SortQJackCtlPresets.scala

val fCfg = userHome / ".config" / "rncbc.org" / "QjackCtl.conf"
assert(fCfg.isFile)

val cOld = {
  import java.io._
  val in = new FileInputStream(fCfg)
  try {
    val sz = in.available()
    val arr = new Array[Byte](sz)
    in.read(arr)
    new String(arr, "UTF-8")
  } finally {
    in.close()
  }
}

val linesOld = cOld.split('\n').toList
val i1 = linesOld.indexOf("[Presets]") + 1
val i2 = linesOld.indexOf("", i1)

val (linesRem, lineOff, names) = {
  var i = 1
  val b = List.newBuilder[String]
  var r = linesOld
  var mn = i2
  var i3 = i2
  while ({
    val key = s"Preset$i="
    val j = r.indexWhere(_ startsWith key, i1)
    j > 0 && j < i3 && {
      b += r(j).substring(key.length)
      r = r.patch(j, Nil, 1)
      i += 1
      i3 -= 1
      mn = math.min(mn, j)
      true
    }
  }) ()
  (r, mn, b.result())
}

assert(names.nonEmpty && linesRem.size + names.size == linesOld.size)

val namesS = names.sortBy(_.toUpperCase(java.util.Locale.US))
val linesNew = namesS.zipWithIndex.foldLeft(linesRem) { case (r, (name, idx)) =>
  val key = s"Preset${idx + 1}=$name"
  r.patch(lineOff + idx, key :: Nil, 0)
}

assert(linesNew.size == linesOld.size)

val cNew = linesNew.mkString("\n")

{
  import java.io._
  val out = new FileOutputStream(fCfg)
  try {
    val arr = cNew.getBytes("UTF-8")
    out.write(arr)
  } finally {
    out.close()
  }
}