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using Enmarcha.Backend.Data;
using Microsoft.EntityFrameworkCore;
namespace Enmarcha.Backend.Services;
/// <summary>
/// Background service that automatically sends push notifications when a service alert
/// transitions into the PreNotice or Active phase without having been notified yet.
/// Runs every 60 seconds and also immediately on startup to handle any missed transitions.
/// </summary>
public class AlertPhaseNotificationHostedService(
IServiceScopeFactory scopeFactory,
ILogger<AlertPhaseNotificationHostedService> logger) : IHostedService, IDisposable
{
private Timer? _timer;
public Task StartAsync(CancellationToken cancellationToken)
{
// Run immediately, then every 60 seconds
_timer = new Timer(_ => _ = RunAsync(), null, TimeSpan.Zero, TimeSpan.FromSeconds(60));
return Task.CompletedTask;
}
private async Task RunAsync()
{
try
{
using var scope = scopeFactory.CreateScope();
var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
var pushService = scope.ServiceProvider.GetRequiredService<IPushNotificationService>();
var now = DateTime.UtcNow;
// Find alerts that are published and not yet hidden, but haven't been notified
// for their current phase (PreNotice: published but event not yet started;
// Active: event in progress).
var alertsToNotify = await db.ServiceAlerts
.Where(a =>
a.PublishDate <= now && a.HiddenDate > now &&
(
// PreNotice: published, event hasn't started, no prenotice notification sent yet
(a.EventStartDate > now && a.PreNoticeNotifiedAt == null) ||
// Active: event started and not finished, no active notification sent yet
(a.EventStartDate <= now && a.EventEndDate > now && a.ActiveNotifiedAt == null)
))
.ToListAsync();
if (alertsToNotify.Count == 0) return;
logger.LogInformation("Sending push notifications for {Count} alert(s)", alertsToNotify.Count);
foreach (var alert in alertsToNotify)
{
try
{
await pushService.SendAlertAsync(alert);
}
catch (Exception ex)
{
logger.LogError(ex, "Error sending push notification for alert {AlertId}", alert.Id);
}
}
}
catch (Exception ex)
{
logger.LogError(ex, "Unexpected error in {ServiceName}", nameof(AlertPhaseNotificationHostedService));
}
}
public Task StopAsync(CancellationToken cancellationToken)
{
_timer?.Change(Timeout.Infinite, 0);
return Task.CompletedTask;
}
public void Dispose() => _timer?.Dispose();
}
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