/*
 * 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.html.form;

import org.apache.wicket.IQueueRegion;
import org.apache.wicket.markup.ComponentTag;
import org.apache.wicket.markup.html.panel.IMarkupSourcingStrategy;
import org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy;
import org.apache.wicket.model.IModel;
import org.apache.wicket.util.visit.IVisitor;

/**
 * Panel (has it's own markup, defined between <wicket:panel> tags), that can act as a form
 * component. It typically wouldn't receive any input yourself, and often you can get by with
 * nesting form components in panels proper. However, using this panel can help you with building
 * components act to the outside world as one component, but internally uses separate components.
 * This component would then use these nested components to handle it's internal state, and would
 * use that internal state to get to one model object.
 * <p>
 * It is recommended that you override {@link #convertInput()} and let it set the value that
 * represents the compound value of the nested components. Often, this goes hand-in-hand with
 * overriding {@link #onBeforeRender()}, where you would analyze the model value, break it up and
 * distribute the appropriate values over the child components.
 * </p>
 * 
 * <p>
 * Here is a simple example of a panel with two components that multiplies and sets that as the
 * master model object. Note that for this simple example, setting the model value wouldn't make
 * sense, as the lhs and rhs cannot be known. For more complete examples of using this class, see
 * the wicket-datetime project.
 * </p>
 * 
 * <pre>
 * public class Multiply extends FormComponentPanel
 * {
 * 	private TextField left;
 * 	private int lhs = 0;
 * 	private int rhs = 0;
 * 	private TextField right;
 * 
 * 	public Multiply(String id)
 * 	{
 * 		super(id);
 * 		init();
 * 	}
 * 
 * 	public Multiply(String id, IModel model)
 * 	{
 * 		super(id, model);
 * 		init();
 * 	}
 * 
 * 	protected void convertInput()
 * 	{
 * 		Integer lhs = (Integer)left.getConvertedInput();
 * 		Integer rhs = (Integer)right.getConvertedInput();
 * 		setConvertedInput(lhs * rhs);
 * 	}
 * 
 * 	private void init()
 * 	{
 * 		add(left = new TextField("left", new PropertyModel(this, "lhs"), Integer.class));
 * 		add(right = new TextField("right", new PropertyModel(this, "rhs"), Integer.class));
 * 		left.setRequired(true);
 * 		right.setRequired(true);
 * 	}
 * }
 * </pre>
 * 
 * With this markup:
 * 
 * <pre>
 *   <wicket:panel>
 *     <input type="text" wicket:id="left" size="2" /> * <input type="text" wicket:id="right" size="2" />
 *   </wicket:panel>
 * </pre>
 * 
 * Which could be used, for example as:
 * 
 * <pre>
 *   add(new Multiply("multiply"), new PropertyModel(m, "multiply")));
 *   add(new Label("multiplyLabel", new PropertyModel(m, "multiply")));
 * </pre>
 * 
 * and:
 * 
 * <pre>
 *   <span wicket:id="multiply">[multiply]</span>
 *   = <span wicket:id="multiplyLabel">[result]</span>
 * </pre>
 * 
 * </p>
 * 
 * @author eelcohillenius
 * 
 * @param <T>
 *            The model object type
 */
public abstract class FormComponentPanel<T> extends FormComponent<T> implements IQueueRegion
{
	private static final long serialVersionUID = 1L;

	/**
	 * Constructor.
	 * 
	 * @param id
	 *          The component id
	 */
	public FormComponentPanel(String id)
	{
		super(id);
	}

	/**
	 * Constructor.
	 * 
	 * @param id
	 *          The component id
	 * @param model
	 *          The component model
	 */
	public FormComponentPanel(String id, IModel<T> model)
	{
		super(id, model);
	}

	@Override
	public boolean checkRequired()
	{
		return true;
	}

	@Override
	protected IMarkupSourcingStrategy newMarkupSourcingStrategy()
	{
		return new PanelMarkupSourcingStrategy(false);
	}

	@Override
	protected void onComponentTag(final ComponentTag tag)
	{
		super.onComponentTag(tag);

		// remove unapplicable attributes that might have been set by the call to super
		tag.remove("name");
		tag.remove("disabled");
	}

	@Override
	public void clearInput()
	{
		super.clearInput();

		// Visit all the (visible) form components and clear the input on each.
		visitFormComponentsPostOrder(this, (IVisitor<FormComponent<?>, Void>) (formComponent, visit) -> {
			if (formComponent != FormComponentPanel.this && formComponent.isVisibleInHierarchy())
			{
				formComponent.clearInput();
			}
		});
	}
}