let assert = require('assert')

return async (env, _out) => {
  let pathname = env.parsed_url.pathname
  assert(pathname.slice(0, 1) === '/')

  // find number of path components, their positions, and names
  let components = [{index: 0, name: 'Home'}]
  for (let i = 1, j; (j = pathname.indexOf('/', i)) !== -1; i = j + 1) {
    let menu = await env.site.get_menu(`${pathname.slice(0, i)}_menu.json`)
    let dir = pathname.slice(i, j)
    components.push({index: j, name: menu.entries[menu.index[dir]].name})
  }

  // present components as breadcrumbs, except last one as text
  h2 {
    for (let i = 0; i < components.length - 1; ++i) {
      a.text-h4(
        href=`${pathname.slice(0, components[i].index)}/index.html`
      ) {`${components[i].name}`}
      ' '
      span.text-h5 {'>'}
      ' '
    }
    `${components[components.length - 1].name}`
  }
}