/*
 * Copyright 2005-2010 the original author or authors.
 * 
 * Licensed 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.wamblee.wicket.behavior;

import org.apache.wicket.Component;
import org.apache.wicket.Page;
import org.apache.wicket.behavior.HeaderContributor;
import org.apache.wicket.markup.html.IHeaderResponse;
import org.apache.wicket.markup.html.JavascriptPackageResource;
import org.wamblee.wicket.jquery.JQueryBehavior;
import org.wamblee.wicket.jquery.JQueryUtils;

/**
 * Preselection behavior that preselects unaltered text in forms. When applied
 * to a certain component, the behavior is valid for all children of the
 * component. Therefore, it is possible to attach this behavior to any component,
 * well as to a form or even individual fields in a form. It is not possible however to apply this
 * behavior to a page. The behavior applies
 * to text input fields and textareas. Upon focus, the text in the field is
 * selected if it it still identical to the default value.
 * 
 * @author Erik Brakkee
 * 
 */
public class PreselectionBehavior extends CompositeBehavior {

    static final String PRESELECT_SCRIPT = "wamblee-preselect.js";

    private static HeaderContributor CACHE = JavascriptPackageResource
        .getHeaderContribution(PreselectionBehavior.class, PRESELECT_SCRIPT);

    private Component component;

    public PreselectionBehavior() {
        super(new JQueryBehavior(), new NamespaceBehavior(), CACHE);
    }

    @Override
    public void bind(Component aComponent) {
        if (component != null) {
            throw new IllegalStateException(
                "this kind of handler cannot be attached to " +
                    "multiple components; it is already attached to component " +
                    component + ", but component " + aComponent +
                    " wants to be attached too");
        }
        if ( aComponent instanceof Page) { 
            throw new IllegalStateException("This behavior cannot be applied to a page: " + aComponent);
        }
        component = aComponent;
        super.bind(aComponent);
        aComponent.setOutputMarkupId(true);
    }

    @Override
    public void renderHead(IHeaderResponse aResponse) {
        super.renderHead(aResponse);
        String jsString = JQueryUtils.createReadyFunction("preselectSetup", component);
        aResponse.renderJavascript(jsString, null);
    }

}