package org.lcsim.util.xml;
   
   import java.lang.reflect.Constructor;
   import java.lang.reflect.InvocationTargetException;
   import java.util.ArrayList;
   import java.util.HashMap;
   import java.util.List;
   import java.util.Map;
   import org.jdom.Element;
  import org.jdom.JDOMException;
  
  
  /**
   * The default implementation of ElementFactory.
   * @author tonyj
   */
  public class DefaultElementFactory implements ElementFactory
  {
     private List<Class> classes = new ArrayList<Class>();
     private Map<Class,String> packageMap = new HashMap<Class,String>();
     
     /**
      * Create the default element factory.
      */
     public DefaultElementFactory()
     {}
     
     public <T> T createElement(Class<T> c, Element node, String type) throws JDOMException, ElementCreationException
     {
        if (type != null)
        {
           Class<T> cand = getElementClass(c,type);
           if (cand != null) return create(cand,node);
        }
        for (Class cand  : classes)
        {
           if (c.isAssignableFrom(cand)) return create((Class<? extends T>) cand,node);
        }
        throw new ElementCreationException("Unknown element "+c);
     }
     
     public void register(Class elementClass,String packageName)
     {
        packageMap.put(elementClass,packageName);
     }
     /**
      * Register a class with the factory. Future calls to create any class which is a subclass 
      * of this class will cause a new instance of this class to be created. The class specificed
      * must have a constructor which takes a jdom Element as its argument.
      * @param elementClass The class to register.
      */
     public void register(Class elementClass)
     {
        classes.add(0,elementClass);
     }
     private <T> T create(Class<T> type, Element node) throws ElementCreationException
     {
        try
        {
           Constructor<T> c = type.getDeclaredConstructor(Element.class);
           c.setAccessible(true);
           return c.newInstance(node);
        }
        catch (NoSuchMethodException x)
        {
           throw new ElementCreationException("Could not create element: "+type,x);
        }
        catch (InvocationTargetException x)
        {
           throw new ElementCreationException("Could not create element: "+type,x.getCause());
        }
        catch (InstantiationException x)
        {
           throw new ElementCreationException("Could not create element: "+type,x.getCause());
        }
        catch (IllegalAccessException x)
        {
           throw new ElementCreationException("Could not create element: "+type,x);
        }
     }
     public <T> Class<T> getElementClass(Class<T> type, String name) throws ElementCreationException
     {
        String packageName = packageMap.get(type);
        if (packageName == null) return null;
        String key = packageName+"."+name;
        try
        {
           Class result = Class.forName(key);
           if (!type.isAssignableFrom(result)) throw new ElementCreationException("Element "+key+" is of wrong type");
           return (Class<T>) result;
        }
        catch (ClassNotFoundException x)
        {
           return null;
        }
     }
  }