BufferedReader enumerator example for Scalaz 7

iteratee-io.scala

import java.io.{ BufferedReader, File, FileReader }
import scalaz._, Scalaz._, effect.IO, iteratee.{ Iteratee => I, _ }

object IterateeIOExample {
  type ErrorOr[A] = Either[Throwable, A]

  def openFile(f: File) = IO(new BufferedReader(new FileReader(f)))
  def readLine(r: BufferedReader) = IO(Option(r.readLine))
  def closeReader(r: BufferedReader) = IO(r.close())

  def tryIO[A, B](action: IO[B]) = I.iterateeT[A, IO, ErrorOr[B]](
    action.catchLeft.map(
      r => I.sdone(r, r.fold(_ => I.eofInput, _ => I.emptyInput))
    )
  )

  def enumBuffered(r: => BufferedReader) = new EnumeratorT[ErrorOr[String], IO] {
    lazy val reader = r
    def apply[A] = (s: StepT[ErrorOr[String], IO, A]) => s.mapCont(k =>
      tryIO(readLine(reader)) flatMap {
        case Right(None)       => s.pointI
        case Right(Some(line)) => k(I.elInput(Right(line))) >>== apply[A]
        case Left(e)           => k(I.elInput(Left(e)))
      }
    )
  }

  def enumFile(f: File) = new EnumeratorT[ErrorOr[String], IO] {
    def apply[A] = (s: StepT[ErrorOr[String], IO, A]) => s.mapCont(k =>
      tryIO(openFile(f)) flatMap {
        case Right(reader) => I.iterateeT(
          enumBuffered(reader).apply(s).value.ensuring(closeReader(reader))
        )
        case Left(e) => k(I.elInput(Left(e)))
      }
    )
  }

  def main(args: Array[String]) {
    val action: IO[ErrorOr[List[String]]] = (
      I.consume[ErrorOr[String], IO, List] %=
      I.filter(_.fold(_ => true, _.count(_ == '0') >= 25)) &=
      enumFile(new File(args(0)))
    ).run.map(_.sequence)

    println(action.unsafePerformIO().map(_.size))
  }
}