using Distribution.Infra.UoW;

namespace Distribution.Features.Notifications;

/// <summary>
/// Daily retention purge: deletes read inbox rows older than <c>Notifications:RetentionDays</c>
/// (default 90), then any notification left with no recipients.
/// </summary>
public class NotificationCleanupJob(
    IServiceScopeFactory scopes,
    IConfiguration config,
    ILogger<NotificationCleanupJob> logger) : BackgroundService
{
    private const int BatchSize = 500;

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        // Let the app finish starting before the first run.
        await Task.Delay(TimeSpan.FromMinutes(1), stoppingToken);

        while (!stoppingToken.IsCancellationRequested)
        {
            try { await RunOnceAsync(stoppingToken); }
            catch (OperationCanceledException) { break; }
            catch (Exception ex) { logger.LogError(ex, "Notification cleanup failed."); }

            await Task.Delay(TimeSpan.FromHours(24), stoppingToken);
        }
    }

    private async Task RunOnceAsync(CancellationToken ct)
    {
        var retentionDays = config.GetValue("Notifications:RetentionDays", 90);
        var cutoff = DateTime.Now.AddDays(-retentionDays);

        using var scope = scopes.CreateScope();
        var repo = scope.ServiceProvider.GetRequiredService<INotificationRepository>();
        var uow = scope.ServiceProvider.GetRequiredService<IUnitOfWork>();

        var removed = 0;
        while (true)
        {
            var expired = await repo.GetExpiredReadRecipientsAsync(cutoff, BatchSize);
            if (expired.Count == 0) break;

            repo.RemoveRecipients(expired);
            await uow.CommitAsync(ct);
            removed += expired.Count;
        }

        while (true)
        {
            var orphans = await repo.GetOrphanNotificationsAsync(BatchSize);
            if (orphans.Count == 0) break;

            repo.RemoveNotifications(orphans);
            await uow.CommitAsync(ct);
        }

        if (removed > 0)
            logger.LogInformation("Notification cleanup removed {Count} read inbox rows older than {Days} days.", removed, retentionDays);
    }
}