package com.onaro.sanscreen.client.jmxframework;

import java.io.IOException;
import java.lang.management.ManagementFactory;
import java.net.BindException;
import java.rmi.registry.LocateRegistry;
import java.rmi.server.ExportException;
import java.util.LinkedList;
import java.util.List;

import javax.management.remote.JMXConnectorServer;
import javax.management.remote.JMXConnectorServerFactory;
import javax.management.remote.JMXServiceURL;
import javax.naming.NameAlreadyBoundException;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import com.onaro.commons.prefs.PreferencesWrapper;
import com.onaro.sanscreen.client.jmxframework.service.ShutdownService;

/**
 * Singleton class. Responsible of managing the life cycle of all the mbean services.
 * 
 * 
 * @since 05/01/2008 
 * @author john.cohen
 */
public final class JmxServiceManager {
    /**
     * Key to search the registry.  The value of this key will be the port number to use, otherwise the default value will
     * be used instead. {@link #DEFAULT_RMI_PORT}
     */
    private static final String JMX_PORT_KEY = "jmx_port"; //$NON-NLS-1$
    
    /**
     * Logger of this class
     */
    private static final Logger logger = LogManager.getLogger(JmxServiceManager.class);
    
    /**
     * List of available services.
     */ 
    private static List<FrameworkService> services; 
    static{
        services = new LinkedList<FrameworkService>();
        services.add(new ShutdownService());
    }
    
    /**
     * Singleton instance created by a private constructor.
     */ 
    private static JmxServiceManager INSTANCE = new JmxServiceManager();
    
    public static JmxServiceManager getInstance(){        
        return INSTANCE;
    }    


    /**
     * Private Constructor.
     */
    private JmxServiceManager() {
        try {
            final int rmiPort = retrieveRMIPort();
            startRMIRegistry(rmiPort);
            
            // Create an RMI connector and start it, Port Number will be stored
            // in the Registry of the Machine
            JMXServiceURL url = new JMXServiceURL(JmxServiceManagerConstants.JMX_BASE_URL + "localhost:" + rmiPort + JmxServiceManagerConstants.GUI_PATH); //$NON-NLS-1$
            JMXConnectorServer cs = JMXConnectorServerFactory.newJMXConnectorServer(url, null, ManagementFactory.getPlatformMBeanServer());
            cs.start();
        } catch (IOException e) {
            if (e.getCause() != null && e.getCause() instanceof NameAlreadyBoundException) {
                logger.warn("An OnCommand Insight client JMX Service is already registered on this machine. JMX Service will not be available for this SANscreen Client instance."); //$NON-NLS-1$
            } else {
                logger.error("Failed to start jmx service - " + e.getMessage(), e); //$NON-NLS-1$
            }
        } catch (Exception e) {
            logger.error("Failed to start jmx service - " + e.getMessage(), e); //$NON-NLS-1$
        }
    }    
    
    /**
     * Retrieves the port number used for the RMI registry.  If the <code>JMX_PORT_KEY</code> doesn't exist
     * then write the <code>DEFAULT_RMI_PORT</code> into the registry.
     * 
     * This method is public only so that the UTs can access it.
     * 
     * @return rmi port associated to the JMX 
     */
    private static int retrieveRMIPort() {
        int rmiPort;
        PreferencesWrapper prefs = FrameworkPref.getJmxClient();
        try{
            rmiPort = prefs.getInt(JMX_PORT_KEY);
        }catch (Exception e){
            // The "key" doesn't exist yet. Apply default value.
            prefs.putInt(JMX_PORT_KEY, JmxServiceManagerConstants.DEFAULT_RMI_PORT);
            rmiPort = JmxServiceManagerConstants.DEFAULT_RMI_PORT;
        }

        return rmiPort;
    }
    
    /**
     * Loops through all the services being managed and starts them one by one.
     */
    public void start(){
        for (FrameworkService service: services){
            service.start();
        }
    }

    /**
     * Starts RMI Registry in this JVM if its not already running.
     * @param rmiPort 
     */
    private void startRMIRegistry(final int rmiPort) {
        try {
            LocateRegistry.createRegistry(rmiPort);
        } catch (ExportException e) {
            if (e.getCause() != null && e.getCause() instanceof BindException) {
                // This means the RMI port is already bound, most likely there's another instance of the client running
                // do nothing
                return;
            } else {
                logger.error("Failed to start RMI Registry in port: [" + rmiPort + "]: ", e);     //$NON-NLS-1$ //$NON-NLS-2$
            }
        } catch (Exception e) {
            // It could be that RMI Registry is not running in this JVM
            // Let's try to create one.
            logger.error("Failed to start RMI Registry in port: [" + rmiPort + "]:", e); //$NON-NLS-1$ //$NON-NLS-2$
            return;
        }
    }

}