<?php
// $Id$

/**
 * @file
 * Functions for use with Drupal's AJAX framework.
 */

/**
 * @defgroup ajax 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
 * @link ajax_form_callback ajax_form_callback @endlink 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 member.
 *   - On the specified element, AJAX processing is triggered by a change to
 *     that element.
 *   - The form is submitted and rebuilt.
 *   - The function named by #ajax['callback'] is called, which returns content
 *     or an array of AJAX framework commands.
 *   - The content returned by the callback replaces the div on the page
 *     referenced by #ajax['wrapper'].
 *
 * 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['method']: The jQuery method to use to place the new HTML.
 *   Defaults to 'replace'. May be: 'replace', 'append', 'prepend',
 *   'before', 'after', or 'html'. See the jQuery documentation 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 http://api.drupal.org/api/drupal/developer--topics--forms_api_reference.html/7 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.
 *   $commands[] = ajax_command_changed('#object-1');
 *   // Output new markup to the browser and end the request.
 *   // Note: Only custom AJAX paths/page callbacks need to do this manually.
 *   ajax_render($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 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 $commands;
 * @endcode
 *
 * See @link ajax_commands AJAX framework commands @endlink
 */

/**
 * Render a commands array into JSON and exit.
 *
 * Commands are immediately handed back to the AJAX requester. This function
 * will render and immediately exit.
 *
 * @param $commands
 *   A list of macro commands generated by the use of ajax_command_*()
 *   functions.
 * @param $header
 *   If set to FALSE the 'text/javascript' header used by drupal_json_output()
 *   will not be used, which is necessary when using an IFRAME. If set to
 *   'multipart' the output will be wrapped in a textarea, which can also be
 *   used as an alternative method when uploading files.
 */
function ajax_render($commands = array(), $header = TRUE) {
  // Automatically extract any 'settings' added via drupal_add_js() and make
  // them the first command.
  $scripts = drupal_add_js(NULL, NULL);
  if (!empty($scripts['settings'])) {
    array_unshift($commands, ajax_command_settings(call_user_func_array('array_merge_recursive', $scripts['settings']['data'])));
  }

  // Allow modules to alter any AJAX response.
  drupal_alter('ajax_render', $commands);

  // Use === here so that bool TRUE doesn't match 'multipart'.
  if ($header === 'multipart') {
    // We do not use drupal_json_output() here because the header is not true.
    // We are not really returning JSON, strictly-speaking, but rather JSON
    // content wrapped in a textarea as per the "file uploads" example here:
    // http://malsup.com/jquery/form/#code-samples
    print '<textarea>' . drupal_json_encode($commands) . '</textarea>';
  }
  elseif ($header) {
    drupal_json_output($commands);
  }
  else {
    print drupal_json_encode($commands);
  }
  drupal_exit();
}

/**
 * Send an error response back via AJAX and immediately exit.
 *
 * This function can be used to quickly create a command array with an error
 * string and send it, short-circuiting the error handling process.
 *
 * @param $error
 *   A string to display in an alert.
 */
function ajax_render_error($error = '') {
  $commands = array();
  $commands[] = ajax_command_alert(empty($error) ? t('An error occurred while handling the request: The server received invalid input.') : $error);
  ajax_render($commands);
}

/**
 * Get 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 and $form_state. Use the list() function
 *   to break these apart:
 *   @code
 *     list($form, $form_state, $form_id, $form_build_id) = 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();
  }

  // Since some of the submit handlers are run, redirects need to be disabled.
  $form_state['no_redirect'] = 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);
}

/**
 * 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.
 *
 * ajax_process_form() defines an additional 'formPath' JavaScript setting
 * that is used by Drupal.ajax.prototype.beforeSubmit() to automatically inject
 * an additional field 'ajax_triggering_element' to the submitted form values,
 * which contains the array #parents of the element in the form structure.
 * This additional field allows ajax_form_callback() to determine which
 * element triggered the action, as non-submit form elements do not
 * provide this information in $form_state['clicked_button'], which can
 * also be used to determine triggering element, but only submit-type
 * form elements.
 *
 * This function is also the canonical example of how to implement
 * #ajax['path']. If processing is required that cannot be accomplished with
 * a callback, re-implement this function and set #ajax['path'] to the
 * enhanced function.
 */
function ajax_form_callback() {
  // Find the triggering element, which was set up for us on the client side.
  if (!empty($_REQUEST['ajax_triggering_element'])) {
    $triggering_element_path = $_REQUEST['ajax_triggering_element'];
    // Remove the value for form validation.
    unset($_REQUEST['ajax_triggering_element']);
  }
  list($form, $form_state, $form_id, $form_build_id) = ajax_get_form();

  // Build, validate and if possible, submit the form.
  drupal_process_form($form_id, $form, $form_state);

  // This call recreates the form relying solely on the $form_state that
  // drupal_process_form() set up.
  $form = drupal_rebuild_form($form_id, $form_state, $form_build_id);

  // $triggering_element_path in a simple form might just be 'myselect', which
  // would mean we should use the element $form['myselect']. For nested form
  // elements we need to recurse into the form structure to find the triggering
  // element, so we can retrieve the #ajax['callback'] from it.
  if (!empty($triggering_element_path)) {
    if (!isset($form['#access']) || $form['#access']) {
      $triggering_element = $form;
      foreach (explode('/', $triggering_element_path) as $key) {
        if (!empty($triggering_element[$key]) && (!isset($triggering_element[$key]['#access']) || $triggering_element[$key]['#access'])) {
          $triggering_element = $triggering_element[$key];
        }
        else {
          // We did not find the $triggering_element or do not have #access,
          // so break out and do not provide it.
          $triggering_element = NULL;
          break;
        }
      }
    }
  }
  if (empty($triggering_element)) {
    $triggering_element = $form_state['clicked_button'];
  }
  // Now that we have the element, get a callback if there is one.
  if (!empty($triggering_element)) {
    $callback = $triggering_element['#ajax']['callback'];
  }
  if (!empty($callback) && function_exists($callback)) {
    return $callback($form, $form_state);
  }
}

/**
 * Package and send the result of a page callback to the browser as an AJAX response.
 *
 * @param $page_callback_result
 *   The result of a page callback. Can be one of:
 *   - NULL: to indicate no content.
 *   - An integer menu status constant: to indicate an error condition.
 *   - A string of HTML content.
 *   - A renderable array of content.
 */
function ajax_deliver($page_callback_result) {
  $commands = array();
  if (!isset($page_callback_result)) {
    // Simply delivering an empty commands array is sufficient. This results
    // in the AJAX request being completed, but nothing being done to the page.
  }
  elseif (is_int($page_callback_result)) {
    switch ($page_callback_result) {
      case MENU_NOT_FOUND:
        $commands[] = ajax_command_alert(t('The requested page could not be found.'));
        break;

      case MENU_ACCESS_DENIED:
        $commands[] = ajax_command_alert(t('You are not authorized to access this page.'));
        break;

      case MENU_SITE_OFFLINE:
        $commands[] = ajax_command_alert(filter_xss_admin(variable_get('maintenance_mode_message',
          t('@site is currently under maintenance. We should be back shortly. Thank you for your patience.', array('@site' => variable_get('site_name', 'Drupal'))))));
        break;
    }
  }
  elseif (is_array($page_callback_result) && isset($page_callback_result['#type']) && ($page_callback_result['#type'] == 'ajax_commands')) {
    // Complex AJAX callbacks can return a result that contains a specific
    // set of commands to send to the browser.
    if (isset($page_callback_result['#ajax_commands'])) {
      $commands = $page_callback_result['#ajax_commands'];
    }
  }
  else {
    // Like normal page callbacks, simple AJAX callbacks can return html
    // content, as a string or renderable array, to replace what was previously
    // there in the wrapper. In this case, in addition to the content, we want
    // to add the status messages, but inside the new wrapper, so that they get
    // replaced on subsequent AJAX calls for the same wrapper.
    $html = is_string($page_callback_result) ? $page_callback_result : drupal_render($page_callback_result);
    $commands[] = ajax_command_replace(NULL, $html);
    $commands[] = ajax_command_prepend(NULL, theme('status_messages'));
  }
  ajax_render($commands);
}

/**
 * Add AJAX information about a form element to the page to communicate with JavaScript.
 *
 * If #ajax['path'] is set on an element, this additional JavaScript is added
 * to the page header to attach the AJAX behaviors. See ajax.js for more
 * information.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:
 *   - #ajax['event']
 *   - #ajax['path']
 *   - #ajax['wrapper']
 *   - #ajax['parameters']
 *   - #ajax['effect']
 *
 * @return
 *   None. Additional code is added to the header of the page using
 *   drupal_add_js().
 */
function ajax_process_form($element, &$form_state) {
  $js_added = &drupal_static(__FUNCTION__, array());

  // Nothing to do if there is neither a callback nor a path.
  if (!(isset($element['#ajax']['callback']) || isset($element['#ajax']['path']))) {
    return $element;
  }

  // Add a reasonable default event handler if none was specified.
  if (isset($element['#ajax']) && !isset($element['#ajax']['event'])) {
    switch ($element['#type']) {
      case 'submit':
      case 'button':
      case 'image_button':
        // Use the mousedown instead of the click event because form
        // submission via pressing the enter key triggers a click event on
        // submit inputs, inappropriately triggering AJAX behaviors.
        $element['#ajax']['event'] = 'mousedown';
        // Attach an additional event handler so that AJAX behaviors
        // can be triggered still via keyboard input.
        $element['#ajax']['keypress'] = TRUE;
        break;

      case 'password':
      case 'textfield':
      case 'textarea':
        $element['#ajax']['event'] = 'blur';
        break;

      case 'radio':
      case 'checkbox':
      case 'select':
        $element['#ajax']['event'] = 'change';
        break;

      default:
        return $element;
    }
  }

  // Adding the same JavaScript settings twice will cause a recursion error,
  // we avoid the problem by checking if the JavaScript has already been added.
  if (!isset($js_added[$element['#id']]) && isset($element['#ajax']['event'])) {
    $element['#attached']['library'][] = array('system', 'form');
    $element['#attached']['js']['misc/ajax.js'] = array('weight' => JS_LIBRARY + 2);

    $settings = $element['#ajax'];

    // Assign default settings.
    $settings += array(
      'selector' => '#' . $element['#id'],
      'effect' => 'none',
      'speed' => 'none',
      'method' => 'replace',
      'progress' => array('type' => 'throbber'),
      'formPath' => implode('/', $element['#array_parents']),
    );

    // Process special settings.
    $settings['url'] = isset($settings['path']) ? url($settings['path']) : url('system/ajax');
    unset($settings['path']);
    $settings['button'] = isset($element['#executes_submit_callback']) ? array($element['#name'] => $element['#value']) : FALSE;

    // Convert a simple #ajax['progress'] string into an array.
    if (is_string($settings['progress'])) {
      $settings['progress'] = array('type' => $settings['progress']);
    }
    // Change progress path to a full URL.
    if (isset($settings['progress']['path'])) {
      $settings['progress']['url'] = url($settings['progress']['path']);
      unset($settings['progress']['path']);
    }
    // Add progress.js if we're doing a bar display.
    if ($settings['progress']['type'] == 'bar') {
      $element['#attached']['js']['misc/progress.js'] = array('cache' => FALSE);
    }

    // @todo This is incompatible with drupal_render() caching, but cannot be
    //   assigned to #attached, because AJAX callbacks render the form in a way
    //   so that #attached settings are not taken over.
    drupal_add_js(array('ajax' => array($element['#id'] => $settings)), 'setting');

    $js_added[$element['#id']] = TRUE;
    $form_state['cache'] = TRUE;
  }
  return $element;
}

/**
 * @} End of "defgroup ajax".
 */

/**
 * @defgroup ajax_commands AJAX framework commands
 * @{
 */

/**
 * Creates a Drupal AJAX 'alert' command.
 *
 * The 'alert' command instructs the client to display a JavaScript alert
 * dialog box.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.alert()
 * defined in misc/ajax.js.
 *
 * @param $text
 *   The message string to display to the user.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 */
function ajax_command_alert($text) {
  return array(
    'command' => 'alert',
    'text' => $text,
  );
}

/**
 * Creates a Drupal AJAX 'insert/replaceWith' command.
 *
 * The 'insert/replaceWith' command instructs the client to use jQuery's
 * replaceWith() method to replace each element matched matched by the given
 * selector with the given HTML.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.insert()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $html
 *   The data to use with the jQuery replaceWith() method.
 * @param $settings
 *   An optional array of settings that will be used for this command only.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/Manipulation/replaceWith#content
 */
function ajax_command_replace($selector, $html, $settings = NULL) {
  return array(
    'command' => 'insert',
    'method' => 'replaceWith',
    'selector' => $selector,
    'data' => $html,
    'settings' => $settings,
  );
}

/**
 * Creates a Drupal AJAX 'insert/html' command.
 *
 * The 'insert/html' command instructs the client to use jQuery's html()
 * method to set the HTML content of each element matched by the given
 * selector while leaving the outer tags intact.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.insert()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $html
 *   The data to use with the jQuery html() method.
 * @param $settings
 *   An optional array of settings that will be used for this command only.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/Attributes/html#val
 */
function ajax_command_html($selector, $html, $settings = NULL) {
  return array(
    'command' => 'insert',
    'method' => 'html',
    'selector' => $selector,
    'data' => $html,
    'settings' => $settings,
  );
}

/**
 * Creates a Drupal AJAX 'insert/prepend' command.
 *
 * The 'insert/prepend' command instructs the client to use jQuery's prepend()
 * method to prepend the given HTML content to the inside each element matched
 * by the given selector.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.insert()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $html
 *   The data to use with the jQuery prepend() method.
 * @param $settings
 *   An optional array of settings that will be used for this command only.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/Manipulation/prepend#content
 */
function ajax_command_prepend($selector, $html, $settings = NULL) {
  return array(
    'command' => 'insert',
    'method' => 'prepend',
    'selector' => $selector,
    'data' => $html,
    'settings' => $settings,
  );
}

/**
 * Creates a Drupal AJAX 'insert/append' command.
 *
 * The 'insert/append' command instructs the client to use jQuery's append()
 * method to append the given HTML content to the inside each element matched
 * by the given selector.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.insert()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $html
 *   The data to use with the jQuery append() method.
 * @param $settings
 *   An optional array of settings that will be used for this command only.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/Manipulation/append#content
 */
function ajax_command_append($selector, $html, $settings = NULL) {
  return array(
    'command' => 'insert',
    'method' => 'append',
    'selector' => $selector,
    'data' => $html,
    'settings' => $settings,
  );
}

/**
 * Creates a Drupal AJAX 'insert/after' command.
 *
 * The 'insert/after' command instructs the client to use jQuery's after()
 * method to insert the given HTML content after each element matched by
 * the given selector.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.insert()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $html
 *   The data to use with the jQuery after() method.
 * @param $settings
 *   An optional array of settings that will be used for this command only.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/Manipulation/after#content
 */
function ajax_command_after($selector, $html, $settings = NULL) {
  return array(
    'command' => 'insert',
    'method' => 'after',
    'selector' => $selector,
    'data' => $html,
    'settings' => $settings,
  );
}

/**
 * Creates a Drupal AJAX 'insert/before' command.
 *
 * The 'insert/before' command instructs the client to use jQuery's before()
 * method to insert the given HTML content before each of elements matched by
 * the given selector.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.insert()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $html
 *   The data to use with the jQuery before() method.
 * @param $settings
 *   An optional array of settings that will be used for this command only.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/Manipulation/before#content
 */
function ajax_command_before($selector, $html, $settings = NULL) {
  return array(
    'command' => 'insert',
    'method' => 'before',
    'selector' => $selector,
    'data' => $html,
    'settings' => $settings,
  );
}

/**
 * Creates a Drupal AJAX 'remove' command.
 *
 * The 'remove' command instructs the client to use jQuery's remove() method
 * to remove each of elements matched by the given selector, and everything
 * within them.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.remove()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/Manipulation/remove#expr
 */
function ajax_command_remove($selector) {
  return array(
    'command' => 'remove',
    'selector' => $selector,
  );
}

/**
 * Creates a Drupal AJAX 'changed' command.
 *
 * This command instructs the client to mark each of the elements matched by the
 * given selector as 'ajax-changed'.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.changed()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $asterisk
 *   An optional CSS selector which must be inside $selector. If specified,
 *   an asterisk will be appended to the HTML inside the $asterisk selector.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 */
function ajax_command_changed($selector, $asterisk = '') {
  return array(
    'command' => 'changed',
    'selector' => $selector,
    'asterisk' => $asterisk,
  );
}

/**
 * Creates a Drupal AJAX 'css' command.
 *
 * The 'css' command will instruct the client to use the jQuery css() method
 * to apply the CSS arguments to elements matched by the given selector.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.insert()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $argument
 *   An array of key/value pairs to set in the CSS for the selector.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/CSS/css#properties
 */
function ajax_command_css($selector, $argument) {
  return array(
    'command' => 'css',
    'selector' => $selector,
    'argument' => $argument,
  );
}

/**
 * Creates a Drupal AJAX 'settings' command.
 *
 * The 'settings' command instructs the client either to use the given array as
 * the settings for ajax-loaded content or to extend Drupal.settings with the
 * given array, depending on the value of the $merge parameter.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.settings()
 * defined in misc/ajax.js.
 *
 * @param $argument
 *   An array of key/value pairs to add to the settings. This will be utilized
 *   for all commands after this if they do not include their own settings
 *   array.
 * @param $merge
 *   Whether or not the passed settings in $argument should be merged into the
 *   global Drupal.settings on the page. By default (FALSE), the settings that
 *   are passed to Drupal.attachBehaviors will not include the global
 *   Drupal.settings.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 */
function ajax_command_settings($argument, $merge = FALSE) {
  return array(
    'command' => 'settings',
    'settings' => $argument,
    'merge' => $merge,
  );
}

/**
 * Creates a Drupal AJAX 'data' command.
 *
 * The 'data' command instructs the client to attach the name=value pair of
 * data to the selector via jQuery's data cache.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.data()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string. If the command is a response to a request from
 *   an #ajax form element then this value can be NULL.
 * @param $name
 *   The name or key (in the key value pair) of the data attached to this
 *   selector.
 * @param $value
 *   The value of the data. Not just limited to strings can be any format.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 *
 * @see http://docs.jquery.com/Core/data#namevalue
 */
function ajax_command_data($selector, $name, $value) {
  return array(
    'command' => 'data',
    'selector' => $selector,
    'name' => $name,
    'value' => $value,
  );
}

/**
 * Creates a Drupal AJAX 'restripe' command.
 *
 * The 'restripe' command instructs the client to restripe a table. This is
 * usually used after a table has been modified by a replace or append command.
 *
 * This command is implemented by Drupal.ajax.prototype.commands.restripe()
 * defined in misc/ajax.js.
 *
 * @param $selector
 *   A jQuery selector string.
 *
 * @return
 *   An array suitable for use with the ajax_render() function.
 */
function ajax_command_restripe($selector) {
  return array(
    'command' => 'restripe',
    'selector' => $selector,
  );
}