class DiskSpaceValidator

class DiskSpaceValidator implements EventSubscriberInterface {
    use BaseRequirementValidatorTrait;
    use StringTranslationTrait;
    public function __construct(PathLocator $pathLocator) {
    }
    
    /**
     * Wrapper around the disk_free_space() function.
     *
     * @param string $path
     *   The path for which to retrieve the amount of free disk space.
     *
     * @return float
     *   The number of bytes of free space on the disk.
     *
     * @throws \RuntimeException
     *   If the amount of free space could not be determined.
     */
    protected function freeSpace(string $path) : float {
        $free_space = disk_free_space($path);
        if ($free_space === FALSE) {
            throw new \RuntimeException("Cannot get disk information for {$path}.");
        }
        return $free_space;
    }
    
    /**
     * Wrapper around the stat() function.
     *
     * @param string $path
     *   The path to check.
     *
     * @return mixed[]
     *   The statistics for the path.
     *
     * @throws \RuntimeException
     *   If the statistics could not be determined.
     */
    protected function stat(string $path) : array {
        $stat = stat($path);
        if ($stat === FALSE) {
            throw new \RuntimeException("Cannot get information for {$path}.");
        }
        return $stat;
    }
    
    /**
     * Checks if two paths are located on the same logical disk.
     *
     * @param string $root
     *   The path of the project root.
     * @param string $vendor
     *   The path of the vendor directory.
     *
     * @return bool
     *   TRUE if the project root and vendor directory are on the same logical
     *   disk, FALSE otherwise.
     */
    protected function areSameLogicalDisk(string $root, string $vendor) : bool {
        $root_statistics = $this->stat($root);
        $vendor_statistics = $this->stat($vendor);
        return $root_statistics['dev'] === $vendor_statistics['dev'];
    }
    
    /**
     * Validates that there is enough free disk space to do stage operations.
     */
    public function validate(PreOperationStageEvent $event) : void {
        $root_path = $this->pathLocator
            ->getProjectRoot();
        $vendor_path = $this->pathLocator
            ->getVendorDirectory();
        $messages = [];
        // @todo Make this configurable or set to a different value in
        //   https://www.drupal.org/i/3166416.
        $minimum_mb = 1024;
        $minimum_bytes = Bytes::toNumber($minimum_mb . 'M');
        if (!$this->areSameLogicalDisk($root_path, $vendor_path)) {
            if ($this->freeSpace($root_path) < $minimum_bytes) {
                $messages[] = $this->t('Drupal root filesystem "@root" has insufficient space. There must be at least @space megabytes free.', [
                    '@root' => $root_path,
                    '@space' => $minimum_mb,
                ]);
            }
            if (is_dir($vendor_path) && $this->freeSpace($vendor_path) < $minimum_bytes) {
                $messages[] = $this->t('Vendor filesystem "@vendor" has insufficient space. There must be at least @space megabytes free.', [
                    '@vendor' => $vendor_path,
                    '@space' => $minimum_mb,
                ]);
            }
        }
        elseif ($this->freeSpace($root_path) < $minimum_bytes) {
            $messages[] = $this->t('Drupal root filesystem "@root" has insufficient space. There must be at least @space megabytes free.', [
                '@root' => $root_path,
                '@space' => $minimum_mb,
            ]);
        }
        $temp = $this->temporaryDirectory();
        if ($this->freeSpace($temp) < $minimum_bytes) {
            $messages[] = $this->t('Directory "@temp" has insufficient space. There must be at least @space megabytes free.', [
                '@temp' => $temp,
                '@space' => $minimum_mb,
            ]);
        }
        if ($messages) {
            $summary = count($messages) > 1 ? $this->t("There is not enough disk space to create a stage directory.") : NULL;
            $event->addError($messages, $summary);
        }
    }
    
    /**
     * Returns the path of the system temporary directory.
     *
     * @return string
     *   The absolute path of the system temporary directory.
     */
    protected function temporaryDirectory() : string {
        return FileSystem::getOsTemporaryDirectory();
    }

}