class SectionComponent

class SectionComponent {
    
    /**
     * The UUID of the component.
     *
     * @var string
     */
    protected $uuid;
    
    /**
     * The region the component is placed in.
     *
     * @var string
     */
    protected $region;
    
    /**
     * An array of plugin configuration.
     *
     * @var mixed[]
     */
    protected $configuration;
    
    /**
     * The weight of the component.
     *
     * @var int
     */
    protected $weight = 0;
    
    /**
     * Any additional properties and values.
     *
     * @var mixed[]
     */
    protected $additional = [];
    
    /**
     * Constructs a new SectionComponent.
     *
     * @param string $uuid
     *   The UUID.
     * @param string $region
     *   The region.
     * @param mixed[] $configuration
     *   The plugin configuration.
     * @param mixed[] $additional
     *   An additional values.
     */
    public function __construct($uuid, $region, array $configuration = [], array $additional = []) {
        $this->uuid = $uuid;
        $this->region = $region;
        $this->configuration = $configuration;
        $this->additional = $additional;
    }
    
    /**
     * Returns the renderable array for this component.
     *
     * @param \Drupal\Core\Plugin\Context\ContextInterface[] $contexts
     *   An array of available contexts.
     * @param bool $in_preview
     *   TRUE if the component is being previewed, FALSE otherwise.
     *
     * @return array
     *   A renderable array representing the content of the component.
     */
    public function toRenderArray(array $contexts = [], $in_preview = FALSE) {
        $event = new SectionComponentBuildRenderArrayEvent($this, $contexts, $in_preview);
        $this->eventDispatcher()
            ->dispatch(LayoutBuilderEvents::SECTION_COMPONENT_BUILD_RENDER_ARRAY, $event);
        $output = $event->getBuild();
        $event->getCacheableMetadata()
            ->applyTo($output);
        return $output;
    }
    
    /**
     * Gets any arbitrary property for the component.
     *
     * @param string $property
     *   The property to retrieve.
     *
     * @return mixed
     *   The value for that property, or NULL if the property does not exist.
     */
    public function get($property) {
        if (property_exists($this, $property)) {
            $value = isset($this->{$property}) ? $this->{$property} : NULL;
        }
        else {
            $value = isset($this->additional[$property]) ? $this->additional[$property] : NULL;
        }
        return $value;
    }
    
    /**
     * Sets a value to an arbitrary property for the component.
     *
     * @param string $property
     *   The property to use for the value.
     * @param mixed $value
     *   The value to set.
     *
     * @return $this
     */
    public function set($property, $value) {
        if (property_exists($this, $property)) {
            $this->{$property} = $value;
        }
        else {
            $this->additional[$property] = $value;
        }
        return $this;
    }
    
    /**
     * Gets the region for the component.
     *
     * @return string
     *   The region.
     */
    public function getRegion() {
        return $this->region;
    }
    
    /**
     * Sets the region for the component.
     *
     * @param string $region
     *   The region.
     *
     * @return $this
     */
    public function setRegion($region) {
        $this->region = $region;
        return $this;
    }
    
    /**
     * Gets the weight of the component.
     *
     * @return int
     *   The zero-based weight of the component.
     *
     * @throws \UnexpectedValueException
     *   Thrown if the weight was never set.
     */
    public function getWeight() {
        return $this->weight;
    }
    
    /**
     * Sets the weight of the component.
     *
     * @param int $weight
     *   The zero-based weight of the component.
     *
     * @return $this
     */
    public function setWeight($weight) {
        $this->weight = $weight;
        return $this;
    }
    
    /**
     * Gets the component plugin configuration.
     *
     * @return mixed[]
     *   The component plugin configuration.
     */
    protected function getConfiguration() {
        return $this->configuration;
    }
    
    /**
     * Sets the plugin configuration.
     *
     * @param mixed[] $configuration
     *   The plugin configuration.
     *
     * @return $this
     */
    public function setConfiguration(array $configuration) {
        $this->configuration = $configuration;
        return $this;
    }
    
    /**
     * Gets the plugin ID.
     *
     * @return string
     *   The plugin ID.
     *
     * @throws \Drupal\Component\Plugin\Exception\PluginException
     *   Thrown if the plugin ID cannot be found.
     */
    public function getPluginId() {
        if (empty($this->configuration['id'])) {
            throw new PluginException(sprintf('No plugin ID specified for component with "%s" UUID', $this->uuid));
        }
        return $this->configuration['id'];
    }
    
    /**
     * Gets the UUID for this component.
     *
     * @return string
     *   The UUID.
     */
    public function getUuid() {
        return $this->uuid;
    }
    
    /**
     * Gets the plugin for this component.
     *
     * @param \Drupal\Core\Plugin\Context\ContextInterface[] $contexts
     *   An array of contexts to set on the plugin.
     *
     * @return \Drupal\Component\Plugin\PluginInspectionInterface
     *   The plugin.
     */
    public function getPlugin(array $contexts = []) {
        $plugin = $this->pluginManager()
            ->createInstance($this->getPluginId(), $this->getConfiguration());
        if ($contexts && $plugin instanceof ContextAwarePluginInterface) {
            $this->contextHandler()
                ->applyContextMapping($plugin, $contexts);
        }
        return $plugin;
    }
    
    /**
     * Wraps the component plugin manager.
     *
     * @return \Drupal\Core\Block\BlockManagerInterface
     *   The plugin manager.
     */
    protected function pluginManager() {
        // @todo Figure out the best way to unify fields and blocks and components
        //   in https://www.drupal.org/node/1875974.
        return \Drupal::service('plugin.manager.block');
    }
    
    /**
     * Wraps the context handler.
     *
     * @return \Drupal\Core\Plugin\Context\ContextHandlerInterface
     *   The context handler.
     */
    protected function contextHandler() {
        return \Drupal::service('context.handler');
    }
    
    /**
     * Wraps the event dispatcher.
     *
     * @return \Symfony\Component\EventDispatcher\EventDispatcherInterface
     *   The event dispatcher.
     */
    protected function eventDispatcher() {
        return \Drupal::service('event_dispatcher');
    }
    
    /**
     * Returns an array representation of the section component.
     *
     * Only use this method if you are implementing custom storage for sections.
     *
     * @return array
     *   An array representation of the section component.
     */
    public function toArray() {
        return [
            'uuid' => $this->getUuid(),
            'region' => $this->getRegion(),
            'configuration' => $this->getConfiguration(),
            'additional' => $this->additional,
            'weight' => $this->getWeight(),
        ];
    }
    
    /**
     * Creates an object from an array representation of the section component.
     *
     * Only use this method if you are implementing custom storage for sections.
     *
     * @param array $component
     *   An array of section component data in the format returned by ::toArray().
     *
     * @return static
     *   The section component object.
     */
    public static function fromArray(array $component) {
        return (new static($component['uuid'], $component['region'], $component['configuration'], $component['additional']))->setWeight($component['weight']);
    }

}