drupal/includes/form.inc

<?php
// $Id$

/**
 * @defgroup form 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, processing, and
 * displaying a rendered 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_execute() 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
 */

/**
 * Retrieves a form from a constructor function, or from the cache if
 * the form was built in a previous page-load. The form is then passesed
 * on for processing, after and rendered for display if necessary.
 *
 * @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 $form_id values to the proper form constructor function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_get_form(), including the unique form constructor function.
 *   For example, the node_edit form requires that a node object be passed
 *   in here when it is called.
 * @return
 *   The rendered form.
 */
function drupal_get_form($form_id) {
  $form_state = array('storage' => NULL, 'submitted' => FALSE);

  $args = func_get_args();
  $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 $_POST contains a form_build_id, we'll check the
    // cache for a copy of the form in question. If it's there, we don't
    // have to rebuild the form to proceed. In addition, if there is stored
    // form_state data from a previous step, we'll retrieve it so it can
    // be passed on to the form processing code.
    if (isset($_POST['form_id']) && $_POST['form_id'] == $form_id && !empty($_POST['form_build_id'])) {
      $form = form_get_cache($_POST['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_state['post'] = $_POST;
      // Use a copy of the function's arguments for manipulation
      $args_temp = $args;
      $args_temp[0] = &$form_state;
      array_unshift($args_temp, $form_id);

      $form = call_user_func_array('drupal_retrieve_form', $args_temp);
      $form_build_id = 'form-'. md5(mt_rand());
      $form['#build_id'] = $form_build_id;
      drupal_prepare_form($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;
      $cacheable = TRUE;
      unset($form_state['post']);
    }
    $form['#post'] = $_POST;

    // 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['#cache'])) {
      // Caching is done past drupal_process_form so #process callbacks can
      // set #cache. By not sending the form state, we avoid storing
      // $form_state['storage'].
      form_set_cache($form_build_id, $original_form, NULL);
    }
  }

  // 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'] have been
  // set by any submit or validate handlers, however, 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($form_state['rebuild']) || !empty($form_state['storage'])) {
    $form = drupal_rebuild_form($form_id, $form_state, $args);
  }

  // If we haven't redirected to a new location by now, we want to
  // render whatever form array is currently in hand.
  return drupal_render_form($form_id, $form);
}

/**
 * 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.
 *
 * @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 $args
 *   Any additional arguments are passed on to the functions called by
 *   drupal_get_form(), plus the original form_state in the beginning. If you
 *   are getting a form from the cache, use $form['#parameters'] to shift off
 *   the $form_id from its beginning then the resulting array can be used as
 *   $arg here.
 * @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, $args, $form_build_id = NULL) {
  // Remove the first argument. This is $form_id.when called from
  // drupal_get_form and the original $form_state when called from some AHAH
  // callback. Neither is needed. After that, put in the current state.
  $args[0] = &$form_state;
  // And the form_id.
  array_unshift($args, $form_id);
  $form = call_user_func_array('drupal_retrieve_form', $args);

  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);

  // Now, we cache the form structure so it can be retrieved later for
  // validation. If $form_state['storage'] is populated, we'll also cache
  // it so that it can be used to resume complex multi-step processes.
  form_set_cache($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.
  $_POST = array();
  $form['#post'] = array();
  drupal_process_form($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 = $cached->data;
    if ($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) {
  $expire = max(ini_get('session.cookie_lifetime'), 86400);

  cache_set('form_'. $form_build_id, $form, 'cache_form', $expire);
  if (!empty($form_state['storage'])) {
    cache_set('storage_'. $form_build_id, $form_state['storage'], 'cache_form', $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_execute(), 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:
 *
 * // 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_execute('user_register', $form_state);
 *
 * // Create a new node
 * $form_state = array();
 * $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_execute('story_node_form', $form_state, $node);
 */
function drupal_execute($form_id, &$form_state) {
  $args = func_get_args();
  $form = call_user_func_array('drupal_retrieve_form', $args);
  $form['#post'] = $form_state['values'];
  drupal_prepare_form($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 $form_state
 *   A keyed array containing the current state of the form.
 * @param ...
 *   Any additional arguments needed by the unique form constructor
 *   function. Generally, these are any arguments passed into the
 *   drupal_get_form() or drupal_execute() functions after the first
 *   argument. If a module implements hook_forms(), it can examine
 *   these additional arguments and conditionally return different
 *   builder functions as well.
 */
function drupal_retrieve_form($form_id, &$form_state) {
  static $forms;

  // 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. We shift out the first argument -- the
  // $form_id itself -- from the list to pass into the constructor function,
  // since it's already known.
  $args = func_get_args();
  $saved_args = $args;
  array_shift($args);
  if (isset($form_state)) {
    array_shift($args);
  }

  // We first check to see if there's a function named after the $form_id.
  // If there is, we simply pass the arguments on to it to get the form.
  if (!function_exists($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'];
    }
  }

  array_unshift($args, NULL);
  $args[0] = &$form_state;

  // 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);

  // We store the original function arguments, rather than the final $arg
  // value, so that form_alter functions can see what was originally
  // passed to drupal_retrieve_form(). This allows the contents of #parameters
  // to be saved and passed in at a later date to recreate the form.
  $form['#parameters'] = $saved_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();

  $form = form_builder($form_id, $form, $form_state);
  // Only process the form if it is programmed or the form_id coming
  // from the POST data is set and matches the current form_id.
  if ((!empty($form['#programmed'])) || (!empty($form['#post']) && (isset($form['#post']['form_id']) && ($form['#post']['form_id'] == $form_id)))) {
    drupal_validate_form($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 scenerios that result in
    // the form being built behind the scenes and again for the
    // browser don't increment all the element IDs needlessly.
    form_clean_id(NULL, TRUE);

    if ((!empty($form_state['submitted'])) && !form_get_errors() && empty($form_state['rebuild'])) {
      $form_state['redirect'] = NULL;
      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_execute).
      if ($batch =& batch_get() && !isset($batch['current_set'])) {
        // The batch uses its own copies of $form and $form_state for
        // late execution of submit handers and post-batch redirection.
        $batch['form'] = $form;
        $batch['form_state'] = $form_state;
        $batch['progressive'] = !$form['#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.
      }

      // If no submit handlers have populated the $form_state['storage']
      // bundle, and the $form_state['rebuild'] flag has not been set,
      // we're finished and should redirect to a new destination page
      // if one has been set (and a fresh, unpopulated copy of the form
      // if one hasn't). If the form was called by drupal_execute(),
      // however, we'll skip this and let the calling function examine
      // the resulting $form_state bundle itself.
      if (!$form['#programmed'] && empty($form_state['rebuild']) && empty($form_state['storage'])) {
        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';
  $form['#programmed'] = isset($form['#post']);

  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 || $form['#programmed']) {
      unset($form['#token']);
    }
    else {
      $form['form_token'] = array('#type' => 'token', '#default_value' => drupal_get_token($form['#token']));
    }
  }
  else if (isset($user->uid) && $user->uid && !$form['#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');

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

  if (!isset($form['#submit'])) {
    if (function_exists($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) {
  static $validated_forms = array();

  if (isset($validated_forms[$form_id])) {
    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;
}

/**
 * Renders a structured form array into themed HTML.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @return
 *   A string containing the path of the page to display when processing
 *   is complete.
 */
function drupal_render_form($form_id, &$form) {
  // Don't override #theme if someone already set it.
  if (!isset($form['#theme'])) {
    init_theme();
    $registry = theme_get_registry();
    if (isset($registry[$form_id])) {
      $form['#theme'] = $form_id;
    }
  }

  $output = drupal_render($form);
  return $output;
}

/**
 * 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', $goto);
      }
      else {
        drupal_goto($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'])) {
      // An empty textfield returns '' so we use empty(). An empty checkbox
      // and a textfield could return '0' and empty('0') returns TRUE so we
      // need a special check for the '0' string.
      if ($elements['#required'] && empty($elements['#value']) && $elements['#value'] !== '0') {
        form_error($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 $function) {
        if (function_exists($function))  {
          $function($elements, $form_state);
        }
      }
    }
    $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 $function) {
    if (function_exists($function))  {
      if ($type == 'submit' && ($batch =& batch_get())) {
        // 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. If the name of the element is
 * edit[foo][bar] then you may pass either foo or foo][bar as $name
 * foo will set an error for all its children.
 */
function form_set_error($name = NULL, $message = '') {
  static $form = array();
  if (isset($name) && !isset($form[$name])) {
    $form[$name] = $message;
    if ($message) {
      drupal_set_message($message, 'error');
    }
  }
  return $form;
}

/**
 * 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 $_POST
 * data to the proper elements.
 *
 * @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. 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, $form, &$form_state) {
  static $complete_form, $cache;

  // Initialize as unprocessed.
  $form['#processed'] = FALSE;

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

  if (isset($form['#type']) && $form['#type'] == 'form') {
    $complete_form = $form;
    if (!empty($form['#programmed'])) {
      $form_state['submitted'] = TRUE;
    }
  }

  if (isset($form['#input']) && $form['#input']) {
    _form_builder_handle_input_element($form_id, $form, $form_state, $complete_form);
  }
  $form['#defaults_loaded'] = TRUE;

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

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

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

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

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

  // After handling the special IE case, we no longer need the buttons collection.
  unset($form_state['buttons']);

  // If some callback set #cache, we need to flip a static flag so later it
  // can be found.
  if (isset($form['#cache'])) {
    $cache = $form['#cache'];
  }
  // We are on the top form, we can copy back #cache if it's set.
  if (isset($form['#type']) && $form['#type'] == 'form' && isset($cache)) {
    $form['#cache'] = TRUE;
  }
  return $form;
}

/**
 * Populate the #value and #name properties of input elements so they
 * can be processed and rendered. Also, execute any #process handlers
 * attached to a specific element.
 */
function _form_builder_handle_input_element($form_id, &$form, &$form_state, $complete_form) {
  if (!isset($form['#name'])) {
    $name = array_shift($form['#parents']);
    $form['#name'] = $name;
    if ($form['#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.
      $form['#name'] = 'files['. $form['#name'] .']';
    }
    elseif (count($form['#parents'])) {
      $form['#name'] .= '['. implode('][', $form['#parents']) .']';
    }
    array_unshift($form['#parents'], $name);
  }
  if (!isset($form['#id'])) {
    $form['#id'] = form_clean_id('edit-'. implode('-', $form['#parents']));
  }

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

  if (!isset($form['#value']) && !array_key_exists('#value', $form)) {
    $function = !empty($form['#value_callback']) ? $form['#value_callback'] : 'form_type_'. $form['#type'] .'_value';
    if (($form['#programmed']) || ((!isset($form['#access']) || $form['#access']) && isset($form['#post']) && (isset($form['#post']['form_id']) && $form['#post']['form_id'] == $form_id))) {
      $edit = $form['#post'];
      foreach ($form['#parents'] as $parent) {
        $edit = isset($edit[$parent]) ? $edit[$parent] : NULL;
      }
      if (!$form['#programmed'] || isset($edit)) {
        // Call #type_value to set the form value;
        if (function_exists($function)) {
          $form['#value'] = $function($form, $edit);
        }
        if (!isset($form['#value']) && isset($edit)) {
          $form['#value'] = $edit;
        }
      }
      // Mark all posted values for validation.
      if (isset($form['#value']) || (isset($form['#required']) && $form['#required'])) {
        $form['#needs_validation'] = TRUE;
      }
    }
    // Load defaults.
    if (!isset($form['#value'])) {
      // Call #type_value without a second argument to request default_value handling.
      if (function_exists($function)) {
        $form['#value'] = $function($form);
      }
      // Final catch. If we haven't set a value yet, use the explicit default value.
      if (!isset($form['#value'])) {
        $form['#value'] = isset($form['#default_value']) ? $form['#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($form['#post']) && isset($form['#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 = $form['#executes_submit_callback'] ? 'submit' : 'button';
    $form_state['buttons'][$button_type][] = $form;

    if (_form_button_was_clicked($form)) {
      $form_state['submitted'] = $form_state['submitted'] || $form['#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'.
      $form_state['values'][$form['#name']] = $form['#value'];
      $form_state['clicked_button'] = $form;

      if (isset($form['#validate'])) {
        $form_state['validate_handlers'] = $form['#validate'];
      }
      if (isset($form['#submit'])) {
        $form_state['submit_handlers'] = $form['#submit'];
      }
    }
  }
  // Allow for elements to expand to multiple elements, e.g., radios,
  // checkboxes and files.
  if (isset($form['#process']) && !$form['#processed']) {
    foreach ($form['#process'] as $process) {
      if (function_exists($process)) {
        $form = $process($form, isset($edit) ? $edit : NULL, $form_state, $complete_form);
      }
    }
    $form['#processed'] = TRUE;
  }
  form_set_value($form, $form['#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) {
  // 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['#post'][$form['#name']]) && $form['#post'][$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 $edit
 *   The incoming POST data 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 $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_image_button_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {
    if (!empty($edit)) {
      // 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'.
      $post = $form['#post'];
      foreach (split('\[', $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($post[$element_name])) {
          if (isset($post[$element_name .'_x'])) {
            return $form['#return_value'];
          }
          return NULL;
        }
        $post = $array[$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 $edit
 *   The incoming POST data 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 $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_checkbox_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {
    return !empty($edit) ? $form['#return_value'] : 0;
  }
}

/**
 * Helper function to determine the value for a checkboxes form element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data 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 $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_checkboxes_value($form, $edit = FALSE) {
  if ($edit === FALSE) {
    $value = array();
    $form += array('#default_value' => array());
    foreach ($form['#default_value'] as $key) {
      $value[$key] = 1;
    }
    return $value;
  }
  elseif (!isset($edit)) {
    return array();
  }
}

/**
 * Helper function to determine the value for a password_confirm form
 * element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data 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 $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_password_confirm_value($form, $edit = FALSE) {
  if ($edit === FALSE) {
    $form += array('#default_value' => array());
    return $form['#default_value'] + array('pass1' => '', 'pass2' => '');
  }
}

/**
 * Helper function to determine the value for a select form element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data 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 $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_select_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {
    if (isset($form['#multiple']) && $form['#multiple']) {
      return (is_array($edit)) ? drupal_map_assoc($edit) : array();
    }
    else {
      return $edit;
    }
  }
}

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

/**
 * Helper function to determine the value for form's token value.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data 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 $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_token_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {
    return (string)$edit;
  }
}

/**
 * Use this function to make changes to form values in the form validate
 * phase, so they will be available in the submit phase in $form_state.
 *
 * Specifically, if $form['#parents'] is array('foo', 'bar')
 * and $value is 'baz' then this function will make
 * $form_state['values']['foo']['bar'] to be 'baz'.
 *
 * @param $form
 *   The form item. Keys used: #parents, #value
 * @param $value
 *   The value for the form item.
 */
function form_set_value($form, $value, &$form_state) {
  _form_set_value($form_state['values'], $form, $form['#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, $form, $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], $form, $parents, $value);
  }
}

/**
 * Retrieve the default properties for the defined element type.
 */
function _element_info($type, $refresh = NULL) {
  static $cache;

  $basic_defaults = array(
    '#description' => NULL,
    '#attributes' => array(),
    '#required' => FALSE,
    '#tree' => FALSE,
    '#parents' => array()
  );
  if (!isset($cache) || $refresh) {
    $cache = array();
    foreach (module_implements('elements') as $module) {
      $elements = module_invoke($module, 'elements');
      if (isset($elements) && is_array($elements)) {
        $cache = array_merge_recursive($cache, $elements);
      }
    }
    if (sizeof($cache)) {
      foreach ($cache as $element_type => $info) {
        $cache[$element_type] = array_merge_recursive($basic_defaults, $info);
      }
    }
  }

  return $cache[$type];
}

function form_options_flatten($array, $reset = TRUE) {
  static $return;

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

  foreach ($array as $key => $value) {
    if (is_object($value)) {
      form_options_flatten($value->option, FALSE);
    }
    else if (is_array($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 theme('form_element', $element, '<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;
    }
    else if (is_object($choice)) {
      if (isset($choice->option[$key])) {
        $keys[] = $index;
      }
    }
    else if ($index == $key) {
      $keys[] = $index;
    }
  }
  return $keys;
}

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

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

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

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

  unset($element['#title']);
  return theme('form_element', $element, $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']) ? $element['#children'] : '') .'</div>';
  if ($element['#title'] || $element['#description']) {
    unset($element['#id']);
    return theme('form_element', $element, $element['#children']);
  }
  else {
    return $element['#children'];
  }
}

/**
 * Format a password_confirm item.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, id, required, error.
 * @return
 *   A themed HTML string representing the form item.
 *
 * @ingroup themeable
 */
function theme_password_confirm($element) {
  return theme('form_element', $element, $element['#children']);
}

/*
 * Expand a password_confirm field into two text boxes.
 */
function expand_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($form, &$form_state) {
  $pass1 = trim($form['pass1']['#value']);
  if (!empty($pass1)) {
    $pass2 = trim($form['pass2']['#value']);
    if ($pass1 != $pass2) {
      form_error($form, t('The specified passwords do not match.'));
    }
  }
  elseif ($form['#required'] && !empty($form['#post'])) {
    form_error($form, 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($form['pass1'], NULL, $form_state);
  form_set_value($form['pass2'], NULL, $form_state);
  form_set_value($form, $pass1, $form_state);

  return $form;

}

/**
 * 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 theme('form_element', $element, '<div class="container-inline">'. $element['#children'] .'</div>');
}

/**
 * Roll out a single date element.
 */
function expand_date($element) {
  // Default to current date
  if (empty($element['#value'])) {
    $element['#value'] = array('day' => format_date(time(), 'custom', 'j'),
                            'month' => format_date(time(), 'custom', 'n'),
                            'year' => format_date(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) {
  return format_date(gmmktime(0, 0, 0, $month, 2, 1970), 'custom', 'M', 0);
}

/**
 * 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;
  }
}

/**
 * Roll out a single radios element to a list of radios,
 * using the options array as index.
 */
function expand_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)),
        );
      }
    }
  }
  return $element;
}

/**
 * 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 $element
 *   An associative array containing the properties of the element.
 *   Properties used: ahah_event, ahah_path, ahah_wrapper, ahah_parameters,
 *   ahah_effect.
 * @return
 *   None. Additional code is added to the header of the page using
 *   drupal_add_js.
 */
function form_expand_ahah($element) {
  static $js_added = array();
  // Add a reasonable default event handler if none specified.
  if (isset($element['#ahah']['path']) && !isset($element['#ahah']['event'])) {
    switch ($element['#type']) {
      case 'submit':
      case 'button':
      case 'image_button':
        $element['#ahah']['event'] = 'click';
        break;
      case 'password':
      case 'textfield':
      case 'textarea':
        $element['#ahah']['event'] = 'blur';
        break;
      case 'radio':
      case 'checkbox':
      case 'select':
        $element['#ahah']['event'] = 'change';
        break;
    }
  }

  // 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($element['#ahah']['path']) && isset($element['#ahah']['event']) && !isset($js_added[$element['#id']])) {
    drupal_add_js('misc/jquery.form.js');
    drupal_add_js('misc/ahah.js');

    $ahah_binding = array(
      'url'      => url($element['#ahah']['path']),
      'event'    => $element['#ahah']['event'],
      'wrapper'  => empty($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'   => $element['#type'] == 'submit' ? array($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');
    }

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

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

/**
 * Format a form item.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  title, value, description, required, error
 * @return
 *   A themed HTML string representing the form item.
 *
 * @ingroup themeable
 */
function theme_item($element) {
  return theme('form_element', $element, $element['#value'] . (!empty($element['#children']) ? $element['#children'] : ''));
}

/**
 * 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">'. $checkbox .' '. $element['#title'] .'</label>';
  }

  unset($element['#title']);
  return theme('form_element', $element, $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']) ? $element['#children'] : '') .'</div>';
  if ($element['#title'] || $element['#description']) {
    unset($element['#id']);
    return theme('form_element', $element, $element['#children']);
  }
  else {
    return $element['#children'];
  }
}

function expand_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']);
      }
    }
  }
  return $element;
}

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

/**
 * Format a form token.
 *
 * @ingroup themeable
 */
function theme_token($element) {
  return theme('hidden', $element);
}

/**
 * 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']) {
    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 theme('form_element', $element, $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 teaser behavior (must come before resizable)
  if (!empty($element['#teaser'])) {
    drupal_add_js('misc/teaser.js');
    // Note: arrays are merged in drupal_get_js().
    drupal_add_js(array('teaserCheckbox' => array($element['#id'] => $element['#teaser_checkbox'])), 'setting');
    drupal_add_js(array('teaser' => array($element['#id'] => $element['#teaser'])), 'setting');
    $class[] = 'teaser';
  }

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

  _form_set_class($element, $class);
  return theme('form_element', $element, '<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.
 *
 * This is used in more advanced forms, such as theme selection and filter format.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: value, children.
 * @return
 *   A themed HTML string representing the HTML markup.
 *
 * @ingroup themeable
 */

function theme_markup($element) {
  return (isset($element['#value']) ? $element['#value'] : '') . (isset($element['#children']) ? $element['#children'] : '');
}

/**
 * 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 theme('form_element', $element, $output);
}

/**
 * Expand weight elements into selects.
 */
function 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 theme('form_element', $element, '<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
 * @param $value
 *   The form element's data.
 * @return
 *   A string representing the form element.
 *
 * @ingroup themeable
 */
function theme_form_element($element, $value) {
  // This is also used in the installer, pre-database setup.
  $t = get_t();

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

  if (!empty($element['#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 .= " $value\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, $flush = FALSE) {
  static $seen_ids = array();

  if ($flush) {
    $seen_ids = array();
    return;
  }
  $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".
 */

/**
 * @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($batch);
 * // only needed if not inside a form _submit handler :
 * batch_process();
 * @endcode
 *
 * Sample batch operations:
 * @code
 * // Simple and artificial: load a node of a given type for a given user
 * function my_function_1($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_result(db_query('SELECT COUNT(DISTINCT nid) FROM {node}'));
 *   }
 *   $limit = 5;
 *   $result = db_query_range("SELECT nid FROM {node} WHERE nid > %d ORDER BY nid ASC", $context['sandbox']['current_node'], 0, $limit);
 *   while ($row = db_fetch_array($result)) {
 *     $node = node_load($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.
 *       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 and @percent.
 *       Defaults to t('Remaining @remaining 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 $_SESSION for display after
 *       final page redirection.
 *     'file': the path to the file containing the definitions of the
 *       'operations' and 'finished' functions, for instance if they don't
 *       reside in the original '.module' file. The path should be relative to
 *       the base_path(), and thus should be built using drupal_get_path().
 *
 * Operations are added as new batch sets. Batch sets are used to ensure
 * clean code independence, ensuring that several batches submitted by
 * different parts of the code (core / contrib modules) can be processed
 * correctly while not interfering or having to cope with each other. Each
 * batch set gets to specify his own UI messages, operates on its own set
 * of operations and results, and triggers its own 'finished' callback.
 * Batch sets are processed sequentially, with the progress bar starting
 * fresh for every new set.
 */
function batch_set($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,
    );
    // Use get_t() to allow batches at install time.
    $t = get_t();
    $defaults = array(
      'title' => $t('Processing'),
      'init_message' => $t('Initializing.'),
      'progress_message' => $t('Remaining @remaining of @total.'),
      'error_message' => $t('An error has occurred.'),
    );
    $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 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']);
      }
      elseif (isset($_REQUEST['edit']['destination'])) {
        $batch['destination'] = $_REQUEST['edit']['destination'];
        unset($_REQUEST['edit']['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.
      db_query("INSERT INTO {batch} (token, timestamp) VALUES ('', %d)", time());
      $batch['id'] = db_last_insert_id('batch', 'bid');

      // 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_query("UPDATE {batch} SET token = '%s', batch = '%s' WHERE bid = %d", drupal_get_token($batch['id']), serialize($batch), $batch['id']);

      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 './includes/batch.inc';
      _batch_process();
    }
  }
}

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

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