class UserSearch

class UserSearch extends SearchPluginBase implements AccessibleInterface {
    
    /**
     * The database connection.
     *
     * @var \Drupal\Core\Database\Connection
     */
    protected $database;
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The module handler.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($container->get('database'), $container->get('entity_type.manager'), $container->get('module_handler'), $container->get('current_user'), $configuration, $plugin_id, $plugin_definition);
    }
    
    /**
     * Creates a UserSearch object.
     *
     * @param \Drupal\Core\Database\Connection $database
     *   The database connection.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler.
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin_id for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     */
    public function __construct(Connection $database, EntityTypeManagerInterface $entity_type_manager, ModuleHandlerInterface $module_handler, AccountInterface $current_user, array $configuration, $plugin_id, $plugin_definition) {
        $this->database = $database;
        $this->entityTypeManager = $entity_type_manager;
        $this->moduleHandler = $module_handler;
        $this->currentUser = $current_user;
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->addCacheTags([
            'user_list',
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function access($operation = 'view', AccountInterface $account = NULL, $return_as_object = FALSE) {
        $result = AccessResult::allowedIf(!empty($account) && $account->hasPermission('access user profiles'))
            ->cachePerPermissions();
        return $return_as_object ? $result : $result->isAllowed();
    }
    
    /**
     * {@inheritdoc}
     */
    public function execute() {
        $results = [];
        if (!$this->isSearchExecutable()) {
            return $results;
        }
        // Process the keywords.
        $keys = $this->keywords;
        // Escape for LIKE matching.
        $keys = $this->database
            ->escapeLike($keys);
        // Replace wildcards with MySQL/PostgreSQL wildcards.
        $keys = preg_replace('!\\*+!', '%', $keys);
        // Run the query to find matching users.
        $query = $this->database
            ->select('users_field_data', 'users')
            ->extend(PagerSelectExtender::class);
        $query->fields('users', [
            'uid',
        ]);
        $query->condition('default_langcode', 1);
        if ($this->currentUser
            ->hasPermission('administer users')) {
            // Administrators can also search in the otherwise private email field,
            // and they don't need to be restricted to only active users.
            $query->fields('users', [
                'mail',
            ]);
            $query->condition($query->orConditionGroup()
                ->condition('name', '%' . $keys . '%', 'LIKE')
                ->condition('mail', '%' . $keys . '%', 'LIKE'));
        }
        else {
            // Regular users can only search via usernames, and we do not show them
            // blocked accounts.
            $query->condition('name', '%' . $keys . '%', 'LIKE')
                ->condition('status', 1);
        }
        $uids = $query->limit(15)
            ->execute()
            ->fetchCol();
        $accounts = $this->entityTypeManager
            ->getStorage('user')
            ->loadMultiple($uids);
        foreach ($accounts as $account) {
            $result = [
                'title' => $account->getDisplayName(),
                'link' => $account->toUrl('canonical', [
                    'absolute' => TRUE,
                ])
                    ->toString(),
            ];
            if ($this->currentUser
                ->hasPermission('administer users')) {
                $result['title'] .= ' (' . $account->getEmail() . ')';
            }
            $this->addCacheableDependency($account);
            $results[] = $result;
        }
        return $results;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getHelp() {
        $help = [
            'list' => [
                '#theme' => 'item_list',
                '#items' => [
                    $this->t('User search looks for user names and partial user names. Example: mar would match usernames mar, delmar, and maryjane.'),
                    $this->t('You can use * as a wildcard within your keyword. Example: m*r would match user names mar, delmar, and elementary.'),
                ],
            ],
        ];
        return $help;
    }

}