module Middleman::Sitemap::Extensions::Traversal

def parent
  root = path.sub(/^#{::Regexp.escape(traversal_root)}/, '')
  parts = root.split('/')
  tail = parts.pop
  is_index = (tail == @app.config[:index_file])
  if parts.empty?
    return is_index ? nil : @store.find_resource_by_path(@app.config[:index_file])
  end
  test_expr = parts.join('\\/')
  # eponymous reverse-lookup
  found = @store.resources.find do |candidate|
    candidate.path =~ %r{^#{test_expr}(?:\.[a-zA-Z0-9]+|\/)$}
  end
  if found
    found
  else
    parts.pop if is_index
    @store.find_resource_by_destination_path("#{parts.join('/')}/#{@app.config[:index_file]}")
  end
end