import oracle.ons.ONS;
import oracle.ons.SenderThread;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.ReflectionUtils;

import javax.management.MBeanServer;
import javax.management.ObjectName;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import java.lang.management.ManagementFactory;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.Driver;
import java.sql.DriverManager;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.List;

public class CleanUpListener implements ServletContextListener {
    private Logger logger = LoggerFactory.getLogger(getClass());

    @Override
    public void contextInitialized(ServletContextEvent sce) {
        // do nothing
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {
        shutdownOns();
        deregisterJdbcDrivers();
    }

    @SuppressWarnings("unchecked")
    private void shutdownOns() {
        logger.info("Shutting down ONS");
        final Method getRunningONS = ReflectionUtils.findMethod(ONS.class, "getRunningONS");
        final Method shutdown = ReflectionUtils.findMethod(ONS.class, "shutdown");
        ReflectionUtils.makeAccessible(getRunningONS);
        ReflectionUtils.makeAccessible(shutdown);
        final ONS ons = (ONS) ReflectionUtils.invokeMethod(getRunningONS, null);
        if (ons == null) {
            return;
        }
        
        ReflectionUtils.invokeMethod(shutdown, ons);

        final Field senders = ReflectionUtils.findField(ONS.class, "senders");
        ReflectionUtils.makeAccessible(senders);
        final List<SenderThread> senderThreads = (List<SenderThread>) ReflectionUtils.getField(senders, ons);
        if (senderThreads == null) {
            return;
        }
        
        final Method stopThread = ReflectionUtils.findMethod(SenderThread.class, "stopThread");
        ReflectionUtils.makeAccessible(stopThread);
        for (SenderThread senderThread : senderThreads) {
            ReflectionUtils.invokeMethod(stopThread, senderThread);
        }
    }
    
    private void deregisterJdbcDrivers() {
        logger.info("Deregistering JDBC Drivers");
        final Enumeration<Driver> driverEnumeration = DriverManager.getDrivers();
        final List<Driver> drivers = new ArrayList<Driver>();
        while (driverEnumeration.hasMoreElements()) {
            drivers.add(driverEnumeration.nextElement());
        }

        for (Driver driver : drivers) {
            if (driver.getClass().getClassLoader() != getClass().getClassLoader()) {
                logger.debug("Not deregistering {} as it does not originate from this webapp", driver.getClass().getName());
                continue;
            }
            try {
                DriverManager.deregisterDriver(driver);
                logger.debug("Deregistered JDBC driver '{}'", driver.getClass().getName());
                if ("oracle.jdbc.OracleDriver".equals(driver.getClass().getName())) {
                    deregisterOracleDiagnosabilityMBean();
                }
            } catch (Throwable e) {
                logger.error("Deregistration error", e);
            }
        }
    }

    private void deregisterOracleDiagnosabilityMBean() {
        final ClassLoader cl = Thread.currentThread().getContextClassLoader();
        try {
            final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
            final Hashtable<String, String> keys = new Hashtable<String, String>();
            keys.put("type", "diagnosability");
            keys.put("name", cl.getClass().getName() + "@" + Integer.toHexString(cl.hashCode()).toLowerCase());
            mbs.unregisterMBean(new ObjectName("com.oracle.jdbc", keys));
            logger.info("Deregistered OracleDiagnosabilityMBean");
        } catch (javax.management.InstanceNotFoundException e) {
            logger.debug("Oracle OracleDiagnosabilityMBean not found", e);
        } catch (Throwable e) {
            logger.error("Oracle JMX unregistration error", e);
        }
    }
}