/*
 * 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;

import java.util.Iterator;

import org.apache.wicket.model.IDetachable;
import org.apache.wicket.model.IModel;

/**
 * Provider of a tree.
 * 
 * You can use the {@link IDetachable#detach()} method for cleaning up your ITreeProvider instance.
 * 
 * @see IDetachable
 * @see AbstractTree
 * 
 * @author svenmeier
 * @param <T>
 *            the node type
 */
public interface ITreeProvider<T> extends IDetachable
{

	/**
	 * Get the roots of the tree.
	 * 
	 * @return roots
	 */
	Iterator<? extends T> getRoots();

	/**
	 * Does the given object have children - note that this method may return <code>true</code> even
	 * if {@link #getChildren(Object)} returns an empty iterator.
	 * 
	 * @param node
	 *            the node to check for children
	 * @return {@code true} if node has children
	 */
	boolean hasChildren(T node);

	/**
	 * Get the children of the given node.
	 * 
	 * @param node
	 *            node to get children for
	 * @return children of node
	 */
	Iterator<? extends T> getChildren(T node);

	/**
	 * Callback used by the consumer of this tree provider to wrap objects retrieved from
	 * {@link #getRoots()} or {@link #getChildren(Object)} with a model (usually a detachable one).
	 * <p>
	 * Important note: The model must implement {@link Object#equals(Object)} and
	 * {@link Object#hashCode()} !
	 * 
	 * @param object
	 *            the object that needs to be wrapped
	 * 
	 * @return the model representation of the object
	 */
	IModel<T> model(T object);
}