/*
 * 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.
 */
package org.apache.wicket.spring.injection.annot;

import javax.servlet.ServletContext;

import org.apache.wicket.Application;
import org.apache.wicket.Component;
import org.apache.wicket.IBehaviorInstantiationListener;
import org.apache.wicket.MetaDataKey;
import org.apache.wicket.Session;
import org.apache.wicket.application.IComponentInstantiationListener;
import org.apache.wicket.behavior.Behavior;
import org.apache.wicket.injection.IFieldValueFactory;
import org.apache.wicket.injection.Injector;
import org.apache.wicket.model.Model;
import org.apache.wicket.protocol.http.WebApplication;
import org.apache.wicket.spring.ISpringContextLocator;
import org.apache.wicket.util.lang.Args;
import org.springframework.context.ApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;

/**
 * {@link IComponentInstantiationListener} that injects component and behavior properties
 * annotated with {@link SpringBean} annotations.
 * 
 * To install in yourapplication.init() call
 * <code>getComponentInstantiationListeners().add(new SpringComponentInjector(this));</code>
 * <p>
 * Only Wicket {@link Component}s and {@link Behavior}s are automatically injected, other classes
 * such as {@link Session}, {@link Model}, and any other POJO can be injected by calling
 * <code>Injector.get().inject(this)</code> in their constructor.
 * </p>
 * 
 * @author Igor Vaynberg (ivaynberg)
 * @author <a href="mailto:jlee@antwerkz.com">Justin Lee</a>
 * 
 */
public class SpringComponentInjector extends Injector
        implements
                IComponentInstantiationListener,
                IBehaviorInstantiationListener
{
        private final IFieldValueFactory fieldValueFactory;

        /**
         * Metadata key used to store application context in application's metadata
         */
        private static MetaDataKey<ApplicationContext> CONTEXT_KEY = new MetaDataKey<>()
        {
                private static final long serialVersionUID = 1L;

        };

        /**
         * Constructor used when spring application context is declared in the spring standard way and
         * can be located through
         * {@link WebApplicationContextUtils#getRequiredWebApplicationContext(ServletContext)}.
         * 
         * @param webapp
         *            wicket web application
         */
        public SpringComponentInjector(final WebApplication webapp)
        {
                this(webapp, getDefaultContext(webapp));
        }

        /**
         * Constructor
         * 
         * @param webapp
         *            wicket web application
         * @param ctx
         *            spring's application context
         */
        public SpringComponentInjector(final WebApplication webapp, final ApplicationContext ctx)
        {
                this(webapp, ctx, true);
        }

        /**
         * Constructor
         * 
         * @param webapp
         *            wicket web application
         * @param ctx
         *            spring's application context
         * 
         * @param wrapInProxies
         *            whether or not wicket should wrap dependencies with specialized proxies that can
         *            be safely serialized. in most cases this should be set to true.
         */
        public SpringComponentInjector(final WebApplication webapp, final ApplicationContext ctx,
                final boolean wrapInProxies)
        {
                Args.notNull(webapp, "webapp");

                Args.notNull(ctx, "ctx");

                // store context in application's metadata ...
                webapp.setMetaData(CONTEXT_KEY, ctx);
                fieldValueFactory = new AnnotProxyFieldValueFactory(new ContextLocator(), wrapInProxies);
                webapp.getBehaviorInstantiationListeners().add(this);
                bind(webapp);
        }

        @Override
        public void inject(final Object object)
        {
                inject(object, fieldValueFactory);
        }

        @Override
        public void onInstantiation(final Component component)
        {
                inject(component);
        }

        @Override
        public void onInstantiation(Behavior behavior)
        {
                inject(behavior);
        }

        /**
         * A context locator that locates the context in application's metadata. This locator also keeps
         * a transient cache of the lookup.
         * 
         * @author ivaynberg
         */
        private static class ContextLocator implements ISpringContextLocator
        {
                private transient ApplicationContext context;

                private static final long serialVersionUID = 1L;

                @Override
                public ApplicationContext getSpringContext()
                {
                        if (context == null)
                        {
                                context = Application.get().getMetaData(CONTEXT_KEY);
                        }
                        return context;
                }

        }

        /**
         * Try to use an already pre-configured application context or locate it through Spring's default
         * location mechanism.
         * 
         * @param webapp
         * @return the application context to use for injection
         */
        private static ApplicationContext getDefaultContext(final WebApplication webapp)
        {
                ApplicationContext context = webapp.getMetaData(CONTEXT_KEY);
                if (context == null)
                {
                        context = WebApplicationContextUtils.getRequiredWebApplicationContext(webapp.getServletContext());
                }
                return context;
        }

        /**
         * Set the default context for the given webapp.
         * 
         * @param webapp
         *            web application
         * @param context
         *            context to use as default if non is explicitely specified for the injector
         */
        public static void setDefaultContext(final WebApplication webapp, ApplicationContext context)
        {
                Args.notNull(context, "context");

                if (webapp.getMetaData(CONTEXT_KEY) == null)
                {
                        webapp.setMetaData(CONTEXT_KEY, context);
                }
        }
}