feat: add InboxMonitorService with classification pipeline and spam moving
This commit is contained in:
216
src/SpamGuard/Services/InboxMonitorService.cs
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216
src/SpamGuard/Services/InboxMonitorService.cs
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// src/SpamGuard/Services/InboxMonitorService.cs
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namespace SpamGuard.Services;
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using MailKit;
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using MailKit.Search;
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using Microsoft.Extensions.Hosting;
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using Microsoft.Extensions.Logging;
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using Microsoft.Extensions.Options;
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using MimeKit;
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using SpamGuard.Configuration;
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using SpamGuard.Models;
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using SpamGuard.State;
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public sealed class InboxMonitorService : BackgroundService
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{
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private readonly ImapClientFactory _imapFactory;
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private readonly TrustedSenderStore _trustedSenders;
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private readonly ProcessedUidStore _processedUids;
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private readonly EmailClassifier _classifier;
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private readonly ActivityLog _activityLog;
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private readonly SpamGuardOptions _options;
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private readonly ILogger<InboxMonitorService> _logger;
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private volatile bool _paused;
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public bool IsPaused => _paused;
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public void Pause() => _paused = true;
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public void Resume() => _paused = false;
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public InboxMonitorService(
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ImapClientFactory imapFactory,
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TrustedSenderStore trustedSenders,
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ProcessedUidStore processedUids,
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EmailClassifier classifier,
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ActivityLog activityLog,
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IOptions<SpamGuardOptions> options,
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ILogger<InboxMonitorService> logger)
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{
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_imapFactory = imapFactory;
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_trustedSenders = trustedSenders;
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_processedUids = processedUids;
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_classifier = classifier;
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_activityLog = activityLog;
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_options = options.Value;
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_logger = logger;
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}
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protected override async Task ExecuteAsync(CancellationToken stoppingToken)
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{
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_logger.LogInformation("InboxMonitorService started");
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// Brief delay to let TrustedSenderService do its first scan
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await Task.Delay(TimeSpan.FromSeconds(10), stoppingToken);
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while (!stoppingToken.IsCancellationRequested)
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{
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if (!_paused)
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{
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try
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{
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await PollInboxAsync(stoppingToken);
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_processedUids.Prune(TimeSpan.FromDays(30));
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_processedUids.Save();
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}
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catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
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{
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break;
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}
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catch (Exception ex)
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{
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_logger.LogError(ex, "Error polling inbox");
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_activityLog.Add(new ActivityEntry(
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DateTime.UtcNow, "", "", Verdict.Error, null, ex.Message));
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}
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}
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await Task.Delay(TimeSpan.FromSeconds(_options.Monitoring.PollIntervalSeconds), stoppingToken);
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}
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}
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private async Task PollInboxAsync(CancellationToken ct)
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{
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using var client = await _imapFactory.CreateConnectedClientAsync(ct);
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var inbox = client.Inbox;
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await inbox.OpenAsync(FolderAccess.ReadWrite, ct);
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// Build search query: recent messages only
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var since = _processedUids.Count == 0
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? SearchQuery.DeliveredAfter(DateTime.UtcNow.AddDays(-_options.Monitoring.InitialScanDays))
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: SearchQuery.All;
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var uids = await inbox.SearchAsync(since, ct);
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_logger.LogDebug("Found {Count} messages in inbox", uids.Count);
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// Find the spam/junk folder
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var spamFolder = await FindSpamFolderAsync(client, ct);
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foreach (var uid in uids)
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{
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if (_processedUids.Contains(uid.Id))
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continue;
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try
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{
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await ProcessMessageAsync(inbox, uid, spamFolder, ct);
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}
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catch (Exception ex)
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{
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_logger.LogError(ex, "Error processing UID={Uid}", uid.Id);
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_activityLog.Add(new ActivityEntry(
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DateTime.UtcNow, "", $"UID {uid.Id}", Verdict.Error, null, ex.Message));
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_processedUids.Add(uid.Id); // Skip on next run to avoid infinite retry
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}
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}
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await client.DisconnectAsync(true, ct);
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}
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private async Task ProcessMessageAsync(
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IMailFolder inbox, UniqueId uid, IMailFolder? spamFolder, CancellationToken ct)
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{
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var message = await inbox.GetMessageAsync(uid, ct);
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var from = message.From.Mailboxes.FirstOrDefault()?.Address ?? "unknown";
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var subject = message.Subject ?? "(no subject)";
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// Check trusted senders
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if (_trustedSenders.IsTrusted(from))
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{
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_logger.LogDebug("UID={Uid} from trusted sender {From}, skipping", uid.Id, from);
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_activityLog.Add(new ActivityEntry(
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DateTime.UtcNow, from, subject, Verdict.Trusted, null, null));
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_processedUids.Add(uid.Id);
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return;
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}
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// Extract body snippet
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var bodySnippet = ExtractBodySnippet(message);
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var emailSummary = new EmailSummary(uid.Id, from, subject, bodySnippet, message.Date);
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// Classify
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var result = await _classifier.ClassifyAsync(emailSummary, ct);
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if (result == null)
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{
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_activityLog.Add(new ActivityEntry(
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DateTime.UtcNow, from, subject, Verdict.Error, null, "Classification failed"));
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_processedUids.Add(uid.Id);
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return;
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}
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if (result.IsSpam && result.Confidence >= _options.Monitoring.SpamConfidenceThreshold)
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{
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// Move to spam folder
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if (spamFolder != null)
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{
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await inbox.MoveToAsync(uid, spamFolder, ct);
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_logger.LogInformation("Moved UID={Uid} to spam: {Reason}", uid.Id, result.Reason);
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}
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else
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{
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_logger.LogWarning("Spam detected but no spam folder found, flagging instead");
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await inbox.AddFlagsAsync(uid, MailKit.MessageFlags.Flagged, true, ct);
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}
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_activityLog.Add(new ActivityEntry(
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DateTime.UtcNow, from, subject, Verdict.Spam, result.Confidence, result.Reason));
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}
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else if (result.IsSpam)
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{
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// Below threshold -- uncertain
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_activityLog.Add(new ActivityEntry(
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DateTime.UtcNow, from, subject, Verdict.Uncertain, result.Confidence, result.Reason));
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}
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else
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{
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_activityLog.Add(new ActivityEntry(
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DateTime.UtcNow, from, subject, Verdict.Legitimate, result.Confidence, result.Reason));
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}
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_processedUids.Add(uid.Id);
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}
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private static string ExtractBodySnippet(MimeMessage message)
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{
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var text = message.TextBody ?? message.HtmlBody ?? "";
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// Strip HTML tags if we fell back to HTML body
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if (message.TextBody == null && message.HtmlBody != null)
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text = System.Text.RegularExpressions.Regex.Replace(text, "<[^>]+>", " ");
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return text.Length > 2000 ? text[..2000] : text;
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}
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private async Task<IMailFolder?> FindSpamFolderAsync(MailKit.Net.Imap.ImapClient client, CancellationToken ct)
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{
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// Try special folder first
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try
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{
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var junk = client.GetFolder(MailKit.SpecialFolder.Junk);
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if (junk != null) return junk;
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}
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catch { }
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// Fall back to configured folder name
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try
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{
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var personal = client.GetFolder(client.PersonalNamespaces[0]);
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var folders = await personal.GetSubfoldersAsync(false, ct);
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return folders.FirstOrDefault(f =>
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f.Name.Equals(_options.Monitoring.SpamFolderName, StringComparison.OrdinalIgnoreCase));
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}
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catch { }
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return null;
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}
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}
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