/*
* Copyright (C) 2011 Virginia Tech Department of Computer Science
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package sofia.internal.events;
import java.lang.reflect.Array;
import java.util.List;
//-------------------------------------------------------------------------
/**
* An event dispatcher that allows some of the rightmost arguments to be
* optional. For example, if the event dispatcher is created with a minimum
* argument count of 1 and it is invoked with the arguments (arg1, arg2, arg3),
* then it will attempt to dispatch the event using any of the following three
* signatures:
* <ul>
* <li>arg1, arg2, arg3</li>
* <li>arg1, arg2</li>
* <li>arg1</li>
* </ul>
* <p>
* If you require more permutability of the arguments than this simple
* rightmost exclusion provides, or to combine it with other kinds of
* transformations, then you should create your own subclass of
* {@link EventDispatcher} to contain that logic.
* </p>
*
* @author Tony Allevato
*/
public class OptionalEventDispatcher extends EventDispatcher
{
//~ Fields ................................................................
private int minimumArgCount;
//~ Constructors ..........................................................
// ----------------------------------------------------------
/**
* Creates an {@code OptionalEventDispatcher} where all of the arguments
* are optional.
*
* @param method the name of the method to invoke
*/
public OptionalEventDispatcher(String method)
{
this(method, 0);
}
// ----------------------------------------------------------
/**
* Creates an {@code OptionalEventDispatcher} that must have at least the
* specified number of arguments, but where those after that are optional.
*
* @param method the name of the method to invoke
* @param minimumArgCount the minimum number of arguments that a handler
* method must take in order to match
*/
public OptionalEventDispatcher(String method, int minimumArgCount)
{
super(method);
this.minimumArgCount = minimumArgCount;
}
//~ Protected methods .....................................................
// ----------------------------------------------------------
@Override
protected List<MethodTransformer> lookupTransformers(
Object receiver, List<Class<?>> argTypes)
{
List<MethodTransformer> descriptors =
super.lookupTransformers(receiver, argTypes);
Class<?>[] argTypeArray = new Class<?>[argTypes.size()];
argTypes.toArray(argTypeArray);
// We start at size - 1 because the superclass implementation handles
// the exact match.
for (int i = argTypes.size() - 1; i >= minimumArgCount; i--)
{
final int thisCount = i;
MethodTransformer transformer =
new MethodTransformer(
firstN(argTypeArray, thisCount, Class.class))
{
protected Object[] transform(Object... args)
{
return firstN(args, thisCount, Object.class);
}
};
transformer.addIfSupportedBy(receiver, descriptors);
}
return descriptors;
}
//~ Private methods .......................................................
// ----------------------------------------------------------
@SuppressWarnings("unchecked")
private static <T> T[] firstN(T[] array, int n, Class<T> klass)
{
T[] firstN = (T[]) Array.newInstance(klass, n);
System.arraycopy(array, 0, firstN, 0, n);
return firstN;
}
}