/*
 * 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.markup.html.repeater.tree.nested;

import java.util.Iterator;

import org.apache.wicket.Component;
import org.apache.wicket.extensions.markup.html.repeater.tree.AbstractTree.State;
import org.apache.wicket.extensions.markup.html.repeater.tree.ITreeProvider;
import org.apache.wicket.extensions.markup.html.repeater.tree.NestedTree;
import org.apache.wicket.markup.html.panel.Panel;
import org.apache.wicket.markup.repeater.IItemFactory;
import org.apache.wicket.markup.repeater.IItemReuseStrategy;
import org.apache.wicket.markup.repeater.Item;
import org.apache.wicket.markup.repeater.RefreshingView;
import org.apache.wicket.model.IModel;

/**
 * A subtree handles all children of a single node (or the root nodes if a <code>null</code> node
 * was given to the constructor).
 * 
 * @see ITreeProvider#getChildren(Object)
 * @see ITreeProvider#getRoots()
 * 
 * @author svenmeier
 */
public class Subtree<T> extends Panel
{

        private static final long serialVersionUID = 1L;

        private NestedTree<T> tree;

        /**
         * Create a subtree for the children of the node contained in the given model or the root nodes
         * if the model contains <code>null</code>.
         * 
         * @param id
         *            component id
         * @param tree
         *            the containing tree
         * @param model
         */
        public Subtree(String id, final NestedTree<T> tree, final IModel<T> model)
        {
                super(id, model);

                if (tree == null)
                {
                        throw new IllegalArgumentException("argument [tree] cannot be null");
                }
                this.tree = tree;

                RefreshingView<T> branches = new RefreshingView<T>("branches")
                {
                        private static final long serialVersionUID = 1L;

                        @Override
                        protected Iterator<IModel<T>> getItemModels()
                        {
                                return new ModelIterator();
                        }

                        @Override
                        protected Item<T> newItem(String id, int index, IModel<T> model)
                        {
                                return newBranchItem(id, index, model);
                        }

                        @Override
                        protected void populateItem(Item<T> item)
                        {
                                IModel<T> model = item.getModel();

                                Component node = tree.newNodeComponent("node", model);
                                item.add(node);

                                item.add(tree.newSubtree("subtree", model));
                        }
                };
                branches.setItemReuseStrategy(new IItemReuseStrategy()
                {
                        private static final long serialVersionUID = 1L;

                        @Override
                        public <S> Iterator<Item<S>> getItems(IItemFactory<S> factory,
                                Iterator<IModel<S>> newModels, Iterator<Item<S>> existingItems)
                        {
                                return tree.getItemReuseStrategy().getItems(factory, newModels, existingItems);
                        }
                });
                add(branches);
        }

        @SuppressWarnings("unchecked")
        public IModel<T> getModel()
        {
                return (IModel<T>)getDefaultModel();
        }

        public T getModelObject()
        {
                return getModel().getObject();
        }

        protected BranchItem<T> newBranchItem(String id, int index, IModel<T> model)
        {
                return new BranchItem<>(id, index, model);
        }

        @Override
        public boolean isVisible()
        {
                T t = getModel().getObject();
                if (t == null)
                {
                        // roots always visible
                        return true;
                }
                else
                {
                        return tree.getState(t) == State.EXPANDED;
                }
        }

        private final class ModelIterator implements Iterator<IModel<T>>
        {
                private Iterator<? extends T> children;

                public ModelIterator()
                {
                        T t = getModel().getObject();
                        if (t == null)
                        {
                                children = tree.getProvider().getRoots();
                        }
                        else
                        {
                                children = tree.getProvider().getChildren(t);
                        }
                }

                @Override
                public void remove()
                {
                        throw new UnsupportedOperationException();
                }

                @Override
                public boolean hasNext()
                {
                        return children.hasNext();
                }

                @Override
                public IModel<T> next()
                {
                        return tree.getProvider().model(children.next());
                }
        }
}