import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.List;

public class ListenerSupport<T> implements InvocationHandler
{
    protected final T target;
    @SuppressWarnings("unchecked")
    public ListenerSupport(Class<? extends T> listenerInterface)
    {
        this.target=(T) Proxy.newProxyInstance(listenerInterface.getClassLoader(),
                new Class[] {listenerInterface}, this);
    }
    
    public static <T> ListenerSupport<T> create(Class<? extends T> listenerInterface)
    {
        return new ListenerSupport<T>(listenerInterface);
    }
    
    protected List<T> listeners=new ArrayList<T>();
    public void add(T listener)
    {
        if (listeners.contains(listener)) return;
        synchronized(listeners)
        {
            listeners.add(listener);
        }
    }
    public void remove(T listener)
    {
        synchronized(listeners)
        {
            listeners.remove(listener);
        }
    }
    
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
    {
        Object ret=null;
        synchronized(listeners)
        {
            for (T l: listeners)
            {
                ret=method.invoke(l, args);
            }
        }
        return ret;
    }
    public T target()
    {
        return target;
    }
}