class Analyzer

class Analyzer {
    
    /**
     * A module handler that invokes the 'views_analyze' hook.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * Constructs an Analyzer object.
     *
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler that invokes the 'views_analyze' hook.
     */
    public function __construct(ModuleHandlerInterface $module_handler) {
        $this->moduleHandler = $module_handler;
    }
    
    /**
     * Analyzes a review and return the results.
     *
     * @param \Drupal\views\ViewExecutable $view
     *   The view to analyze.
     *
     * @return array
     *   An array of analyze results organized into arrays keyed by 'ok',
     *   'warning' and 'error'.
     */
    public function getMessages(ViewExecutable $view) {
        $view->initDisplay();
        $messages = $this->moduleHandler
            ->invokeAll('views_analyze', [
            $view,
        ]);
        return $messages;
    }
    
    /**
     * Formats the analyze result into a message string.
     *
     * This is based upon the format of
     * \Drupal\Core\Messenger\MessengerInterface::addMessage() which uses separate
     * boxes for "ok", "warning" and "error".
     */
    public function formatMessages(array $messages) {
        if (empty($messages)) {
            $messages = [
                static::formatMessage(t('View analysis can find nothing to report.'), 'ok'),
            ];
        }
        $types = [
            'ok' => [],
            'warning' => [],
            'error' => [],
        ];
        foreach ($messages as $message) {
            if (empty($types[$message['type']])) {
                $types[$message['type']] = [];
            }
            $types[$message['type']][] = $message['message'];
        }
        $output = '';
        foreach ($types as $type => $messages) {
            $type .= ' messages';
            $message = '';
            if (count($messages) > 1) {
                $item_list = [
                    '#theme' => 'item_list',
                    '#items' => $messages,
                ];
                $message = \Drupal::service('renderer')->render($item_list);
            }
            elseif ($messages) {
                $message = array_shift($messages);
            }
            if ($message) {
                $output .= "<div class=\"{$type}\">{$message}</div>";
            }
        }
        return $output;
    }
    
    /**
     * Formats an analysis message.
     *
     * This tool should be called by any module responding to the analyze hook
     * to properly format the message. It is usually used in the form:
     * @code
     *   $ret[] = Analyzer::formatMessage(t('This is the message'), 'ok');
     * @endcode
     *
     * The 'ok' status should be used to provide information about things
     * that are acceptable. In general analysis isn't interested in 'ok'
     * messages, but instead the 'warning', which is a category for items
     * that may be broken unless the user knows what they are doing, and 'error'
     * for items that are definitely broken are much more useful.
     *
     * @param string $message
     *   The message.
     * @param string $type
     *   The type of message. This should be "ok", "warning" or "error". Other
     *   values can be used but how they are treated by the output routine
     *   is undefined.
     *
     * @return array
     *   A single formatted message, consisting of a key message and a key type.
     */
    public static function formatMessage($message, $type = 'error') {
        return [
            'message' => $message,
            'type' => $type,
        ];
    }

}