<?php

/**

 * @file

 * Functions for use with Drupal's Ajax framework.

 */

/**

 * @defgroup ajax Ajax framework

 * @{

 * Functions for Drupal's Ajax framework.

 *

 * Drupal's Ajax framework is used to dynamically update parts of a page's HTML

 * based on data from the server. Upon a specified event, such as a button

 * click, a callback function is triggered which performs server-side logic and

 * may return updated markup, which is then replaced on-the-fly with no page

 * refresh necessary.

 *

 * This framework creates a PHP macro language that allows the server to

 * instruct JavaScript to perform actions on the client browser. When using

 * forms, it can be used with the #ajax property.

 * The #ajax property can be used to bind events to the Ajax framework. By

 * default, #ajax uses 'system/ajax' as its path for submission and thus calls

 * ajax_form_callback() and a defined #ajax['callback'] function.

 * However, you may optionally specify a different path to request or a

 * different callback function to invoke, which can return updated HTML or can

 * also return a richer set of

 * @link ajax_commands Ajax framework commands @endlink.

 *

 * Standard form handling is as follows:

 *   - A form element has a #ajax property that includes #ajax['callback'] and

 *     omits #ajax['path']. See below about using #ajax['path'] to implement

 *     advanced use-cases that require something other than standard form

 *     handling.

 *   - On the specified element, Ajax processing is triggered by a change to

 *     that element.

 *   - The browser submits an HTTP POST request to the 'system/ajax' Drupal

 *     path.

 *   - The menu page callback for 'system/ajax', ajax_form_callback(), calls

 *     drupal_process_form() to process the form submission and rebuild the

 *     form if necessary. The form is processed in much the same way as if it

 *     were submitted without Ajax, with the same #process functions and

 *     validation and submission handlers called in either case, making it easy

 *     to create Ajax-enabled forms that degrade gracefully when JavaScript is

 *     disabled.

 *   - After form processing is complete, ajax_form_callback() calls the

 *     function named by #ajax['callback'], which returns the form element that

 *     has been updated and needs to be returned to the browser, or

 *     alternatively, an array of custom Ajax commands.

 *   - The page delivery callback for 'system/ajax', ajax_deliver(), renders the

 *     element returned by #ajax['callback'], and returns the JSON string

 *     created by ajax_render() to the browser.

 *   - The browser unserializes the returned JSON string into an array of

 *     command objects and executes each command, resulting in the old page

 *     content within and including the HTML element specified by

 *     #ajax['wrapper'] being replaced by the new content returned by

 *     #ajax['callback'], using a JavaScript animation effect specified by

 *     #ajax['effect'].

 *

 * A simple example of basic Ajax use from the

 * @link http://drupal.org/project/examples Examples module @endlink follows:

 * @code

 * function main_page() {

 *   return drupal_get_form('ajax_example_simplest');

 * }

 *

 * function ajax_example_simplest($form, &$form_state) {

 *   $form = array();

 *   $form['changethis'] = array(

 *     '#type' => 'select',

 *     '#options' => array(

 *       'one' => 'one',

 *       'two' => 'two',

 *       'three' => 'three',

 *     ),

 *     '#ajax' => array(

 *       'callback' => 'ajax_example_simplest_callback',

 *       'wrapper' => 'replace_textfield_div',

 *      ),

 *   );

 *   // This entire form element will be replaced with an updated value.

 *   $form['replace_textfield'] = array(

 *     '#type' => 'textfield',

 *     '#title' => t("The default value will be changed"),

 *     '#description' => t("Say something about why you chose") . "'" .

 *       (!empty($form_state['values']['changethis'])

 *       ? $form_state['values']['changethis'] : t("Not changed yet")) . "'",

 *     '#prefix' => '<div id="replace_textfield_div">',

 *     '#suffix' => '</div>',

 *   );

 *   return $form;

 * }

 *

 * function ajax_example_simplest_callback($form, $form_state) {

 *   // The form has already been submitted and updated. We can return the replaced

 *   // item as it is.

 *   return $form['replace_textfield'];

 * }

 * @endcode

 *

 * In the above example, the 'changethis' element is Ajax-enabled. The default

 * #ajax['event'] is 'change', so when the 'changethis' element changes,

 * an Ajax call is made. The form is submitted and reprocessed, and then the

 * callback is called. In this case, the form has been automatically

 * built changing $form['replace_textfield']['#description'], so the callback

 * just returns that part of the form.

 *

 * To implement Ajax handling in a form, add '#ajax' to the form

 * definition of a field. That field will trigger an Ajax event when it is

 * clicked (or changed, depending on the kind of field). #ajax supports

 * the following parameters (either 'path' or 'callback' is required at least):

 * - #ajax['callback']: The callback to invoke to handle the server side of the

 *   Ajax event, which will receive a $form and $form_state as arguments, and

 *   returns a renderable array (most often a form or form fragment), an HTML

 *   string, or an array of Ajax commands. If returning a renderable array or

 *   a string, the value will replace the original element named in

 *   #ajax['wrapper'], and

 *   theme_status_messages()

 *   will be prepended to that

 *   element. (If the status messages are not wanted, return an array

 *   of Ajax commands instead.)

 *   #ajax['wrapper']. If an array of Ajax commands is returned, it will be

 *   executed by the calling code.

 * - #ajax['path']: The menu path to use for the request. This is often omitted

 *   and the default is used. This path should map

 *   to a menu page callback that returns data using ajax_render(). Defaults to

 *   'system/ajax', which invokes ajax_form_callback(), eventually calling

 *   the function named in #ajax['callback']. If you use a custom

 *   path, you must set up the menu entry and handle the entire callback in your

 *   own code.

 * - #ajax['wrapper']: The CSS ID of the area to be replaced by the content

 *   returned by the #ajax['callback'] function. The content returned from

 *   the callback will replace the entire element named by #ajax['wrapper'].

 *   The wrapper is usually created using #prefix and #suffix properties in the

 *   form. Note that this is the wrapper ID, not a CSS selector. So to replace

 *   the element referred to by the CSS selector #some-selector on the page,

 *   use #ajax['wrapper'] = 'some-selector', not '#some-selector'.

 * - #ajax['effect']: The jQuery effect to use when placing the new HTML.

 *   Defaults to no effect. Valid options are 'none', 'slide', or 'fade'.

 * - #ajax['speed']: The effect speed to use. Defaults to 'slow'. May be

 *   'slow', 'fast' or a number in milliseconds which represents the length

 *   of time the effect should run.

 * - #ajax['event']: The JavaScript event to respond to. This is normally

 *   selected automatically for the type of form widget being used, and

 *   is only needed if you need to override the default behavior.

 * - #ajax['prevent']: A JavaScript event to prevent when 'event' is triggered.

 *   Defaults to 'click' for #ajax on #type 'submit', 'button', and

 *   'image_button'. Multiple events may be specified separated by spaces.

 *   For example, when binding #ajax behaviors to form buttons, pressing the

 *   ENTER key within a textfield triggers the 'click' event of the form's first

 *   submit button. Triggering Ajax in this situation leads to problems, like

 *   breaking autocomplete textfields. Because of that, Ajax behaviors are bound

 *   to the 'mousedown' event on form buttons by default. However, binding to

 *   'mousedown' rather than 'click' means that it is possible to trigger a

 *   click by pressing the mouse, holding the mouse button down until the Ajax

 *   request is complete and the button is re-enabled, and then releasing the

 *   mouse button. For this case, 'prevent' can be set to 'click', so an

 *   additional event handler is bound to prevent such a click from triggering a

 *   non-Ajax form submission. This also prevents a textfield's ENTER press

 *   triggering a button's non-Ajax form submission behavior.

 * - #ajax['method']: The jQuery method to use to place the new HTML.

 *   Defaults to 'replaceWith'. May be: 'replaceWith', 'append', 'prepend',

 *   'before', 'after', or 'html'. See the

 *   @link http://api.jquery.com/category/manipulation/ jQuery manipulators documentation @endlink

 *   for more information on these methods.

 * - #ajax['progress']: Choose either a throbber or progress bar that is

 *   displayed while awaiting a response from the callback, and add an optional

 *   message. Possible keys: 'type', 'message', 'url', 'interval'.

 *   More information is available in the

 *   @link forms_api_reference.html Form API Reference @endlink

 *

 * In addition to using Form API for doing in-form modification, Ajax may be

 * enabled by adding classes to buttons and links. By adding the 'use-ajax'

 * class to a link, the link will be loaded via an Ajax call. When using this

 * method, the href of the link can contain '/nojs/' as part of the path. When

 * the Ajax framework makes the request, it will convert this to '/ajax/'.

 * The server is then able to easily tell if this request was made through an

 * actual Ajax request or in a degraded state, and respond appropriately.

 *

 * Similarly, submit buttons can be given the class 'use-ajax-submit'. The

 * form will then be submitted via Ajax to the path specified in the #action.

 * Like the ajax-submit class above, this path will have '/nojs/' replaced with

 * '/ajax/' so that the submit handler can tell if the form was submitted

 * in a degraded state or not.

 *

 * When responding to Ajax requests, the server should do what it needs to do

 * for that request, then create a commands array. This commands array will

 * be converted to a JSON object and returned to the client, which will then

 * iterate over the array and process it like a macro language.

 *

 * Each command item is an associative array which will be converted to a

 * command object on the JavaScript side. $command_item['command'] is the type

 * of command, e.g. 'alert' or 'replace', and will correspond to a method in the

 * Drupal.ajax[command] space. The command array may contain any other data that

 * the command needs to process, e.g. 'method', 'selector', 'settings', etc.

 *

 * Commands are usually created with a couple of helper functions, so they

 * look like this:

 * @code

 *   $commands = array();

 *   // Replace the content of '#object-1' on the page with 'some html here'.

 *   $commands[] = ajax_command_replace('#object-1', 'some html here');

 *   // Add a visual "changed" marker to the '#object-1' element.

 *   $commands[] = ajax_command_changed('#object-1');

 *   // Menu 'page callback' and #ajax['callback'] functions are supposed to

 *   // return render arrays. If returning an Ajax commands array, it must be

 *   // encapsulated in a render array structure.

 *   return array('#type' => 'ajax', '#commands' => $commands);

 * @endcode

 *

 * When returning an Ajax command array, it is often useful to have

 * status messages rendered along with other tasks in the command array.

 * In that case the Ajax commands array may be constructed like this:

 * @code

 *   $commands = array();

 *   $commands[] = ajax_command_replace(NULL, $output);

 *   $commands[] = ajax_command_prepend(NULL, theme('status_messages'));

 *   return array('#type' => 'ajax', '#commands' => $commands);

 * @endcode

 *

 * See @link ajax_commands Ajax framework commands @endlink

 */

/**

 * Renders a commands array into JSON.

 *

 * @param $commands

 *   A list of macro commands generated by the use of ajax_command_*()

 *   functions.

 */

function ajax_render($commands = array()) {

  // Although ajax_deliver() does this, some contributed and custom modules

  // render Ajax responses without using that delivery callback.

  ajax_set_verification_header();

  // Ajax responses aren't rendered with html.tpl.php, so we have to call

  // drupal_get_css() and drupal_get_js() here, in order to have new files added

  // during this request to be loaded by the page. We only want to send back

  // files that the page hasn't already loaded, so we implement simple diffing

  // logic using array_diff_key().

  foreach (array('css', 'js') as $type) {

    // It is highly suspicious if $_POST['ajax_page_state'][$type] is empty,

    // since the base page ought to have at least one JS file and one CSS file

    // loaded. It probably indicates an error, and rather than making the page

    // reload all of the files, instead we return no new files.

    if (empty($_POST['ajax_page_state'][$type])) {

      $items[$type] = array();

    }

    else {

      $function = 'drupal_add_' . $type;

      $items[$type] = $function();

      drupal_alter($type, $items[$type]);

      // @todo Inline CSS and JS items are indexed numerically. These can't be

      //   reliably diffed with array_diff_key(), since the number can change

      //   due to factors unrelated to the inline content, so for now, we strip

      //   the inline items from Ajax responses, and can add support for them

      //   when drupal_add_css() and drupal_add_js() are changed to use a hash

      //   of the inline content as the array key.

      foreach ($items[$type] as $key => $item) {

        if (is_numeric($key)) {

          unset($items[$type][$key]);

        }

      }

      // Ensure that the page doesn't reload what it already has.

      $items[$type] = array_diff_key($items[$type], $_POST['ajax_page_state'][$type]);

    }

  }

  // Render the HTML to load these files, and add AJAX commands to insert this

  // HTML in the page. We pass TRUE as the $skip_alter argument to prevent the

  // data from being altered again, as we already altered it above. Settings are

  // handled separately, afterwards.

  if (isset($items['js']['settings'])) {

    unset($items['js']['settings']);

  }

  $styles = drupal_get_css($items['css'], TRUE);

  $scripts_footer = drupal_get_js('footer', $items['js'], TRUE);

  $scripts_header = drupal_get_js('header', $items['js'], TRUE);

  $extra_commands = array();

  if (!empty($styles)) {

    $extra_commands[] = ajax_command_add_css($styles);

  }

  if (!empty($scripts_header)) {

    $extra_commands[] = ajax_command_prepend('head', $scripts_header);

  }

  if (!empty($scripts_footer)) {

    $extra_commands[] = ajax_command_append('body', $scripts_footer);

  }

  if (!empty($extra_commands)) {

    $commands = array_merge($extra_commands, $commands);

  }

  // Now add a command to merge changes and additions to Drupal.settings.

  $scripts = drupal_add_js();

  if (!empty($scripts['settings'])) {

    $settings = $scripts['settings'];

    array_unshift($commands, ajax_command_settings(drupal_array_merge_deep_array($settings['data']), TRUE));

  }

  // Allow modules to alter any Ajax response.

  drupal_alter('ajax_render', $commands);

  return drupal_json_encode($commands);

}

/**

 * Gets a form submitted via #ajax during an Ajax callback.

 *

 * This will load a form from the form cache used during Ajax operations. It

 * pulls the form info from $_POST.

 *

 * @return

 *   An array containing the $form, $form_state, $form_id, $form_build_id and an

 *   initial list of Ajax $commands. Use the list() function to break these

 *   apart:

 *   @code

 *     list($form, $form_state, $form_id, $form_build_id, $commands) = ajax_get_form();

 *   @endcode

 */

function ajax_get_form() {

  $form_state = form_state_defaults();

  $form_build_id = $_POST['form_build_id'];

  // Get the form from the cache.

  $form = form_get_cache($form_build_id, $form_state);

  if (!$form) {

    // If $form cannot be loaded from the cache, the form_build_id in $_POST

    // must be invalid, which means that someone performed a POST request onto

    // system/ajax without actually viewing the concerned form in the browser.

    // This is likely a hacking attempt as it never happens under normal

    // circumstances, so we just do nothing.

    watchdog('ajax', 'Invalid form POST data.', array(), WATCHDOG_WARNING);

    drupal_exit();

  }

  // When a page level cache is enabled, the form-build id might have been

  // replaced from within form_get_cache. If this is the case, it is also

  // necessary to update it in the browser by issuing an appropriate Ajax

  // command.

  $commands = array();

  if (isset($form['#build_id_old']) && $form['#build_id_old'] != $form['#build_id']) {

    // If the form build ID has changed, issue an Ajax command to update it.

    $commands[] = ajax_command_update_build_id($form);

    $form_build_id = $form['#build_id'];

  }

  // Since some of the submit handlers are run, redirects need to be disabled.

  $form_state['no_redirect'] = TRUE;

  // When a form is rebuilt after Ajax processing, its #build_id and #action

  // should not change.

  // @see drupal_rebuild_form()

  $form_state['rebuild_info']['copy']['#build_id'] = TRUE;

  $form_state['rebuild_info']['copy']['#action'] = TRUE;

  // The form needs to be processed; prepare for that by setting a few internal

  // variables.

  $form_state['input'] = $_POST;

  $form_id = $form['#form_id'];

  return array($form, $form_state, $form_id, $form_build_id, $commands);

}

/**

 * Menu callback; handles Ajax requests for the #ajax Form API property.

 *

 * This rebuilds the form from cache and invokes the defined #ajax['callback']

 * to return an Ajax command structure for JavaScript. In case no 'callback' has

 * been defined, nothing will happen.

 *

 * The Form API #ajax property can be set both for buttons and other input

 * elements.

 *

 * This function is also the canonical example of how to implement

 * #ajax['path']. If processing is required that cannot be accomplished with

 * a callback, re-implement this function and set #ajax['path'] to the

 * enhanced function.

 *

 * @see system_menu()

 */

function ajax_form_callback() {

  list($form, $form_state, $form_id, $form_build_id, $commands) = ajax_get_form();

  drupal_process_form($form['#form_id'], $form, $form_state);

  // We need to return the part of the form (or some other content) that needs

  // to be re-rendered so the browser can update the page with changed content.

  // Since this is the generic menu callback used by many Ajax elements, it is

  // up to the #ajax['callback'] function of the element (may or may not be a

  // button) that triggered the Ajax request to determine what needs to be

  // rendered.

  if (!empty($form_state['triggering_element'])) {

    $callback = $form_state['triggering_element']['#ajax']['callback'];

  }

  if (!empty($callback) && is_callable($callback)) {

    $result = $callback($form, $form_state);

    if (!(is_array($result) && isset($result['#type']) && $result['#type'] == 'ajax')) {

      // Turn the response into a #type=ajax array if it isn't one already.

      $result = array(

        '#type' => 'ajax',

        '#commands' => ajax_prepare_response($result),

      );

    }

    $result['#commands'] = array_merge($commands, $result['#commands']);

    return $result;

  }

}

/**

 * Theme callback for Ajax requests.

 *

 * Many different pages can invoke an Ajax request to system/ajax or another

 * generic Ajax path. It is almost always desired for an Ajax response to be

 * rendered using the same theme as the base page, because most themes are built

 * with the assumption that they control the entire page, so if the CSS for two

 * themes are both loaded for a given page, they may conflict with each other.

 * For example, Bartik is Drupal's default theme, and Seven is Drupal's default

 * administration theme. Depending on whether the "Use the administration theme

 * when editing or creating content" checkbox is checked, the node edit form may

 * be displayed in either theme, but the Ajax response to the Field module's

 * "Add another item" button should be rendered using the same theme as the rest

 * of the page. Therefore, system_menu() sets the 'theme callback' for

 * 'system/ajax' to this function, and it is recommended that modules

 * implementing other generic Ajax paths do the same.

 *

 * @see system_menu()

 * @see file_menu()

 */

function ajax_base_page_theme() {

  if (!empty($_POST['ajax_page_state']['theme']) && !empty($_POST['ajax_page_state']['theme_token'])) {

    $theme = $_POST['ajax_page_state']['theme'];

    $token = $_POST['ajax_page_state']['theme_token'];

    // Prevent a request forgery from giving a person access to a theme they

    // shouldn't be otherwise allowed to see. However, since everyone is allowed

    // to see the default theme, token validation isn't required for that, and

    // bypassing it allows most use-cases to work even when accessed from the

    // page cache.

    if ($theme === variable_get('theme_default', 'bartik') || drupal_valid_token($token, $theme)) {

      return $theme;

    }

  }

}

/**

 * Packages and sends the result of a page callback as an Ajax response.

 *

 * This function is the equivalent of drupal_deliver_html_page(), but for Ajax

 * requests. Like that function, it:

 * - Adds needed HTTP headers.

 * - Prints rendered output.

 * - Performs end-of-request tasks.

 *

 * @param $page_callback_result

 *   The result of a page callback. Can be one of:

 *   - NULL: to indicate no content.

 *   - An integer menu status constant: to indicate an error condition.

 *   - A string of HTML content.

 *   - A renderable array of content.

 *