@Service @Slf4j @RequiredArgsConstructor
public class AwsMetricsService {

    private final CloudWatchClient      cloudWatchClient;
    private final SimpMessagingTemplate  broker;         // pushes to /topic/alerts
    private final Map<String, Double>    thresholds = new ConcurrentHashMap<>();

    // Called every 60s by Spring's @Scheduled task executor
    @Scheduled(fixedDelay = 60_000)
    public void pollAndEvaluate() {
        SERVICES.forEach(svc -> {
            List<MetricDataPoint> pts = getMetrics(svc, "1h");
            pts.stream()
               .filter(p -> p.getAverage() > thresholds.getOrDefault(svc, 80.0))
               .findFirst()
               .ifPresent(p -> fireAlert(svc, p.getAverage()));
        });
    }

    private void fireAlert(String svc, double value) {
        Map<String, Object> payload = Map.of(
            "service", svc,  "value", value,
            "severity", value > 90 ? "CRITICAL" : "WARNING",
            "firedAt", Instant.now().toString()
        );
        broker.convertAndSend("/topic/alerts", payload); // pushed to all WebSocket clients
        log.warn("ALERT {} → CPU {}", svc, value);
    }
}