/*
 * 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.extensions.breadcrumb;

import java.util.ArrayList;
import java.util.List;

import org.apache.wicket.Component;
import org.apache.wicket.markup.html.basic.Label;
import org.apache.wicket.markup.html.list.ListItem;
import org.apache.wicket.markup.html.list.ListView;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.model.IDetachable;
import org.apache.wicket.model.LoadableDetachableModel;


/**
 * A component that renders bread crumbs. By default, it renders a horizontal list from left to
 * right (oldest left) with bread crumb links and a ' / ' as a separator, e.g.
 * 
 * <pre>
 * first / second / third
 * </pre>
 * 
 * <p>
 * Delegates how the bread crumb model works to {@link DefaultBreadCrumbsModel}.
 * </p>
 * <p>
 * Override and provide your own markup file if you want to work with other elements, e.g. uls
 * instead of spans.
 * </p>
 * 
 * @author Eelco Hillenius
 */
public class BreadCrumbBar extends Panel implements IBreadCrumbModel
{
        /** Default crumb component. */
        private static final class BreadCrumbComponent extends Panel
        {
                private static final long serialVersionUID = 1L;

                /**
                 * Construct.
                 * 
                 * @param id
                 *            Component id
                 * @param separatorMarkup
                 *            markup used as a separator between breadcrumbs
                 * @param index
                 *            The index of the bread crumb
                 * @param breadCrumbModel
                 *            The bread crumb model
                 * @param breadCrumbParticipant
                 *            The bread crumb
                 * @param enableLink
                 *            Whether the link should be enabled
                 */
                public BreadCrumbComponent(final String id, final String separatorMarkup, final long index,
                        final IBreadCrumbModel breadCrumbModel,
                        final IBreadCrumbParticipant breadCrumbParticipant, final boolean enableLink)
                {
                        super(id);
                        add(new Label("sep", (index > 0) ? separatorMarkup : "").setEscapeModelStrings(false)
                                .setRenderBodyOnly(true));
                        BreadCrumbLink link = new BreadCrumbLink("link", breadCrumbModel)
                        {
                                private static final long serialVersionUID = 1L;

                                @Override
                                protected IBreadCrumbParticipant getParticipant(final String componentId)
                                {
                                        return breadCrumbParticipant;
                                }
                        };
                        link.setEnabled(enableLink);
                        add(link);
                        link.add(new Label("label", breadCrumbParticipant.getTitle()).setRenderBodyOnly(true));
                }
        }

        /**
         * List view for rendering the bread crumbs.
         */
        protected class BreadCrumbsListView extends ListView<IBreadCrumbParticipant>
                implements
                        IBreadCrumbModelListener
        {
                private static final long serialVersionUID = 1L;

                private transient boolean dirty = false;

                private transient int size = 0;

                /**
                 * Construct.
                 * 
                 * @param id
                 *            Component id
                 */
                public BreadCrumbsListView(final String id)
                {
                        super(id);
                        setReuseItems(false);
                        setDefaultModel(new LoadableDetachableModel<List<IBreadCrumbParticipant>>()
                        {
                                private static final long serialVersionUID = 1L;

                                @Override
                                protected List<IBreadCrumbParticipant> load()
                                {
                                        // save a copy
                                        List<IBreadCrumbParticipant> l = new ArrayList<IBreadCrumbParticipant>(
                                                allBreadCrumbParticipants());
                                        size = l.size();
                                        return l;
                                }
                        });
                }

                @Override
                public void breadCrumbActivated(final IBreadCrumbParticipant previousParticipant,
                        final IBreadCrumbParticipant breadCrumbParticipant)
                {
                        signalModelChange();
                }

                @Override
                public void breadCrumbAdded(final IBreadCrumbParticipant breadCrumbParticipant)
                {
                }

                @Override
                public void breadCrumbRemoved(final IBreadCrumbParticipant breadCrumbParticipant)
                {
                }

                /**
                 * Signal model change.
                 */
                private void signalModelChange()
                {
                        // else let the listview recalculate it's children immediately;
                        // it was attached, but it needs to go through that again now
                        // as the signaling component attached after this
                        getDefaultModel().detach();
                }

                /**
                 * @see org.apache.wicket.markup.html.list.ListView#onBeforeRender()
                 */
                @Override
                protected void onBeforeRender()
                {
                        super.onBeforeRender();
                        if (dirty)
                        {
                                dirty = false;
                        }
                }

                @Override
                protected void populateItem(final ListItem<IBreadCrumbParticipant> item)
                {
                        long index = item.getIndex();
                        IBreadCrumbParticipant breadCrumbParticipant = (IBreadCrumbParticipant)item.getDefaultModelObject();
                        item.add(newBreadCrumbComponent("crumb", index, size, breadCrumbParticipant));
                }
        }

        private static final long serialVersionUID = 1L;

        private final IBreadCrumbModel decorated;

        /**
         * Construct.
         * 
         * @param id
         *            Component id
         */
        public BreadCrumbBar(final String id)
        {
                super(id);
                decorated = new DefaultBreadCrumbsModel();
                BreadCrumbsListView breadCrumbsListView = new BreadCrumbsListView("crumbs");
                addListener(breadCrumbsListView);
                add(breadCrumbsListView);
        }


        @Override
        public void addListener(final IBreadCrumbModelListener listener)
        {
                decorated.addListener(listener);
        }

        @Override
        public List<IBreadCrumbParticipant> allBreadCrumbParticipants()
        {
                return decorated.allBreadCrumbParticipants();
        }

        @Override
        public IBreadCrumbParticipant getActive()
        {
                return decorated.getActive();
        }

        @Override
        public void removeListener(final IBreadCrumbModelListener listener)
        {
                decorated.removeListener(listener);
        }

        @Override
        public void setActive(final IBreadCrumbParticipant breadCrumbParticipant)
        {
                decorated.setActive(breadCrumbParticipant);
        }

        /**
         * Gets whether the current bread crumb should be displayed as a link (e.g. for refreshing) or
         * as a disabled link (effectively just a label). The latter is the default. Override if you
         * want different behavior.
         * 
         * @return Whether the current bread crumb should be displayed as a link; this method returns
         *         false
         */
        protected boolean getEnableLinkToCurrent()
        {
                return false;
        }

        /**
         * @return markup used as a separator between breadcrumbs. By default <code>/</code> is used,
         *         but <code>&gt;&gt;</code> is also a popular choice.
         */
        protected String getSeparatorMarkup()
        {
                return "/";
        }

        /**
         * Creates a new bread crumb component. That component will be rendered as part of the bread
         * crumbs list (which is a &lt;ul&gt; &lt;li&gt; structure).
         * 
         * @param id
         *            The component id
         * @param index
         *            The index of the bread crumb
         * @param total
         *            The total number of bread crumbs in the current model
         * @param breadCrumbParticipant
         *            the bread crumb
         * @return A new bread crumb component
         */
        protected Component newBreadCrumbComponent(final String id, final long index, final int total,
                final IBreadCrumbParticipant breadCrumbParticipant)
        {
                boolean enableLink = getEnableLinkToCurrent() || (index < (total - 1));
                return new BreadCrumbComponent(id, getSeparatorMarkup(), index, this,
                        breadCrumbParticipant, enableLink);
        }

        @Override
        protected void onDetach()
        {
                super.onDetach();
                for (IBreadCrumbParticipant crumb : decorated.allBreadCrumbParticipants())
                {
                        if (crumb instanceof Component)
                        {
                                ((Component)crumb).detach();
                        }
                        else if (crumb instanceof IDetachable)
                        {
                                ((IDetachable)crumb).detach();
                        }
                }
        }
}