text: """Command-line interface."""
  
  import click
  
  from . import __version__, server
  
  
  CONTEXT_SETTINGS = dict(help_option_names=["-h", "--help"])
  
  ReadableDirectory = click.Path(exists=True, readable=True, file_okay=False)
  
  
  @click.command(context_settings=CONTEXT_SETTINGS)
  @click.argument("root", type=ReadableDirectory, required=False)
  @click.option("-p", "--port", type=int, help="Port for the web server.")
  @click.option("-l", "--launch", is_flag=True, help="Launch the page's index.")
  @click.version_option(version=__version__)
  def main(root=None, port=None, launch=False):
      """Serve a single-page application from a directory."""
      path, httpd = server.init(root, port)
  
      click.echo("Serving {d}/ on {p}".format(d=path, p=httpd.server_port))
      if launch:
          click.launch("http://localhost:{p}".format(p=httpd.server_port))
      httpd.serve_forever()
  