structure Converter =
struct
  fun endsWithDsc str =
    if String.size str >= 4 then
      let
        val size = String.size str
        val expectedExtension = String.substring (str, size - 4, 4)
      in
        expectedExtension = ".dsc"
      end
    else
      false

  fun convertFile path = ()

  fun loop (dir, rootPath) =
    case OS.FileSys.readDir dir of
      SOME path =>
        let
          val folderPath = String.concat [rootPath, "/", path]
          val () = print (folderPath ^ "\n")
          val () =
            if OS.FileSys.isDir folderPath then
              (* handle recursive directory *)
              let val newDir = OS.FileSys.openDir folderPath
              in loop (newDir, folderPath)
              end
            else if OS.FileSys.isLink folderPath then
              (* ignore *)
              ()
            else if endsWithDsc path then
              (* is a file ending with .dsc extension *)
              convertFile folderPath
            else
              (* is a file but doesn't end with .dsc, so ignore *)
              ()
        in
          loop (dir, rootPath)
        end
    | NONE => OS.FileSys.closeDir dir

  fun main () =
    let
      val path = OS.FileSys.getDir ()
      val dir = OS.FileSys.openDir path
    in
      loop (dir, path)
    end
end