class SwitchUserListHelper

class SwitchUserListHelper {
    use StringTranslationTrait;
    
    /**
     * The Current User object.
     */
    protected AccountInterface $currentUser;
    
    /**
     * The user storage.
     */
    protected UserStorageInterface $userStorage;
    
    /**
     * The redirect destination service.
     */
    protected RedirectDestinationInterface $redirectDestination;
    
    /**
     * The role storage.
     */
    protected RoleStorageInterface $roleStorage;
    
    /**
     * Constructs a new SwitchUserListHelper service.
     *
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   Current user.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager.
     * @param \Drupal\Core\Routing\RedirectDestinationInterface $redirect_destination
     *   The redirect destination service.
     * @param \Drupal\Core\StringTranslation\TranslationInterface $string_translation
     *   The translation manager.
     */
    public function __construct(AccountInterface $current_user, EntityTypeManagerInterface $entity_type_manager, RedirectDestinationInterface $redirect_destination, TranslationInterface $string_translation) {
        $this->currentUser = $current_user;
        $this->userStorage = $entity_type_manager->getStorage('user');
        $this->redirectDestination = $redirect_destination;
        $this->stringTranslation = $string_translation;
        $this->roleStorage = $entity_type_manager->getStorage('user_role');
    }
    
    /**
     * Provides the list of accounts that can be used for the user switch.
     *
     * Inactive users are omitted from all of the following db selects. Users
     * with 'switch users' permission and anonymous user if include_anon property
     * is set to TRUE, are prioritized.
     *
     * @param int $limit
     *   The number of accounts to use for the list.
     * @param bool $include_anonymous
     *   Whether or not to include the anonymous user.
     *
     * @return \Drupal\Core\Session\AccountInterface[]
     *   List of accounts to be used for the switch.
     */
    public function getUsers(int $limit = 50, bool $include_anonymous = FALSE) {
        $limit = $include_anonymous ? $limit - 1 : $limit;
        // Users with 'switch users' permission are prioritized so get these first.
        $query = $this->userStorage
            ->getQuery()
            ->condition('uid', 0, '>')
            ->condition('status', 0, '>')
            ->sort('access', 'DESC')
            ->accessCheck(FALSE)
            ->range(0, $limit);
        
        /** @var array<string, RoleInterface> $roles */
        $roles = $this->roleStorage
            ->loadMultiple();
        unset($roles[AccountInterface::ANONYMOUS_ROLE]);
        $roles = array_filter($roles, static fn($role): bool => $role->hasPermission('switch users'));
        if ($roles !== [] && !isset($roles[RoleInterface::AUTHENTICATED_ID])) {
            $query->condition('roles', array_keys($roles), 'IN');
        }
        $user_ids = $query->execute();
        // If we don't have enough users with 'switch users' permission, add more
        // users until we hit $limit.
        if (count($user_ids) < $limit) {
            $query = $this->userStorage
                ->getQuery()
                ->condition('uid', 0, '>')
                ->condition('status', 0, '>')
                ->sort('access', 'DESC')
                ->accessCheck(FALSE)
                ->range(0, $limit);
            // Exclude the prioritized user ids if the previous query returned some.
            if (!empty($user_ids)) {
                $query->condition('uid', array_keys($user_ids), 'NOT IN');
                $query->range(0, $limit - count($user_ids));
            }
            $user_ids += $query->execute();
        }
        
        /** @var \Drupal\Core\Session\AccountInterface[] $accounts */
        $accounts = $this->userStorage
            ->loadMultiple($user_ids);
        if ($include_anonymous) {
            $anonymous = new AnonymousUserSession();
            $accounts[$anonymous->id()] = $anonymous;
        }
        // Syntax comes from https://php.watch/versions/8.2/partially-supported-callable-deprecation.
        uasort($accounts, self::class . '::sortUserList');
        return $accounts;
    }
    
    /**
     * Builds the user listing as renderable array.
     *
     * @param \Drupal\Core\Session\AccountInterface[] $accounts
     *   The accounts to be rendered in the list.
     *
     * @return array
     *   A renderable array.
     */
    public function buildUserList(array $accounts) : array {
        $links = [];
        foreach ($accounts as $account) {
            $links[$account->id()] = [
                'title' => $account->getDisplayName(),
                'url' => Url::fromRoute('devel.switch', [
                    'name' => $account->getAccountName(),
                ]),
                'query' => $this->redirectDestination
                    ->getAsArray(),
                'attributes' => [
                    'title' => $account->hasPermission('switch users') ? $this->t('This user can switch back.') : $this->t('Caution: this user will be unable to switch back.'),
                ],
            ];
            if ($account->isAnonymous()) {
                $links[$account->id()]['url'] = Url::fromRoute('user.logout');
            }
            if ($this->currentUser
                ->id() === $account->id()) {
                $links[$account->id()]['title'] = new FormattableMarkup('<strong>%user</strong>', [
                    '%user' => $account->getDisplayName(),
                ]);
            }
        }
        return [
            '#theme' => 'links',
            '#links' => $links,
            '#attached' => [
                'library' => [
                    'devel/devel',
                ],
            ],
        ];
    }
    
    /**
     * Helper callback for uasort() to sort accounts by last access.
     *
     * @param \Drupal\Core\Session\AccountInterface $a
     *   First account.
     * @param \Drupal\Core\Session\AccountInterface $b
     *   Second account.
     *
     * @return int
     *   Result of comparing the last access times:
     *   - -1 if $a was more recently accessed
     *   -  0 if last access times compare equal
     *   -  1 if $b was more recently accessed
     */
    public static function sortUserList(AccountInterface $a, AccountInterface $b) : int {
        $a_access = (int) $a->getLastAccessedTime();
        $b_access = (int) $b->getLastAccessedTime();
        if ($a_access === $b_access) {
            return 0;
        }
        // User never access to site.
        if ($a_access === 0) {
            return 1;
        }
        return $a_access > $b_access ? -1 : 1;
    }

}