Backfill preview-only incoming messages

2026-07-05 23:35:11 +03:00
parent 3bc6456ed7
commit 9940f9e43c
3 changed files with 347 additions and 36 deletions
@@ -83,6 +83,11 @@ public sealed class ChatsController(
            }
        }

+        if (before is null)
+        {
+            await EnsureLastPreviewMessageAsync(chat, cancellationToken);
+        }
+
        if (before is null && chat.UnreadCount > 0)
        {
            chat.UnreadCount = 0;
@@ -108,6 +113,95 @@ public sealed class ChatsController(
        return messages.OrderBy(x => x.SentAt).Select(projection.ToDto).ToArray();
    }

+    private async Task EnsureLastPreviewMessageAsync(Chat chat, CancellationToken cancellationToken)
+    {
+        var preview = MessageTextSanitizer.CleanChatPreview(chat.LastMessagePreview);
+        if (string.IsNullOrWhiteSpace(preview) || chat.LastMessageAt is null)
+        {
+            return;
+        }
+
+        var previewAt = chat.LastMessageAt.Value;
+        if (chat.HistoryClearedAt is { } historyClearedAt && previewAt <= historyClearedAt)
+        {
+            return;
+        }
+
+        var latestMessage = (await db.Messages
+            .AsNoTracking()
+            .Where(x => x.ChatId == chat.Id && x.DeletedAt == null)
+            .ToArrayAsync(cancellationToken))
+            .OrderByDescending(x => x.SentAt)
+            .FirstOrDefault();
+        if (latestMessage is not null && latestMessage.SentAt >= previewAt.AddSeconds(-1))
+        {
+            return;
+        }
+
+        var externalId = PreviewExternalId(chat.Id, preview, previewAt);
+        if (await HasPreviewPlaceholderAsync(chat.Id, externalId, preview, previewAt, cancellationToken))
+        {
+            return;
+        }
+
+        db.Messages.Add(new Message
+        {
+            ChatId = chat.Id,
+            ExternalId = externalId,
+            Direction = MessageDirection.Incoming,
+            Text = preview,
+            SentAt = previewAt,
+            DeliveryState = MessageDeliveryState.Delivered,
+            SenderExternalId = chat.ExternalId,
+            SenderName = chat.Title
+        });
+        await db.SaveChangesAsync(cancellationToken);
+    }
+
+    private async Task<bool> HasPreviewPlaceholderAsync(
+        Guid chatId,
+        string externalId,
+        string preview,
+        DateTimeOffset previewAt,
+        CancellationToken cancellationToken)
+    {
+        var previewMessages = await db.Messages
+            .AsNoTracking()
+            .Where(x =>
+                x.ChatId == chatId &&
+                x.DeletedAt == null &&
+                x.Direction == MessageDirection.Incoming &&
+                x.ExternalId != null &&
+                (x.ExternalId == externalId || x.ExternalId.StartsWith("preview:")))
+            .ToArrayAsync(cancellationToken);
+
+        return previewMessages.Any(message =>
+            string.Equals(message.ExternalId, externalId, StringComparison.Ordinal) ||
+            string.Equals(
+                MessageTextSanitizer.CleanMessageText(message.Text, false),
+                preview,
+                StringComparison.Ordinal) &&
+            Math.Abs((message.SentAt.ToUniversalTime() - previewAt.ToUniversalTime()).TotalMinutes) <= 30);
+    }
+
+    private static string PreviewExternalId(Guid chatId, string preview, DateTimeOffset previewAt)
+    {
+        var previewMinute = previewAt.ToUniversalTime().Ticks / TimeSpan.TicksPerMinute;
+        return $"preview:{chatId:N}:{previewMinute}:{StableHash(preview.Trim().ToLowerInvariant())}";
+    }
+
+    private static string StableHash(string value)
+    {
+        var hash = 2166136261u;
+        foreach (var character in value)
+        {
+            hash ^= character;
+            hash *= 16777619;
+        }
+
+        return hash.ToString("x8");
+    }
+
    [HttpPost("{chatId:guid}/read")]
    public async Task<IActionResult> MarkRead(Guid chatId, CancellationToken cancellationToken)
    {