List contents of a directory with scalaz-stream

os.scala

package scalaz.stream

import java.nio.file.{DirectoryStream, Path}
import java.nio.file.Files._
import scalaz.concurrent.Task

import Process._

object os {
  def listDirectory(dir: Path): Process[Task, Path] =
    evalIterable(newDirectoryStream(dir))

  def listDirectoryDeep(dir: Path, followSymlinks: Boolean = false): Process[Task, Path] =
    listDirectory(dir).flatMap { path =>
      emit(path) ++ {
        val recur = isDirectory(path) && (!isSymbolicLink(path) || followSymlinks)
        if (recur) listDirectoryDeep(path, followSymlinks) else halt
      }
    }

  private type CloseableIterable[A] =
    java.lang.Iterable[A] with java.io.Closeable

  private def evalIterable[A](iterable: => CloseableIterable[A]): Process[Task, A] =
    io.resource(Task.delay(iterable))(r => Task.delay(r.close())) { r =>
      lazy val it = r.iterator()
      Task.delay { if (it.hasNext) it.next() else throw End }
    }
}