<?php
// $Id$

/**
 * @defgroup forms Form builder functions
 * @{
 * Functions that build an abstract representation of a HTML form.
 *
 * All modules should declare their form builder functions to be in this
 * group and each builder function should reference its validate and submit
 * functions using \@see. Conversely, validate and submit functions should
 * reference the form builder function using \@see. For examples, of this see
 * system_modules_uninstall() or user_pass(), the latter of which has the
 * following in its doxygen documentation:
 *
 * \@ingroup forms
 * \@see user_pass_validate().
 * \@see user_pass_submit().
 *
 * @} End of "defgroup forms".
 */

/**
 * @defgroup form_api Form generation
 * @{
 * Functions to enable the processing and display of HTML forms.
 *
 * Drupal uses these functions to achieve consistency in its form processing and
 * presentation, while simplifying code and reducing the amount of HTML that
 * must be explicitly generated by modules.
 *
 * The drupal_get_form() function handles retrieving and processing an HTML
 * form for modules automatically. For example:
 *
 * @code
 * // Display the user registration form.
 * $output = drupal_get_form('user_register');
 * @endcode
 *
 * Forms can also be built and submitted programmatically without any user input
 * using the drupal_form_submit() function.
 *
 * For information on the format of the structured arrays used to define forms,
 * and more detailed explanations of the Form API workflow, see the
 * @link http://api.drupal.org/api/file/developer/topics/forms_api_reference.html reference @endlink
 * and the @link http://api.drupal.org/api/file/developer/topics/forms_api.html quickstart guide. @endlink
 */

/**
 * Wrapper for drupal_build_form() for use when $form_state is not needed.
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function with that
 *   name exists, it is called to build the form array. Modules that need to
 *   generate the same form (or very similar forms) using different $form_ids
 *   can implement hook_forms(), which maps different $form_id values to the
 *   proper form constructor function. Examples may be found in node_forms(),
 *   search_forms(), and user_forms().
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_get_form(), including the unique form constructor function. For
 *   example, the node_edit form requires that a node object is passed in here
 *   when it is called.
 * @return
 *   The form array.
 *
 * @see drupal_build_form()
 */
function drupal_get_form($form_id) {
  $form_state = array();

  $args = func_get_args();
  // Remove $form_id from the arguments.
  array_shift($args);
  $form_state['args'] = $args;

  return drupal_build_form($form_id, $form_state);
}

/**
 * Build and process a form based on a form id.
 *
 * The form may also be retrieved from the cache if the form was built in a
 * previous page-load. The form is then passed on for processing, validation
 * and submission if there is proper input.
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function with that
 *   name exists, it is called to build the form array. Modules that need to
 *   generate the same form (or very similar forms) using different $form_ids
 *   can implement hook_forms(), which maps different $form_id values to the
 *   proper form constructor function. Examples may be found in node_forms(),
 *   search_forms(), and user_forms().
 * @param &$form_state
 *   An array which stores information about the form. This is passed as a
 *   reference so that the caller can use it to examine what the form changed
 *   when the form submission process is complete.
 *
 *   The following parameters may be set in $form_state to affect how the form
 *   is rendered:
 *   - args: An array of arguments to pass to the form builder.
 *   - input: An array of input that corresponds to $_POST or $_GET, depending
 *     on the 'method' chosen (see below).
 *   - method: The HTTP form method to use for finding the input for this form.
 *     May be 'post' or 'get'. Defaults to 'post'. Note that 'get' method
 *     forms do not use form ids so are always considered to be submitted, which
 *     can have unexpected effects. The 'get' method should only be used on
 *     forms that do not change data, as that is exclusively the domain of post.
 *   - no_redirect: If set to TRUE the form will NOT perform a drupal_goto(),
 *     even if a redirect is set.
 *   - always_process: If TRUE and the method is GET, a form_id is not
 *     necessary. This should only be used on RESTful GET forms that do NOT
 *     write data, as this could lead to security issues. It is useful so that
 *     searches do not need to have a form_id in their query arguments to
 *     trigger the search.
 *   - must_validate: Ordinarily, a form is only validated once but there are
 *     times when a form is resubmitted internally and should be validated
 *     again. Setting this to TRUE will force that to happen. This is most
 *     likely to occur during AHAH or AJAX operations.
 * @return
 *   The rendered form or NULL, depending upon the $form_state flags that were set.
 */
function drupal_build_form($form_id, &$form_state) {
  // Ensure some defaults; if already set they will not be overridden.
  $form_state += form_state_defaults();

  if (!isset($form_state['input'])) {
    $form_state['input'] = $form_state['method'] == 'get' ? $_GET : $_POST;
  }

  $cacheable = FALSE;

  if (isset($_SESSION['batch_form_state'])) {
    // We've been redirected here after a batch processing : the form has
    // already been processed, so we grab the post-process $form_state value
    // and move on to form display. See _batch_finished() function.
    $form_state = $_SESSION['batch_form_state'];
    unset($_SESSION['batch_form_state']);
  }
  else {
    // If the incoming input contains a form_build_id, we'll check the
    // cache for a copy of the form in question. If it's there, we don't
    // have to rebuild the form to proceed. In addition, if there is stored
    // form_state data from a previous step, we'll retrieve it so it can
    // be passed on to the form processing code.
    if (isset($form_state['input']['form_id']) && $form_state['input']['form_id'] == $form_id && !empty($form_state['input']['form_build_id'])) {
      $form = form_get_cache($form_state['input']['form_build_id'], $form_state);
    }

    // If the previous bit of code didn't result in a populated $form
    // object, we're hitting the form for the first time and we need
    // to build it from scratch.
    if (!isset($form)) {
      $form = drupal_retrieve_form($form_id, $form_state);
      $form_build_id = 'form-' . md5(uniqid(mt_rand(), TRUE));
      $form['#build_id'] = $form_build_id;

      // Fix the form method, if it is 'get' in $form_state, but not in $form.
      if ($form_state['method'] == 'get' && !isset($form['#method'])) {
        $form['#method'] = 'get';
      }

      drupal_prepare_form($form_id, $form, $form_state);
      // Store a copy of the unprocessed form for caching and indicate that it
      // is cacheable if #cache will be set.
      $original_form = $form;
      $cacheable = TRUE;
    }

    // Now that we know we have a form, we'll process it (validating,
    // submitting, and handling the results returned by its submission
    // handlers. Submit handlers accumulate data in the form_state by
    // altering the $form_state variable, which is passed into them by
    // reference.
    drupal_process_form($form_id, $form, $form_state);

    if ($cacheable && !empty($form_state['cache']) && empty($form['#no_cache'])) {
      // Caching is done past drupal_process_form so #process callbacks can
      // set #cache.
      form_set_cache($form_build_id, $original_form, $form_state);
    }
  }

  // Most simple, single-step forms will be finished by this point --
  // drupal_process_form() usually redirects to another page (or to
  // a 'fresh' copy of the form) once processing is complete. If one
  // of the form's handlers has set $form_state['redirect'] to FALSE,
  // the form will simply be re-rendered with the values still in its
  // fields.
  //
  // If $form_state['storage'] or $form_state['rebuild'] has been set
  // and the form has been submitted, we know that we're in a complex
  // multi-part process of some sort and the form's workflow is NOT
  // complete. We need to construct a fresh copy of the form, passing
  // in the latest $form_state in addition to any other variables passed
  // into drupal_get_form().

  if ((!empty($form_state['storage']) || $form_state['rebuild']) && $form_state['submitted'] && !form_get_errors()) {
    $form = drupal_rebuild_form($form_id, $form_state);
  }

  // Don't override #theme if someone already set it.
  if (!isset($form['#theme'])) {
    drupal_theme_initialize();
    $registry = theme_get_registry();
    if (isset($registry[$form_id])) {
      $form['#theme'] = $form_id;
    }
  }

  return $form;
}

/**
 * Retrieve default values for the $form_state array.
 */
function form_state_defaults() {
  return array(
    'rebuild' => FALSE,
    'redirect' => NULL,
    'storage' => NULL,
    'submitted' => FALSE,
    'programmed' => FALSE,
    'cache'=> FALSE,
    'method' => 'post',
    'groups' => array(),
  );
}

/**
 * Retrieves a form, caches it and processes it with an empty $_POST.
 *
 * This function clears $_POST and passes the empty $_POST to the form_builder.
 * To preserve some parts from $_POST, pass them in $form_state.
 *
 * If your AHAH callback simulates the pressing of a button, then your AHAH
 * callback will need to do the same as what drupal_get_form would do when the
 * button is pressed: get the form from the cache, run drupal_process_form over
 * it and then if it needs rebuild, run drupal_rebuild_form over it. Then send
 * back a part of the returned form.
 * $form_state['clicked_button']['#array_parents'] will help you to find which
 * part.
 *
 * When getting a form from the cache, the $form_id must be shifted off from
 * $form['#args'], so the resulting array can be given to $form_state['args'].
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form constructor function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param $form_state
 *   A keyed array containing the current state of the form. Most
 *   important is the $form_state['storage'] collection.
 * @param $form_build_id
 *   If the AHAH callback calling this function only alters part of the form,
 *   then pass in the existing form_build_id so we can re-cache with the same
 *   csid.
 * @return
 *   The newly built form.
 */
function drupal_rebuild_form($form_id, &$form_state, $form_build_id = NULL) {
  $form = drupal_retrieve_form($form_id, $form_state);

  if (!isset($form_build_id)) {
    // We need a new build_id for the new version of the form.
    $form_build_id = 'form-' . md5(mt_rand());
  }
  $form['#build_id'] = $form_build_id;
  drupal_prepare_form($form_id, $form, $form_state);

  if (empty($form['#no_cache'])) {
    // We cache the form structure so it can be retrieved later for validation.
    // If $form_state['storage'] is populated, we also cache it so that it can
    // be used to resume complex multi-step processes.
    form_set_cache($form_build_id, $form, $form_state);
  }

  // Clear out all post data, as we don't want the previous step's
  // data to pollute this one and trigger validate/submit handling,
  // then process the form for rendering.
  $form_state['input'] = array();

  // Also clear out all group associations as these might be different
  // when rerendering the form.
  $form_state['groups'] = array();

  // Do not call drupal_process_form(), since it would prevent the rebuilt form
  // to submit.
  $form = form_builder($form_id, $form, $form_state);
  return $form;
}

/**
 * Fetch a form from cache.
 */
function form_get_cache($form_build_id, &$form_state) {
  if ($cached = cache_get('form_' . $form_build_id, 'cache_form')) {
    $form = $cached->data;
    global $user;
    if ((isset($form['#cache_token']) && drupal_valid_token($form['#cache_token'])) || (!isset($form['#cache_token']) && !$user->uid)) {
      if ($cached = cache_get('storage_' . $form_build_id, 'cache_form')) {
        $form_state['storage'] = $cached->data;
      }
      return $form;
    }
  }
}

/**
 * Store a form in the cache
 */
function form_set_cache($form_build_id, $form, $form_state) {
  // 6 hours cache life time for forms should be plenty.
  $expire = 21600;
  global $user;
  if ($user->uid) {
    $form['#cache_token'] = drupal_get_token();
  }
  cache_set('form_' . $form_build_id, $form, 'cache_form', REQUEST_TIME + $expire);
  if (!empty($form_state['storage'])) {
    cache_set('storage_' . $form_build_id, $form_state['storage'], 'cache_form', REQUEST_TIME + $expire);
  }
}

/**
 * Retrieves a form using a form_id, populates it with $form_state['values'],
 * processes it, and returns any validation errors encountered. This
 * function is the programmatic counterpart to drupal_get_form().
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form constructor function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param $form_state
 *   A keyed array containing the current state of the form. Most
 *   important is the $form_state['values'] collection, a tree of data
 *   used to simulate the incoming $_POST information from a user's
 *   form submission.
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_form_submit(), including the unique form constructor function.
 *   For example, the node_edit form requires that a node object be passed
 *   in here when it is called.
 * For example:
 *
 * @code
 * // register a new user
 * $form_state = array();
 * $form_state['values']['name'] = 'robo-user';
 * $form_state['values']['mail'] = 'robouser@example.com';
 * $form_state['values']['pass'] = 'password';
 * $form_state['values']['op'] = t('Create new account');
 * drupal_form_submit('user_register', $form_state);
 *
 * // Create a new node
 * $form_state = array();
 * module_load_include('inc', 'node', 'node.pages');
 * $node = array('type' => 'story');
 * $form_state['values']['title'] = 'My node';
 * $form_state['values']['body'] = 'This is the body text!';
 * $form_state['values']['name'] = 'robo-user';
 * $form_state['values']['op'] = t('Save');
 * drupal_form_submit('story_node_form', $form_state, (object)$node);
 * @endcode
 */
function drupal_form_submit($form_id, &$form_state) {
  if (!isset($form_state['args'])) {
    $args = func_get_args();
    array_shift($args);
    array_shift($args);
    $form_state['args'] = $args;
  }

  $form = drupal_retrieve_form($form_id, $form_state);
  $form_state['input'] = $form_state['values'];
  $form_state['programmed'] = TRUE;
  // Programmed forms are always submitted.
  $form_state['submitted'] = TRUE;
  // Merge in default values.
  $form_state += form_state_defaults();

  drupal_prepare_form($form_id, $form, $form_state);
  drupal_process_form($form_id, $form, $form_state);
}

/**
 * Retrieves the structured array that defines a given form.
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form constructor function.
 * @param $form_state
 *   A keyed array containing the current state of the form.
 * @param ...
 *   Any additional arguments needed by the unique form constructor
 *   function. Generally, these are any arguments passed into the
 *   drupal_get_form() or drupal_form_submit() functions after the first
 *   argument. If a module implements hook_forms(), it can examine
 *   these additional arguments and conditionally return different
 *   builder functions as well.
 */
function drupal_retrieve_form($form_id, &$form_state) {
  $forms = &drupal_static(__FUNCTION__);

  // We save two copies of the incoming arguments: one for modules to use
  // when mapping form ids to constructor functions, and another to pass to
  // the constructor function itself.
  $args = $form_state['args'];

  // We first check to see if there's a function named after the $form_id.
  // If there is, we simply pass the arguments on to it to get the form.
  if (!drupal_function_exists($form_id)) {
    // In cases where many form_ids need to share a central constructor function,
    // such as the node editing form, modules can implement hook_forms(). It
    // maps one or more form_ids to the correct constructor functions.
    //
    // We cache the results of that hook to save time, but that only works
    // for modules that know all their form_ids in advance. (A module that
    // adds a small 'rate this comment' form to each comment in a list
    // would need a unique form_id for each one, for example.)
    //
    // So, we call the hook if $forms isn't yet populated, OR if it doesn't
    // yet have an entry for the requested form_id.
    if (!isset($forms) || !isset($forms[$form_id])) {
      $forms = module_invoke_all('forms', $form_id, $args);
    }
    $form_definition = $forms[$form_id];
    if (isset($form_definition['callback arguments'])) {
      $args = array_merge($form_definition['callback arguments'], $args);
    }
    if (isset($form_definition['callback'])) {
      $callback = $form_definition['callback'];
      drupal_function_exists($callback);
    }
  }

  $args = array_merge(array(&$form_state), $args);

  // If $callback was returned by a hook_forms() implementation, call it.
  // Otherwise, call the function named after the form id.
  $form = call_user_func_array(isset($callback) ? $callback : $form_id, $args);
  $form['#form_id'] = $form_id;
  $form['#args'] = $form_state['args'];
  return $form;
}

/**
 * This function is the heart of form API. The form gets built, validated and in
 * appropriate cases, submitted.
 *
 * @param $form_id
 *   The unique string identifying the current form.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. This
 *   includes the current persistent storage data for the form, and
 *   any data passed along by earlier steps when displaying a
 *   multi-step form. Additional information, like the sanitized $_POST
 *   data, is also accumulated here.
 */
function drupal_process_form($form_id, &$form, &$form_state) {
  $form_state['values'] = array();

  // With $_GET, these forms are always submitted if requested.
  if ($form_state['method'] == 'get' && !empty($form_state['always_process'])) {
    if (!isset($form_state['input']['form_build_id'])) {
      $form_state['input']['form_build_id'] = $form['#build_id'];
    }
    if (!isset($form_state['input']['form_id'])) {
      $form_state['input']['form_id'] = $form_id;
    }
    if (!isset($form_state['input']['form_token']) && isset($form['#token'])) {
      $form_state['input']['form_token'] = drupal_get_token($form['#token']);
    }
  }

  // Build the form.
  $form = form_builder($form_id, $form, $form_state);

  // Only process the input if we have a correct form submission.
  if ($form_state['process_input']) {
    drupal_validate_form($form_id, $form, $form_state);

    // form_clean_id() maintains a cache of element IDs it has seen,
    // so it can prevent duplicates. We want to be sure we reset that
    // cache when a form is processed, so scenarios that result in
    // the form being built behind the scenes and again for the
    // browser don't increment all the element IDs needlessly.
    drupal_static_reset('form_clean_id');

    if ($form_state['submitted'] && !form_get_errors() && !$form_state['rebuild']) {
      // Execute form submit handlers.
      form_execute_handlers('submit', $form, $form_state);

      // We'll clear out the cached copies of the form and its stored data
      // here, as we've finished with them. The in-memory copies are still
      // here, though.
      if (variable_get('cache', CACHE_DISABLED) == CACHE_DISABLED && !empty($form_state['values']['form_build_id'])) {
        cache_clear_all('form_' . $form_state['values']['form_build_id'], 'cache_form');
        cache_clear_all('storage_' . $form_state['values']['form_build_id'], 'cache_form');
      }

      // If batches were set in the submit handlers, we process them now,
      // possibly ending execution. We make sure we do not react to the batch
      // that is already being processed (if a batch operation performs a
      // drupal_form_submit).
      if ($batch =& batch_get() && !isset($batch['current_set'])) {
        // The batch uses its own copies of $form and $form_state for
        // late execution of submit handlers and post-batch redirection.
        $batch['form'] = $form;
        $batch['form_state'] = $form_state;
        $batch['progressive'] = !$form_state['programmed'];
        batch_process();
        // Execution continues only for programmatic forms.
        // For 'regular' forms, we get redirected to the batch processing
        // page. Form redirection will be handled in _batch_finished(),
        // after the batch is processed.
      }

      // Set a flag to indicate the the form has been processed and executed.
      $form_state['executed'] = TRUE;

      // The form is executed. By default, we're finished now and redirect to a
      // new destination page. The path of the destination page can be set in
      // $form['#redirect'] or $form_state['redirect']. If neither of the two is
      // set, the user is redirect to the current page, which means a fresh,
      // unpopulated copy of the form.
      // Redirection is skipped, though, if
      // - the form was called by drupal_form_submit(),
      // - the form has to be rebuilt because either $form_state['rebuild'] was
      //   set to TRUE or $form_state['storage'] was populated by a submit handler.
      // - $form_state['no_redirect'] is set to TRUE,
      // - $form_state['redirect'] or $form['#redirect'] is set to FALSE.
      if (!$form_state['programmed'] && empty($form_state['rebuild']) && empty($form_state['storage']) && empty($form_state['no_redirect'])) {
        drupal_redirect_form($form, $form_state['redirect']);
      }
    }
  }
}

/**
 * Prepares a structured form array by adding required elements,
 * executing any hook_form_alter functions, and optionally inserting
 * a validation token to prevent tampering.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. Passed
 *   in here so that hook_form_alter() calls can use it, as well.
 */
function drupal_prepare_form($form_id, &$form, &$form_state) {
  global $user;

  $form['#type'] = 'form';
  $form_state['programmed'] = isset($form_state['programmed']) ? $form_state['programmed'] : FALSE;

  if (isset($form['#build_id'])) {
    $form['form_build_id'] = array(
      '#type' => 'hidden',
      '#value' => $form['#build_id'],
      '#id' => $form['#build_id'],
      '#name' => 'form_build_id',
    );
  }

  // Add a token, based on either #token or form_id, to any form displayed to
  // authenticated users. This ensures that any submitted form was actually
  // requested previously by the user and protects against cross site request
  // forgeries.
  if (isset($form['#token'])) {
    if ($form['#token'] === FALSE || $user->uid == 0 || $form_state['programmed']) {
      unset($form['#token']);
    }
    else {
      $form['form_token'] = array('#type' => 'token', '#default_value' => drupal_get_token($form['#token']));
    }
  }
  elseif (isset($user->uid) && $user->uid && !$form_state['programmed']) {
    $form['#token'] = $form_id;
    $form['form_token'] = array(
      '#id' => form_clean_id('edit-' . $form_id . '-form-token'),
      '#type' => 'token',
      '#default_value' => drupal_get_token($form['#token']),
    );
  }

  if (isset($form_id)) {
    $form['form_id'] = array(
      '#type' => 'hidden',
      '#value' => $form_id,
      '#id' => form_clean_id("edit-$form_id"),
    );
  }
  if (!isset($form['#id'])) {
    $form['#id'] = form_clean_id($form_id);
  }

  $form += element_info('form');
  $form += array('#tree' => FALSE, '#parents' => array());

  if (!isset($form['#validate'])) {
    if (drupal_function_exists($form_id . '_validate')) {
      $form['#validate'] = array($form_id . '_validate');
    }
  }

  if (!isset($form['#submit'])) {
    if (drupal_function_exists($form_id . '_submit')) {
      // We set submit here so that it can be altered.
      $form['#submit'] = array($form_id . '_submit');
    }
  }

  // Normally, we would call drupal_alter($form_id, $form, $form_state).
  // However, drupal_alter() normally supports just one byref parameter. Using
  // the __drupal_alter_by_ref key, we can store any additional parameters
  // that need to be altered, and they'll be split out into additional params
  // for the hook_form_alter() implementations.
  // @todo: Remove this in Drupal 7.
  $data = &$form;
  $data['__drupal_alter_by_ref'] = array(&$form_state);
  drupal_alter('form_' . $form_id, $data);

  // __drupal_alter_by_ref is unset in the drupal_alter() function, we need
  // to repopulate it to ensure both calls get the data.
  $data['__drupal_alter_by_ref'] = array(&$form_state);
  drupal_alter('form', $data, $form_id);
}


/**
 * Validates user-submitted form data from the $form_state using
 * the validate functions defined in a structured form array.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. The current
 *   user-submitted data is stored in $form_state['values'], though
 *   form validation functions are passed an explicit copy of the
 *   values for the sake of simplicity. Validation handlers can also
 *   $form_state to pass information on to submit handlers. For example:
 *     $form_state['data_for_submision'] = $data;
 *   This technique is useful when validation requires file parsing,
 *   web service requests, or other expensive requests that should
 *   not be repeated in the submission step.
 */
function drupal_validate_form($form_id, $form, &$form_state) {
  $validated_forms = &drupal_static(__FUNCTION__, array());

  if (isset($validated_forms[$form_id]) && empty($form_state['must_validate'])) {
    return;
  }

  // If the session token was set by drupal_prepare_form(), ensure that it
  // matches the current user's session.
  if (isset($form['#token'])) {
    if (!drupal_valid_token($form_state['values']['form_token'], $form['#token'])) {
      // Setting this error will cause the form to fail validation.
      form_set_error('form_token', t('Validation error, please try again. If this error persists, please contact the site administrator.'));
    }
  }

  _form_validate($form, $form_state, $form_id);
  $validated_forms[$form_id] = TRUE;
}

/**
 * Redirect the user to a URL after a form has been processed.
 *
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $redirect
 *   An optional value containing the destination path to redirect
 *   to if none is specified by the form.
 */
function drupal_redirect_form($form, $redirect = NULL) {
  $goto = NULL;
  if (isset($redirect)) {
    $goto = $redirect;
  }
  if ($goto !== FALSE && isset($form['#redirect'])) {
    $goto = $form['#redirect'];
  }
  if (!isset($goto) || ($goto !== FALSE)) {
    if (isset($goto)) {
      if (is_array($goto)) {
        call_user_func_array('drupal_goto', $goto);
      }
      else {
        // This function can be called from the installer, which guarantees
        // that $redirect will always be a string, so catch that case here
        // and use the appropriate redirect function.
        $function = drupal_installation_attempted() ? 'install_goto' : 'drupal_goto';
        $function($goto);
      }
    }
    drupal_goto($_GET['q']);
  }
}

/**
 * Performs validation on form elements. First ensures required fields are
 * completed, #maxlength is not exceeded, and selected options were in the
 * list of options given to the user. Then calls user-defined validators.
 *
 * @param $elements
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. The current
 *   user-submitted data is stored in $form_state['values'], though
 *   form validation functions are passed an explicit copy of the
 *   values for the sake of simplicity. Validation handlers can also
 *   $form_state to pass information on to submit handlers. For example:
 *     $form_state['data_for_submision'] = $data;
 *   This technique is useful when validation requires file parsing,
 *   web service requests, or other expensive requests that should
 *   not be repeated in the submission step.
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 */
function _form_validate($elements, &$form_state, $form_id = NULL) {
  // Also used in the installer, pre-database setup.
  $t = get_t();

  // Recurse through all children.
  foreach (element_children($elements) as $key) {
    if (isset($elements[$key]) && $elements[$key]) {
      _form_validate($elements[$key], $form_state);
    }
  }
  // Validate the current input.
  if (!isset($elements['#validated']) || !$elements['#validated']) {
    if (isset($elements['#needs_validation'])) {
      // Make sure a value is passed when the field is required.
      // A simple call to empty() will not cut it here as some fields, like
      // checkboxes, can return a valid value of '0'. Instead, check the
      // length if it's a string, and the item count if it's an array.
      if ($elements['#required'] && (!count($elements['#value']) || (is_string($elements['#value']) && strlen(trim($elements['#value'])) == 0))) {
        form_error($elements, $t('!name field is required.', array('!name' => $elements['#title'])));
      }

      // Verify that the value is not longer than #maxlength.
      if (isset($elements['#maxlength']) && drupal_strlen($elements['#value']) > $elements['#maxlength']) {
        form_error($elements, $t('!name cannot be longer than %max characters but is currently %length characters long.', array('!name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title'], '%max' => $elements['#maxlength'], '%length' => drupal_strlen($elements['#value']))));
      }

      if (isset($elements['#options']) && isset($elements['#value'])) {
        if ($elements['#type'] == 'select') {
          $options = form_options_flatten($elements['#options']);
        }
        else {
          $options = $elements['#options'];
        }
        if (is_array($elements['#value'])) {
          $value = $elements['#type'] == 'checkboxes' ? array_keys(array_filter($elements['#value'])) : $elements['#value'];
          foreach ($value as $v) {
            if (!isset($options[$v])) {
              form_error($elements, $t('An illegal choice has been detected. Please contact the site administrator.'));
              watchdog('form', 'Illegal choice %choice in !name element.', array('%choice' => $v, '!name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title']), WATCHDOG_ERROR);
            }
          }
        }
        elseif (!isset($options[$elements['#value']])) {
          form_error($elements, $t('An illegal choice has been detected. Please contact the site administrator.'));
          watchdog('form', 'Illegal choice %choice in %name element.', array('%choice' => $elements['#value'], '%name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title']), WATCHDOG_ERROR);
        }
      }
    }

    // Call user-defined form level validators.
    if (isset($form_id)) {
      form_execute_handlers('validate', $elements, $form_state);
    }
    // Call any element-specific validators. These must act on the element
    // #value data.
    elseif (isset($elements['#element_validate'])) {
      foreach ($elements['#element_validate'] as $function) {
        if (drupal_function_exists($function))  {
          $function($elements, $form_state, $form_state['complete form']);
        }
      }
    }
    $elements['#validated'] = TRUE;
  }
}

/**
 * A helper function used to execute custom validation and submission
 * handlers for a given form. Button-specific handlers are checked
 * first. If none exist, the function falls back to form-level handlers.
 *
 * @param $type
 *   The type of handler to execute. 'validate' or 'submit' are the
 *   defaults used by Form API.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. If the user
 *   submitted the form by clicking a button with custom handler functions
 *   defined, those handlers will be stored here.
 */
function form_execute_handlers($type, &$form, &$form_state) {
  $return = FALSE;
  if (isset($form_state[$type . '_handlers'])) {
    $handlers = $form_state[$type . '_handlers'];
  }
  elseif (isset($form['#' . $type])) {
    $handlers = $form['#' . $type];
  }
  else {
    $handlers = array();
  }

  foreach ($handlers as $function) {
    if (drupal_function_exists($function))  {
      // Check to see if a previous _submit handler has set a batch, but
      // make sure we do not react to a batch that is already being processed
      // (for instance if a batch operation performs a drupal_form_submit()).
      if ($type == 'submit' && ($batch =& batch_get()) && !isset($batch['current_set'])) {
        // Some previous _submit handler has set a batch. We store the call
        // in a special 'control' batch set, for execution at the correct
        // time during the batch processing workflow.
        $batch['sets'][] = array('form_submit' => $function);
      }
      else {
        $function($form, $form_state);
      }
      $return = TRUE;
    }
  }
  return $return;
}

/**
 * File an error against a form element.
 *
 * @param $name
 *   The name of the form element. If the #parents property of your form
 *   element is array('foo', 'bar', 'baz') then you may set an error on 'foo'
 *   or 'foo][bar][baz'. Setting an error on 'foo' sets an error for every
 *   element where the #parents array starts with 'foo'.
 * @param $message
 *   The error message to present to the user.
 * @param $reset
 *   Reset the form errors static cache.
 * @return
 *   Never use the return value of this function, use form_get_errors and
 *   form_get_error instead.
 */
function form_set_error($name = NULL, $message = '') {
  $form = &drupal_static(__FUNCTION__, array());
  if (isset($name) && !isset($form[$name])) {
    $form[$name] = $message;
    if ($message) {
      drupal_set_message($message, 'error');
    }
  }
  return $form;
}

/**
 * Clear all errors against all form elements made by form_set_error().
 */
function form_clear_error() {
  drupal_static_reset('form_set_error');
}

/**
 * Return an associative array of all errors.
 */
function form_get_errors() {
  $form = form_set_error();
  if (!empty($form)) {
    return $form;
  }
}

/**
 * Return the error message filed against the form with the specified name.
 */
function form_get_error($element) {
  $form = form_set_error();
  $key = $element['#parents'][0];
  if (isset($form[$key])) {
    return $form[$key];
  }
  $key = implode('][', $element['#parents']);
  if (isset($form[$key])) {
    return $form[$key];
  }
}

/**
 * Flag an element as having an error.
 */
function form_error(&$element, $message = '') {
  form_set_error(implode('][', $element['#parents']), $message);
}

/**
 * Walk through the structured form array, adding any required
 * properties to each element and mapping the incoming input
 * data to the proper elements. Also, execute any #process handlers
 * attached to a specific element.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $element
 *   An associative array containing the structure of the current element.
 * @param $form_state
 *   A keyed array containing the current state of the form. In this
 *   context, it is used to accumulate information about which button
 *   was clicked when the form was submitted, as well as the sanitized
 *   $_POST data.
 */
function form_builder($form_id, $element, &$form_state) {
  // Initialize as unprocessed.
  $element['#processed'] = FALSE;

  // Use element defaults.
  if ((!empty($element['#type'])) && ($info = element_info($element['#type']))) {
    // Overlay $info onto $element, retaining preexisting keys in $element.
    $element += $info;
    $element['#defaults_loaded'] = TRUE;
  }

  // Special handling if we're on the top level form element.
  if (isset($element['#type']) && $element['#type'] == 'form') {
    // Store a complete copy of the form in form_state prior to building the form.
    $form_state['complete form'] = $element;
    // Set a flag if we have a correct form submission. This is always TRUE for
    // programmed forms coming from drupal_form_submit(), or if the form_id coming
    // from the POST data is set and matches the current form_id.
    if ($form_state['programmed'] || (!empty($form_state['input']) && (isset($form_state['input']['form_id']) && ($form_state['input']['form_id'] == $form_id)))) {
      $form_state['process_input'] = TRUE;
    }
    else {
      $form_state['process_input'] = FALSE;
    }
  }

  if (!isset($element['#id'])) {
    $element['#id'] = form_clean_id('edit-' . implode('-', $element['#parents']));
  }
  // Handle input elements.
  if (!empty($element['#input'])) {
    _form_builder_handle_input_element($form_id, $element, $form_state);
  }
  // Allow for elements to expand to multiple elements, e.g., radios,
  // checkboxes and files.
  if (isset($element['#process']) && !$element['#processed']) {
    foreach ($element['#process'] as $process) {
      if (drupal_function_exists($process)) {
        $element = $process($element, $form_state, $form_state['complete form']);
      }
    }
    $element['#processed'] = TRUE;
  }

  // We start off assuming all form elements are in the correct order.
  $element['#sorted'] = TRUE;

  // Recurse through all child elements.
  $count = 0;
  foreach (element_children($element) as $key) {
    // Don't squash an existing tree value.
    if (!isset($element[$key]['#tree'])) {
      $element[$key]['#tree'] = $element['#tree'];
    }

    // Deny access to child elements if parent is denied.
    if (isset($element['#access']) && !$element['#access']) {
      $element[$key]['#access'] = FALSE;
    }

    // Don't squash existing parents value.
    if (!isset($element[$key]['#parents'])) {
      // Check to see if a tree of child elements is present. If so,
      // continue down the tree if required.
      $element[$key]['#parents'] = $element[$key]['#tree'] && $element['#tree'] ? array_merge($element['#parents'], array($key)) : array($key);
      $array_parents = isset($element['#array_parents']) ? $element['#array_parents'] : array();
      $array_parents[] = $key;
      $element[$key]['#array_parents'] = $array_parents;
    }

    // Assign a decimal placeholder weight to preserve original array order.
    if (!isset($element[$key]['#weight'])) {
      $element[$key]['#weight'] = $count/1000;
    }
    else {
      // If one of the child elements has a weight then we will need to sort
      // later.
      unset($element['#sorted']);
    }
    $element[$key] = form_builder($form_id, $element[$key], $form_state);
    $count++;
  }

  // The #after_build flag allows any piece of a form to be altered
  // after normal input parsing has been completed.
  if (isset($element['#after_build']) && !isset($element['#after_build_done'])) {
    foreach ($element['#after_build'] as $function) {
      $element = $function($element, $form_state);
      $element['#after_build_done'] = TRUE;
    }
  }

  // Now that we've processed everything, we can go back to handle the funky
  // Internet Explorer button-click scenario.
  _form_builder_ie_cleanup($element, $form_state);

  // We should keep the buttons array until the IE clean up function
  // has recognized the submit button so the form has been marked
  // as submitted. If we already know which button was submitted,
  // we don't need the array.
  if (!empty($form_state['submitted'])) {
    unset($form_state['buttons']);
  }

  // If some callback set #cache, we need to flip a flag so later it
  // can be found.
  if (!empty($element['#cache'])) {
    $form_state['cache'] = $element['#cache'];
  }

  // If there is a file element, we need to flip a flag so later the
  // form encoding can be set.
  if (isset($element['#type']) && $element['#type'] == 'file') {
    $form_state['has_file_element'] = TRUE;
  }

  if (isset($element['#type']) && $element['#type'] == 'form') {
    // We are on the top form.
    // If there is a file element, we set the form encoding.
    if (isset($form_state['has_file_element'])) {
      $element['#attributes']['enctype'] = 'multipart/form-data';
    }
    // Update the copy of the complete form for usage in validation handlers.
    $form_state['complete form'] = $element;
  }
  return $element;
}

/**
 * Populate the #value and #name properties of input elements so they
 * can be processed and rendered.
 */
function _form_builder_handle_input_element($form_id, &$element, &$form_state) {
  if (!isset($element['#name'])) {
    $name = array_shift($element['#parents']);
    $element['#name'] = $name;
    if ($element['#type'] == 'file') {
      // To make it easier to handle $_FILES in file.inc, we place all
      // file fields in the 'files' array. Also, we do not support
      // nested file names.
      $element['#name'] = 'files[' . $element['#name'] . ']';
    }
    elseif (count($element['#parents'])) {
      $element['#name'] .= '[' . implode('][', $element['#parents']) . ']';
    }
    array_unshift($element['#parents'], $name);
  }

  if (!empty($element['#disabled'])) {
    $element['#attributes']['disabled'] = 'disabled';
  }

  // Set the element's #value property.
  if (!isset($element['#value']) && !array_key_exists('#value', $element)) {
    $value_callback = !empty($element['#value_callback']) ? $element['#value_callback'] : 'form_type_' . $element['#type'] . '_value';

    if ($form_state['programmed'] || ($form_state['process_input'] && (!isset($element['#access']) || $element['#access']))) {
      $input = $form_state['input'];
      foreach ($element['#parents'] as $parent) {
        $input = isset($input[$parent]) ? $input[$parent] : NULL;
      }
      // If we have input for the current element, assign it to the #value property.
      if (!$form_state['programmed'] || isset($input)) {
        // Call #type_value to set the form value;
        if (drupal_function_exists($value_callback)) {
          $element['#value'] = $value_callback($element, $input, $form_state);
        }
        if (!isset($element['#value']) && isset($input)) {
          $element['#value'] = $input;
        }
      }
      // Mark all posted values for validation.
      if (isset($element['#value']) || (!empty($element['#required']))) {
        $element['#needs_validation'] = TRUE;
      }
    }
    // Load defaults.
    if (!isset($element['#value'])) {
      // Call #type_value without a second argument to request default_value handling.
      if (drupal_function_exists($value_callback)) {
        $element['#value'] = $value_callback($element, FALSE, $form_state);
      }
      // Final catch. If we haven't set a value yet, use the explicit default value.
      // Avoid image buttons (which come with garbage value), so we only get value
      // for the button actually clicked.
      if (!isset($element['#value']) && empty($element['#has_garbage_value'])) {
        $element['#value'] = isset($element['#default_value']) ? $element['#default_value'] : '';
      }
    }
  }

  // Determine which button (if any) was clicked to submit the form.
  // We compare the incoming values with the buttons defined in the form,
  // and flag the one that matches. We have to do some funky tricks to
  // deal with Internet Explorer's handling of single-button forms, though.
  if (!empty($form_state['input']) && isset($element['#executes_submit_callback'])) {
    // First, accumulate a collection of buttons, divided into two bins:
    // those that execute full submit callbacks and those that only validate.
    $button_type = $element['#executes_submit_callback'] ? 'submit' : 'button';
    $form_state['buttons'][$button_type][] = $element;

    if (_form_button_was_clicked($element, $form_state)) {
      $form_state['submitted'] = $form_state['submitted'] || $element['#executes_submit_callback'];

      // In most cases, we want to use form_set_value() to manipulate
      // the global variables. In this special case, we want to make sure that
      // the value of this element is listed in $form_variables under 'op'.
      $form_state['values'][$element['#name']] = $element['#value'];
      $form_state['clicked_button'] = $element;

      if (isset($element['#validate'])) {
        $form_state['validate_handlers'] = $element['#validate'];
      }
      if (isset($element['#submit'])) {
        $form_state['submit_handlers'] = $element['#submit'];
      }
    }
  }
  form_set_value($element, $element['#value'], $form_state);
}

/**
 * Helper function to handle the sometimes-convoluted logic of button
 * click detection.
 *
 * In Internet Explorer, if ONLY one submit button is present, AND the
 * enter key is used to submit the form, no form value is sent for it
 * and we'll never detect a match. That special case is handled by
 * _form_builder_ie_cleanup().
 */
function _form_button_was_clicked($form, &$form_state) {
  // First detect normal 'vanilla' button clicks. Traditionally, all
  // standard buttons on a form share the same name (usually 'op'),
  // and the specific return value is used to determine which was
  // clicked. This ONLY works as long as $form['#name'] puts the
  // value at the top level of the tree of $_POST data.
  if (isset($form_state['input'][$form['#name']]) && $form_state['input'][$form['#name']] == $form['#value']) {
    return TRUE;
  }
  // When image buttons are clicked, browsers do NOT pass the form element
  // value in $_POST. Instead they pass an integer representing the
  // coordinates of the click on the button image. This means that image
  // buttons MUST have unique $form['#name'] values, but the details of
  // their $_POST data should be ignored.
  elseif (!empty($form['#has_garbage_value']) && isset($form['#value']) && $form['#value'] !== '') {
    return TRUE;
  }
  return FALSE;
}

/**
 * In IE, if only one submit button is present, AND the enter key is
 * used to submit the form, no form value is sent for it and our normal
 * button detection code will never detect a match. We call this
 * function after all other button-detection is complete to check
 * for the proper conditions, and treat the single button on the form
 * as 'clicked' if they are met.
 */
function _form_builder_ie_cleanup($form, &$form_state) {
  // Quick check to make sure we're always looking at the full form
  // and not a sub-element.
  if (!empty($form['#type']) && $form['#type'] == 'form') {
    // If we haven't recognized a submission yet, and there's a single
    // submit button, we know that we've hit the right conditions. Grab
    // the first one and treat it as the clicked button.
    if (empty($form_state['submitted']) && !empty($form_state['buttons']['submit']) && empty($form_state['buttons']['button'])) {
      $button = $form_state['buttons']['submit'][0];

      // Set up all the $form_state information that would have been
      // populated had the button been recognized earlier.
      $form_state['submitted'] = TRUE;
      $form_state['submit_handlers'] = empty($button['#submit']) ? NULL : $button['#submit'];
      $form_state['validate_handlers'] = empty($button['#validate']) ? NULL : $button['#validate'];
      $form_state['values'][$button['#name']] = $button['#value'];
      $form_state['clicked_button'] = $button;
    }
  }
}

/**
 * Helper function to determine the value for an image button form element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $input
 *   The incoming input to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @param $form_state
 *   A keyed array containing the current state of the form.
 * @return
 *   The data that will appear in the $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_image_button_value($form, $input, $form_state) {
  if ($input !== FALSE) {
    if (!empty($input)) {
      // If we're dealing with Mozilla or Opera, we're lucky. It will
      // return a proper value, and we can get on with things.
      return $form['#return_value'];
    }
    else {
      // Unfortunately, in IE we never get back a proper value for THIS
      // form element. Instead, we get back two split values: one for the
      // X and one for the Y coordinates on which the user clicked the
      // button. We'll find this element in the #post data, and search
      // in the same spot for its name, with '_x'.
      $input = $form_state['input'];
      foreach (explode('[', $form['#name']) as $element_name) {
        // chop off the ] that may exist.
        if (substr($element_name, -1) == ']') {
          $element_name = substr($element_name, 0, -1);
        }

        if (!isset($input[$element_name])) {
          if (isset($input[$element_name . '_x'])) {
            return $form['#return_value'];
          }
          return NULL;
        }
        $input = $input[$element_name];
      }
      return $form['#return_value'];
    }
  }
}

/**
 * Helper function to determine the value for a checkbox form element.
 *
 * @param $form
 *   The form element whose value is being populated.
*  @param $input
 *   The incoming input to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $element_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_checkbox_value($element, $input = FALSE) {
  if ($input !== FALSE) {
    if (empty($element['#disabled'])) {
      return !empty($input) ? $element['#return_value'] : 0;
    }
    else {
      return $element['#default_value'];
    }
  }
}

/**
 * Helper function to determine the value for a checkboxes form element.
 *
 * @param $element
 *   The form element whose value is being populated.
 * @param $input
 *   The incoming input to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $element_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_checkboxes_value($element, $input = FALSE) {
  if ($input === FALSE) {
    $value = array();
    $element += array('#default_value' => array());
    foreach ($element['#default_value'] as $key) {
      $value[$key] = 1;
    }
    return $value;
  }
  elseif (!isset($input)) {
    return array();
  }
}

/**
 * Helper function to determine the value for a password_confirm form
 * element.
 *
 * @param $element
 *   The form element whose value is being populated.
 * @param $input
 *   The incoming input to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $element_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_password_confirm_value($element, $input = FALSE) {
  if ($input === FALSE) {
    $element += array('#default_value' => array());
    return $element['#default_value'] + array('pass1' => '', 'pass2' => '');
  }
}

/**
 * Helper function to determine the value for a select form element.
 *
 * @param $element
 *   The form element whose value is being populated.
 * @param $input
 *   The incoming input to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $element_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_select_value($element, $input = FALSE) {
  if ($input !== FALSE) {
    if (isset($element['#multiple']) && $element['#multiple']) {
      return (is_array($input)) ? drupal_map_assoc($input) : array();
    }
    else {
      return $input;
    }
  }
}

/**
 * Helper function to determine the value for a textfield form element.
 *
 * @param $element
 *   The form element whose value is being populated.
 * @param $input
 *   The incoming input to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $element_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_textfield_value($element, $input = FALSE) {
  if ($input !== FALSE) {
    // Equate $input to the form value to ensure it's marked for
    // validation.
    return str_replace(array("\r", "\n"), '', $input);
  }
}

/**
 * Helper function to determine the value for form's token value.
 *
 * @param $element
 *   The form element whose value is being populated.
 * @param $input
 *   The incoming input to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $element_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_token_value($element, $input = FALSE) {
  if ($input !== FALSE) {
    return (string)$input;
  }
}

/**
 * Change submitted form values during the form processing cycle.
 *
 * Use this function to change the submitted value of a form item in the
 * validation phase so that it persists in $form_state through to the
 * submission handlers in the submission phase.
 *
 * Since $form_state['values'] can either be a flat array of values, or a tree
 * of nested values, some care must be taken when using this function.
 * Specifically, $element['#parents'] is an array that describes the branch of
 * the tree whose value should be updated. For example, if we wanted to update
 * $form_state['values']['one']['two'] to 'new value', we'd pass in
 * $element['#parents'] = array('one', 'two') and $value = 'new value'.
 *
 * @param $element
 *   The form item that should have its value updated. Keys used: #parents,
 *   #value. In most cases you can just pass in the right element from the $form
 *   array.
 * @param $value
 *   The new value for the form item.
 * @param $form_state
 *   The array where the value change should be recorded.
 */
function form_set_value($element, $value, &$form_state) {
  _form_set_value($form_state['values'], $element, $element['#parents'], $value);
}

/**
 * Helper function for form_set_value().
 *
 * We iterate over $parents and create nested arrays for them
 * in $form_state['values'] if needed. Then we insert the value into
 * the right array.
 */
function _form_set_value(&$form_values, $element, $parents, $value) {
  $parent = array_shift($parents);
  if (empty($parents)) {
    $form_values[$parent] = $value;
  }
  else {
    if (!isset($form_values[$parent])) {
      $form_values[$parent] = array();
    }
    _form_set_value($form_values[$parent], $element, $parents, $value);
  }
}

function form_options_flatten($array, $reset = TRUE) {
  // $reset has been ignored here as the function recurses, retaining
  // its value while recursing and resetting itself when called.
  static $return;

  if ($reset) {
    $return = array();
  }

  foreach ($array as $key => $value) {
    if (is_object($value)) {
      form_options_flatten($value->option, FALSE);
    }
    elseif (is_array($value)) {
      form_options_flatten($value, FALSE);
    }
    else {
      $return[$key] = 1;
    }
  }

  return $return;
}

/**
 * Format a dropdown menu or scrolling selection box.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, options, description, extra, multiple, required
 * @return
 *   A themed HTML string representing the form element.
 *
 * @ingroup themeable
 *
 * It is possible to group options together; to do this, change the format of
 * $options to an associative array in which the keys are group labels, and the
 * values are associative arrays in the normal $options format.
 */
function theme_select($element) {
  $select = '';
  $size = $element['#size'] ? ' size="' . $element['#size'] . '"' : '';
  _form_set_class($element, array('form-select'));
  $multiple = $element['#multiple'];
  return '<select name="' . $element['#name'] . '' . ($multiple ? '[]' : '') . '"' . ($multiple ? ' multiple="multiple" ' : '') . drupal_attributes($element['#attributes']) . ' id="' . $element['#id'] . '" ' . $size . '>' . form_select_options($element) . '</select>';
}

function form_select_options($element, $choices = NULL) {
  if (!isset($choices)) {
    $choices = $element['#options'];
  }
  // array_key_exists() accommodates the rare event where $element['#value'] is NULL.
  // isset() fails in this situation.
  $value_valid = isset($element['#value']) || array_key_exists('#value', $element);
  $value_is_array = is_array($element['#value']);
  $options = '';
  foreach ($choices as $key => $choice) {
    if (is_array($choice)) {
      $options .= '<optgroup label="' . $key . '">';
      $options .= form_select_options($element, $choice);
      $options .= '</optgroup>';
    }
    elseif (is_object($choice)) {
      $options .= form_select_options($element, $choice->option);
    }
    else {
      $key = (string)$key;
      if ($value_valid && (!$value_is_array && (string)$element['#value'] === $key || ($value_is_array && in_array($key, $element['#value'])))) {
        $selected = ' selected="selected"';
      }
      else {
        $selected = '';
      }
      $options .= '<option value="' . check_plain($key) . '"' . $selected . '>' . check_plain($choice) . '</option>';
    }
  }
  return $options;
}

/**
 * Traverses a select element's #option array looking for any values
 * that hold the given key. Returns an array of indexes that match.
 *
 * This function is useful if you need to modify the options that are
 * already in a form element; for example, to remove choices which are
 * not valid because of additional filters imposed by another module.
 * One example might be altering the choices in a taxonomy selector.
 * To correctly handle the case of a multiple hierarchy taxonomy,
 * #options arrays can now hold an array of objects, instead of a
 * direct mapping of keys to labels, so that multiple choices in the
 * selector can have the same key (and label). This makes it difficult
 * to manipulate directly, which is why this helper function exists.
 *
 * This function does not support optgroups (when the elements of the
 * #options array are themselves arrays), and will return FALSE if
 * arrays are found. The caller must either flatten/restore or
 * manually do their manipulations in this case, since returning the
 * index is not sufficient, and supporting this would make the
 * "helper" too complicated and cumbersome to be of any help.
 *
 * As usual with functions that can return array() or FALSE, do not
 * forget to use === and !== if needed.
 *
 * @param $element
 *   The select element to search.
 * @param $key
 *   The key to look for.
 * @return
 *   An array of indexes that match the given $key. Array will be
 *   empty if no elements were found. FALSE if optgroups were found.
 */
function form_get_options($element, $key) {
  $keys = array();
  foreach ($element['#options'] as $index => $choice) {
    if (is_array($choice)) {
      return FALSE;
    }
    elseif (is_object($choice)) {
      if (isset($choice->option[$key])) {
        $keys[] = $index;
      }
    }
    elseif ($index == $key) {
      $keys[] = $index;
    }
  }
  return $keys;
}

/**
 * Formats a group of items as an HTML fieldset element.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: #attributes, #children, #collapsed, #collapsible,
 *   #description, #id, #title, #value.
 * @return
 *   A themed HTML string representing the group of items.
 *
 * @ingroup themeable
 */
function theme_fieldset($element) {
  if (!empty($element['#collapsible'])) {
    drupal_add_js('misc/collapse.js');

    if (!isset($element['#attributes']['class'])) {
      $element['#attributes']['class'] = '';
    }

    $element['#attributes']['class'] .= ' collapsible';
    if (!empty($element['#collapsed'])) {
      $element['#attributes']['class'] .= ' collapsed';
    }
  }
  $element['#attributes']['id'] = $element['#id'];

  return '<fieldset' . drupal_attributes($element['#attributes']) . '>' . ($element['#title'] ? '<legend>' . $element['#title'] . '</legend>' : '') . (isset($element['#description']) && $element['#description'] ? '<div class="fieldset-description">' . $element['#description'] . '</div>' : '') . (!empty($element['#children']) ? $element['#children'] : '') . (isset($element['#value']) ? $element['#value'] : '') . "</fieldset>\n";
}

/**
 * Format a radio button.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: required, return_value, value, attributes, title, description
 * @return
 *   A themed HTML string representing the form item group.
 *
 * @ingroup themeable
 */
function theme_radio($element) {
  _form_set_class($element, array('form-radio'));
  $output = '<input type="radio" ';
  $output .= 'id="' . $element['#id'] . '" ';
  $output .= 'name="' . $element['#name'] . '" ';
  $output .= 'value="' . $element['#return_value'] . '" ';
  $output .= (check_plain($element['#value']) == $element['#return_value']) ? ' checked="checked" ' : ' ';
  $output .= drupal_attributes($element['#attributes']) . ' />';
  if (!is_null($element['#title'])) {
    $output = '<label class="option" for="' . $element['#id'] . '">' . $output . ' ' . $element['#title'] . '</label>';
  }

  return $output;
}

/**
 * Format a set of radio buttons.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, options, description, required and attributes.
 * @return
 *   A themed HTML string representing the radio button set.
 *
 * @ingroup themeable
 */
function theme_radios($element) {
  $class = 'form-radios';
  if (isset($element['#attributes']['class'])) {
    $class .= ' ' . $element['#attributes']['class'];
  }
  $element['#children'] = '<div class="' . $class . '">' . (!empty($element['#children']) ? $element['#children'] : '') . '</div>';

  return $element['#children'];
}

/**
 * Expand a password_confirm field into two text boxes.
 */
function form_process_password_confirm($element) {
  $element['pass1'] =  array(
    '#type' => 'password',
    '#title' => t('Password'),
    '#value' => empty($element['#value']) ? NULL : $element['#value']['pass1'],
    '#required' => $element['#required'],
    '#attributes' => array('class' => 'password-field'),
  );
  $element['pass2'] =  array(
    '#type' => 'password',
    '#title' => t('Confirm password'),
    '#value' => empty($element['#value']) ? NULL : $element['#value']['pass2'],
    '#required' => $element['#required'],
    '#attributes' => array('class' => 'password-confirm'),
  );
  $element['#element_validate'] = array('password_confirm_validate');
  $element['#tree'] = TRUE;

  if (isset($element['#size'])) {
    $element['pass1']['#size'] = $element['pass2']['#size'] = $element['#size'];
  }

  return $element;
}

/**
 * Validate password_confirm element.
 */
function password_confirm_validate($element, &$element_state) {
  $pass1 = trim($element['pass1']['#value']);
  if (!empty($pass1)) {
    $pass2 = trim($element['pass2']['#value']);
    if (strcmp($pass1, $pass2)) {
      form_error($element, t('The specified passwords do not match.'));
    }
  }
  elseif ($element['#required'] && !empty($element_state['input'])) {
    form_error($element, t('Password field is required.'));
  }

  // Password field must be converted from a two-element array into a single
  // string regardless of validation results.
  form_set_value($element['pass1'], NULL, $element_state);
  form_set_value($element['pass2'], NULL, $element_state);
  form_set_value($element, $pass1, $element_state);

  return $element;

}

/**
 * Format a date selection element.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, options, description, required and attributes.
 * @return
 *   A themed HTML string representing the date selection boxes.
 *
 * @ingroup themeable
 */
function theme_date($element) {
  return '<div class="container-inline">' . drupal_render_children($element) . '</div>';
}

/**
 * Roll out a single date element.
 */
function form_process_date($element) {
  // Default to current date
  if (empty($element['#value'])) {
    $element['#value'] = array('day' => format_date(REQUEST_TIME, 'custom', 'j'),
                            'month' => format_date(REQUEST_TIME, 'custom', 'n'),
                            'year' => format_date(REQUEST_TIME, 'custom', 'Y'));
  }

  $element['#tree'] = TRUE;

  // Determine the order of day, month, year in the site's chosen date format.
  $format = variable_get('date_format_short', 'm/d/Y - H:i');
  $sort = array();
  $sort['day'] = max(strpos($format, 'd'), strpos($format, 'j'));
  $sort['month'] = max(strpos($format, 'm'), strpos($format, 'M'));
  $sort['year'] = strpos($format, 'Y');
  asort($sort);
  $order = array_keys($sort);

  // Output multi-selector for date.
  foreach ($order as $type) {
    switch ($type) {
      case 'day':
        $options = drupal_map_assoc(range(1, 31));
        break;
      case 'month':
        $options = drupal_map_assoc(range(1, 12), 'map_month');
        break;
      case 'year':
        $options = drupal_map_assoc(range(1900, 2050));
        break;
    }
    $parents = $element['#parents'];
    $parents[] = $type;
    $element[$type] = array(
      '#type' => 'select',
      '#value' => $element['#value'][$type],
      '#attributes' => $element['#attributes'],
      '#options' => $options,
    );
  }

  return $element;
}

/**
 * Validates the date type to stop dates like February 30, 2006.
 */
function date_validate($form) {
  if (!checkdate($form['#value']['month'], $form['#value']['day'], $form['#value']['year'])) {
    form_error($form, t('The specified date is invalid.'));
  }
}

/**
 * Helper function for usage with drupal_map_assoc to display month names.
 */
function map_month($month) {
  $months = &drupal_static(__FUNCTION__, array(
    1 => 'Jan',
    2 => 'Feb',
    3 => 'Mar',
    4 => 'Apr',
    5 => 'May',
    6 => 'Jun',
    7 => 'Jul',
    8 => 'Aug',
    9 => 'Sep',
    10 => 'Oct',
    11 => 'Nov',
    12 => 'Dec',
  ));
  return t($months[$month]);
}

/**
 * If no default value is set for weight select boxes, use 0.
 */
function weight_value(&$form) {
  if (isset($form['#default_value'])) {
    $form['#value'] = $form['#default_value'];
  }
  else {
    $form['#value'] = 0;
  }
}

/**
 * Menu callback for AHAH callbacks through the #ahah['callback'] FAPI property.
 */
function form_ahah_callback() {
  $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/ahah 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.
    exit;
  }

  // We will run some of the submit handlers so we need to disable redirecting.
  $form['#redirect'] = FALSE;

  // We need to process the form, prepare for that by setting a few internals
  // variables.
  $form_state['input'] = $_POST;
  $form_state['args'] = $form['#args'];
  $form_id = $form['#form_id'];

  // 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 the
  // drupal_process_form set up.
  $form = drupal_rebuild_form($form_id, $form_state, $form_build_id);

  // Get the callback function from the clicked button.
  $callback = $form_state['clicked_button']['#ahah']['callback'];
  if (drupal_function_exists($callback)) {
    $callback($form, $form_state);
  }
}

/**
 * Roll out a single radios element to a list of radios,
 * using the options array as index.
 */
function form_process_radios($element) {
  if (count($element['#options']) > 0) {
    foreach ($element['#options'] as $key => $choice) {
      if (!isset($element[$key])) {
        // Generate the parents as the autogenerator does, so we will have a
        // unique id for each radio button.
        $parents_for_id = array_merge($element['#parents'], array($key));
        $element[$key] = array(
          '#type' => 'radio',
          '#title' => $choice,
          '#return_value' => check_plain($key),
          '#default_value' => isset($element['#default_value']) ? $element['#default_value'] : NULL,
          '#attributes' => $element['#attributes'],
          '#parents' => $element['#parents'],
          '#id' => form_clean_id('edit-' . implode('-', $parents_for_id)),
          '#ahah' => isset($element['#ahah']) ? $element['#ahah'] : NULL,
        );
      }
    }
  }
  return $element;
}

/**
 * Add text format selector to text elements with the #text_format property.
 *
 * The #text_format property should be the ID of an text format, found in
 * {filter_format}.format, which gets passed to filter_form().
 *
 * If the property #text_format is set, the form element will be expanded into
 * two separate form elements, one holding the content of the element, and the
 * other holding the text format selector. The original element is shifted into
 * a child element, but is otherwise unaltered, so that the format selector is
 * at the same level as the text field which it affects.
 *
 * For example:
 * @code
 *   // A simple textarea, such as a node body.
 *   $form['body'] = array(
 *     '#type' => 'textarea',
 *     '#title' => t('Body'),
 *     '#text_format' => isset($node->format) ? $node->format : FILTER_FORMAT_DEFAULT,
 *   );
 * @endcode
 *
 * Becomes:
 * @code
 *   $form['body'] = array(
 *     // Type switches to 'markup', as we're only interested in submitting the child elements.
 *     '#type' => 'markup',
 *     // 'value' holds the original element.
 *     'value' => array(
 *       '#type' => 'textarea',
 *       '#title' => t('Body'),
 *       '#parents' => array('body'),
 *     ),
 *     // 'format' holds the text format selector.
 *     'format' => array(
 *       '#parents' => array('body_format'),
 *       ...
 *     ),
 *   );
 * @endcode
 *
 * And would result in:
 * @code
 *   // Original, unaltered form element value.
 *   $form_state['values']['body'] = 'Example content';
 *   // Chosen text format.
 *   $form_state['values']['body_format'] = 1;
 * @endcode
 *
 * @see system_elements(), filter_form()
 */
function form_process_text_format($element) {
  if (isset($element['#text_format'])) {
    // Determine the form element parents and element name to use for the input
    // format widget. This simulates the 'element' and 'element_format' pair of
    // parents that filter_form() expects.
    $element_parents = $element['#parents'];
    $element_name = array_pop($element_parents);
    $element_parents[] = $element_name . '_format';

    // We need to break references, otherwise form_builder recurses infinitely.
    $element['value'] = (array)$element;
    $element['value']['#weight'] = 0;
    unset($element['value']['#description']);
    $element['#type'] = 'markup';
    $element['#theme'] = NULL;
    $element['#theme_wrappers'] = array('text_format_wrapper');
    $element['format'] = filter_form($element['#text_format'], 1, $element_parents);

    // We need to clear the #text_format from the new child otherwise we
    // would get into an infinite loop.
    unset($element['value']['#text_format']);
  }
  return $element;
}

/**
 * Return a themed text format form element.
 *
 * @param element
 *   An associative array containing the properties of the element.
 *   Properties used: children, description
 * @return
 *   A string representing the form element.
 *
 * @ingroup themeable
 */
function theme_text_format_wrapper($element) {
  $output = '<div class="text-format-wrapper">' . "\n";

  $output .= $element['#children'] . "\n";

  if (!empty($element['#description'])) {
    $output .= '<div class="description">' . $element['#description'] . "</div>\n";
  }

  $output .= "</div>\n";

  return $output;
}

/**
 * Add AHAH information about a form element to the page to communicate with
 * javascript. If #ahah[path] is set on an element, this additional javascript is
 * added to the page header to attach the AHAH behaviors. See ahah.js for more
 * information.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: ahah_event, ahah_path, ahah_wrapper, ahah_parameters,
 *   ahah_effect.
 * @return
 *   None. Additional code is added to the header of the page using
 *   drupal_add_js.
 */
function form_process_ahah($element) {
  $js_added = &drupal_static(__FUNCTION__, array());
  // Add a reasonable default event handler if none specified.
  if (isset($element['#ahah']) && !isset($element['#ahah']['event'])) {
    switch ($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 AHAH behaviors.
        $element['#ahah']['event'] = 'mousedown';
        // Attach an additional event handler so that AHAH behaviors
        // can be triggered still via keyboard input.
        $element['#ahah']['keypress'] = TRUE;
        break;
      case 'password':
      case 'textfield':
      case 'textarea':
        $element['#ahah']['event'] = 'blur';
        break;
      case 'radio':
      case 'checkbox':
      case 'select':
        $element['#ahah']['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($element['#ahah']['callback']) || isset($element['#ahah']['path'])) && isset($element['#ahah']['event']) && !isset($js_added[$element['#id']])) {
    drupal_add_library('system', 'form');
    drupal_add_js('misc/ahah.js');

    $ahah_binding = array(
      'url'      => isset($element['#ahah']['callback']) ? url('system/ahah') : url($element['#ahah']['path']),
      'event'    => $element['#ahah']['event'],
      'keypress' => empty($element['#ahah']['keypress']) ? NULL : $element['#ahah']['keypress'],
      'wrapper'  => empty($element['#ahah']['wrapper']) ? NULL : $element['#ahah']['wrapper'],
      'selector' => empty($element['#ahah']['selector']) ? '#' . $element['#id'] : $element['#ahah']['selector'],
      'effect'   => empty($element['#ahah']['effect']) ? 'none' : $element['#ahah']['effect'],
      'method'   => empty($element['#ahah']['method']) ? 'replace' : $element['#ahah']['method'],
      'progress' => empty($element['#ahah']['progress']) ? array('type' => 'throbber') : $element['#ahah']['progress'],
      'button'   => isset($element['#executes_submit_callback']) ? array($element['#name'] => $element['#value']) : FALSE,
    );

    // Convert a simple #ahah[progress] type string into an array.
    if (is_string($ahah_binding['progress'])) {
      $ahah_binding['progress'] = array('type' => $ahah_binding['progress']);
    }
    // Change progress path to a full url.
    if (isset($ahah_binding['progress']['path'])) {
      $ahah_binding['progress']['url'] = url($ahah_binding['progress']['path']);
    }

    // Add progress.js if we're doing a bar display.
    if ($ahah_binding['progress']['type'] == 'bar') {
      drupal_add_js('misc/progress.js', array('cache' => FALSE));
    }

    drupal_add_js(array('ahah' => array($element['#id'] => $ahah_binding)), 'setting');

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

/**
 * Format a checkbox.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  title, value, return_value, description, required
 * @return
 *   A themed HTML string representing the checkbox.
 *
 * @ingroup themeable
 */
function theme_checkbox($element) {
  _form_set_class($element, array('form-checkbox'));
  $checkbox = '<input ';
  $checkbox .= 'type="checkbox" ';
  $checkbox .= 'name="' . $element['#name'] . '" ';
  $checkbox .= 'id="' . $element['#id'] . '" ' ;
  $checkbox .= 'value="' . $element['#return_value'] . '" ';
  $checkbox .= $element['#value'] ? ' checked="checked" ' : ' ';
  $checkbox .= drupal_attributes($element['#attributes']) . ' />';

  if (!is_null($element['#title'])) {
    $checkbox = '<label class="option" for="' . $element['#id'] . '">' . $checkbox . ' ' . $element['#title'] . '</label>';
  }

  return $checkbox;
}

/**
 * Format a set of checkboxes.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 * @return
 *   A themed HTML string representing the checkbox set.
 *
 * @ingroup themeable
 */
function theme_checkboxes($element) {
  $class = 'form-checkboxes';
  if (isset($element['#attributes']['class'])) {
    $class .= ' ' . $element['#attributes']['class'];
  }
  $element['#children'] = '<div class="' . $class . '">' . (!empty($element['#children']) ? $element['#children'] : '') . '</div>';

  return $element['#children'];
}

/**
 * Add form_element theming to an element if title or description is set.
 *
 * This is used as a pre render function for checkboxes and radios.
 */
function form_pre_render_conditional_form_element($element) {
  if ($element['#title'] || $element['#description']) {
    unset($element['#id']);
    $element['#theme_wrappers'][] = 'form_element';
  }
  return $element;
}

function form_process_checkboxes($element) {
  $value = is_array($element['#value']) ? $element['#value'] : array();
  $element['#tree'] = TRUE;
  if (count($element['#options']) > 0) {
    if (!isset($element['#default_value']) || $element['#default_value'] == 0) {
      $element['#default_value'] = array();
    }
    foreach ($element['#options'] as $key => $choice) {
      if (!isset($element[$key])) {
        $element[$key] = array(
          '#type' => 'checkbox',
          '#processed' => TRUE,
          '#title' => $choice,
          '#return_value' => $key,
          '#default_value' => isset($value[$key]),
          '#attributes' => $element['#attributes'],
          '#ahah' => isset($element['#ahah']) ? $element['#ahah'] : NULL,
        );
      }
    }
  }
  return $element;
}

/**
 * Format a table with radio buttons or checkboxes.
 *
 * @param $element
 *   An associative array containing the properties and children of the
 *   tableselect element.
 *   Each option in $element['#options'] can contain an array keyed by
 *   '#attributes' which is added to the row's HTML attributes.
 *   @see theme_table
 *   Properties used: header, options, empty, js_select.
 * @return
 *   A themed HTML string representing the table.
 *
 * Example:
 *
 * @code
 * $options = array();
 * $options[0]['title'] = "A red row"
 * $options[0]['#attributes'] = array ('class' => 'red-row');
 * $options[1]['title'] = "A blue row"
 * $options[1]['#attributes'] = array ('class' => 'blue-row');
 *
 * $form['myselector'] = array (
 * '#type' => 'tableselect',
 * '#title' => 'My Selector'
 * '#options' => $options,
 * );
 * @ingroup themeable
 */
function theme_tableselect($element) {
  $rows = array();
  if (!empty($element['#options'])) {
    // Generate a table row for each selectable item in #options.
    foreach ($element['#options'] as $key => $value) {
      $row = array();

      $row['data'] = array();
      if (isset($value['#attributes'])) {
        $row += $value['#attributes'];
      }
      // Render the checkbox / radio element.
      $row['data'][] = drupal_render($element[$key]);

      // As theme_table only maps header and row columns by order, create the
      // correct order by iterating over the header fields.
      foreach ($element['#header'] as $fieldname => $title) {
        $row['data'][] = $element['#options'][$key][$fieldname];
      }
      $rows[] = $row;
    }
    // Add an empty header or a "Select all" checkbox to provide room for the
    // checkboxes/radios in the first table column.
    $first_col = $element['#js_select'] ? array(theme('table_select_header_cell')) : array('');
    $header = array_merge($first_col, $element['#header']);
  }
  else {
    // If there are no selectable options, display the empty text over the
    // entire width of the table.
    $header = $element['#header'];
    $rows[] = array(array('data' => $element['#empty'], 'colspan' => count($header)));
  }
  return theme('table', $header, $rows);
}

/**
 * Create the correct amount of checkbox or radio elements to populate the table.
 *
 * @param $element
 *   An associative array containing the properties and children of the
 *   tableselect element.
 * @return
 *   The processed element.
 */
function form_process_tableselect($element) {

  if ($element['#multiple']) {
    $value = is_array($element['#value']) ? $element['#value'] : array();
  }
  else {
    // Advanced selection behaviour make no sense for radios.
    $element['#js_select'] = FALSE;
  }

  $element['#tree'] = TRUE;

  if (count($element['#options']) > 0) {
    if (!isset($element['#default_value']) || $element['#default_value'] === 0) {
      $element['#default_value'] = array();
    }

    // Sort the options by their #weight if they have a #weight.
    uasort($element['#options'], 'element_sort');
    // Create a checkbox or radio for each item in #options in such a way that
    // the value of the tableselect element behaves as if it had been of type
    // checkboxes or radios.
    foreach ($element['#options'] as $key => $choice) {
      // Do not overwrite manually created children.
      if (!isset($element[$key])) {
        if ($element['#multiple']) {
          $element[$key] = array(
            '#type' => 'checkbox',
            '#title' => '',
            '#return_value' => $key,
            '#default_value' => isset($value[$key]),
            '#attributes' => $element['#attributes'],
            '#ahah' => isset($element['#ahah']) ? $element['#ahah'] : NULL,
          );
        }
        else {
          // Generate the parents as the autogenerator does, so we will have a
          // unique id for each radio button.
          $parents_for_id = array_merge($element['#parents'], array($key));
          $element[$key] = array(
            '#type' => 'radio',
            '#title' => '',
            '#return_value' => $key,
            '#default_value' => ($element['#default_value'] == $key) ? $key : NULL,
            '#attributes' => $element['#attributes'],
            '#parents' => $element['#parents'],
            '#id' => form_clean_id('edit-' . implode('-', $parents_for_id)),
            '#ahah' => isset($element['#ahah']) ? $element['#ahah'] : NULL,
          );
        }
      }
    }
  }
  else {
    $element['#value'] = array();
  }
  return $element;
}

/**
 * Adds fieldsets to the specified group or adds group members to this
 * fieldset.
 *
 * @param $element
 *   An associative array containing the properties and children of the
 *   fieldset.
 * @param $form_state
 *   The $form_state array for the form this fieldset belongs to.
 * @return
 *   The processed element.
 */
function form_process_fieldset(&$element, &$form_state) {
  $parents = implode('][', $element['#parents']);

  // Add this fieldset to a group if one is set and if it's not being
  // added to itself.
  if (isset($element['#group']) && $element['#group'] != $parents) {
    if (isset($form_state['groups'][$element['#group']]) && !empty($form_state['groups'][$element['#group']]['#group_exists'])) {
      // Trick drupal_render() into believing this has already been output.
      // The group widget will rerender this later. This only happens when the
      // group is actually defined ('#group_exists' is TRUE). This prevents
      // fieldsets from disappearing when the group they are associated to
      // does not exist.
      // If the group does not exist yet, the element's #printed value is left
      // as is. As soon as the group is processed (fieldsets are also groups;
      // see below), this element's #printed value is set to TRUE to prevent
      // rendering in the original context.
      $element['#printed'] = TRUE;
    }

    // Store a reference to this fieldset for the vertical tabs processing
    // function.
    $form_state['groups'][$element['#group']][] = &$element;
  }

  // Each fieldset can be a group itself and gets a reference to all
  // elements in its group.
  $form_state['groups'][$parents]['#group_exists'] = TRUE;
  // There might already be elements associated with this group. Since the
  // group did not exist yet at the time they were added to this group, they
  // couldn't set #printed to TRUE (see above). We now know that this group
  // does in fact exist and set #printed to TRUE to prevent rendering in the
  // original context.
  foreach (element_children($form_state['groups'][$parents]) as $key) {
    $form_state['groups'][$parents][$key]['#printed'] = TRUE;
  }
  $element['#group_members'] = &$form_state['groups'][$parents];

  // Contains form element summary functionalities.
  drupal_add_js('misc/form.js', array('weight' => JS_LIBRARY + 1));

  return $element;
}

/**
 * Adds members of this group as actual elements for rendering.
 *
 * @param $element
 *   An associative array containing the properties and children of the
 *   fieldset.
 * @return
 *   The modified element with all group members.
 */
function form_pre_render_fieldset($element) {
  if (!empty($element['#group_members'])) {
    // Add the group members to this fieldset for rendering purposes only.
    foreach (element_children($element['#group_members']) as $key) {
      // This was set in form_process_fieldset so that fieldsets which are
      // added to groups are not rendered at their original location.
      // drupal_render_children() will set this back to TRUE.
      unset($element['#group_members'][$key]['#printed']);
      $element[] = &$element['#group_members'][$key];
    }

    // Resort the element's children after the group members have been added.
    $element['#sorted'] = FALSE;
  }

  return $element;
}

/**
 * Creates a group formatted as vertical tabs.
 *
 * @param $element
 *   An associative array containing the properties and children of the
 *   fieldset.
 * @param $form_state
 *   The $form_state array for the form this vertical tab widget belongs to.
 * @return
 *   The processed element.
 */
function form_process_vertical_tabs($element, &$form_state) {
  // To save us from modifying the existing element and changing its #type,
  // a new form element is created as a child. The default #process hooks
  // are called automatically by the form renderer and we don't have to do
  // that manually.
  $element['group'] = array(
    '#type' => 'fieldset',
    '#theme_wrappers' => array(),
    '#parents' => $element['#parents'],
  );

  // The JavaScript stores the currently selected tab in this hidden
  // field so that the active tab can be restored the next time the
  // form is rendered, e.g. on preview pages or when form validation
  // fails.
  $name = implode('__', $element['#parents']);
  if (isset($form_state['values'][$name . '__active_tab'])) {
    $element['#default_tab'] = $form_state['values'][$name . '__active_tab'];
  }
  $element[$name . '__active_tab'] = array(
    '#type' => 'hidden',
    '#default_value' => $element['#default_tab'],
    '#attributes' => array('class' => 'vertical-tabs-active-tab'),
  );

  return $element;
}

/**
 * Makes the element's children fieldsets be vertical tabs.
 *
 * @param $element
 *   An associative array containing the properties and children of the
 *   fieldset.
 */
function theme_vertical_tabs($element) {
  // Add required JavaScript and Stylesheet.
  drupal_add_js('misc/vertical-tabs.js', array('weight' => JS_DEFAULT - 1));
  drupal_add_css('misc/vertical-tabs.css');

  return '<div class="vertical-tabs-panes">' . $element['#children'] . '</div>';
}

/**
 * Theme a form submit button.
 *
 * @ingroup themeable
 */
function theme_submit($element) {
  return theme('button', $element);
}

/**
 * Theme a form button.
 *
 * @ingroup themeable
 */
function theme_button($element) {
  // Make sure not to overwrite classes.
  if (isset($element['#attributes']['class'])) {
    $element['#attributes']['class'] = 'form-' . $element['#button_type'] . ' ' . $element['#attributes']['class'];
  }
  else {
    $element['#attributes']['class'] = 'form-' . $element['#button_type'];
  }

  return '<input type="submit" ' . (empty($element['#name']) ? '' : 'name="' . $element['#name'] . '" ') . 'id="' . $element['#id'] . '" value="' . check_plain($element['#value']) . '" ' . drupal_attributes($element['#attributes']) . " />\n";
}

/**
 * Theme a form image button.
 *
 * @ingroup themeable
 */
function theme_image_button($element) {
  // Make sure not to overwrite classes.
  if (isset($element['#attributes']['class'])) {
    $element['#attributes']['class'] = 'form-' . $element['#button_type'] . ' ' . $element['#attributes']['class'];
  }
  else {
    $element['#attributes']['class'] = 'form-' . $element['#button_type'];
  }

  return '<input type="image" name="' . $element['#name'] . '" ' .
    (!empty($element['#value']) ? ('value="' . check_plain($element['#value']) . '" ') : '') .
    'id="' . $element['#id'] . '" ' .
    drupal_attributes($element['#attributes']) .
    ' src="' . base_path() . $element['#src'] . '" ' .
    (!empty($element['#title']) ? 'alt="' . check_plain($element['#title']) . '" title="' . check_plain($element['#title']) . '" ' : '' ) .
    "/>\n";
}

/**
 * Format a hidden form field.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 * @return
 *   A themed HTML string representing the hidden form field.
 *
 * @ingroup themeable
 */
function theme_hidden($element) {
  return '<input type="hidden" name="' . $element['#name'] . '" id="' . $element['#id'] . '" value="' . check_plain($element['#value']) . "\" " . drupal_attributes($element['#attributes']) . " />\n";
}

/**
 * Format a textfield.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  title, value, description, size, maxlength, required, attributes autocomplete_path
 * @return
 *   A themed HTML string representing the textfield.
 *
 * @ingroup themeable
 */
function theme_textfield($element) {
  $size = empty($element['#size']) ? '' : ' size="' . $element['#size'] . '"';
  $maxlength = empty($element['#maxlength']) ? '' : ' maxlength="' . $element['#maxlength'] . '"';
  $class = array('form-text');
  $extra = '';
  $output = '';

  if ($element['#autocomplete_path'] && menu_valid_path(array('link_path' => $element['#autocomplete_path']))) {
    drupal_add_js('misc/autocomplete.js');
    $class[] = 'form-autocomplete';
    $extra =  '<input class="autocomplete" type="hidden" id="' . $element['#id'] . '-autocomplete" value="' . check_url(url($element['#autocomplete_path'], array('absolute' => TRUE))) . '" disabled="disabled" />';
  }
  _form_set_class($element, $class);

  if (isset($element['#field_prefix'])) {
    $output .= '<span class="field-prefix">' . $element['#field_prefix'] . '</span> ';
  }

  $output .= '<input type="text"' . $maxlength . ' name="' . $element['#name'] . '" id="' . $element['#id'] . '"' . $size . ' value="' . check_plain($element['#value']) . '"' . drupal_attributes($element['#attributes']) . ' />';

  if (isset($element['#field_suffix'])) {
    $output .= ' <span class="field-suffix">' . $element['#field_suffix'] . '</span>';
  }
  return $output . $extra;
}

/**
 * Format a form.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: action, method, attributes, children
 * @return
 *   A themed HTML string representing the form.
 *
 * @ingroup themeable
 */
function theme_form($element) {
  // Anonymous div to satisfy XHTML compliance.
  $action = $element['#action'] ? 'action="' . check_url($element['#action']) . '" ' : '';
  return '<form ' . $action . ' accept-charset="UTF-8" method="' . $element['#method'] . '" id="' . $element['#id'] . '"' . drupal_attributes($element['#attributes']) . ">\n<div>" . $element['#children'] . "\n</div></form>\n";
}

/**
 * Format a textarea.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, description, rows, cols, required, attributes
 * @return
 *   A themed HTML string representing the textarea.
 *
 * @ingroup themeable
 */
function theme_textarea($element) {
  $class = array('form-textarea');

  // Add resizable behavior
  if ($element['#resizable'] !== FALSE) {
    drupal_add_js('misc/textarea.js');
    $class[] = 'resizable';
  }

  _form_set_class($element, $class);
  return '<textarea cols="' . $element['#cols'] . '" rows="' . $element['#rows'] . '" name="' . $element['#name'] . '" id="' . $element['#id'] . '" ' . drupal_attributes($element['#attributes']) . '>' . check_plain($element['#value']) . '</textarea>';
}

/**
 * Format HTML markup for use in forms.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: markup, children.
 * @return
 *   A themed HTML string representing the HTML markup.
 *
 * @ingroup themeable
 */

function theme_markup($element) {
  return (!empty($element['#markup']) ? $element['#markup'] : '') . drupal_render_children($element);
}

/**
 * Format a password field.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  title, value, description, size, maxlength, required, attributes
 * @return
 *   A themed HTML string representing the form.
 *
 * @ingroup themeable
 */
function theme_password($element) {
  $size = $element['#size'] ? ' size="' . $element['#size'] . '" ' : '';
  $maxlength = $element['#maxlength'] ? ' maxlength="' . $element['#maxlength'] . '" ' : '';

  _form_set_class($element, array('form-text'));
  $output = '<input type="password" name="' . $element['#name'] . '" id="' . $element['#id'] . '" ' . $maxlength . $size . drupal_attributes($element['#attributes']) . ' />';
  return $output;
}

/**
 * Expand weight elements into selects.
 */
function form_process_weight($element) {
  for ($n = (-1 * $element['#delta']); $n <= $element['#delta']; $n++) {
    $weights[$n] = $n;
  }
  $element['#options'] = $weights;
  $element['#type'] = 'select';
  $element['#is_weight'] = TRUE;
  $element += element_info('select');
  return $element;
}

/**
 * Format a file upload field.
 *
 * @param $title
 *   The label for the file upload field.
 * @param $name
 *   The internal name used to refer to the field.
 * @param $size
 *   A measure of the visible size of the field (passed directly to HTML).
 * @param $description
 *   Explanatory text to display after the form item.
 * @param $required
 *   Whether the user must upload a file to the field.
 * @return
 *   A themed HTML string representing the field.
 *
 * @ingroup themeable
 *
 * For assistance with handling the uploaded file correctly, see the API
 * provided by file.inc.
 */
function theme_file($element) {
  _form_set_class($element, array('form-file'));
  return '<input type="file" name="' . $element['#name'] . '"' . ($element['#attributes'] ? ' ' . drupal_attributes($element['#attributes']) : '') . ' id="' . $element['#id'] . '" size="' . $element['#size'] . "\" />\n";
}

/**
 * Return a themed form element.
 *
 * @param element
 *   An associative array containing the properties of the element.
 *   Properties used: title, description, id, required, children
 * @return
 *   A string representing the form element.
 *
 * @ingroup themeable
 */
function theme_form_element($element) {
  // This is also used in the installer, pre-database setup.
  $t = get_t();

  // Add element's #type and #name as class to aid with JS/CSS selectors.
  $class = array('form-item');
  if (!empty($element['#type'])) {
    $class[] = 'form-item-' . strtr($element['#type'], array('_' => '-'));
  }
  if (!empty($element['#name'])) {
    $class[] = strtr($element['#name'], array(' ' => '-', '_' => '-', '[' => '-', ']' => '')) . '-wrapper';
  }

  $output = '<div class="' . implode(' ', $class) . '">' . "\n";
  $required = !empty($element['#required']) ? '<span class="form-required" title="' . $t('This field is required.') . '">*</span>' : '';

  if (!empty($element['#title']) && empty($element['#form_element_skip_title'])) {
    $title = $element['#title'];
    if (!empty($element['#id'])) {
      $output .= ' <label for="' . $element['#id'] . '">' . $t('!title !required', array('!title' => filter_xss_admin($title), '!required' => $required)) . "</label>\n";
    }
    else {
      $output .= ' <label>' . $t('!title !required', array('!title' => filter_xss_admin($title), '!required' => $required)) . "</label>\n";
    }
  }

  $output .= " " . $element['#children'] . "\n";

  if (!empty($element['#description'])) {
    $output .= ' <div class="description">' . $element['#description'] . "</div>\n";
  }

  $output .= "</div>\n";

  return $output;
}

/**
 * Sets a form element's class attribute.
 *
 * Adds 'required' and 'error' classes as needed.
 *
 * @param &$element
 *   The form element.
 * @param $name
 *   Array of new class names to be added.
 */
function _form_set_class(&$element, $class = array()) {
  if ($element['#required']) {
    $class[] = 'required';
  }
  if (form_get_error($element)) {
    $class[] = 'error';
  }
  if (isset($element['#attributes']['class'])) {
    $class[] = $element['#attributes']['class'];
  }
  $element['#attributes']['class'] = implode(' ', $class);
}

/**
 * Prepare an HTML ID attribute string for a form item.
 *
 * Remove invalid characters and guarantee uniqueness.
 *
 * @param $id
 *   The ID to clean.
 * @param $flush
 *   If set to TRUE, the function will flush and reset the static array
 *   which is built to test the uniqueness of element IDs. This is only
 *   used if a form has completed the validation process. This parameter
 *   should never be set to TRUE if this function is being called to
 *   assign an ID to the #ID element.
 * @return
 *   The cleaned ID.
 */
function form_clean_id($id = NULL) {
  $seen_ids = &drupal_static(__FUNCTION__, array());
  $id = str_replace(array('][', '_', ' '), '-', $id);

  // Ensure IDs are unique. The first occurrence is held but left alone.
  // Subsequent occurrences get a number appended to them. This incrementing
  // will almost certainly break code that relies on explicit HTML IDs in
  // forms that appear more than once on the page, but the alternative is
  // outputting duplicate IDs, which would break JS code and XHTML
  // validity anyways. For now, it's an acceptable stopgap solution.
  if (isset($seen_ids[$id])) {
    $id = $id . '-' . $seen_ids[$id]++;
  }
  else {
    $seen_ids[$id] = 1;
  }

  return $id;
}

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

/**
 * @defgroup batch Batch operations
 * @{
 * Functions allowing forms processing to be spread out over several page
 * requests, thus ensuring that the processing does not get interrupted
 * because of a PHP timeout, while allowing the user to receive feedback
 * on the progress of the ongoing operations.
 *
 * The API is primarily designed to integrate nicely with the Form API
 * workflow, but can also be used by non-FAPI scripts (like update.php)
 * or even simple page callbacks (which should probably be used sparingly).
 *
 * Example:
 * @code
 * $batch = array(
 *   'title' => t('Exporting'),
 *   'operations' => array(
 *     array('my_function_1', array($account->uid, 'story')),
 *     array('my_function_2', array()),
 *   ),
 *   'finished' => 'my_finished_callback',
 * );
 * batch_set($batch);
 * // only needed if not inside a form _submit handler :
 * batch_process();
 * @endcode
 *
 * Note - if the batch 'title', 'init_message', 'progress_message',
 * or 'error_message' could contain any user input, it is the responsibility of
 * the code calling batch_set() to sanitize them first with a function like
 * check_plain() or filter_xss().
 *
 * Sample batch operations:
 * @code
 * // Simple and artificial: load a node of a given type for a given user
 * function my_function_1($uid, $type, &$context) {
 *   // The $context array gathers batch context information about the execution (read),
 *   // as well as 'return values' for the current operation (write)
 *   // The following keys are provided :
 *   // 'results' (read / write): The array of results gathered so far by
 *   //   the batch processing, for the current operation to append its own.
 *   // 'message' (write): A text message displayed in the progress page.
 *   // The following keys allow for multi-step operations :
 *   // 'sandbox' (read / write): An array that can be freely used to
 *   //   store persistent data between iterations. It is recommended to
 *   //   use this instead of $_SESSION, which is unsafe if the user
 *   //   continues browsing in a separate window while the batch is processing.
 *   // 'finished' (write): A float number between 0 and 1 informing
 *   //   the processing engine of the completion level for the operation.
 *   //   1 (or no value explicitly set) means the operation is finished
 *   //   and the batch processing can continue to the next operation.
 *
 *   $node = node_load(array('uid' => $uid, 'type' => $type));
 *   $context['results'][] = $node->nid . ' : ' . $node->title;
 *   $context['message'] = $node->title;
 * }
 *
 * // More advanced example: multi-step operation - load all nodes, five by five
 * function my_function_2(&$context) {
 *   if (empty($context['sandbox'])) {
 *     $context['sandbox']['progress'] = 0;
 *     $context['sandbox']['current_node'] = 0;
 *     $context['sandbox']['max'] = db_query('SELECT COUNT(DISTINCT nid) FROM {node}')->fetchField();
 *   }
 *   $limit = 5;
 *   $result = db_select('node')
 *     ->fields('node', array('nid'))
 *     ->condition('nid', $context['sandbox']['current_node'], '>')
 *     ->orderBy('nid')
 *     ->range(0, $limit)
 *     ->execute();
 *   foreach ($result as $row) {
 *     $node = node_load($row->nid, NULL, TRUE);
 *     $context['results'][] = $node->nid . ' : ' . $node->title;
 *     $context['sandbox']['progress']++;
 *     $context['sandbox']['current_node'] = $node->nid;
 *     $context['message'] = $node->title;
 *   }
 *   if ($context['sandbox']['progress'] != $context['sandbox']['max']) {
 *     $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
 *   }
 * }
 * @endcode
 *
 * Sample 'finished' callback:
 * @code
 * function batch_test_finished($success, $results, $operations) {
 *   if ($success) {
 *     $message = format_plural(count($results), 'One post processed.', '@count posts processed.');
 *   }
 *   else {
 *     $message = t('Finished with an error.');
 *   }
 *   drupal_set_message($message);
 *   // Providing data for the redirected page is done through $_SESSION.
 *   foreach ($results as $result) {
 *     $items[] = t('Loaded node %title.', array('%title' => $result));
 *   }
 *   $_SESSION['my_batch_results'] = $items;
 * }
 * @endcode
 */

/**
 * Open a new batch.
 *
 * @param $batch
 *   An array defining the batch. The following keys can be used:
 *     'operations': an array of function calls to be performed.
 *        Example:
 *        @code
 *        array(
 *          array('my_function_1', array($arg1)),
 *          array('my_function_2', array($arg2_1, $arg2_2)),
 *        )
 *        @endcode
 *     All the other values below are optional.
 *     batch_init() provides default values for the messages.
 *     'title': title for the progress page. Only safe strings should be passed.
 *       Defaults to t('Processing').
 *     'init_message': message displayed while the processing is initialized.
 *       Defaults to t('Initializing.').
 *     'progress_message': message displayed while processing the batch.
 *       Available placeholders are @current, @remaining, @total, @percentage,
 *       @estimate and @elapsed.
 *       Defaults to t('Completed @current of @total.').
 *     'error_message': message displayed if an error occurred while processing
 *       the batch.
 *       Defaults to t('An error has occurred.').
 *     'finished': the name of a function to be executed after the batch has
 *       completed. This should be used to perform any result massaging that
 *       may be needed, and possibly save data in $_SESSION for display after
 *       final page redirection.
 *     'file': the path to the file containing the definitions of the
 *       'operations' and 'finished' functions, for instance if they don't
 *       reside in the original '.module' file. The path should be relative to
 *       the base_path(), and thus should be built using drupal_get_path().
 *     'css' : an array of paths to CSS files to be used on the progress page.
 *
 * Operations are added as new batch sets. Batch sets are used to ensure
 * clean code independence, ensuring that several batches submitted by
 * different parts of the code (core / contrib modules) can be processed
 * correctly while not interfering or having to cope with each other. Each
 * batch set gets to specify his own UI messages, operates on its own set
 * of operations and results, and triggers its own 'finished' callback.
 * Batch sets are processed sequentially, with the progress bar starting
 * fresh for every new set.
 */
function batch_set($batch_definition) {
  if ($batch_definition) {
    $batch =& batch_get();
    // Initialize the batch
    if (empty($batch)) {
      $batch = array(
        'sets' => array(),
      );
    }

    $init = array(
      'sandbox' => array(),
      'results' => array(),
      'success' => FALSE,
      'start' => microtime(TRUE),
      'elapsed' => 0,
    );
    // Use get_t() to allow batches at install time.
    $t = get_t();
    $defaults = array(
      'title' => $t('Processing'),
      'init_message' => $t('Initializing.'),
      'progress_message' => $t('Completed @current of @total.'),
      'error_message' => $t('An error has occurred.'),
      'css' => array(),
    );
    $batch_set = $init + $batch_definition + $defaults;

    // Tweak init_message to avoid the bottom of the page flickering down after init phase.
    $batch_set['init_message'] .= '<br/>&nbsp;';
    $batch_set['total'] = count($batch_set['operations']);

    // If the batch is being processed (meaning we are executing a stored submit handler),
    // insert the new set after the current one.
    if (isset($batch['current_set'])) {
      // array_insert does not exist...
      $slice1 = array_slice($batch['sets'], 0, $batch['current_set'] + 1);
      $slice2 = array_slice($batch['sets'], $batch['current_set'] + 1);
      $batch['sets'] = array_merge($slice1, array($batch_set), $slice2);
    }
    else {
      $batch['sets'][] = $batch_set;
    }
  }
}

/**
 * Process the batch.
 *
 * Unless the batch has been marked with 'progressive' = FALSE, the function
 * issues a drupal_goto and thus ends page execution.
 *
 * This function is generally not needed in form submit handlers;
 * Form API takes care of batches that were set during form submission.
 *
 * @param $redirect
 *   (optional) Path to redirect to when the batch has finished processing.
 * @param $url
 *   (optional - should only be used for separate scripts like update.php)
 *   URL of the batch processing page.
 */
function batch_process($redirect = NULL, $url = NULL) {
  $batch =& batch_get();

  if (isset($batch)) {
    // Add process information
    $url = isset($url) ? $url : 'batch';
    $process_info = array(
      'current_set' => 0,
      'progressive' => TRUE,
      'url' => isset($url) ? $url : 'batch',
      'source_page' => $_GET['q'],
      'redirect' => $redirect,
    );
    $batch += $process_info;

    if ($batch['progressive']) {
      // Clear the way for the drupal_goto redirection to the batch processing
      // page, by saving and unsetting the 'destination' if any, on both places
      // drupal_goto looks for it.
      if (isset($_REQUEST['destination'])) {
        $batch['destination'] = $_REQUEST['destination'];
        unset($_REQUEST['destination']);
      }

      // Initiate db storage in order to get a batch id. We have to provide
      // at least an empty string for the (not null) 'token' column.
      $batch['id'] = db_insert('batch')
        ->fields(array(
          'token' => '',
          'timestamp' => REQUEST_TIME,
        ))
        ->execute();

      // Now that we have a batch id, we can generate the redirection link in
      // the generic error message.
      $t = get_t();
      $batch['error_message'] = $t('Please continue to <a href="@error_url">the error page</a>', array('@error_url' => url($url, array('query' => array('id' => $batch['id'], 'op' => 'finished')))));

      // Actually store the batch data and the token generated form the batch id.
      db_update('batch')
        ->condition('bid', $batch['id'])
        ->fields(array(
          'token' => drupal_get_token($batch['id']),
          'batch' => serialize($batch),
        ))
        ->execute();

      // Set the batch number in the session to guarantee that it will stay alive.
      $_SESSION['batches'][$batch['id']] = TRUE;

      drupal_goto($batch['url'], 'op=start&id=' . $batch['id']);
    }
    else {
      // Non-progressive execution: bypass the whole progressbar workflow
      // and execute the batch in one pass.
      require_once DRUPAL_ROOT . '/includes/batch.inc';
      _batch_process();
    }
  }
}

/**
 * Retrieve the current batch.
 */
function &batch_get() {
  $batch = &drupal_static(__FUNCTION__, array());
  return $batch;
}

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