open Core

let archive ~src ~dst =
  if not (Sys.is_directory src) then failwithf "%s: not a directory" src ();
  if Sys.file_exists dst && not (Sys.is_directory dst) then begin
    try Unix.unlink dst with _e -> ();
  end;
  try Unix.mkdir dst with _e -> ();
  List.iter (Sys.ls_dir src) ~f:(fun fn ->
    let srcf = src ^/ fn and dstf = dst ^/ fn in
    if Sys.is_directory srcf then archive ~src:srcf ~dst:dstf
    else begin
      Out_channel.write_all dstf ~data:(Ezgzip.compress ~level:9 (In_channel.read_all srcf));
      let st = Unix.stat srcf in
      Unix.utimes dstf ~access:st.Unix.st_atime ~modif:st.Unix.st_mtime
    end)
;;

let () =
  archive ~src:"/a" ~dst:"b"
;;