class RefinableCalculatedPermissions

class RefinableCalculatedPermissions implements RefinableCalculatedPermissionsInterface {
    use CalculatedPermissionsTrait;
    use RefinableCacheableDependencyTrait;
    
    /**
     * {@inheritdoc}
     */
    public function addItem(CalculatedPermissionsItemInterface $item, bool $overwrite = FALSE) : self {
        if (!$overwrite && ($existing = $this->getItem($item->getScope(), $item->getIdentifier()))) {
            $item = static::mergeItems($existing, $item);
        }
        $this->items[$item->getScope()][$item->getIdentifier()] = $item;
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function removeItem(string $scope = AccessPolicyInterface::SCOPE_DRUPAL, string|int $identifier = AccessPolicyInterface::SCOPE_DRUPAL) : self {
        unset($this->items[$scope][$identifier]);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function removeItems() : self {
        $this->items = [];
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function removeItemsByScope(string $scope) : self {
        unset($this->items[$scope]);
        return $this;
    }
    
    /**
     * {@inheritdoc}
     */
    public function merge(CalculatedPermissionsInterface $calculated_permissions) : self {
        foreach ($calculated_permissions->getItems() as $item) {
            $this->addItem($item);
        }
        $this->addCacheableDependency($calculated_permissions);
        return $this;
    }
    
    /**
     * Merges two items of identical scope and identifier.
     *
     * @param \Drupal\Core\Session\CalculatedPermissionsItemInterface $a
     *   The first item to merge.
     * @param \Drupal\Core\Session\CalculatedPermissionsItemInterface $b
     *   The second item to merge.
     *
     * @return \Drupal\Core\Session\CalculatedPermissionsItemInterface
     *   A new item representing the merger of both items.
     */
    protected static function mergeItems(CalculatedPermissionsItemInterface $a, CalculatedPermissionsItemInterface $b) : CalculatedPermissionsItemInterface {
        // If either of the items is admin, the new one is too.
        $is_admin = $a->isAdmin() || $b->isAdmin();
        // Admin items don't need to have any permissions.
        $permissions = [];
        if (!$is_admin) {
            $permissions = array_unique(array_merge($a->getPermissions(), $b->getPermissions()));
        }
        return new CalculatedPermissionsItem($permissions, $is_admin, $a->getScope(), $a->getIdentifier());
    }

}