Automatic discovery of reference.conf files in OSGi

OsgiConfigFactory.scala

import scala.collection.JavaConverters._
import java.net.URL
import java.util.Enumeration
import com.typesafe.config._
import org.osgi.framework.Bundle
import org.osgi.framework.wiring._


object OsgiConfigFactory {

  def load(bundle: Bundle): Config = {
    val bundles = transitiveBundles(bundle)
    val classLoader = new ClassLoader() {
      override def findResource(name: String): URL = {
        def tryGetResource(bundle: Bundle): Option[URL] =
          Option(bundle.getResource(name))

        val cls = bundles.foldLeft(None: Option[URL]) { (cls, bundle) => cls orElse tryGetResource(bundle) }
        cls getOrElse getParent.getResource(name)
      }

      override def findResources(name: String): Enumeration[URL] = {
        val resources = bundles.map { bundle => Option(bundle.getResources(name)).map { _.asScala.toList }.getOrElse(Nil) }.flatten
        java.util.Collections.enumeration(resources.asJava)
      }
    }
    ConfigFactory.load(classLoader)
  }

  private def transitiveBundles(b: Bundle): Set[Bundle] = {
    @annotation.tailrec def process(processed: Set[Bundle], remaining: Set[Bundle]): Set[Bundle] = {
      if (remaining.isEmpty) {
        processed
      } else {
        val (bundle, rest) = (remaining.head, remaining.tail)
        if (processed contains bundle) {
          process(processed, rest)
        } else {
          val wiring = bundle.adapt(classOf[BundleWiring])
          val requiredWires: List[BundleWire] = wiring.getRequiredWires(BundleRevision.PACKAGE_NAMESPACE).asScala.toList
          val direct: Set[Bundle] = requiredWires.flatMap { wire => Option(wire.getProviderWiring) map { _.getBundle } }.toSet
          process(processed + bundle, rest ++ (direct -- processed))
        }
      }
    }
    process(Set.empty, Set(b))
  }
}