class Opal::CliRunners::Firefox

def prepare_files_in(dir) 

def prepare_files_in(dir)
  js = builder.to_s
  map = builder.source_map.to_json
  ext = builder.output_extension
  module_type = ' type="module"' if builder.esm?
  # CDP can't handle huge data passed to `addScriptToEvaluateOnLoad`
  # https://groups.google.com/a/chromium.org/forum/#!topic/chromium-discuss/U5qyeX_ydBo
  # The only way is to create temporary files and pass them to the browser.
  File.binwrite("#{dir}/index.#{ext}", js)
  File.binwrite("#{dir}/index.#{ext}.map", map)
  File.binwrite("#{dir}/index.html", <<~HTML)
    <!DOCTYPE html>
    <html><head>
      <meta charset='utf-8'>
      <link rel="shortcut icon" href="data:image/x-icon;," type="image/x-icon">
      <script>
      window.opalheadlessfirefox = true;
      </script>
    </head><body>
      <script src='/index.#{ext}'#{module_type}></script>
    </body></html>
  HTML
end