(******************************************************************************)

(*  ocaml-fileutils: files and filenames common operations                    *)

(*                                                                            *)

(*  Copyright (C) 2003-2014, Sylvain Le Gall                                  *)

(*                                                                            *)

(*  This library is free software; you can redistribute it and/or modify it   *)

(*  under the terms of the GNU Lesser General Public License as published by  *)

(*  the Free Software Foundation; either version 2.1 of the License, or (at   *)

(*  your option) any later version, with the OCaml static compilation         *)

(*  exception.                                                                *)

(*                                                                            *)

(*  This library is distributed in the hope that it will be useful, but       *)

(*  WITHOUT ANY WARRANTY; without even the implied warranty of                *)

(*  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the file         *)

(*  COPYING for more details.                                                 *)

(*                                                                            *)

(*  You should have received a copy of the GNU Lesser General Public License  *)

(*  along with this library; if not, write to the Free Software Foundation,   *)

(*  Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA             *)

(******************************************************************************)

open FileUtilTypes

open FilePath

open FileUtilMisc

open FileUtilPWD

open FileUtilTEST

let readlink fln =

  let all_upper_dir fln =

    let rec all_upper_dir_aux lst fln =

      let dir = dirname fln in

        match lst with

        | prev_dir :: _ when prev_dir = dir -> lst

        | _ -> all_upper_dir_aux (dir :: lst) dir

    in

    all_upper_dir_aux [fln] fln

  in

  let ctst =

    let st_opt, stL_opt = None, None in

    compile_filter ?st_opt ?stL_opt Is_link

  in

  let rec readlink_aux already_read fln =

    let newly_read = prevent_recursion already_read fln in

    let dirs = all_upper_dir fln in

    try

        let src_link = List.find ctst (List.rev dirs) in

        let dst_link = Unix.readlink src_link in

        let real_link =

          if is_relative dst_link then

            reduce (concat (dirname src_link) dst_link)

          else

            reduce dst_link

        in

        readlink_aux newly_read (reparent src_link real_link fln)

      with Not_found ->

        fln

  in

  readlink_aux SetFilename.empty (make_absolute (pwd ()) fln)