<?php

/**
 * @file
 * Contains \workflow\Form\WorkflowTransitionForm.
 */

/**
 * Provides a Transition Form to be used in the Workflow Widget.
 */
class WorkflowTransitionForm { // extends FormBase {

  /**
   * The Workflow Transition storage.
   */
  protected $field;
  protected $instance;
  protected $entity;

  /**
   * Constructs a WorkflowTransitionForm object.
   * @param array $field
   * @param array $instance
   * @param $entity_type
   * @param $entity
   */
  public function __construct(array $field, array $instance, $entity_type, $entity) {
    $this->field = $field; // TODO : needed?
    $this->instance = $instance;  // TODO : needed?
    $this->entity = $entity;  // TODO : needed?
    $this->entity_type = $entity_type;  // TODO : needed?
  }

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    $field = $this->field;
    // No entity may be set on VBO form.
    $entity_id = ($this->entity) ? entity_id($this->entity_type, $this->entity) : '';
    // The field is not set when editing a stand alone Transition.
    $field_id = isset($field['id']) ? $field['id'] : '';

    return implode('_', array('workflow_transition_form', $this->entity_type, $entity_id, $field_id));
  }

  /**
   * {@inheritdoc}
   *
   * @param array $form
   * @param array $form_state
   * @param WorkflowTransition
   *  The Transition to be edited, created.
   *
   * @return
   *  The enhanced form structure.
   */
  public function buildForm(array $form, array &$form_state) {
    global $user;

    /* @var $transition WorkflowTransition */
    $transition = NULL;
    if (isset($form_state['WorkflowTransition'])) {
      // If provided, get data from WorkflowTransition.
      // This happens when calling entity_ui_get_form(), like in the
      // WorkflowTransition Comment Edit form.
      $transition = $form_state['WorkflowTransition'];

      $field_name = $transition->field_name;
      $workflow = $transition->getWorkflow();
      $wid = $transition->wid;

      $entity = $this->entity = $transition->getEntity();
      $entity_type = $this->entity_type = $transition->entity_type;
      // Figure out the $entity's bundle and id.
      list(, , $entity_bundle) = entity_extract_ids($entity_type, $entity);
      $entity_id = entity_id($entity_type, $entity);

      // Show the current state and the Workflow form to allow state changing.
      // N.B. This part is replicated in hook_node_view, workflow_tab_page, workflow_vbo, transition_edit.
      // @todo: support multiple workflows per entity.
      // For workflow_tab_page with multiple workflows, use a separate view. See [#2217291].
      $field = _workflow_info_field($field_name, $workflow);
      $instance = $this->instance + field_info_instance($entity_type, $field_name, $entity_bundle);
    }
    else {
      // Get data from normal parameters.
      $entity = $this->entity;
      $entity_type = $this->entity_type;
      $entity_id = ($entity) ? entity_id($entity_type, $entity) : 0;

      $field = $this->field;
      $field_name = $field['field_name'];
      $instance = $this->instance;

      // $field['settings']['wid'] can be numeric or named.
      // $wid may not be specified.
      $wid = $field['settings']['wid'];
      $workflow = workflow_load_single($wid);
    }

    $force = FALSE;

    // Get values.
    // Current sid and default value may differ in a scheduled transition.
    // Set 'grouped' option. Only valid for select list and undefined/multiple workflows.
    $settings_options_type = $field['settings']['widget']['options'];
    $grouped = ($settings_options_type == 'select');
    if ($transition) {
      // If a Transition is passed as parameter, use this.
      if ($transition->isExecuted()) {
        // We are editing an existing/executed/not-scheduled transition.
        // Only the comments may be changed!
        // Fetch the old state for the formatter on top of form.
        $current_state = $transition->getOldState();
        $current_sid = $current_state->sid;

        // The states may not be changed anymore.
        $new_state = $transition->getNewState();
        $options = array($new_state->sid => $new_state->label());
        // We need the widget to edit the comment.
        $show_widget = TRUE;
      }
      else {
        $current_state = $transition->getOldState();
        $current_sid = $current_state->sid;
        $options = $current_state->getOptions($entity_type, $entity, $field_name, $user, $force);
        $show_widget = $current_state->showWidget($entity_type, $entity, $field_name, $user, $force);
      }
      $default_value = $transition->new_sid;
    }
    elseif (!$entity) {
      // Sometimes, no entity is given. We encountered the following cases:
      // - the Field settings page,
      // - the VBO action form;
      // - the Advance Action form on admin/config/system/actions;
      // If so, show all options for the given workflow(s).
      $options = workflow_get_workflow_state_names($wid, $grouped, $all = FALSE);
      $show_widget = TRUE;
      $default_value = $current_sid = isset($items[0]['value']) ? $items[0]['value'] : '0';
    }
    else {
      $current_sid = workflow_node_current_state($entity, $entity_type, $field_name);
      if ($current_state = workflow_state_load_single($current_sid)) {
        /* @var $current_state WorkflowTransition */
        $options = $current_state->getOptions($entity_type, $entity, $field_name, $user, $force);
        $show_widget = $current_state->showWidget($entity_type, $entity, $field_name, $user, $force);
        $default_value = !$current_state->isCreationState() ? $current_sid : $workflow->getFirstSid($entity_type, $entity, $field_name, $user, FALSE);
      }
      else {
        // We are in trouble! A message is already set in workflow_node_current_state().
        $options = array();
        $show_widget = FALSE;
        $default_value = $current_sid;
      }

      // Get the scheduling info. This may change the $default_value on the Form.
      // Read scheduled information, only if an entity exists.
      // Technically you could have more than one scheduled, but this will only add the soonest one.
      foreach (WorkflowScheduledTransition::load($entity_type, $entity_id, $field_name, 1) as $transition) {
        $default_value = $transition->new_sid;
        break;
      }
    }
    // Prepare a new transition, if still not provided.
    if (!$transition) {
      $transition = new WorkflowTransition(array(
        'old_sid' => $default_value,
        'stamp' => REQUEST_TIME,
      ));
    }

    // Fetch the form ID. This is unique for each entity, to allow multiple form per page (Views, etc.).
    // Make it uniquer by adding the field name, or else the scheduling of
    // multiple workflow_fields is not independent of each other.
    // IF we are truly on a Transition form (so, not a Node Form with widget)
    // then change the form id, too.
    $form_id = $this->getFormId();
    if (!isset($form_state['build_info']['base_form_id'])) {
      // Strange: on node form, the base_form_id is node_form,
      // but on term form, it is not set.
      // In both cases, it is OK. 
    }
    else {
      if ($form_state['build_info']['base_form_id'] == 'workflow_transition_wrapper_form') {
        $form_state['build_info']['base_form_id'] = 'workflow_transition_form';
      }
      if ($form_state['build_info']['base_form_id'] == 'workflow_transition_form') {
        $form_state['build_info']['form_id'] = $form_id;
      }
    }

    $workflow_label = $workflow ? $workflow->label() : '';

    // Change settings locally.
    if (!$field_name) {
      // This is a Workflow Node workflow. Set widget options as in v7.x-1.2
      if ($form_state['build_info']['base_form_id'] == 'node_form') {
        $field['settings']['widget']['comment'] = isset($workflow->options['comment_log_node']) ? $workflow->options['comment_log_node'] : 1; // vs. ['comment_log_tab'];
        $field['settings']['widget']['current_status'] = TRUE;
      }
      else {
        $field['settings']['widget']['comment'] = isset($workflow->options['comment_log_tab']) ? $workflow->options['comment_log_tab'] : 1; // vs. ['comment_log_node'];
        $field['settings']['widget']['current_status'] = TRUE;
      }
    }

    // Capture settings to format the form/widget.
    $settings_title_as_name = !empty($field['settings']['widget']['name_as_title']);
    $settings_fieldset = isset($field['settings']['widget']['fieldset']) ? $field['settings']['widget']['fieldset'] : 0;
    $settings_options_type = $field['settings']['widget']['options'];
    // The scheduling info can be hidden via field settings, ...
    // You may not schedule an existing Transition.
    // You must have the correct permission.
    $settings_schedule = !empty($field['settings']['widget']['schedule']) && !$transition->isExecuted() && user_access('schedule workflow transitions');
    if ($settings_schedule) {
      if (isset($form_state['step']) && ($form_state['step'] == 'views_bulk_operations_config_form')) {
        // On VBO 'modify entity values' form, leave field settings.
        $settings_schedule = TRUE;
      }
      else {
        // ... and cannot be shown on a Content add page (no $entity_id),
        // ...but can be shown on a VBO 'set workflow state to..'page (no entity).
        $settings_schedule = !($entity && !$entity_id);
      }
    }
    $settings_schedule_timezone = !empty($field['settings']['widget']['schedule_timezone']);
    // Show comment, when both Field and Instance allow this.
    $settings_comment = $field['settings']['widget']['comment'];

    // Save the current value of the node in the form, for later Workflow-module specific references.
    // We add prefix, since #tree == FALSE.
    $element['workflow']['workflow_entity'] = array(
      '#type' => 'value',
      '#value' => $this->entity,
    );
    $element['workflow']['workflow_entity_type'] = array(
      '#type' => 'value',
      '#value' => $this->entity_type,
    );
    $element['workflow']['workflow_field'] = array(
      '#type' => 'value',
      '#value' => $field,
    );
    $element['workflow']['workflow_instance'] = array(
      '#type' => 'value',
      '#value' => $instance,
    );

    // Save the form_id, so the form values can be retrieved in submit function.
    $element['workflow']['form_id'] = array(
      '#type' => 'value',
      '#value' => $form_id,
    );

    // Save the hid, when editing an existing transition.
    $element['workflow']['workflow_hid'] = array(
      '#type' => 'hidden',
      '#value' => $transition->hid,
    );

    // Add the default value in the place where normal fields
    // have it. This is to cater for 'preview' of the entity.
    $element['#default_value'] = $default_value;

    // Decide if we show a widget or a formatter.
    // There is no need for a widget when the only option is the current sid.

    // Show state formatter before the rest of the form,
    // when transition is scheduled or widget is hidden.
    if ( (!$show_widget) || $transition->isScheduled() || $transition->isExecuted()) {
      $form['workflow_current_state'] = workflow_state_formatter($entity_type, $entity, $field, $instance, $current_sid);
      // Set a proper weight, which works for Workflow Options in select list AND action buttons.
      $form['workflow_current_state']['#weight'] = -0.005;
    }

    // Add class following node-form pattern (both on form and container).
    $workflow_type_id = ($workflow) ? $workflow->getName() : 'none'; // No workflow on New Action form.
    $element['workflow']['#attributes']['class'][] = 'workflow-transition-container';
    $element['workflow']['#attributes']['class'][] = 'workflow-transition-' . $workflow_type_id . '-container';
    // Add class for D7-backwards compatibility (only on container).
    $element['workflow']['#attributes']['class'][] = 'workflow-form-container';

    if (!$show_widget) {
      // Show no widget.
      $element['workflow']['workflow_sid']['#type'] = 'value';
      $element['workflow']['workflow_sid']['#value'] = $default_value;
      $element['workflow']['workflow_sid']['#options'] = $options; // In case action buttons need them.

      $form += $element;
      return $form;  // <-- exit.
    }
    else {
      // Prepare a UI wrapper. This might be a fieldset or a container.
      if ($settings_fieldset == 0) { // Use 'container'.
        $element['workflow'] += array(
          '#type' => 'container',
        );
      }
      else {
        $element['workflow'] += array(
          '#type' => 'fieldset',
          '#title' => $workflow_label,
          '#collapsible' => TRUE,
          '#collapsed' => ($settings_fieldset == 1) ? FALSE : TRUE,
        );
      }

      // The 'options' widget. May be removed later if 'Action buttons' are chosen.
      // The help text is not available for container. Let's add it to the
      // State box.
      $help_text = isset($instance['description']) ? $instance['description'] : '';
      $element['workflow']['workflow_sid'] = array(
        '#type' => $settings_options_type,
        '#title' => $settings_title_as_name ? t('Change @name state', array('@name' => $workflow_label)) : t('Target state'),
        '#access' => TRUE,
        '#options' => $options,
        // '#name' => $workflow_label,
        // '#parents' => array('workflow'),
        '#default_value' => $default_value,
        '#description' => t('@help', array('@help' => $help_text)),
      );
    }

    // Display scheduling form, but only if entity is being edited and user has
    // permission. State change cannot be scheduled at entity creation because
    // that leaves the entity in the (creation) state.
    if ($settings_schedule == TRUE) {
      if (variable_get('configurable_timezones', 1) && $user->uid && drupal_strlen($user->timezone)) {
        $timezone = $user->timezone;
      }
      else {
        $timezone = variable_get('date_default_timezone', 0);
      }
      $timezones = drupal_map_assoc(timezone_identifiers_list());
      $timestamp = $transition->getTimestamp();
      $hours = (!$transition->isScheduled()) ? '00:00' : format_date($timestamp, 'custom', 'H:i', $timezone);
      // Add a container, so checkbox and time stay together in extra fields.
      $element['workflow']['workflow_scheduling'] = array(
        '#type' => 'container',
        '#tree' => TRUE,
      );
      $element['workflow']['workflow_scheduling']['scheduled'] = array(
        '#type' => 'radios',
        '#title' => t('Schedule'),
        '#options' => array(
          '0' => t('Immediately'),
          '1' => t('Schedule for state change'),
        ),
        '#default_value' => $transition->isScheduled() ? '1' : '0',
        '#attributes' => array(
          // 'id' => 'scheduled_' . $form_id,
          'class' => array(drupal_html_class('scheduled_' .  $form_id)),
        ),
      );
      $element['workflow']['workflow_scheduling']['date_time'] = array(
        '#type' => 'fieldset',
        '#title' => t('At'),
        '#attributes' => array('class' => array('container-inline')),
        '#prefix' => '<div style="margin-left: 1em;">',
        '#suffix' => '</div>',
        '#states' => array(
          //'visible' => array(':input[id="' . 'scheduled_' . $form_id . '"]' => array('value' => '1')),
          'visible' => array('input.' . drupal_html_class('scheduled_' .  $form_id) => array('value' => '1')),
        ),
      );
      $element['workflow']['workflow_scheduling']['date_time']['workflow_scheduled_date'] = array(
        '#type' => 'date',
        '#default_value' => array(
          'day' => date('j', $timestamp),
          'month' => date('n', $timestamp),
          'year' => date('Y', $timestamp),
        ),
      );
      $element['workflow']['workflow_scheduling']['date_time']['workflow_scheduled_hour'] = array(
        '#type' => 'textfield',
        '#title' => t('Time'),
        '#maxlength' => 7,
        '#size' => 6,
        '#default_value' => $hours,
        '#element_validate' => array('_workflow_transition_form_element_validate_time'),
      );
      $element['workflow']['workflow_scheduling']['date_time']['workflow_scheduled_timezone'] = array(
        '#type' => $settings_schedule_timezone ? 'select' : 'hidden',
        '#title' => t('Time zone'),
        '#options' => $timezones,
        '#default_value' => array($timezone => $timezone),
      );
      $element['workflow']['workflow_scheduling']['date_time']['workflow_scheduled_help'] = array(
        '#type' => 'item',
        '#prefix' => '<br />',
        '#description' => t('Please enter a time.
          If no time is included, the default will be midnight on the specified date.
          The current time is: @time.', array('@time' => format_date(REQUEST_TIME, 'custom', 'H:i', $timezone))
        ),
      );
    }

    $element['workflow']['workflow_comment'] = array(
      '#type' => 'textarea',
      '#required' => $settings_comment == '2',
      '#access' => $settings_comment !='0', // Align with action buttons.
      '#title' => t('Workflow comment'),
      '#description' => t('A comment to put in the workflow log.'),
      '#default_value' => $transition->comment,
      '#rows' => 2,
    );

    // Add the fields and extra_fields from the WorkflowTransition.
    // Because we have a 'workflow' wrapper, it doesn't work flawlessly.
    field_attach_form('WorkflowTransition', $transition, $element['workflow'], $form_state);
    // Undo the following elements from field_attach_from. They mess up $this->getTransition().
    // - '#parents' corrupts the Defaultwidget.
    unset($element['workflow']['#parents']);
    // - '#pre_render' adds the exra_fields from workflow_field_extra_fields().
    //   That doesn't work, since 'workflow' is not of #type 'form', but
    //   'container' or 'fieldset', and must be executed separately,.
    $element['workflow']['#pre_render'] = array_diff( $element['workflow']['#pre_render'], array('_field_extra_fields_pre_render') );
    // Add extra fields.
    $rescue_value = $element['workflow']['#type'];
    $element['workflow']['#type'] = 'form';
    $element['workflow'] = _field_extra_fields_pre_render($element['workflow']);
    $element['workflow']['#type'] = $rescue_value;

    // Finally, add Submit buttons/Action buttons.
    // Either a default 'Submit' button is added, or a button per permitted state.
    if ($settings_options_type == 'buttons') {
      // How do action buttons work? See also d.o. issue #2187151.
      // Create 'action buttons' per state option. Set $sid property on each button.
      // 1. Admin sets ['widget']['options']['#type'] = 'buttons'.
      // 2. This function formElement() creates 'action buttons' per state option;
      //    sets $sid property on each button.
      // 3. User clicks button.
      // 4. Callback _workflow_transition_form_validate_buttons() sets proper State.
      // 5. Callback _workflow_transition_form_validate_buttons() sets Submit function.
      // @todo: this does not work yet for the Add Comment form.

      // Performance: inform workflow_form_alter() to do its job.
      _workflow_use_action_buttons(TRUE);

      // Hide the options box. It will be replaced by action buttons.
      $element['workflow']['workflow_sid']['#type'] = 'select';
      $element['workflow']['workflow_sid']['#access'] = FALSE;
    }

    // Some forms (Term) do not have 'base_form_id' set.
    if (isset($form_state['build_info']['base_form_id']) && $form_state['build_info']['base_form_id'] == 'workflow_transition_form') {
      // Add action buttons on WorkflowTransitionForm (history tab, formatter)
      // but not on Entity form, and not if action_buttons is selected.

      // you can explicitly NOT add a submit button, e.g., on VBO page.
      if ($instance['widget']['settings']['submit_function'] !== '') {
        // @todo D8: put buttons outside of 'workflow' element, in the standard location.
        $element['workflow']['actions']['#type'] = 'actions';
        $element['workflow']['actions']['submit'] = array(
          '#type' => 'submit',
//        '#access' => TRUE,
          '#value' => t('Update workflow'),
          '#weight' => -5,
//        '#submit' => array( isset($instance['widget']['settings']['submit_function']) ? $instance['widget']['settings']['submit_function'] : NULL),
          // '#executes_submit_callback' => TRUE,
          '#attributes' => array('class' => array('form-save-default-button')),
        );
        // The 'add submit' can explicitly set by workflowfield_field_formatter_view(),
        // to add the submit button on the Content view page and the Workflow history tab.
        // Add a submit button, but only on Entity View and History page.
        // Add the submit function only if one provided. Set the submit_callback accordingly.
        if (!empty($instance['widget']['settings']['submit_function'])) {
          $element['workflow']['actions']['submit']['#submit'] = array($instance['widget']['settings']['submit_function']);
        }
        else {
          // '#submit' Must be empty, or else the submit function is not called.
          // $element['workflow']['actions']['submit']['#submit'] = array();
        }
      }
    }
    /*
    $submit_functions = empty($instance['widget']['settings']['submit_function']) ? array() : array($instance['widget']['settings']['submit_function']);
    if ($settings_options_type == 'buttons' || $submit_functions) {
    }
    else {
      // In some cases, no submit callback function is specified. This is
      // explicitly done on e.g., the node edit form, because the workflow form
      // is 'just a field'.
      // So, no Submit button is to be shown.
    }
     */

    $form += $element;

    // Add class following node-form pattern (both on form and container).
    $workflow_type_id = ($workflow) ? $workflow->getName() : 'none'; // No workflow on New Action form.
    $form['#attributes']['class'][] = 'workflow-transition-form';
    $form['#attributes']['class'][] = 'workflow-transition-' . $workflow_type_id . '-form';

    return $form;
  }

  /**
   * {@inheritdoc}
   */
  public function validateForm(array &$form, array $form_state) {
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, array &$form_state, array &$items) {
    // $items is a D7 parameter.
    // @todo: clean this code up. It is the result of gluing code together.
    global $user; // @todo #2287057: verify if submit() really is only used for UI. If not, $user must be passed.

    $entity = $this->entity;
    $entity_type = $this->entity_type;

    $field = $this->field;
    $field_name = $field['field_name'];

    // Retrieve the data from the form.
    if (isset($form_state['values']['workflow_field'])) {
      // If $entity filled: We are on a Entity View page or Workflow History Tab page.
      // If $entity empty: We are on an Advanced Action page.
//      $field = $form_state['values']['workflow_field'];
//      $instance = $form_state['values']['workflow_instance'];
//      $entity_type = $form_state['values']['workflow_entity_type'];
//      $entity = $form_state['values']['workflow_entity'];
//      $field_name = $field['field_name'];
    }
    elseif (isset($form_state['triggering_element'])) {
      // We are on an Entity/Node/Comment Form page (add/edit).
      $field_name = $form_state['triggering_element']['#workflow_field_name'];
    }
    else {
      // We are on an Entity/Comment Form page (add/edit).
    }

    // Determine if the transition is forced.
    // This can be set by a 'workflow_vbo action' in an additional form element.
    $force = isset($form_state['input']['workflow_force']) ? $form_state['input']['workflow_force'] : FALSE;

    // Set language. Multi-language is not supported for Workflow Node.
    $langcode = _workflow_metadata_workflow_get_properties($entity, array(), 'langcode', $entity_type, $field_name);

    if (!$entity) {
      // E.g., on VBO form.
    }
    elseif ($field_name) {
      // Save the entity, but only if we were not in edit mode.
      // Perhaps there is a better way, but for now we use 'changed' property.
      // Also test for 'is_new'. When Migrating content, the 'changed' property may be set externally.
      // Caveat: Some entities do not have 'changed' property set.
      if ((!empty($entity->is_new)) || (isset($entity->changed) && $entity->changed == REQUEST_TIME)) {
        // N.B. ONLY for Nodes!
        // We are in add/edit mode. No need to save the entity explicitly.

//        // Add the $form_state to the $items, so we can do a getTransition() later on.
//        $items[0]['workflow'] = $form_state['input'];
//        // Create a Transition. The Widget knows if it is scheduled.
//        $widget = new WorkflowDefaultWidget($field, $instance, $entity_type, $entity);
//        $new_sid = $widget->submit($form, $form_state, $items, $force);
      }
      elseif (isset($form_state['input'])) {
        // Save $entity, but only if sid has changed.
        // Use field_attach_update for this? Save always?
        $entity->{$field_name}[$langcode][0]['workflow'] = $form_state['input'];
        // @todo & totest: Save ony the field, not the complete entity.
        // workflow_entity_field_save($entity_type, $entity, $field_name, $langcode, FALSE);
        entity_save($entity_type, $entity);

        return; // <-- exit!
      }
      elseif ($entity_type == 'node') {
        // N.B. ONLY for Nodes!
        // We are saving a node from a comment.
        $entity->{$field_name}[$langcode] = $items;
        // @todo & totest: Save ony the field, not the complete entity.
        // workflow_entity_field_save($entity_type, $entity, $field_name, $langcode, FALSE);
        entity_save($entity_type, $entity);

        return; // <-- exit!
      }
      else {
        // We are saving a non-node from an entity form.
        $entity->{$field_name}[$langcode] = $items;
      }
    }
    else {
      // For a Node API form, only contrib fields need to be filled.
      // No updating of the node itself.
      // (Unless we need to record the timestamp.)

      // Add the $form_state to the $items, so we can do a getTransition() later on.
      $items[0]['workflow'] = $form_state['input'];
//      // Create a Transition. The Widget knows if it is scheduled.
//      $widget = new WorkflowDefaultWidget($field, $instance, $entity_type, $entity);
//      $new_sid = $widget->submit($form, $form_state, $items, $force);
    }

    // Extract the data from $items, depending on the type of widget.
    // @todo D8: use MassageFormValues($values, $form, $form_state).
    $old_sid = workflow_node_previous_state($entity, $entity_type, $field_name);
    if (!$old_sid) {
      // At this moment, $old_sid should have a value. If the content does not
      // have a state yet, old_sid contains '(creation)' state. But if the
      // content is not associated to a workflow, old_sid is now 0. This may
      // happen in workflow_vbo, if you assign a state to non-relevant nodes.
      $entity_id = entity_id($entity_type, $entity);
      drupal_set_message(t('Error: content @id has no workflow attached. The data is not saved.', array('@id' => $entity_id)), 'error');
      // The new state is still the previous state.
      $new_sid = $old_sid;
      return $new_sid;
    }

    // Now, save/execute the transition.
    $transition = $this->getTransition($old_sid, $items, $field_name, $user, $form, $form_state);

    // Try to execute the transition. Return $old_sid when error.
    if (!$transition) {
      // This should only happen when testing/developing.
      drupal_set_message(t('Error: the transition from @old_sid to @new_sid could not be generated.',
        array('@old_sid' => $old_sid, '@new_sid' => $new_sid)), 'error');
      // The current value is still the previous state.
      $new_sid = $old_sid;
    }
    elseif ($transition->isScheduled() || $transition->isExecuted()) {
      // A scheduled or executed transition must only be saved to the database.
      // The entity is not changed.
      $force = $force || $transition->isForced();
      $transition->save();

      // The current value is still the previous state.
      $new_sid = $old_sid;
    }
    elseif (!$transition->isScheduled()) {
      // Now the data is captured in the Transition, and before calling the
      // Execution, restore the default values for Workflow Field.
      // For instance, workflow_rules evaluates this.
      if ($field_name) {
        // $items = array();
        // $items[0]['value'] = $old_sid;
        // $entity->{$field_name}[$transition->language] = $items;
      }

      // It's an immediate change. Do the transition.
      // - validate option; add hook to let other modules change comment.
      // - add to history; add to watchdog
      // Return the new State ID. (Execution may fail and return the old Sid.)
      $force = $force || $transition->isForced();
      $new_sid = $transition->execute($force);
    }

    // The entity is still to be saved, so set to a 'normal' value.
    if ($field_name) {
      $items = array();
      $items[0]['value'] = $new_sid;
      $entity->{$field_name}[$transition->language] = $items;
    }

    return $new_sid;
  }

  /**
   * Extract WorkflowTransition or WorkflowScheduledTransition from the form.
   *
   * This merely extracts the transition from the form/widget. No validation.
   *
   * @param $old_sid
   * @param array $items
   * @param $field_name
   * @param \stdClass $user
   *
   * @return \WorkflowScheduledTransition|\WorkflowTransition|null
   */
  public function getTransition($old_sid, array $items, $field_name, stdClass $user, array &$form = array(), array &$form_state = array()) {
    $entity_type = $this->entity_type;
    $entity = $this->entity;
    // $entity_id = entity_id($entity_type, $entity);
    $field_name = !empty($this->field) ? $this->field['field_name'] : '';

    if (isset($items[0]['transition'])) {
      // a complete transition was already passed on.
      $transition = $items[0]['transition'];
    }
    else {
      // Get the new Transition properties. First the new State ID.
      if (isset($items[0]['workflow']['workflow_sid'])) {
        // We have shown a workflow form.
        $new_sid = $items[0]['workflow']['workflow_sid'];
      }
      elseif (isset($items[0]['value'])) {
        // We have shown a core options widget (radios, select).
        $new_sid = $items[0]['value'];
      }
      else {
        // This may happen if only 1 option is left, and a formatter is shown.
        $state = workflow_state_load_single($old_sid);
        if (!$state->isCreationState()) {
          $new_sid = $old_sid;
        }
        else {
          // This only happens on workflows, when only one transition from
          // '(creation)' to another state is allowed.
          /* @var $workflow Workflow */
          $workflow = $state->getWorkflow();
          $new_sid = $workflow->getFirstSid($this->entity_type, $this->entity, $field_name, $user, FALSE);
        }
      }
      // If an existing Transition has been edited, $hid is set.
      $hid = isset($items[0]['workflow']['workflow_hid']) ? $items[0]['workflow']['workflow_hid'] : '';
      // Get the comment.
      $comment = isset($items[0]['workflow']['workflow_comment']) ? $items[0]['workflow']['workflow_comment'] : '';
      // Remember, the workflow_scheduled element is not set on 'add' page.
      $scheduled = !empty($items[0]['workflow']['workflow_scheduling']['scheduled']);
      if ($hid) {
        // We are editing an existing transition. Only comment may be changed.
        $transition = workflow_transition_load($hid);
        $transition->comment = $comment;
      }
      elseif (!$scheduled) {
        $transition = new WorkflowTransition();
        $transition->setValues($entity_type, $entity, $field_name, $old_sid, $new_sid, $user->uid, REQUEST_TIME, $comment);
      }
      else {
        // Schedule the time to change the state.
        // If Field Form is used, use plain values;
        // If Node Form is used, use fieldset 'date_time'.
        $schedule = isset($items[0]['workflow']['workflow_scheduling']['date_time']) ? $items[0]['workflow']['workflow_scheduling']['date_time'] : $items[0]['workflow'];
        if (!isset($schedule['workflow_scheduled_hour'])) {
          $schedule['workflow_scheduled_hour'] = '00:00';
        }

        $scheduled_date_time
          = $schedule['workflow_scheduled_date']['year']
          . substr('0' . $schedule['workflow_scheduled_date']['month'], -2, 2)
          . substr('0' . $schedule['workflow_scheduled_date']['day'], -2, 2)
          . ' '
          . $schedule['workflow_scheduled_hour']
          . ' '
          . $schedule['workflow_scheduled_timezone'];

        if ($timestamp = strtotime($scheduled_date_time)) {
          $transition = new WorkflowScheduledTransition();
          $transition->setValues($entity_type, $entity, $field_name, $old_sid, $new_sid, $user->uid, $timestamp, $comment);
        }
        else {
          $transition = NULL;
        }
      }
    }
    return $transition;
  }

}