import static com.codahale.metrics.MetricRegistry.name;

import java.lang.management.ManagementFactory;
import java.util.Collections;
import java.util.Date;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import javax.management.AttributeNotFoundException;
import javax.management.InstanceNotFoundException;
import javax.management.MBeanException;
import javax.management.MBeanServer;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import javax.management.ReflectionException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.codahale.metrics.Gauge;
import com.codahale.metrics.JmxReporter;
import com.codahale.metrics.Metric;
import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.MetricSet;

/**
 * Metrics for time since last successful exchange for camel routes .
 * Assumes managementNamePattern="#name#"
 */
public class RouteMetrics {

	private static final Logger log = LoggerFactory.getLogger(RouteMetrics.class);

	private final MetricRegistry metricsRegistry;

	private final JmxReporter jmxReporter;

	/**
	 * @param routeNames
	 *            comma separated list of routes to instrument
	 * 
	 * @throws NullPointerException
	 * @throws IllegalArgumentException
	 * @throws MalformedObjectNameException
	 */
	public RouteMetrics(String routeNames) {
		log.info("Setting up route metrics for ESB");
		String[] routes = routeNames.split(",");
		metricsRegistry = new MetricRegistry();

		metricsRegistry.registerAll(getRoutesMetricsSet(routes));

		jmxReporter = JmxReporter.forRegistry(metricsRegistry).build();
		jmxReporter.start();
		log.info("Started JMX reporter for ESB route metrics");

	}

	private MetricSet getRoutesMetricsSet(String... route) {

		final Map<String, Metric> gauges = new HashMap<String, Metric>();
		for (final String routeName : route) {
			log.debug("Setting up gauges for {}", routeName);
			gauges.put(name("route", routeName, "secondsSinceLastSuccess"), new Gauge<Long>() {

				@Override
				public Long getValue() {
					Date lastExchange = (Date) getRouteAttribute(routeName, "LastExchangeCompletedTimestamp");
					if (lastExchange != null) {
						long age = System.currentTimeMillis() - lastExchange.getTime();
						return age / 1000;
					}
					return -100L;
				}

			});
		}

		return new MetricSet() {

			@Override
			public Map<String, Metric> getMetrics() {
				return Collections.unmodifiableMap(gauges);
			}
		};

	}

	private static Object getRouteAttribute(String routeName, String AttributeName) {
		final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
		try {
			Iterator<ObjectName> mbeanNames = mbs.queryNames(getObjectNamePattern(routeName), null).iterator();
			if (mbeanNames.hasNext()) {
				ObjectName mbeanName = mbeanNames.next();
				log.debug("Getting {} for: {}", AttributeName, mbeanName);
				Object value = mbs.getAttribute(mbeanName, AttributeName);
				return value;
			}
			log.warn("Route MBean not found for {}", routeName);
		} catch (AttributeNotFoundException e) {
			logWarning(e);
		} catch (InstanceNotFoundException e) {
			logWarning(e);
		} catch (MBeanException e) {
			logWarning(e);
		} catch (ReflectionException e) {
			logWarning(e);
		} catch (MalformedObjectNameException e) {
			logWarning(e);
		} catch (NullPointerException e) {
			logWarning(e);
		}
		return null;

	}

	private static ObjectName getObjectNamePattern(String routeName) throws MalformedObjectNameException, NullPointerException {
		StringBuilder sb = new StringBuilder("org.apache.camel:type=routes,name=\"");
		sb.append(routeName).append("\",*");
		log.debug("ObjecNamePattern: {}", sb.toString());
		return new ObjectName(sb.toString());
	}

	private static void logWarning(Exception e) {
		log.warn("Exception while getting route metrics: {}", e.toString());
		log.debug(e.toString(), e);
	}