/*
    * Copyright (c) 2019 Matthias Sohn <matthias.sohn@sap.com>
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  package org.eclipse.jgit.util;
  
  import java.io.IOException;
  import java.lang.management.ManagementFactory;
  
  import javax.management.InstanceAlreadyExistsException;
  import javax.management.InstanceNotFoundException;
  import javax.management.MBeanRegistrationException;
  import javax.management.MBeanServer;
  import javax.management.MalformedObjectNameException;
  import javax.management.NotCompliantMBeanException;
  import javax.management.ObjectInstance;
  import javax.management.ObjectName;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.errors.ConfigInvalidException;
  import org.eclipse.jgit.lib.ConfigConstants;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * Enables monitoring JGit via JMX
   *
   * @since 5.1.13
   */
  public class Monitoring {
  	private static final Logger LOG = LoggerFactory.getLogger(Monitoring.class);
  
  	/**
  	 * Register a MBean with the platform MBean server
  	 *
  	 * @param mbean
  	 *            the mbean object to register
  	 * @param metricName
  	 *            name of the JGit metric, will be prefixed with
  	 *            "org.eclipse.jgit/"
  	 * @return the registered mbean's object instance
  	 */
  	public static @Nullable ObjectInstance registerMBean(Object mbean,
  			String metricName) {
  		boolean register = false;
  		try {
  			Class<?>[] interfaces = mbean.getClass().getInterfaces();
  			for (Class<?> i : interfaces) {
  				register = SystemReader.getInstance().getUserConfig()
  						.getBoolean(
  					ConfigConstants.CONFIG_JMX_SECTION,
  								i.getSimpleName(), false);
  				if (register) {
  					break;
  				}
  			}
  		} catch (IOException | ConfigInvalidException e) {
  			LOG.error(e.getMessage(), e);
  			return null;
  		}
  		if (!register) {
  			return null;
  		}
  		MBeanServer server = ManagementFactory.getPlatformMBeanServer();
  		try {
  			ObjectName mbeanName = objectName(mbean.getClass(), metricName);
  			if (server.isRegistered(mbeanName)) {
  				server.unregisterMBean(mbeanName);
  			}
  			return server.registerMBean(mbean, mbeanName);
  		} catch (MalformedObjectNameException | InstanceAlreadyExistsException
  				| MBeanRegistrationException | NotCompliantMBeanException
  				| InstanceNotFoundException e) {
  			LOG.error(e.getMessage(), e);
  			return null;
  		}
  	}
  
  	private static ObjectName objectName(Class mbean, String metricName)
  			throws MalformedObjectNameException {
  		return new ObjectName(String.format("org.eclipse.jgit/%s:type=%s", //$NON-NLS-1$
  				metricName, mbean.getSimpleName()));
  	}
  }