class FieldInstanceSettings

class FieldInstanceSettings extends ProcessPluginBase {
    
    /**
     * {@inheritdoc}
     */
    public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
        [
            $instance_settings,
            $widget_settings,
            $field_definition,
        ] = $value;
        $widget_type = $widget_settings['type'];
        $field_data = unserialize($field_definition['data']);
        // Get taxonomy term reference handler settings from allowed values.
        if ($row->getSourceProperty('type') == 'taxonomy_term_reference') {
            $instance_settings['handler_settings']['sort'] = [
                'field' => '_none',
            ];
            $allowed_values = $row->get('@allowed_values');
            foreach ($allowed_values as $allowed_value) {
                foreach ($allowed_value as $vocabulary) {
                    $instance_settings['handler_settings']['target_bundles'][$vocabulary] = $vocabulary;
                }
            }
        }
        // Get entityreference handler settings from source field configuration.
        if ($row->getSourceProperty('type') == "entityreference") {
            $field_settings = $field_data['settings'];
            $instance_settings['handler'] = 'default:' . $field_settings['target_type'];
            // Transform the sort settings to D8 structure.
            $sort = [
                'field' => '_none',
                'direction' => 'ASC',
            ];
            if (!empty(array_filter($field_settings['handler_settings']['sort']))) {
                if ($field_settings['handler_settings']['sort']['type'] == "property") {
                    $sort = [
                        'field' => $field_settings['handler_settings']['sort']['property'],
                        'direction' => $field_settings['handler_settings']['sort']['direction'],
                    ];
                }
                elseif ($field_settings['handler_settings']['sort']['type'] == "field") {
                    $sort = [
                        'field' => $field_settings['handler_settings']['sort']['field'],
                        'direction' => $field_settings['handler_settings']['sort']['direction'],
                    ];
                }
            }
            if (empty($field_settings['handler_settings']['target_bundles'])) {
                $field_settings['handler_settings']['target_bundles'] = NULL;
            }
            $field_settings['handler_settings']['sort'] = $sort;
            $instance_settings['handler_settings'] = $field_settings['handler_settings'];
        }
        if ($row->getSourceProperty('type') == 'node_reference') {
            $instance_settings['handler'] = 'default:node';
            $instance_settings['handler_settings'] = [
                'sort' => [
                    'field' => '_none',
                    'direction' => 'ASC',
                ],
                'target_bundles' => array_filter($field_data['settings']['referenceable_types'] ?? []),
            ];
        }
        if ($row->getSourceProperty('type') == 'user_reference') {
            $instance_settings['handler'] = 'default:user';
            $instance_settings['handler_settings'] = [
                'include_anonymous' => TRUE,
                'filter' => [
                    'type' => '_none',
                ],
                'sort' => [
                    'field' => '_none',
                    'direction' => 'ASC',
                ],
                'auto_create' => FALSE,
            ];
            if ($row->hasSourceProperty('roles')) {
                $instance_settings['handler_settings']['filter']['type'] = 'role';
                foreach ($row->get('roles') as $role) {
                    $instance_settings['handler_settings']['filter']['role'] = [
                        $role['name'] => $role['name'],
                    ];
                }
            }
        }
        // Get the labels for the list_boolean type.
        if ($row->getSourceProperty('type') === 'list_boolean') {
            if (isset($field_data['settings']['allowed_values'][1])) {
                $instance_settings['on_label'] = $field_data['settings']['allowed_values'][1];
            }
            if (isset($field_data['settings']['allowed_values'][0])) {
                $instance_settings['off_label'] = $field_data['settings']['allowed_values'][0];
            }
        }
        switch ($widget_type) {
            case 'image_image':
            case 'image_miw':
                $settings = $instance_settings;
                $settings['default_image'] = [
                    'alt' => '',
                    'title' => '',
                    'width' => NULL,
                    'height' => NULL,
                    'uuid' => '',
                ];
                break;
            default:
                $settings = $instance_settings;
        }
        return $settings;
    }

}