* 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.

*/

* A button that uses Handlebars JavaScript templating library to

* update HTML element's content

*/

  /**

   * Uses JQueryPluginResourceReference to specify that it depends on jQuery.

   * This way jQuery will be delivered before handlebars.js

   */

  private static final JavaScriptResourceReference HANDLEBARS_JS =

      new JQueryPluginResourceReference(HandlebarsButton.class, "handlebars-1.0.0.beta.6.js");

  /**

   * The body of a Wicket.Ajax's #onSuccess() listener that uses the Ajax response

   * which is passed with the special argument name 'data'

   */

  private final JsonFunction onSuccessFunction;

  /**

   * Constructor.

   *

   * @param id the component id

   * @param templateId the id of the Handlebars template

   *      E.g. <script id="THIS_ID" type="text/x-handlebars-template">

   * @param targetSelector the css selector to use to find the HTML element that

   *      should be updated with the populated Handlebars template

   */

  public HandlebarsButton(String id, String templateId, String targetSelector)

  {

    super(id);

    Args.notEmpty(templateId, "templateId");

    Args.notEmpty(targetSelector, "targetSelector");

    PackageTextTemplate blogJs = new PackageTextTemplate(HandlebarsButton.class, "HandlebarsButton.js.tmpl");

    Map<String, Object> variables = Generics.newHashMap();

    variables.put("templateId", templateId);

    variables.put("targetSelector", targetSelector);

    this.onSuccessFunction = new JsonFunction(blogJs.asString(variables));

  }

  @Override

  protected void updateAjaxAttributes(AjaxRequestAttributes attributes)

  {

    super.updateAjaxAttributes(attributes);

    // let Wicket.Ajax/jQuery know that the result is JSON so it will parse it for you

    attributes.setDataType("json");

    // tell Wicket.Ajax to not try to process the Ajax response because it is not the normal <ajax-response>

    attributes.setWicketAjaxResponse(false);

    // register the onSuccess listener that will execute Handlebars logic

    AjaxCallListener listener = new AjaxCallListener() {

      @Override

      public CharSequence getSuccessHandler(Component component)

      {

        // returns an instance of JsonFunction, so Wicket will render it as is

        return onSuccessFunction;

      }

    };

    // the following handlers are not JsonFunction and they will be wrapped in JsonFunction by Wicket and the

    // appropriate parameters will be passed.

    // For the 'before' handler it looks like: function(attrs, jqXHR, settings){Wicket.Log.info('[Wicket Ajax 6 demo]: executing a before handler');}

    listener.onBefore("Wicket.Log.info('[Wicket Ajax 6 demo]: executing a before handler');");

    // For the 'complete' handler it looks like: function(attrs, jqXHR, textStatus){Wicket.Log.info('[Wicket Ajax 6 demo]: executing a complete handler');}

    listener.onComplete("Wicket.Log.info('[Wicket Ajax 6 demo]: executing a complete handler. Status: ' + textStatus);");

    // change the return to 'false' and the Ajax call wont be executed at all.

    listener.onPrecondition("return true;");

    attributes.getAjaxCallListeners().add(listener);

  }

  /**

   * Serializes the object to its JSON representation that will be used as

   * an Ajax response.

   * This method that should be implemented by the client of this component.

   *

   * @param object the object to serialize

   * @return the JSON representation of the passed object

   */

  protected abstract CharSequence asJson(T object);

  /**

   * Serializes the form's model object to JSON and delivers it to the browser.

   *

   * @param target the Ajax request handler. Since we work with JSON we just ignore it.

   * @param form the form that contains this button. Keeps the POJO as a model object.

   */

  @Override

  protected final void onSubmit(AjaxRequestTarget target, Form<?> form)

  {

    T object = ((Form<T>) form).getModelObject();

    String json = asJson(object).toString();

    // schedule a request handler that will serve the JSON response

    TextRequestHandler jsonHandler = new TextRequestHandler("application/json", "UTF-8", json);

    // replace AjaxRequestHandler with the JSON one

    getRequestCycle().replaceAllRequestHandlers(jsonHandler);

  }

  /**

   * Contribute Handlebars.js

   *

   * @param response the response that writes the page headers

   */

  @Override

  public void renderHead(IHeaderResponse response)

  {

    super.renderHead(response);

    response.render(JavaScriptHeaderItem.forReference(HANDLEBARS_JS));

  }

}