md.compilers.commonmark = (() => {
  var defaults = {
    safe: false,
    smart: false,
  }

  var description = {
    safe: 'Raw HTML will not be rendered',
    smart: [
      'Straight quotes will be made curly',
      '-- will be changed to an en dash',
      '--- will be changed to an em dash',
      'and ... will be changed to ellipses'
    ].join('\n'),
  }

  var ctor = ({storage: {state}}) => ({
    defaults,
    description,
    compile: (markdown) => ((
      reader = new commonmark.Parser(),
      writer = new commonmark.HtmlRenderer(state.commonmark)
    ) =>
      writer.render(reader.parse(markdown))
    )()
  })

  return Object.assign(ctor, {defaults, description})
})()