module Rails::Dom::Testing

def choose_html_parser(parser_classes, html_version: nil)
  html_version ||= Rails::Dom::Testing.default_html_version
  case html_version
  when :html4
    parser_classes[:html4]
  when :html5
    unless Rails::Dom::Testing.html5_support?
      raise NotImplementedError, "html5 parser is not supported on this platform"
    end
    parser_classes[:html5]
  else
    raise ArgumentError, "html_version must be :html4 or :html5, received #{html_version.inspect}"
  end
end

def html5_support?
  defined?(Nokogiri::HTML5)
end

def html_document(html_version: nil)
  parser_classes = { html4: Nokogiri::HTML4::Document }
  parser_classes[:html5] = Nokogiri::HTML5::Document if html5_support?
  choose_html_parser(parser_classes, html_version: html_version)
end

def html_document_fragment(html_version: nil)
  parser_classes = { html4: Nokogiri::HTML4::DocumentFragment }
  parser_classes[:html5] = Nokogiri::HTML5::DocumentFragment if html5_support?
  choose_html_parser(parser_classes, html_version: html_version)
end