellationToken))
+            {
+                genericMediaHistoryRequests.Add((update.ExternalId, nextWebUrl ?? chat.WebUrl, previewAt));
+            }
+
             if (previewResult.Changed)
             {
                 changed++;
@@ -387,6 +402,29 @@ public sealed class MaxBridgeSyncService(
             await hubContext.Clients.All.SendAsync("ChatListInvalidated", cancellationToken);
         }
 
+        foreach (var request in genericMediaHistoryRequests
+            .GroupBy(x => x.ExternalChatId, StringComparer.Ordinal)
+            .Select(x => x.OrderByDescending(item => item.PreviewAt).First()))
+        {
+            try
+            {
+                var history = await maxBridgeClient.FetchChatHistoryAsync(request.ExternalChatId, request.ChatUrl, cancellationToken);
+                if (history is not null)
+                {
+                    changed += await ApplyUpdatesAsync(
+                        [history],
+                        incrementUnread,
+                        sendPushNotifications,
+                        cancellationToken,
+                        allowGenericMediaHistoryFetch: false);
+                }
+            }
+            catch (Exception ex)
+            {
+                logger.LogWarning(ex, "MAX media preview history fetch failed for {ExternalChatId}.", request.ExternalChatId);
+            }
+        }
+
         return changed;
     }
 
@@ -400,12 +438,12 @@ public sealed class MaxBridgeSyncService(
         var preview = MessageTextSanitizer.CleanChatPreview(update.LastMessagePreview);
         if (string.IsNullOrWhiteSpace(preview))
         {
-            return new ListPreviewApplyResult(false, null, null);
+            return new ListPreviewApplyResult(false, null, null, false, null);
         }
 
         if (IsPresencePreview(preview))
         {
-            return new ListPreviewApplyResult(false, null, null);
+            return new ListPreviewApplyResult(false, null, null, false, null);
         }
 
         var previousPreview = chat.LastMessagePreview;
@@ -413,15 +451,19 @@ public sealed class MaxBridgeSyncService(
         var previewAt = ResolveListPreviewAt(update, previousPreviewAt ?? chat.UpdatedAt);
         if (chat.HistoryClearedAt is { } historyClearedAt && previewAt <= historyClearedAt)
         {
-            return new ListPreviewApplyResult(false, null, null);
+            return new ListPreviewApplyResult(false, null, null, false, null);
         }
 
+        var isGenericMediaPreview = MessageTextSanitizer.IsGenericMediaLabel(preview);
+        var shouldFetchHistory = isGenericMediaPreview &&
+            update.Messages.Count == 0 &&
+            HasListClockTime(update.LastMessageTimeText);
         var samePreview = string.Equals(previousPreview, preview, StringComparison.Ordinal);
         var samePreviewAt = previousPreviewAt is not null &&
             Math.Abs((previousPreviewAt.Value - previewAt).TotalSeconds) < 1;
         if (samePreview && samePreviewAt)
         {
-            return new ListPreviewApplyResult(false, null, null);
+            return new ListPreviewApplyResult(false, null, null, shouldFetchHistory, previewAt);
         }
 
         chat.LastMessagePreview = preview;
@@ -438,18 +480,15 @@ public sealed class MaxBridgeSyncService(
         var shouldNotify = shouldNotifyCandidate &&
             RememberPreviewNotification(chat.Id, preview, previewAt);
 
-        if (incrementUnread && shouldNotify)
+        if (incrementUnread && shouldNotify && !isGenericMediaPreview)
         {
             chat.UnreadCount++;
         }
 
-        var message = shouldNotify && !MessageTextSanitizer.IsGenericMediaLabel(preview)
+        var message = shouldNotify && !isGenericMediaPreview
             ? CreatePreviewMessage(chat, preview, previewAt)
             : null;
-        var notificationMessage = shouldNotify && message is null && MessageTextSanitizer.IsGenericMediaLabel(preview)
-            ? CreatePreviewMessage(chat, preview, previewAt)
-            : null;
-        return new ListPreviewApplyResult(true, message, notificationMessage);
+        return new ListPreviewApplyResult(true, message, null, shouldFetchHistory, previewAt);
     }
 
     private static bool IsKnownOutgoingPreviewEcho(
@@ -628,7 +667,12 @@ public sealed class MaxBridgeSyncService(
             text.Contains("file", StringComparison.Ordinal);
     }
 
-    private sealed record ListPreviewApplyResult(bool Changed, Message? Message, Message? NotificationMessage);
+    private sealed record ListPreviewApplyResult(
+        bool Changed,
+        Message? Message,
+        Message? NotificationMessage,
+        bool ShouldFetchHistory,
+        DateTimeOffset? PreviewAt);
 
     private sealed record MessageMergeResult(bool Changed, IReadOnlyList<MessageAttachment> AddedAttachments);
 
@@ -715,6 +759,22 @@ public sealed class MaxBridgeSyncService(
             Math.Abs((candidate.SentAt.ToUniversalTime() - previewMessage.SentAt.ToUniversalTime()).TotalMinutes) <= 30);
     }
 
+    private static async Task<bool> HasMessageAtOrAfterAsync(
+        QMaxDbContext db,
+        Guid chatId,
+        DateTimeOffset previewAt,
+        CancellationToken cancellationToken)
+    {
+        var cutoff = previewAt.ToUniversalTime().AddSeconds(-1);
+        var sentAtValues = await db.Messages
+            .AsNoTracking()
+            .Where(x => x.ChatId == chatId && x.DeletedAt == null)
+            .Select(x => x.SentAt)
+            .ToArrayAsync(cancellationToken);
+
+        return sentAtValues.Any(sentAt => sentAt.ToUniversalTime() >= cutoff);
+    }
+
     private static string PreviewExternalId(Guid chatId, string preview, DateTimeOffset previewAt)
     {
         var previewMinute = previewAt.ToUniversalTime().Ticks / TimeSpan.TicksPerMinute;