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

(*  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 FileUtilTEST

let which ?(path) fln =

  let real_path =

    match path with

      | None ->

          path_of_string

            (try

               Sys.getenv "PATH"

             with Not_found ->

               "")

      | Some x ->

        x

  in

  let exec_test = test (And(Is_exec, Is_file)) in

  let which_path =

    match Sys.os_type with

    | "Win32" ->

      begin

        let real_ext =

          List.map

            (fun dot_ext ->

               (* Remove leading "." if it exists *)

               if (String.length dot_ext) >= 1 && dot_ext.[0] = '.' then

                 String.sub dot_ext 1 ((String.length dot_ext) - 1)

               else

                 dot_ext)

            (* Extract possible extension from PATHEXT *)

            (path_of_string

               (try

                  Sys.getenv "PATHEXT"

                with Not_found ->

                  ""))

        in

        let to_filename dirname ext = add_extension (concat dirname fln) ext in

        let ctst dirname ext = exec_test (to_filename dirname ext) in

        List.fold_left

          (fun found dirname ->

             if found = None then begin

               try

                 let ext = List.find (ctst dirname) real_ext in

                 Some (to_filename dirname ext)

               with Not_found ->

                 None

             end else

               found)

          None

          real_path

      end

    | _ ->

      begin

        let to_filename dirname = concat dirname fln in

        try

          Some

            (to_filename

               (List.find

                  (fun dirname ->

                     exec_test (to_filename dirname)) real_path))

        with Not_found ->

          None

      end

  in

  match which_path with

  | Some fn -> fn

  | None -> raise Not_found