/*****************************************************************************
 * Copyright (C) PicoContainer Organization. All rights reserved.            *
 * ------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the BSD      *
 * style license a copy of which has been included with this distribution in *
 * the LICENSE.txt file.                                                     *
 *                                                                           *
 * Original code by Mauro Talevi                                             *
 *****************************************************************************/

package org.picocontainer.monitors;

import java.io.Serializable;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Member;

import org.picocontainer.ComponentMonitor;
import org.picocontainer.ComponentMonitorStrategy;
import org.picocontainer.ComponentAdapter;
import org.picocontainer.MutablePicoContainer;
import org.picocontainer.PicoContainer;
import org.picocontainer.monitors.NullComponentMonitor;

/**
 * <p>
 * A {@link ComponentMonitor monitor} which delegates to another monitor.
 * It provides a {@link NullComponentMonitor default ComponentMonitor},
 * but does not allow to use <code>null for the delegate.
 * </p>
 * <p>
 * It also supports a {@link org.picocontainer.ComponentMonitorStrategy monitor strategy}
 * that allows to change the delegate.
 * </p>
 * 
 * @author Mauro Talevi
 * @version $Revision: $
 */
public class AbstractComponentMonitor implements ComponentMonitor, ComponentMonitorStrategy, Serializable {

    private  ComponentMonitor delegate;
    
    /**
     * Creates a AbstractComponentMonitor with a given delegate
     * @param delegate the ComponentMonitor to which this monitor delegates
     */
    public AbstractComponentMonitor(ComponentMonitor delegate) {
        checkMonitor(delegate);
        this.delegate = delegate;
    }

    /**
     * Creates a AbstractComponentMonitor with an instance of
     * {@link NullComponentMonitor}.
     */
    public AbstractComponentMonitor() {
        this(NullComponentMonitor.getInstance());
    }
    
    public Constructor instantiating(PicoContainer container, ComponentAdapter componentAdapter,
                                     Constructor constructor
    ) {
        return delegate.instantiating(container, componentAdapter, constructor);
    }

    public void instantiated(PicoContainer container, ComponentAdapter componentAdapter,
                             Constructor constructor,
                             Object instantiated,
                             Object[] injected,
                             long duration) {
        delegate.instantiated(container, componentAdapter, constructor, instantiated, injected, duration);
    }

    public void instantiationFailed(PicoContainer container,
                                    ComponentAdapter componentAdapter,
                                    Constructor constructor,
                                    Exception e) {
        delegate.instantiationFailed(container, componentAdapter, constructor, e);
    }

    public void invoking(PicoContainer container,
                         ComponentAdapter componentAdapter,
                         Member member,
                         Object instance) {
        delegate.invoking(container, componentAdapter, member, instance);
    }

    public void invoked(PicoContainer container,
                        ComponentAdapter componentAdapter,
                        Method method,
                        Object instance,
                        long duration) {
        delegate.invoked(container, componentAdapter, method, instance, duration);
    }

    public void invocationFailed(Member member, Object instance, Exception e) {
        delegate.invocationFailed(member, instance, e);
    }

    public void lifecycleInvocationFailed(MutablePicoContainer container,
                                          ComponentAdapter componentAdapter, Method method,
                                          Object instance,
                                          RuntimeException cause) {
        delegate.lifecycleInvocationFailed(container, componentAdapter, method,instance, cause);
    }

    public Object noComponentFound(MutablePicoContainer container, Object componentKey) {
        return delegate.noComponentFound(container, componentKey);
    }

    /**
     * If the delegate supports a {@link ComponentMonitorStrategy monitor strategy},
     * this is used to changed the monitor while keeping the same delegate.
     * Else the delegate is replaced by the new monitor.
     * {@inheritDoc}
     */
    public void changeMonitor(ComponentMonitor monitor) {
        checkMonitor(monitor);
        if ( delegate instanceof ComponentMonitorStrategy ){
            ((ComponentMonitorStrategy)delegate).changeMonitor(monitor);
        } else {
            delegate = monitor;
        }
    }

    public ComponentMonitor currentMonitor() {
        if ( delegate instanceof ComponentMonitorStrategy ){
            return ((ComponentMonitorStrategy)delegate).currentMonitor();
        } else {
            return delegate;
        }
    }
    
    private void checkMonitor(ComponentMonitor monitor) {
        if ( monitor == null ){
            throw new NullPointerException("monitor");
        }
    }

}