trait ContextProviderTrait

trait ContextProviderTrait {
    
    /**
     * The data objects that are provided by this plugin.
     *
     * @var \Drupal\Component\Plugin\Context\ContextInterface[]
     */
    protected $providedContext;
    
    /**
     * @see \Drupal\rules\Context\ContextProviderInterface
     */
    public function setProvidedValue($name, $value) {
        $context = $this->getProvidedContext($name);
        $new_context = Context::createFromContext($context, $value);
        $this->providedContext[$name] = $new_context;
        return $this;
    }
    
    /**
     * @see \Drupal\rules\Context\ContextProviderInterface
     */
    public function getProvidedContext($name) {
        // Check for a valid context value.
        if (!isset($this->providedContext[$name])) {
            $this->providedContext[$name] = new Context($this->getProvidedContextDefinition($name));
        }
        return $this->providedContext[$name];
    }
    
    /**
     * @see \Drupal\rules\Context\ContextProviderInterface
     */
    public function getProvidedContextDefinition($name) {
        $definition = $this->getPluginDefinition();
        if (empty($definition['provides'][$name])) {
            throw new ContextException(sprintf("The provided context '%s' is not valid.", $name));
        }
        return $definition['provides'][$name];
    }
    
    /**
     * @see \Drupal\rules\Context\ContextProviderInterface
     */
    public function getProvidedContextDefinitions() {
        $definition = $this->getPluginDefinition();
        return !empty($definition['provides']) ? $definition['provides'] : [];
    }
    
    /**
     * Upcasts an entity id to a full entity object.
     *
     * Returns the entity object if the upcast was successful, otherwise returns
     * NULL.
     *
     * @todo Rather than returning NULL, we should probably throw an exception.
     * That way the calling code may attempt an upcast, then continue on as it
     * used to if the upcast fails.
     *
     * @param string $id
     *   The unique entity id to upcast to a full entity.
     * @param string $type
     *   The entity data type. For example, "entity:node".
     *
     * @return \Drupal\Core\Entity\EntityInterface|null
     *   The upcasted entity object (if successful) or null (if not).
     */
    public function upcastEntityId($id, $type) {
        // If the passed value is (accidentally) already an object, just return it.
        if (is_object($id)) {
            return $id;
        }
        $paramConverterManager = \Drupal::service('paramconverter_manager');
        
        /** @var \Drupal\Core\ParamConverter\ParamConverterInterface $param_converter */
        $param_converter = $paramConverterManager->getConverter('paramconverter.entity');
        // The $name variable is just an arbitrary slug for use in the route object.
        $name = 'id_to_upcast';
        // The $definition variable declares what datatype the slug represents.
        $definition = [
            'type' => $type,
        ];
        // The Route class used here is just a data structure for holding data
        // necessary for a route definition. Creating an object of this type does
        // not in any way affect routing on the site. We only use Route here because
        // the paramconverter_manager requires this structure for one of its inputs.
        $route = new Route('/{$name}');
        // Check that the definition can be upcast and if so do it.
        if ($param_converter->applies($definition, $name, $route)) {
            $defaults = [
                $name => $id,
            ];
            $upcasted_object = $param_converter->convert(strtolower($id), $definition, $name, $defaults);
            return $upcasted_object;
        }
        else {
            return NULL;
        }
    }

}