class Asciidoctor::Converter::TemplateConverter

def scan
  path_resolver = PathResolver.new
  backend = @backend
  engine = @engine
  @template_dirs.each do |template_dir|
    # FIXME need to think about safe mode restrictions here
    # Ruby 2.3 requires the extra brackets around the path_resolver.system_path method call
    next unless ::File.directory?(template_dir = (path_resolver.system_path template_dir))
    if engine
      file_pattern = %(*.#{engine})
      # example: templates/haml
      if ::File.directory?(engine_dir = %(#{template_dir}/#{engine}))
        template_dir = engine_dir
      end
    else
      # NOTE last matching template wins for template name if no engine is given
      file_pattern = '*'
    end
    # example: templates/html5 (engine not set) or templates/haml/html5 (engine set)
    if ::File.directory?(backend_dir = %(#{template_dir}/#{backend}))
      template_dir = backend_dir
    end
    pattern = %(#{template_dir}/#{file_pattern})
    if (scan_cache = @caches[:scans])
      template_cache = @caches[:templates]
      unless (templates = scan_cache[pattern])
        templates = scan_cache[pattern] = scan_dir template_dir, pattern, template_cache
      end
      templates.each do |name, template|
        @templates[name] = template_cache[template.file] = template
      end
    else
      @templates.update scan_dir(template_dir, pattern, @caches[:templates])
    end
  end
  nil
end