class Middleman::CoreExtensions::DefaultHelpers

def url_for(path_or_resource, options={})
  # Handle Resources and other things which define their own url method
  url = path_or_resource.respond_to?(:url) ? path_or_resource.url : path_or_resource
  begin
    uri = URI(url)
  rescue URI::InvalidURIError
    # Nothing we can do with it, it's not really a URI
    return url
  end
  relative = options.delete(:relative)
  raise "Can't use the relative option with an external URL" if relative && uri.host
  # Allow people to turn on relative paths for all links with
  # set :relative_links, true
  # but still override on a case by case basis with the :relative parameter.
  effective_relative = relative || false
  effective_relative = true if relative.nil? && config[:relative_links]
  # Try to find a sitemap resource corresponding to the desired path
  this_resource = current_resource # store in a local var to save work
  if path_or_resource.is_a?(::Middleman::Sitemap::Resource)
    resource = path_or_resource
    resource_url = url
  elsif this_resource && uri.path
    # Handle relative urls
    url_path = Pathname(uri.path)
    current_source_dir = Pathname('/' + this_resource.path).dirname
    url_path = current_source_dir.join(url_path) if url_path.relative?
    resource = sitemap.find_resource_by_path(url_path.to_s)
    resource_url = resource.url if resource
  end
  if resource
    # Switch to the relative path between this_resource and the given resource
    # if we've been asked to.
    if effective_relative
      # Output urls relative to the destination path, not the source path
      current_dir = Pathname('/' + this_resource.destination_path).dirname
      relative_path = Pathname(resource_url).relative_path_from(current_dir).to_s
      # Put back the trailing slash to avoid unnecessary Apache redirects
      if resource_url.end_with?('/') && !relative_path.end_with?('/')
        relative_path << '/'
      end
      uri.path = relative_path
    else
      uri.path = resource_url
    end
  else
    # If they explicitly asked for relative links but we can't find a resource...
    raise "No resource exists at #{url}" if relative
  end
  # Support a :query option that can be a string or hash
  if query = options.delete(:query)
    uri.query = query.respond_to?(:to_param) ? query.to_param : query.to_s
  end
  # Support a :fragment or :anchor option just like Padrino
  fragment = options.delete(:anchor) || options.delete(:fragment)
  uri.fragment = fragment.to_s if fragment
  # Finally make the URL back into a string
  uri.to_s
end