Chris@0: <?php
Chris@0: 
Chris@0: namespace Drupal\Core\Plugin;
Chris@0: 
Chris@0: /**
Chris@0:  * Handles context assignments for context-aware plugins.
Chris@0:  */
Chris@0: trait ContextAwarePluginAssignmentTrait {
Chris@0: 
Chris@0:   /**
Chris@0:    * Ensures the t() method is available.
Chris@0:    *
Chris@0:    * @see \Drupal\Core\StringTranslation\StringTranslationTrait
Chris@0:    */
Chris@0:   abstract protected function t($string, array $args = [], array $options = []);
Chris@0: 
Chris@0:   /**
Chris@0:    * Wraps the context handler.
Chris@0:    *
Chris@0:    * @return \Drupal\Core\Plugin\Context\ContextHandlerInterface
Chris@0:    */
Chris@0:   protected function contextHandler() {
Chris@0:     return \Drupal::service('context.handler');
Chris@0:   }
Chris@0: 
Chris@0:   /**
Chris@0:    * Builds a form element for assigning a context to a given slot.
Chris@0:    *
Chris@0:    * @param \Drupal\Core\Plugin\ContextAwarePluginInterface $plugin
Chris@0:    *   The context-aware plugin.
Chris@0:    * @param \Drupal\Component\Plugin\Context\ContextInterface[] $contexts
Chris@0:    *   An array of contexts.
Chris@0:    *
Chris@0:    * @return array
Chris@0:    *   A form element for assigning context.
Chris@0:    */
Chris@0:   protected function addContextAssignmentElement(ContextAwarePluginInterface $plugin, array $contexts) {
Chris@0:     $element = [];
Chris@0:     foreach ($plugin->getContextDefinitions() as $context_slot => $definition) {
Chris@0:       $valid_contexts = $this->contextHandler()->getMatchingContexts($contexts, $definition);
Chris@0:       $options = [];
Chris@0:       foreach ($valid_contexts as $context_id => $context) {
Chris@0:         $element['#tree'] = TRUE;
Chris@0:         $options[$context_id] = $context->getContextDefinition()->getLabel();
Chris@0:         $element[$context_slot] = [
Chris@0:           '#type' => 'value',
Chris@0:           '#value' => $context_id,
Chris@0:         ];
Chris@0:       }
Chris@0: 
Chris@17:       // Show the context selector only if there is more than 1 option to choose
Chris@17:       // from. Also, show if there is a single option but the plugin does not
Chris@17:       // require a context.
Chris@17:       if (count($options) > 1 || (count($options) == 1 && !$definition->isRequired())) {
Chris@0:         $assignments = $plugin->getContextMapping();
Chris@0:         $element[$context_slot] = [
Chris@0:           '#title' => $definition->getLabel() ?: $this->t('Select a @context value:', ['@context' => $context_slot]),
Chris@0:           '#type' => 'select',
Chris@0:           '#options' => $options,
Chris@0:           '#required' => $definition->isRequired(),
Chris@0:           '#default_value' => !empty($assignments[$context_slot]) ? $assignments[$context_slot] : '',
Chris@0:           '#description' => $definition->getDescription(),
Chris@0:         ];
Chris@0:         if (!$definition->isRequired()) {
Chris@0:           $element[$context_slot]['#empty_value'] = '';
Chris@0:         }
Chris@0:       }
Chris@0:     }
Chris@0:     return $element;
Chris@0:   }
Chris@0: 
Chris@0: }