class DuplicateInfoFileValidator

final class DuplicateInfoFileValidator implements EventSubscriberInterface {
    use StringTranslationTrait;
    public function __construct(PathLocator $pathLocator) {
    }
    
    /**
     * Validates the stage does not have duplicate info.yml not present in active.
     */
    public function validate(PreApplyEvent $event) : void {
        $active_dir = $this->pathLocator
            ->getProjectRoot();
        $stage_dir = $event->stage
            ->getStageDirectory();
        $active_info_files = $this->findInfoFiles($active_dir);
        $stage_info_files = $this->findInfoFiles($stage_dir);
        foreach ($stage_info_files as $stage_info_file => $stage_info_count) {
            if (isset($active_info_files[$stage_info_file])) {
                // Check if stage directory has more info.yml files matching
                // $stage_info_file than in the active directory.
                if ($stage_info_count > $active_info_files[$stage_info_file]) {
                    $event->addError([
                        $this->t('The stage directory has @stage_count instances of @stage_info_file as compared to @active_count in the active directory. This likely indicates that a duplicate extension was installed.', [
                            '@stage_info_file' => $stage_info_file,
                            '@stage_count' => $stage_info_count,
                            '@active_count' => $active_info_files[$stage_info_file],
                        ]),
                    ]);
                }
            }
            elseif ($stage_info_count > 1) {
                $event->addError([
                    $this->t('The stage directory has @stage_count instances of @stage_info_file. This likely indicates that a duplicate extension was installed.', [
                        '@stage_info_file' => $stage_info_file,
                        '@stage_count' => $stage_info_count,
                    ]),
                ]);
            }
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() : array {
        return [
            PreApplyEvent::class => 'validate',
        ];
    }
    
    /**
     * Recursively finds info.yml files in a directory.
     *
     * @param string $dir
     *   The path of the directory to check.
     *
     * @return int[]
     *   Array of count of info.yml files in the directory keyed by file name.
     */
    private function findInfoFiles(string $dir) : array {
        // Use the official extension discovery mechanism, but tweak it, because by
        // default it resolves duplicates.
        // @see \Drupal\Core\Extension\ExtensionDiscovery::process()
        $duplicate_aware_extension_discovery = new class ($dir, FALSE, []) extends ExtensionDiscovery {
            
            /**
             * {@inheritdoc}
             */
            protected function process(array $all_files) {
                // Unlike parent implementation: no processing, to retain duplicates.
                return $all_files;
            }

};
        // Scan all 4 extension types, explicitly ignoring tests.
        $extension_info_files = array_merge(array_keys($duplicate_aware_extension_discovery->scan('module', FALSE)), array_keys($duplicate_aware_extension_discovery->scan('theme', FALSE)), array_keys($duplicate_aware_extension_discovery->scan('profile', FALSE)), array_keys($duplicate_aware_extension_discovery->scan('theme_engine', FALSE)));
        $info_files = [];
        foreach ($extension_info_files as $info_file) {
            $file_name = basename($info_file);
            $info_files[$file_name] = ($info_files[$file_name] ?? 0) + 1;
        }
        return $info_files;
    }

}