class DevelMailLog

class DevelMailLog implements MailInterface, ContainerFactoryPluginInterface {
    
    /**
     * The devel.settings config object.
     *
     * @var \Drupal\Core\Config\Config
     */
    protected $config;
    
    /**
     * The file system service.
     *
     * @var \Drupal\Core\File\FileSystemInterface
     */
    protected $fileSystem;
    
    /**
     * Constructs a new DevelMailLog object.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin_id for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
     *   The config factory service.
     * @param \Drupal\Core\File\FileSystemInterface $file_system
     *   The file system service.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, ConfigFactoryInterface $config_factory, FileSystemInterface $file_system) {
        $this->config = $config_factory->get('devel.settings');
        $this->fileSystem = $file_system;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('config.factory'), $container->get('file_system'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function mail(array $message) {
        $directory = $this->config
            ->get('debug_mail_directory');
        if (!$this->prepareDirectory($directory)) {
            return FALSE;
        }
        $pattern = $this->config
            ->get('debug_mail_file_format');
        $filename = $this->replacePlaceholders($pattern, $message);
        $output = $this->composeMessage($message);
        return (bool) file_put_contents($directory . '/' . $filename, $output);
    }
    
    /**
     * {@inheritdoc}
     */
    public function format(array $message) {
        // Join the body array into one string.
        $message['body'] = implode("\n\n", $message['body']);
        // Convert any HTML to plain-text.
        $message['body'] = MailFormatHelper::htmlToText($message['body']);
        // Wrap the mail body for sending.
        $message['body'] = MailFormatHelper::wrapMail($message['body']);
        return $message;
    }
    
    /**
     * Compose the output message.
     *
     * @param array $message
     *   A message array, as described in hook_mail_alter().
     *
     * @return string
     *   The output message.
     */
    protected function composeMessage(array $message) {
        $mimeheaders = [];
        $message['headers']['To'] = $message['to'];
        foreach ($message['headers'] as $name => $value) {
            $mimeheaders[] = $name . ': ' . Unicode::mimeHeaderEncode($value);
        }
        $line_endings = Settings::get('mail_line_endings', PHP_EOL);
        $output = implode($line_endings, $mimeheaders) . $line_endings;
        // 'Subject:' is a mail header and should not be translated.
        $output .= 'Subject: ' . $message['subject'] . $line_endings;
        // Blank line to separate headers from body.
        $output .= $line_endings;
        $output .= preg_replace('@\\r?\\n@', $line_endings, $message['body']);
        return $output;
    }
    
    /**
     * Replaces placeholders with sanitized values in a string.
     *
     * @param string $filename
     *   The string that contains the placeholders. The following placeholders
     *   are considered in the replacement:
     *   - %to: replaced by the email recipient value.
     *   - %subject: replaced by the email subject value.
     *   - %datetime: replaced by the current datetime in 'y-m-d_his' format.
     * @param array $message
     *   A message array, as described in hook_mail_alter().
     *
     * @return string
     *   The formatted string.
     */
    protected function replacePlaceholders($filename, array $message) {
        $tokens = [
            '%to' => $message['to'],
            '%subject' => $message['subject'],
            '%datetime' => date('y-m-d_his'),
        ];
        $filename = str_replace(array_keys($tokens), array_values($tokens), $filename);
        return preg_replace('/[^a-zA-Z0-9_\\-\\.@]/', '_', $filename);
    }
    
    /**
     * Checks that the directory exists and is writable.
     *
     * Public directories will be protected by adding an .htaccess which
     * indicates that the directory is private.
     *
     * @param string $directory
     *   A string reference containing the name of a directory path or URI.
     *
     * @return bool
     *   TRUE if the directory exists (or was created), is writable and is
     *   protected (if it is public). FALSE otherwise.
     */
    protected function prepareDirectory($directory) {
        if (!$this->fileSystem
            ->prepareDirectory($directory, FileSystemInterface::CREATE_DIRECTORY)) {
            return FALSE;
        }
        if (0 === strpos($directory, 'public://')) {
            return FileSecurity::writeHtaccess($directory);
        }
        return TRUE;
    }

}