/*
 * 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.markup.renderStrategy;

import java.lang.reflect.InvocationTargetException;

import org.apache.wicket.Application;
import org.apache.wicket.Component;
import org.apache.wicket.ajax.AjaxRequestTarget;
import org.apache.wicket.application.HeaderContributorListenerCollection;
import org.apache.wicket.markup.head.IHeaderResponse;
import org.apache.wicket.markup.html.IHeaderContributor;
import org.apache.wicket.markup.html.internal.HtmlHeaderContainer;
import org.apache.wicket.markup.html.internal.HtmlHeaderContainer.HeaderStreamState;
import org.apache.wicket.markup.html.internal.InlineEnclosure;
import org.apache.wicket.util.lang.Args;
import org.apache.wicket.util.visit.IVisit;
import org.apache.wicket.util.visit.IVisitor;

/**
 * An abstract implementation of a header render strategy which is only missing the code to traverse
 * the child hierarchy, since the sequence of that traversal is what will make the difference
 * between the different header render strategies.
 * 
 * Besides the child hierarchy the render sequence by default (may be changed via subclassing) is as
 * follows:
 * <ul>
 * <li>1. application level headers</li>
 * <li>2. the root component's headers</li>
 * <li>3. the children hierarchy (to be implemented per subclass)</li>
 * </ul>
 * 
 * @author Juergen Donnerstag
 */
public abstract class AbstractHeaderRenderStrategy implements IHeaderRenderStrategy
{
        /**
         * @return Gets the strategy registered with the application
         */
        public static IHeaderRenderStrategy get()
        {
                // NOT OFFICIALLY SUPPORTED BY WICKET
                // By purpose it is "difficult" to change to another render strategy.
                // We don't want it to be modifiable by users, but we needed a way to easily test other
                // strategies.
                String className = System.getProperty("Wicket_HeaderRenderStrategy");
                if (className != null)
                {
                        Class<?> clazz;
                        try
                        {
                                clazz = Application.get()
                                        .getApplicationSettings()
                                        .getClassResolver()
                                        .resolveClass(className);

                                if (clazz != null)
                                {
                                        return (IHeaderRenderStrategy)clazz.getDeclaredConstructor().newInstance();
                                }
                        }
                        catch (ClassNotFoundException | InstantiationException | IllegalAccessException
                                        | NoSuchMethodException | InvocationTargetException ex)
                        {
                                // ignore
                        }
                }

                // Our default header render strategy
                // Pre 1.5
                // return new ParentFirstHeaderRenderStrategy();

                // Since 1.5
                return new ChildFirstHeaderRenderStrategy();
        }

        /**
         * Construct.
         */
        public AbstractHeaderRenderStrategy()
        {
        }

        @Override
        public void renderHeader(final HtmlHeaderContainer headerContainer,
                HeaderStreamState headerStreamState, final Component rootComponent)
        {
                Args.notNull(headerContainer, "headerContainer");
                Args.notNull(rootComponent, "rootComponent");

                // First the application level headers
                renderApplicationLevelHeaders(headerContainer);

                // Then the root component's headers
                renderRootComponent(headerContainer, headerStreamState, rootComponent);

                // Then its child hierarchy
                renderChildHeaders(headerContainer, rootComponent);
        }

        /**
         * Render the root component (e.g. Page).
         * 
         * @param headerContainer
         * @param headerStreamState
         * @param rootComponent
         */
        protected void renderRootComponent(final HtmlHeaderContainer headerContainer,
                final HeaderStreamState headerStreamState, final Component rootComponent)
        {
                headerContainer.renderHeaderTagBody(headerStreamState);

                rootComponent.internalRenderHead(headerContainer);

                if (rootComponent instanceof InlineEnclosure) {
                        renderInlineEnclosure(headerContainer, (InlineEnclosure) rootComponent);
                }
        }


        /**
         * Searches for the siblings of the given enclosure for the controller of the given enclosure and
         * renders that controller's header contributions.
         *
         * This is done explicitly because when an enclosed component is added to the {@link AjaxRequestTarget}
         * and is consequently replaced for render by the enclosure, the component's header contributions would not make
         * it to the response as the enclosure is a sibling of the component in the hierarchy and only children's header contributions
         * are added to the response.
         *
         * Fixes WICKET-6459
         *
         * @param container the header container to render the header contributions of the enclosure's controller
         * @param enclosure the enclosure whose controller's contributions are going to be rendered
         */
        protected void renderInlineEnclosure(HtmlHeaderContainer container, InlineEnclosure enclosure){

                final String childId = enclosure.getChildId();

                // Visit the siblings of the enclosure to attempt and find the controller of the enclosure
                Component enclosureController = enclosure.getParent().visitChildren(new IVisitor<Component, Component>() {
                        @Override
                        public void component(Component object, IVisit<Component> visit) {
                                if (object.getId().equals(childId)){
                                        visit.stop(object);
                                } else {
                                        visit.dontGoDeeper();
                                }
                        }
                });

                if (enclosureController != null){
                        enclosureController.internalRenderHead(container);
                }
        }

        /**
         * Render the child hierarchy headers.
         * 
         * @param headerContainer
         * @param rootComponent
         */
        abstract protected void renderChildHeaders(final HtmlHeaderContainer headerContainer,
                final Component rootComponent);

        /**
         * Render the application level headers
         * 
         * @param headerContainer
         */
        protected final void renderApplicationLevelHeaders(final HtmlHeaderContainer headerContainer)
        {
                Args.notNull(headerContainer, "headerContainer");

                if (Application.exists())
                {
                        HeaderContributorListenerCollection headerContributorListenerCollection =
                                        Application.get().getHeaderContributorListeners();
                        IHeaderResponse headerResponse = headerContainer.getHeaderResponse();

                        for (IHeaderContributor listener : headerContributorListenerCollection)
                        {
                                listener.renderHead(headerResponse);
                        }
                }
        }
}