class ExtensionPathResolver

class ExtensionPathResolver {
    
    /**
     * A associative array of ExtensionList objects keyed by type.
     *
     * @var \Drupal\Core\Extension\ExtensionList[]
     */
    protected $extensionLists;
    
    /**
     * ExtensionPathResolver constructor.
     *
     * @param \Drupal\Core\Extension\ModuleExtensionList $module_extension_list
     *   The module extension list.
     * @param \Drupal\Core\Extension\ProfileExtensionList $profile_extension_list
     *   The profile extension list.
     * @param \Drupal\Core\Extension\ThemeExtensionList $theme_extension_list
     *   The theme extension list.
     * @param \Drupal\Core\Extension\ThemeEngineExtensionList $theme_engine_extension_list
     *   The theme engine extension list.
     */
    public function __construct(ModuleExtensionList $module_extension_list, ProfileExtensionList $profile_extension_list, ThemeExtensionList $theme_extension_list, ThemeEngineExtensionList $theme_engine_extension_list) {
        $this->extensionLists['module'] = $module_extension_list;
        $this->extensionLists['profile'] = $profile_extension_list;
        $this->extensionLists['theme'] = $theme_extension_list;
        $this->extensionLists['theme_engine'] = $theme_engine_extension_list;
    }
    
    /**
     * Gets the info file path for the extension.
     *
     * @param string $type
     *   The extension type.
     * @param string $name
     *   The extension name.
     *
     * @return string|null
     *   The extension path, or NULL if unknown.
     */
    public function getPathname(string $type, string $name) : ?string {
        if ($type === 'core') {
            return 'core/core.info.yml';
        }
        if (!isset($this->extensionLists[$type])) {
            throw new UnknownExtensionTypeException(sprintf('Extension type %s is unknown.', $type));
        }
        try {
            return $this->extensionLists[$type]
                ->getPathname($name);
        } catch (UnknownExtensionException $e) {
            // Catch the exception. This will result in triggering an error.
            // If the filename is still unknown, create a user-level error message.
            trigger_error(sprintf('The following %s is missing from the file system: %s', $type, $name), E_USER_WARNING);
            return NULL;
        }
    }
    
    /**
     * Gets the extension directory path.
     *
     * @param string $type
     *   The extension type.
     * @param string $name
     *   The extension name.
     *
     * @return string
     *   The extension info file path.
     *
     * @throws \Drupal\Core\Extension\Exception\UnknownExtensionTypeException
     *   If the extension type is unknown.
     * @throws \Drupal\Core\Extension\Exception\UnknownExtensionException
     *   If the extension is unknown.
     */
    public function getPath(string $type, string $name) : string {
        return dirname($this->getPathname($type, $name));
    }

}