// Copyright 2026 The Nomulus Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package google.registry.module;

import com.google.common.flogger.FluentLogger;
import com.google.monitoring.metrics.MetricReporter;
import jakarta.servlet.ServletContextEvent;
import jakarta.servlet.ServletContextListener;
import jakarta.servlet.annotation.WebListener;
import java.time.Duration;

/** Starts and stops the single global JVM MetricReporter on application startup/shutdown. */
@WebListener
public class MetricsLifecycleListener implements ServletContextListener {

  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
  private MetricReporter metricReporter;

  @Override
  public void contextInitialized(ServletContextEvent sce) {
    logger.atInfo().log("Initializing global MetricReporter...");
    try {
      metricReporter = RegistryServlet.component.metricReporter().get();
      metricReporter.startAsync().awaitRunning(Duration.ofSeconds(10));
      logger.atInfo().log("Global MetricReporter started successfully.");
    } catch (Exception e) {
      logger.atSevere().withCause(e).log("Failed to start global MetricReporter.");
    }
  }

  @Override
  public void contextDestroyed(ServletContextEvent sce) {
    if (metricReporter != null) {
      try {
        metricReporter.stopAsync().awaitTerminated(Duration.ofSeconds(10));
        logger.atInfo().log("Global MetricReporter stopped.");
      } catch (Exception e) {
        logger.atSevere().withCause(e).log("Failed to stop global MetricReporter.");
      }
    }
  }
}
