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 *   Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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.
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package org.apache.cayenne.di.spi;

import java.lang.ref.WeakReference;
import java.lang.reflect.Method;

import org.apache.cayenne.di.DIRuntimeException;

/**
 * A class that wraps an annotated method call of an object, passing it DI scope events.
 * 
 * @since 3.1
 */
public class ScopeEventBinding {

    private WeakReference<Object> objectReference;
    private Method eventHandlerMethod;
    private int argWidth;

    public ScopeEventBinding(Object object, Method eventHandlerMethod) {

        // store weak references for objects to avoid retaining them when they go out of
        // scope
        this.objectReference = new WeakReference<Object>(object);
        this.eventHandlerMethod = eventHandlerMethod;
        this.argWidth = eventHandlerMethod.getParameterTypes().length;

        // allow public methods of non-public classes to be annotated
        eventHandlerMethod.setAccessible(true);
    }

    public Object getObject() {
        return objectReference.get();
    }

    public boolean onScopeEvent(Object... eventArgs) {

        Object object = objectReference.get();
        if (object == null) {
            return false;
        }

        try {
            eventHandlerMethod.invoke(object, invocationArguments(eventArgs));
        }
        catch (Exception e) {
            throw new DIRuntimeException(
                    "Error invoking event method %s",
                    e,
                    eventHandlerMethod.getName());
        }

        return true;
    }

    private Object[] invocationArguments(Object[] eventArgs) {

        int eventArgWidth = (eventArgs == null) ? 0 : eventArgs.length;

        if (argWidth != eventArgWidth) {
            throw new DIRuntimeException(
                    "Event argument list size (%d) is different "
                            + "from the handler method argument list size (%d)",
                    eventArgWidth,
                    argWidth);
        }

        return eventArgs;
    }
}