/*
    * $Id: Services.java,v 1.1 2008/01/22 13:28:59 oeuillot Exp $
    */
   package org.rcfaces.core.internal;
   
   import java.io.CharArrayReader;
   import java.io.IOException;
   import java.io.InputStream;
   import java.net.URL;
  import java.util.Enumeration;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.commons.digester.Digester;
  import org.apache.commons.digester.Rule;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.xml.sax.Attributes;
  import org.xml.sax.EntityResolver;
  import org.xml.sax.InputSource;
  import org.xml.sax.SAXException;
  
  /**
   * 
   * @author Olivier Oeuillot (latest modification by $Author: oeuillot $)
   * @version $Revision: 1.1 $ $Date: 2008/01/22 13:28:59 $
   */
  public class Services {
      private static final String REVISION = "$Revision: 1.1 $";
  
      private static final Log LOG = LogFactory.getLog(Services.class);
  
      private static final Services SINGLETON = new Services();
  
      private static final String RESOURCE_NAME = "META-INF/rcfaces-services.xml";
  
      private boolean servicesLoaded = false;
  
      private final Map services = new HashMap(32);
  
      public static Services get() {
          return SINGLETON;
      }
  
      private Services() {
      }
  
      public Object getService(String id) {
          synchronized (services) {
              if (servicesLoaded == false) {
                  servicesLoaded = true;
  
                  loadServices();
              }
          }
  
          Object service = services.get(id);
  
          if (LOG.isDebugEnabled()) {
              LOG.debug("Service '" + id + "' => " + service);
          }
  
          return service;
      }
  
      private void loadServices() {
          LOG.info("Load services ...");
  
          ClassLoader threadClassLoader = Thread.currentThread()
                  .getContextClassLoader();
  
          ClassLoader classLoader = Services.class.getClassLoader();
  
          if (threadClassLoader != null) {
              loadServices(threadClassLoader);
          }
  
          if (classLoader != threadClassLoader) {
              loadServices(classLoader);
          }
  
          LOG.info(services.size() + " service(s) loaded.");
      }
  
      private void loadServices(ClassLoader classLoader) {
          LOG.info("Load services using '" + classLoader + "'");
  
          Enumeration enumeration;
          try {
              enumeration = classLoader.getResources(RESOURCE_NAME);
  
          } catch (IOException ex) {
              LOG.error("Can not get Resources '" + RESOURCE_NAME + "'.", ex);
              return;
          }
  
          for (; enumeration.hasMoreElements();) {
              URL url = (URL) enumeration.nextElement();
  
             loadService(classLoader, url);
         }
     }
 
     private void loadService(final ClassLoader classLoader, URL url) {
         LOG.info("Load service '" + url + "'");
 
         Digester digester = new Digester();
         digester.setUseContextClassLoader(true);
 
         digester.setEntityResolver(new EntityResolver() {
             private static final String REVISION = "$Revision: 1.1 $";
 
             public InputSource resolveEntity(String string, String string1) {
                 return new InputSource(new CharArrayReader(new char[0]));
             }
 
         });
 
         digester.addRule("rcfaces-services/service", new Rule() {
             private static final String REVISION = "$Revision: 1.1 $";
 
             public void begin(String namespace, String name,
                     Attributes attributes) throws Exception {
 
                 super.digester.push(new Service());
             }
 
             public void end(String namespace, String name) throws Exception {
                 Service service = (Service) super.digester.pop();
 
                 LOG.debug("Load service '" + service.getId() + "' className='"
                         + service.getClassName() + "'");
 
                 if (service.getClassName() == null) {
                     return;
                 }
 
                 Class clazz;
                 try {
                     clazz = classLoader.loadClass(service.getClassName());
 
                 } catch (Exception ex) {
                     LOG.error("Can not load class '" + service.getClassName()
                             + "'.", ex);
                     return;
                 }
 
                 Object serviceObject;
                 try {
                     serviceObject = clazz.newInstance();
 
                 } catch (Exception ex) {
                     LOG.error("Can not instanciate class '" + clazz + "'.", ex);
                     return;
                 }
 
                 services.put(service.getId(), serviceObject);
 
                 LOG.info("Service '" + service.getId() + "' loaded: "
                         + serviceObject);
             }
         });
 
         digester.addBeanPropertySetter("rcfaces-services/service/service-id",
                 "id");
 
         digester.addBeanPropertySetter(
                 "rcfaces-services/service/service-class", "className");
 
         InputStream ins;
         try {
             ins = url.openStream();
 
         } catch (IOException ex) {
             LOG.error("Can not open stream from '" + url + "'.", ex);
             return;
         }
 
         if (ins == null) {
             LOG.info("Can not open stream from '" + url + "'.");
             return;
         }
 
         try {
             try {
 
                 digester.parse(ins);
 
             } finally {
                 ins.close();
             }
         } catch (IOException ex) {
             LOG.error("Can not load stream from '" + url + "'.", ex);
 
         } catch (SAXException ex) {
             LOG.error("Invalid XML resource '" + url + "'.", ex);
         }
     }
 
     /**
      * 
      * @author Olivier Oeuillot (latest modification by $Author: oeuillot $)
      * @version $Revision: 1.1 $ $Date: 2008/01/22 13:28:59 $
      */
     public static class Service {
         private String id;
 
         private String className;
 
         public final String getId() {
             return id;
         }
 
         public final void setId(String id) {
             this.id = id;
         }
 
         public final String getClassName() {
             return className;
         }
 
         public final void setClassName(String className) {
             this.className = className;
         }
 
     }
 }