PlayFrameworkRelativeRoutes.scala

package object controllers {
  private def rel(url: String)(implicit request: Request[AnyContent]): String = {
    val count = request.uri.count(c => c == '/')

    (url, count) match {
      /**
        * Requested url is '/' and we are at the root of the app.  Link to root route with '.'.
        */
      case ("/", 1) => "."
      /**
        * Requested url is anything and we are the root of the app.  Make link relative by stripping '/' prefix.
        */
      case (_, 1) => url.stripPrefix("/")
      /**
        * All other url's are made relative by adding '..' for the depth between requested url and root of the app, -1.
        */
      case _ => (1 until count).map(_ => "..").mkString("/") + url
    }
  }
  
  implicit class RelativeCall(call: Call) {
    def relative(implicit request: Request[AnyContent]): Call = call.copy(url = rel(call.url))
  }
}

// Example calls to reverse router from view
// To a static asset:
<link rel="stylesheet" media="screen" href="@routes.Assets.versioned("bootstrap.css").relative">
// To a controller method:
<a href="@routes.Topic.topic(cluster,topic).relative" class="cancel-button btn btn-default" role="button">Cancel</a>