class SiteConfigurationExcluder

class SiteConfigurationExcluder implements EventSubscriberInterface {
    public function __construct(string $sitePath, PathLocator $pathLocator, FileSystemInterface $fileSystem) {
    }
    
    /**
     * Excludes site configuration files from stage operations.
     *
     * @param \Drupal\package_manager\Event\CollectPathsToExcludeEvent $event
     *   The event object.
     */
    public function excludeSiteConfiguration(CollectPathsToExcludeEvent $event) : void {
        // These two files are never relevant to existing sites.
        $paths = [
            'sites/default/default.settings.php',
            'sites/default/default.services.yml',
        ];
        // Exclude site-specific settings files, which are always in the web root.
        // By default, Drupal core will always try to write-protect these files.
        // @see system_requirements()
        $settings_files = [
            'settings.php',
            'settings.local.php',
            'services.yml',
        ];
        foreach ($settings_files as $settings_file) {
            $paths[] = $this->sitePath . '/' . $settings_file;
            $paths[] = 'sites/default/' . $settings_file;
        }
        // Site configuration files are always excluded relative to the web root.
        $event->addPathsRelativeToWebRoot($paths);
    }
    
    /**
     * Makes the staged `sites/default` directory owner-writable.
     *
     * This allows the core scaffold plugin to make changes in `sites/default`,
     * if needed. Otherwise, it would break if `sites/default` is not writable.
     * This can happen because rsync preserves directory permissions (and Drupal
     * tries to write-protect the site directory).
     *
     * We specifically exclude `default.settings.php` and `default.services.yml`
     * from Package Manager operations. This allows the scaffold plugin to change
     * those files in the stage directory.
     *
     * @param \Drupal\package_manager\Event\PostCreateEvent $event
     *   The event being handled.
     *
     * @see ::excludeSiteConfiguration()
     */
    public function makeDefaultSiteDirectoryWritable(PostCreateEvent $event) : void {
        $dir = $this->getDefaultSiteDirectoryPath($event->stage
            ->getStageDirectory());
        // If the directory doesn't even exist, there's nothing to do here.
        if (!is_dir($dir)) {
            return;
        }
        if (!$this->fileSystem
            ->chmod($dir, 0700)) {
            throw new FileException("Could not change permissions on '{$dir}'.");
        }
    }
    
    /**
     * Makes `sites/default` permissions the same in live and stage directories.
     *
     * @param \Drupal\package_manager\Event\PreApplyEvent $event
     *   The event being handled.
     *
     * @throws \Drupal\Core\File\Exception\FileException
     *   If the permissions of the live `sites/default` cannot be determined, or
     *   cannot be changed on the staged `sites/default`.
     */
    public function syncDefaultSiteDirectoryPermissions(PreApplyEvent $event) : void {
        $staged_dir = $this->getDefaultSiteDirectoryPath($event->stage
            ->getStageDirectory());
        // If the directory doesn't even exist, there's nothing to do here.
        if (!is_dir($staged_dir)) {
            return;
        }
        $live_dir = $this->getDefaultSiteDirectoryPath($this->pathLocator
            ->getProjectRoot());
        $permissions = fileperms($live_dir);
        if ($permissions === FALSE) {
            throw new FileException("Could not determine permissions for '{$live_dir}'.");
        }
        if (!$this->fileSystem
            ->chmod($staged_dir, $permissions)) {
            throw new FileException("Could not change permissions on '{$staged_dir}'.");
        }
    }
    
    /**
     * Returns the full path to `sites/default`, relative to a root directory.
     *
     * @param string $root_dir
     *   The root directory.
     *
     * @return string
     *   The full path to `sites/default` within the given root directory.
     */
    private function getDefaultSiteDirectoryPath(string $root_dir) : string {
        $dir = [
            $root_dir,
        ];
        $web_root = $this->pathLocator
            ->getWebRoot();
        if ($web_root) {
            $dir[] = $web_root;
        }
        return implode(DIRECTORY_SEPARATOR, [
            $dir,
            'sites',
            'default',
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        return [
            CollectPathsToExcludeEvent::class => 'excludeSiteConfiguration',
            PostCreateEvent::class => 'makeDefaultSiteDirectoryWritable',
            PreApplyEvent::class => 'syncDefaultSiteDirectoryPermissions',
        ];
    }

}