class WidgetPluginManager

class WidgetPluginManager extends DefaultPluginManager {
    
    /**
     * The field type manager to define field.
     *
     * @var \Drupal\Core\Field\FieldTypePluginManagerInterface
     */
    protected $fieldTypeManager;
    
    /**
     * An array of widget options for each field type.
     *
     * @var array
     */
    protected $widgetOptions;
    
    /**
     * Constructs a WidgetPluginManager object.
     *
     * @param \Traversable $namespaces
     *   An object that implements \Traversable which contains the root paths
     *   keyed by the corresponding namespace to look for plugin implementations.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   Cache backend instance to use.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler.
     * @param \Drupal\Core\Field\FieldTypePluginManagerInterface $field_type_manager
     *   The 'field type' plugin manager.
     */
    public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, FieldTypePluginManagerInterface $field_type_manager) {
        parent::__construct('Plugin/Field/FieldWidget', $namespaces, $module_handler, 'Drupal\\Core\\Field\\WidgetInterface', 'Drupal\\Core\\Field\\Annotation\\FieldWidget');
        $this->setCacheBackend($cache_backend, 'field_widget_types_plugins');
        $this->alterInfo('field_widget_info');
        $this->fieldTypeManager = $field_type_manager;
    }
    
    /**
     * Overrides PluginManagerBase::getInstance().
     *
     * @param array $options
     *   An array with the following key/value pairs:
     *   - field_definition: (FieldDefinitionInterface) The field definition.
     *   - form_mode: (string) The form mode.
     *   - prepare: (bool, optional) Whether default values should get merged in
     *     the 'configuration' array. Defaults to TRUE.
     *   - configuration: (array) the configuration for the widget. The
     *     following key value pairs are allowed, and are all optional if
     *     'prepare' is TRUE:
     *     - type: (string) The widget to use. Defaults to the
     *       'default_widget' for the field type. The default widget will also be
     *       used if the requested widget is not available.
     *     - settings: (array) Settings specific to the widget. Each setting
     *       defaults to the default value specified in the widget definition.
     *     - third_party_settings: (array) Settings provided by other extensions
     *       through hook_field_formatter_third_party_settings_form().
     *
     * @return \Drupal\Core\Field\WidgetInterface|null
     *   A Widget object or NULL when plugin is not found.
     */
    public function getInstance(array $options) {
        // Fill in defaults for missing properties.
        $options += [
            'configuration' => [],
            'prepare' => TRUE,
        ];
        $configuration = $options['configuration'];
        $field_definition = $options['field_definition'];
        $field_type = $field_definition->getType();
        // Fill in default configuration if needed.
        if ($options['prepare']) {
            $configuration = $this->prepareConfiguration($field_type, $configuration);
        }
        $plugin_id = $configuration['type'];
        // Switch back to default widget if either:
        // - the configuration does not specify a widget class
        // - the field type is not allowed for the widget
        // - the widget is not applicable to the field definition.
        $definition = $this->getDefinition($configuration['type'], FALSE);
        if (!isset($definition['class']) || !in_array($field_type, $definition['field_types']) || !$definition['class']::isApplicable($field_definition)) {
            // Grab the default widget for the field type.
            $field_type_definition = $this->fieldTypeManager
                ->getDefinition($field_type);
            if (empty($field_type_definition['default_widget'])) {
                return NULL;
            }
            $plugin_id = $field_type_definition['default_widget'];
        }
        $configuration += [
            'field_definition' => $field_definition,
        ];
        return $this->createInstance($plugin_id, $configuration);
    }
    
    /**
     * {@inheritdoc}
     */
    public function createInstance($plugin_id, array $configuration = []) {
        $plugin_definition = $this->getDefinition($plugin_id);
        $plugin_class = DefaultFactory::getPluginClass($plugin_id, $plugin_definition);
        // If the plugin provides a factory method, pass the container to it.
        if (is_subclass_of($plugin_class, 'Drupal\\Core\\Plugin\\ContainerFactoryPluginInterface')) {
            return $plugin_class::create(\Drupal::getContainer(), $configuration, $plugin_id, $plugin_definition);
        }
        return new $plugin_class($plugin_id, $plugin_definition, $configuration['field_definition'], $configuration['settings'], $configuration['third_party_settings']);
    }
    
    /**
     * Merges default values for widget configuration.
     *
     * @param string $field_type
     *   The field type.
     * @param array $configuration
     *   An array of widget configuration.
     *
     * @return array
     *   The display properties with defaults added.
     */
    public function prepareConfiguration($field_type, array $configuration) {
        // Fill in defaults for missing properties.
        $configuration += [
            'settings' => [],
            'third_party_settings' => [],
        ];
        // If no widget is specified, use the default widget.
        if (!isset($configuration['type'])) {
            $field_type = $this->fieldTypeManager
                ->getDefinition($field_type);
            $configuration['type'] = isset($field_type['default_widget']) ? $field_type['default_widget'] : NULL;
        }
        // Filter out unknown settings, and fill in defaults for missing settings.
        $default_settings = $this->getDefaultSettings($configuration['type']);
        $configuration['settings'] = array_intersect_key($configuration['settings'], $default_settings) + $default_settings;
        return $configuration;
    }
    
    /**
     * Returns an array of widget type options for a field type.
     *
     * @param string|null $field_type
     *   (optional) The name of a field type, or NULL to retrieve all widget
     *   options. Defaults to NULL.
     *
     * @return array
     *   If no field type is provided, returns a nested array of all widget types,
     *   keyed by field type human name.
     */
    public function getOptions($field_type = NULL) {
        if (!isset($this->widgetOptions)) {
            $options = [];
            $field_types = $this->fieldTypeManager
                ->getDefinitions();
            $widget_types = $this->getDefinitions();
            uasort($widget_types, [
                'Drupal\\Component\\Utility\\SortArray',
                'sortByWeightElement',
            ]);
            foreach ($widget_types as $name => $widget_type) {
                foreach ($widget_type['field_types'] as $widget_field_type) {
                    // Check that the field type exists.
                    if (isset($field_types[$widget_field_type])) {
                        $options[$widget_field_type][$name] = $widget_type['label'];
                    }
                }
            }
            $this->widgetOptions = $options;
        }
        if (isset($field_type)) {
            return !empty($this->widgetOptions[$field_type]) ? $this->widgetOptions[$field_type] : [];
        }
        return $this->widgetOptions;
    }
    
    /**
     * Returns the default settings of a field widget.
     *
     * @param string $type
     *   A field widget type name.
     *
     * @return array
     *   The widget type's default settings, as provided by the plugin
     *   definition, or an empty array if type or settings are undefined.
     */
    public function getDefaultSettings($type) {
        $plugin_definition = $this->getDefinition($type, FALSE);
        if (!empty($plugin_definition['class'])) {
            $plugin_class = DefaultFactory::getPluginClass($type, $plugin_definition);
            return $plugin_class::defaultSettings();
        }
        return [];
    }

}